Neuroscience

Question 1

Describe the early development of the CNS.

Answer 1

1. proliferation of the ectoderm in the dorsal midline of the embryonic disc - this forms the NEURAL PLATE
2. as the plate thickens further it starts to fold up on the sides
3. eventually, the two neural folds fuse dorsally to form a tube (lined by NEUROEPITHELIUM, in which the space in the middle is called the NEURAL CANAL
4. at the tip of the neural fold you get little bunches of cells called NEURAL CRESTS, these crests separate form the tube and lie unfused alongside them
5. at the other end of the process the neural tube lies in the midline, dorsally to the embryo, on the other side there are two strips of neural crest tissue

Question 2

State what the neural tube and neural crest go on to become.

Answer 2

• Neural Tube = CNS cells
• Neural Crest = PNS cells

Question 3

State the 3 cell types the arise from neuroepithelium

Answer 3

1. neuroblasts 2. glioblasts 3. ependymal cells

Question 4

Describe neuroblasts.

Answer 4

• precursors for all neurones that have their cell bodies within the CNS

Question 5

Describe glioblasts

Answer 5

• become neuroglia -> astrocytes, oligodendrocytes etc

Question 6

Describe ependymal cells.

Answer 6

• lining of ventricles and central canal - remain close to the inner membrane of the neural tube and they spread out and form a lining around the developing ventricular system

Question 7

State the differentiation of neural crest cells.

Answer 7

• sensory neurones of dorsal root ganglia and cranial ganglia
• post-ganglionic autonomic neurones
• schwann cells
• non-neuronal derivatives

Question 8

Explain the layout of neuroepithelium.

Answer 8

• almost all cells are attached to BOTH the inner and outer membranes - it’s just that the nuclei are in different positions
• the cross-section shows fat cells going through mitosis at the bottom

Question 9

Describe the differentiation of neuroepithelium.

Answer 9

1. cells withdraw from the outer membrane towards the inner membrane and go through mitosis
2. one of the daughter cells will stay attached to the inner cell membrane, it gets bigger and goes into the cell cycle again
3. the other daughter cell migrates away from the inner membrane and then develops into neuroblasts
4. they develop processes (one will become the axon) and these axons are directed away from the inner membrane again, as the above occurs over and over you end up with THREE layers
   - there is one layer by the inner membrane where you get mitosis occurring, another layer where you mainly have cell bodies and another that has mainly axons -> this is the beginning of the difference between grey and white matter

Question 10

Answer 10

Question 11

What controls the process of differntiation and migration?

Answer 11

• signalling molecules (sonic hedgehog), secreted by surrounding tissues, interact with receptors on neuroblasts
• control migration & axonal growth by attraction and repulsion
• depends on concentration gradient and timing

Question 12

Describe the developing spinal cord.

Answer 12

o 2 significant features:

• > neural canal is even smaller compared to the thickness of the wall
• > grey matter has split into TWO different types: -> alar plate - dorsal and basal plate - ventral

o interneurons in the alar plates are becoming specialised to receive sensory information -> information comes from the developing dorsal root ganglia that developed from the neural crest

in the basal plate there are some interneurons and the development of motor neurones -> means the basal plate has a motor function -> the axons leave the spinal cord to go towards muscles

Question 13

Describe the anatomy of a mature spinal cord compared to a developing spinal cord.

Answer 13

• the neural canal becomes the central canal carrying CSF
• alar plates develop into the dorsal horns
• basal plates develop into ventral horns
• the whole spinal cord is surrounded by a thick layer of white matter

Question 14

Describe the organisation of the nuclei in the brainstem.

Answer 14

• the cranial nerve nuclei within the brainstem that have a motor function tend to lie more medially (because that’s where the basal plates have ended up after the split)

o Motor = Medial

o Sensory = Lateral

o Autonomic = in between

Question 15

Explain the development of the brainstem.

Answer 15

1. the 4th ventricle develops -> makes a mess of the tubular organisation
2. the roof plate starts proliferating rapidly causing the dorsal part of the brainstem expands laterally
3. as the roof plate expands it pushes the alar plates aside so they are no longer dorsal to the roof plate, this is the developing brainstem

Question 16

Describe the appearance of the brain at 4 weeks in an embryo.

Answer 16

o only the most anterior bit of the neural tube develops into the brain

• differentiation of the wall of the anterior neural tube occurs to form THREE primary vesicles:
• > prosencephalon = future forebrain
• > mesencephalon = future midbrain
• > rhombencephalon = future hindbrain

o the rest becomes the spinal cord

Question 17

Describe the appearance of the brain in an embryo at 5 weeks

Answer 17

• enormous expansion of the top part of the developing forebrain -> telencephalon will become the cerebral hemispheres
• less expansion in the lower part of the developing forebrain because that part becomes the diencephalon
• the developing midbrain doesn’t expand very much
• the developing hindbrain divides in two becoming the pons and the medulla

Question 18

Describe the structure of the brain in a n embryo of 8 weeks of age.

Answer 18

• as development continues you get more and more growth of the wall of the neural tube
• the space within it has become smaller relative to the wall and this space becomes the ventricular system
• late on, you have the first development of the cerebellum -> out-pouching from the back of the pons

Question 19

Explain the folding of the developing brain.

Answer 19

o there are THREE flexures: cephalic, pontine and cervical

o as you go through development these flexures become exaggerated -> by 8 weeks, the telencephalon has got so big that it’s starting to move back and cover the diencephalon

Question 20

Explain the development of the cortex

Answer 20

o the brain has a core of white matter with grey matter around the outside -> opposite to the spinal cord

o the grey matter consists of nuclei that have migrated from the inner membrane of the neural tube

• migration takes place by the neuroblasts attaching themselves to radial glial cells -> have their cell bodies anchored in the inner membrane and have a single long process that goes to the outer membrane
• neuroblasts attach themselves to radial glial cells and climb up towards the outer membrane
• a wave of proliferation near the inner membrane occurs followed by a wave of migration towards the other surface -> one layer of the cortex is formed
• another wave of proliferation and another wave of migration forming the 2nd layer of cortex -> continues until you have SIX LAYERS of cells within the cerebral cortex

Back

Question 21

What are the general causes for the occurence of developmental disorders.

Answer 21

• genetic mutation and environmental factors such as the mother’s lifestyle, diet and teratogens

Question 22

What is the cause of schizophrenia

Answer 22

• malfunction of neural development early on in develomet

Question 23

Name a cause of spina bifida

Answer 23

• folic acid deficiency in vivo

Question 24

What is cranioarchischisis.

Answer 24

• completely open brain and spinal cord
• incompatible with life -> misscarriage, still born or die shortly after birth

Question 25

What is anenceephaly.

Answer 25

- open brain and lack of skull vault - as a consequency patients never have a fully developed brain, usually isnt compatible with life (are still born)

Question 26

What is encephalocele.

Answer 26

- herniation of the meninges (and brain) -\> large bump outside of the skull, usually at the back of the head

Question 27

What is iniencephaly

Answer 27

occipital skull and spine defects with extreme retroflextion of the head

Question 28

What is spina bifida occulta

Answer 28

- closed asympatomatic NTD in which some vertebrate are not completely closed

Question 29

What is closed spinal dysraphism

Answer 29

- deficiency of at least two vertebrate arches - can become covered by lipoma

Question 30

What is meningocele

Answer 30

- production of the meninges filled with CSF due to a defect in the skull or spine

Question 31

What is myelomeningocele

Answer 31

- open spinal cord, which can lead to meningeal cysts

Question 32

Explain the significance of neural stem cells.

Answer 32

- there are still some germinal cells in the subependymal areas and hippocampus of the adult brain, but in very small numbers with none around mid-60s - after strokes it is sometimes possible for recovery via these stem cells - research is being done to see if they can be targetted in other neurodegenerative diseases - Huntington's being one

Question 33

Define the brainstem.

Answer 33

- the part of the CNS, exclusive of the cerebellum that lies between the cerebrum and the spinal cord

Question 34

What are the three major divisions of the brainstem from top to bottom?

Answer 34

- midbrain - pons - medulla oblongata

Question 35

State the role of the pineal gland.

Answer 35

- releases melatonin and is important in regulating circadian rhythm -\> does so by light via training from vision

Question 36

What is the role of the superior colliculus.

Answer 36

- important in the coordination of eye and head movements at the same time (think about watching tennis)

Question 37

What is the role of the inferior colliculus.

Answer 37

- auditory reflexes, if there is a loud bang you tend to look in the direction of the bang immediately

Question 38

Which cranial nerve emerges from the back of the brainstem?

Answer 38

- trochlear nerve (CN IV) -\> out of the back of the pons

Question 39

State the role of the trochlear nerve

Answer 39

- suppling one of the extrinsic muscles of the eye (superior oblique muscle in particular)

Question 40

Which sensory pathways are the dorsal corsal columns involved in.

Answer 40

- fine touch - proprioception (space perception)

Question 41

What is very clear from the anteroinferior view of the brainstem?

Answer 41

- the pons

Question 42

Name the 4 functional subtypes of the cranial nerves.

Answer 42

- General Somatic Afferent (GSA) - General Visceral Afferent (GVA) - General Somatic Efferent (GSE) - General Visceral Efferent (GVE)

Question 43

Describe the function of the special somatic afferent nerve.

Answer 43

- vision, hearing and equilibrium (only the cranial nerves)

Question 44

State the function of special visceral afferent nerves.

Answer 44

- smell (CN I) and taste

Question 45

Name the functions of the special visceral efferent nerves.

Answer 45

- muscles involved in chewing, facial expression, swallowing, vocal sounds and turning the head

Question 46

What is the general rule about the positioning of motor and sensory nerves?

Answer 46

- motor tend to be medial while sensory tend to be lateral

Question 47

Describe the arrangement of the general somatic efferent nerve.

Answer 47

o GSE are the most medial of all the pathways - oculomotor = most rostal -\> top of the midbrain - trochlear = immediately below but still in the midbrain - abducens = in the pons -\> nerve move down before emerging from the ponto-medullary junction - hypoglossal = in the medulla

Question 48

Describe the anatomy of the special visceral efferent nerves

Answer 48

o SVE lateral to the GSE (2^nd) - trigerminal = in the pons - facial = in the pons - ambiguus = in the medulla (involved in swallowing) - accessory = in the cervical spinal cord

Question 49

Describe the anatomy of the general visceral efferent nerves.

Answer 49

o GVE are lateral to the SVE (3^rd) - edinger westphal = in the midbrain (parasympathetic imput into the eye) - salivatory = three pairs of nuclei at the ponto-medullary border - vagus = in the pons

Question 50

What is the anatomy of the special somatic afferent nerve.

Answer 50

o most lateral (6^th) - vestibulocochlear = nucleus mainly resides in the pons but also partly in the medulla

Question 51

What is the arrangement of the general somatic afferent nerves?

Answer 51

o lateral to the GVA (5^th) - there are THREE trigerminal nuclei, one spans across from the midbrain to the pons, another is completely in the pons while the last starts in the pons and goes all the way down the cervical spinal cord

Question 52

Describe the arrangement of the general visceral afferent nerve.

Answer 52

o most medial of the sensory nuclei but still lateral to all motor (4^th) - solitarius = 90% in the medulla with a fraction in the pons

Question 53

Describe the appearance of the midbrain.

Answer 53

- has a typical MICKEY MOUSE appearance - you can see the cerebral aqueduct then you're in the midbrain - cerebral peduncle will vary in appearance - the inferior colliculus which is low down in the midbrain - MOST OBVIOUS SIGN IS THE SUBSTANTIA NIGRA -\> are dopaminergic neurones which normally produce neuromelanin, a pigment that gives its BLACK colour -\> as you get old it gets blacker and blacker NOTE: In Parkinson's disease you lose these dopaminergic neurones so a pale substantia nigra could be a sign of Parkinson's disease

Question 54

What is the anatomy of the pons?

Answer 54

o the pons is in the region of the 4th Ventricle - just underneath the cerebellum o MOST PBVIOUS FEATURE ARE THE TRANSVERSE FIBRES o cerebral peduncles hold onto the cerebrum onto the back of the brainstem - the main peduncle is the middle cerebellar peduncle

Question 55

Describe the anatomy of the open/upper medulla.

Answer 55

- the medulla changes a lot as you go down the brainstem - at the top you still have the 4th ventricle but the rest of the shape is very different to the pons - MAIN FEATURE = PYRAMIDS start to be seen - a bit of a bulge in the side of the medulla called the inferior olivary nucleus - this is connected to the cerebellum and is involved in fine tuning motor movements - inferior olivary nucleus can be seen

Question 56

Wha is the anatomy of the lower medulla?

Answer 56

o at the junction with the spinal cord the cross-section is very round o dorsal columns can be seen here (touch and proprioception) - the smaller of the columns is the gracilis - sensory information from the lower limb - more laterally you have the cuneatus - sensory information from the upper limb o central canal can be seen in the cross-section of the lower medulla o crossing over of the fibres at the pyramidal decussation in the lower medulla

Question 57

State the signs and symptoms of Lateral Medullary Syndrome.

Answer 57

- vertigo - ipsilateral Cerebellar Ataxia - problem with gait on the same side of the body as the lesion (broad-based gate with a tendency to shuffle) - ipsilateral loss of pain/thermal sense (face) - Horner's Syndrome - loss of sympathetic innervation to the head and neck -\> ptosis, lack of sweating around the eye, hoarseness of voice and difficulty swallowing - contralateral loss of pain/thermal sense in the trunk and limbs

Question 58

What is the cause of lateral medullary syndrome?

Answer 58

- caused by thrombosis of the vertebral artery or the posterior inferior cerebellar artery

Question 59

Using this image match the areas to the consequences of lateral medullary syndrome.

Answer 59

- PICA supplies the shaded section of the medulla - disturbing the vestibular nucleus = vertigo - disturbing the inferior cerebellar peduncle = the balance problem - sympathetic tract = Horner's Syndrome - spinothalamic tract = pain and sensory information coming from the body - damage is catastrophic because everything is packed close together in the medulla

Question 60

What are the demands of the brain?

Answer 60

- 2% of his body weight (around 1.3 kg) - 10-20% of CO - 20% of body oxygen consumption - 66% of liver glucose - brain is very vunerable if blood supply becomes impaired

Question 61

What are the two blood supplies to the brain?

Answer 61

- internal carotid arteries (front) - vertebral arteries (back)

Question 62

Name the structure that the ICA and VA give rise to.

Answer 62

- circle of Willis - cerebral arteries come off the circle

Question 63

Where do the external carotid arteries supply?

Answer 63

- the face

Question 64

What arteries supply the cerebral hemispheres?

Answer 64

- internal carotid

Question 65

Describe the pathway of the vertebral arteries which branch of the subclavian arteries.

Answer 65

- travel through the tranverse foramina in the cervical vertebrate and the foramen magnum and onto the brain

Question 66

Name the major vessels in the venous drainage of the brain.

Answer 66

- cerebral veins - venous sinuses - dura mater - internal jugular veins

Question 67

Describe the system of the dural venous sinuses

Answer 67

- running along the top is the superior sagittal sinus, inbetween the two folds of dura, at this point the CSF drains back into the venous system - along the bottom of the dural fold is the inferior sagittal sinus - these sinuses run backwards to form a big space filled with blood called the CONFLUENCE OF THE SINUSES -\> a bleed at the confluence of sinuses can be terrible

Question 68

What is the medical term for a stroke?

Answer 68

- cerebrovascular accident (CVA)

Question 69

Define Stroke.

Answer 69

- rapidly developing focal disturbance of brain function of presumed vascular origin lasting more than 24 hours

Question 70

What percentage of strokes are due to infarction?

Answer 70

- 85%, the other 15% is due to haemorrhage

Question 71

Define Transient Ischaemic Attack (TIA).

Answer 71

- rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours

Question 72

Why are TIA clinically so important?

Answer 72

- a massive risk factor for a stroke -\> may have been a small bit of atherosclerotic debris that blocks more distally and resolves itself

Question 73

State 2 causes of occlusions.

Answer 73

- thrombosis -\> formation of a blood clot - embolism -\> plugging of small vessel by material carried from larger vessel

Question 74

How many people die of strokes each year in the UK?

Answer 74

- 100,000, making it the 3rd most common cause of death

Question 75

What perecentage of survivors have some kind of damage?

Answer 75

- 70% show an obvious neurological defect - 50% are permenently disabled

Question 76

Name 5 key risk factors to having a stroke.

Answer 76

- age - hypertension - cardiac disease - smoking - diabetes mellitus

Question 77

Describe the path of the middle cerebral artery.

Answer 77

- extends laterally and emerges through the lateral fissure between the frontal and temporal lobes

Question 78

State the area which is supplied by the middle cerebral artery.

Answer 78

- it supplies the front 2/3 of the lateral part of the hemisphere

Question 79

Which section of the brain is supplied by the posterior cerebral artery?

Answer 79

- posterior cerebral artery supplies the medial and lateral parts of the posterior part of the hemisphere

Question 80

What artery supplies the medial part of each hemisphere?

Answer 80

- the anterior cerebral artery

Question 81

State the symptoms specific to a stroke caused by disturbance to the anterior cerebral artery.

Answer 81

- paralysis of the contralateral LEG more so than the arm or face -\> due to motor homunculus part of the motor cortex that controls the leg is more medial than the part controlling the arm - disturbance of intellect, executive function and judgement (abulia - absence of willpower) - loss of appropriate social behaviour

Question 82

State the symptoms specific to a stroke caused by disturbance to the middle cerebral artery.

Answer 82

- CLASSIC STROKE - contralateral hemiplegia - more the contralateral ARM than leg -\> the lesion is more lateral -\> closer to the motor cortex controlling the arms than legs - contralateral hemisensory deficits - hemianopia (loss of half the visual field) - aphasia (if a left sided lesion) - can't speak -\> the language centres are more on the left side of the brain

Question 83

What are the areas of the brain involved in speech?

Answer 83

- Broca's Area

Question 84

Name the symptoms specific to a stroke caused by disturbance to the posterior cerebral artery.

Answer 84

o this leads to visual defects -\> supplies the occipital lobe where the primary visual cortex is - omonymous hemianopia - visual agnosia (loss ability to recognise things) Back

Question 85

What are lacunes?

Answer 85

- a lacune is a small cavity, that appear in deep structures as a result of small vessel occlusion, the exact deficit is dependent on anatomical location - often caused by strokes

Question 86

Name a cause of lacunar infarcts.

Answer 86

- hypertension

Question 87

Name the 4 types of haemorrhagic strokes.

Answer 87

- extradural - subdural - subarachnoid - intracerebral

Question 88

State the cause and consequence of extradural haemorrhagic strokes.

Answer 88

- trauma - immediate effects - high pressure arterial bleed -\> massive increase in intracranial pressure -\> herniation -\> will be terminal if surgical intervention to relieve pressure is not carried out - it treated quickly it has good prognosis

Question 89

State the cause and consequence of a subdural haemorrhagic stroke.

Answer 89

- trauma - delayed effects due to lower pressure venous bleed -\> blood accumulates in the subdural space -\> still an emergency -\> good outcome if treated - not uncommon for them to have been initial unconscious and then to have recovered

Question 90

State the cause of subarahnoid haemorrhagic stroke.

Answer 90

- usually a ruptured aneurysm

Question 91

State the cause of intracerebral haemorrhagic stroke.

Answer 91

- spontaneous hypertensive rupture of small vessels

Question 92

What is the difference between dura in the skull and in the vertebral column?

Answer 92

- vertebral column has a SINGLE LAYER of dura with fat between the bone and the dura - the skull has TWO LAYERS of dura that are mostly stuck together

Question 93

What are the two layers of dura in the skull?

Answer 93

- periosteal - meningeal

Question 94

Describe an extradural haematoma.

Answer 94

- high pressure arterial supply to the brain leads to the splitting of some of the arteries that are running in the meninges themselves (between the dura and the skull), causing compression of the skull underneath - the periosteal dura is stuck to the skull so it is only a potential space that is there, which can be filled by blood in an extradural haemorrhage - usually always due to a blow to the side of the head

Question 95

Describe a subdural haematoma.

Answer 95

- are slower to cause issues than an extradural haematoma - is caused by the rupture of VEINS in the skull - so is at much lower pressure - because of the slow onset of symptoms, patients may initially think that they are ok and then experience symptoms a few hours later

Question 96

What is the fold of dura that extends between the medial surfaces of the two hemispheres called?

Answer 96

- falx cerebri

Question 97

What does the peeling apart of the two layers of dura at the top of the falx cerebri form and what is found in this space?

Answer 97

- superior sagittal sinus - within the gap arachnoid granules are found

Question 98

How is the CSF filtered?

Answer 98

- it leaks through holes in the arachnoid membrane and enters the superior sagittao sinus

Question 99

Which vertebrate is the most to likely herniate?

Answer 99

- L5 disk -\> change in angle between lumbar vertebra and sacral -\> has the most pressure going through it

Question 100

In terms of meningeal layers, what are the differences between the brain and the spinal cord?

Answer 100

- no epidural space in the brain unless a pathological issue is present but there is in the spinal cord - two layers/folds of dura around to the brain but only one around the spinal cord - if there isn't a space then there is some sort of pathology present -\> haemorrhage being one

Question 101

From the outside travelling inwards, name the meningeal layers and the space linked to them around the spinal cord.

Answer 101

- epidural space - dura mater - arachnoid mater - subarachnoid space - pia mater

Question 102

State some clincial relevances of the epidural space.

Answer 102

- can be used to insert anaesthetic or painkillers -\> sometimes done in childbirth - epidural nerve block for pain relief or to carry out surgery

Question 103

State the clincial relevance of the subarachnoid space.

Answer 103

- sampling of CSF - insertion of anaesthtics or painkillers-\> if there is a good idea of how long a surgery will take it is used instead of a general anaesthetic -\> especially in the elderly or those with co-morbidites - spinal nerve block for pain relief or to make surgery possible

Question 104

Define dermatomes.

Answer 104

- an area of skin that is supplied by a pair of neurones

Question 105

Define myotome

Answer 105

muscles that are supplied by a pair of neurones

Question 106

Which spinal nerve supplies the dermatome that the umbilicus lies in?

Answer 106

- T10

Question 107

At what point does a nerve become a mixed spinal nerve?

Answer 107

- once the sensory and motor nerve have joined laterally from the roots

Question 108

Describe the cross section the spinal cord, including some key landmarks.

Answer 108

Question 109

What is the general rule about sensory neurone crossing in the spinal cord.

Answer 109

- sensory neurones usually cross over when it synapses -\> if the neurone synapses when entering spinal cord it will immediatelycross etc

Question 110

When do discriminative touch and proprioception sensory fibres cross over?

Answer 110

- sensory fibres enter the dorsal horn and travel in the dorsal columns without synapsing in the posterior horn so don’t cross until the medulla

Question 111

When do pain and temperatue sensory fibres cross over?

Answer 111

- sensory fibres enter the dorsal horn, then may travel up or down 1-2 segments in the Lissauer tract, and synapse in the nucleus proprius before crossing the midline in the anterior commissure and travelling in the spinothalamic tract

Question 112

At what point do motor neurones cross over?

Answer 112

- all motor neurones cross over deep in the medulla, therefore they always emerge on the ‘correct’ side

Question 113

Name the major tracts the spinal cord in a clockwise direction form back to front while also stating their function.

Answer 113

o corticospinal tracts = voluntary movement pathway - lateral = limbs - anterior = trunk (proximal muscles) o spinothalamic tract = pain and temperature from contralateral side of body o dorsal columns = sensory info for fine (discriminative) touch - fasciculus gracillis – lower limbs - fasciculus cuneatus – upper limbs

Question 114

What is the path of the lateral corticospinal tract?

Answer 114

- a neurone travels from the fine motor cortex to the medulla where is synapses and therefore crosses over before a spinal nerve which synapses onto a lower motor neurone before becoming a periphary nerve with other spinal nerves and travelling to an effector/muscle

Question 115

Name some factors that affect the severity of spinal lesions.

Answer 115

- loss of neural tissue - small if due to trauma but extensive if due to metastases or degenerative disease - vertical level - transverse plane

Question 116

What is the link between the height of a lesion and the level of disability?

Answer 116

- the higher the lesion, the greater the disability - REMEMBER C3,4,5 keep the diaphragm alive -\> segmets which the phrenic nerve emerges from

Question 117

Why is the brains glucose supply so surplus?

Answer 117

· the brain can't synthesise or utilise any other source of energy, estimated that the brain use 50-60% of the bodies glucose · ketones can be metabolised, for a short period of time, if there is a shortage of glucose but glucose is the main nutrient

Question 118

Describe the stages of lateral corticospinal tract injury including recovery

Answer 118

· Stage 1 - spinal shock: loss of reflex activity below the lesion, lasting for days or weeks = flaccid paralysis · Stage 2 - return of reflexes (happens over weeks/months): hyperreflexia and/or spasticity = rigid paralysis

Question 119

What percentage decrease in blood flow to the brain is required before its function becomes significantly impaired?

Answer 119

- 50%

Question 120

State the consequence of a 4 second interruption of cerebral blood flow.

Answer 120

- unconsciousness - after a few minutes irreversible damage starts to occur

Question 121

Describe the symptoms of hypoglycaemia caused by the loss of brain function.

Answer 121

- individual appears disoriented - slurred speech - impaired motor function o similar to be being drunk

Question 122

What is the blood glucose conc. that if values fall below becomes catastrophic?

Answer 122

- below 2 mM (normally between 4-6mM) it can result in unconsciousness, coma and DEATH

Question 123

How is cerebral blood flow maintained?

Answer 123

- via autoregulation by stretch-sensitive cerebral vascular smooth muscle which can contact and relax to maintain cerebral blood flow when arterial blood flow is between 60-160mmHg

Question 124

What happens if the arterial blood flow rises above 160mmHg?

Answer 124

- increased flow can lead to swelling of brain tissue which is not accommodated by the “closed” cranium, therefore intracranial pressure increases -\> becomes dangerous

Question 125

What two factors contribute to local regulation of cerebral blood flow?

Answer 125

- neural - chemical

Question 126

Describe the pattern of vascularisation in the CNS tissues.

Answer 126

- arteries enter the CNS tissue from branches of the surface pial vessels, branches penetrate into the brain parenchyma branching to form capillaries which drain into venules and veins which drain into surface pial veins - no neurone is ever more than 100µm from a capillary

Question 127

What 4 neural factors alter local cerebral blood flow?

Answer 127

- sympathetic nerve stimulation -\> vasoconstriction - only happens when the arterial blood pressure is HIGH - parasympathetic (facial nerve) stimulation -\> facial nerve fibres are innervated by parasympathetic fibres -\> causes a slight vasodilation - central cortical neurones -\> neuronal neurotransmitter (catecholamines) release -\> vasoconstriction) - dopaminergic neurones -\> produce vasoconstriction -\> important in regulating local blood flow to areas of the brain that are more active

Question 128

Define pericytes.

Answer 128

- cells that wrap around capillaries which have diverse activities e.g. immune function, transport properties, contractile - effectively a type of brain macrophage

Question 129

Explain how dopaminergic neurones control local cerebral blood flow.

Answer 129

- when dopaminergic neurones are active, they can cause the contraction of pericytes to decrease the blood flow to a particular area thus diverting blood to other, more active areas of the brain - dopamine may also cause contraction of pericytes via aminergic and serotoninergic receptors - IMPORTANT FOR DIVERTING BLOOD TO ACTIVE AREAS OF THE BRAIN

Question 130

What chemical factors can alter local cerebral blood flow?

Answer 130

- CO_² (indirect) -\> vasodilator - pH -\> vasodilator - nitric oxide -\> vasodilator - K⁺ -\> vasodilator - adenosine -\> vasodilator - anoxia -\> vasodilator - other (e.g. kinins, prostaglandins, histamine, endothelins)

Question 131

Explain how CO₂ can cause cerebral artery flow to increase.

Answer 131

- H⁺ ion cannot cros the BBB to influcence smooth muscle cells - CO₂ from the blood or from local metabolic activity gets converted to H⁺ by carbonic anhydrase in surrounding neural tissue and in the smooth muscle cells -\> elevated H⁺ means decreased pH -\> relaxation of the contractile smooth muscle cells and increased blood flow

Question 132

Where is the CSF formed?

Answer 132

- choroid plexus -\> are present in the lateral ventricle, 4th ventricle etc

Question 133

Name an adaptation that makes the choroid plexus good for CSF formation.

Answer 133

- the capillaries are leaky but, are surrounded by ependymal cells with tight junctions -\> can freely lsecrete molecules into the ventricle to make CSF

Question 134

Describe the flow route of CSF.

Answer 134

lateral ventricles -\> 3rd ventricle (via interventricular foramina) -\> cerebral aqueduct -\> 4th ventricle -\> subarachnoid space (via medial and lateral apertures) -\> lateral ventricles

Question 135

State the volume of CSF as well as the amount produced formed everyday.

Answer 135

- volume of CSF = 80 - 150 mL - volume of CSF formed per day = 450 mL/day

Question 136

What is the function of the CSF?

Answer 136

- protection (chemical and physical) - nutrition of neurones - transport of molecules

Question 137

What are the functions of the Blood-Brain-Barrier?

Answer 137

- protects the brain tissue from toxins and circulating transmitters like catecholamines - it also protects the brain from wide variations in ion concentrations

Question 138

Compare plasma to CSF.

Answer 138

o very similar composition - amino acids are much lower in CSF, Ca²⁺ and Na⁺ are also lower - CSF has very little protein where plasma has a lot

Question 139

What is the clinical relevance of there being very little protein in CSF?

Answer 139

- if there is protein in the CSF it is a marker for brain infection, injury or other damage

Question 140

What is Brown-Sequard Syndrom?

Answer 140

- a rare neurological condition characterized by a lesion in the spinal cord which results in weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side

Question 141

What changes occur in a vessel of the CNS parenchyma as it travels away from the pial?

Answer 141

- the junctions become tighter and therefore the vessel become less and less permeable

Question 142

What classes of molecules can relatively easily cross the BBB?

Answer 142

- lipophilic molecules (alcohol and anaesthetics) - hydrophobic

Question 143

How do hydrophilic substances cross throught the BBB and into the brain and CSF?

Answer 143

o only certain hydrophilic substances are allowed through the BBB by means of specific transport mechanisms including: - water via aquaporin channels - glucose via GLUT1 proteins - amino acids via 3 different transporters - electrolytes via specific transporter systems

Question 144

What are the general roles of circumventricular organs (CVOs)?

Answer 144

- sampling plasma for toxins -\> will induce vomiting - sensing electrolytes - regulating water intake

Question 145

Name some circumventricular organs (CVOs)

Answer 145

- median eminence region of the hypothalamus - subfornical organ (SFO) - organum vasculosum of the lamina terminalis (OVLT)

Question 146

What is special about circumventricular organs?

Answer 146

- even though they are in the brain they lie outside of the BBB and actually have fenestrated capillaries - molecules can readily pass from the blood to the CSF/ ECF -\> vital for their relative functions - ventricular ependymal lining close to these areas can be much tighter than in other areas, limiting the exchange between them and the CSF

Question 147

Name some pathological states that cause the breakdown of the BBB.

Answer 147

- inflammation - infection - trauma - stroke

Question 148

How does the BBB affect the treatment for Parkinson's Disease?

Answer 148

o a key therapy in Parkinson’s disease is pharmacologically raising the levels of dopamine in the brain, however dopamine cannot cross the BBB o L-DOPA can cross the BBB via an amino acid transporter, and is converted to dopamine in the brain by DOPA decarboxylase -\> is a pharmacology way of increasing dopamine in the brain - however lots of L-DOPA gets converted before it reaches the brain -\> L-DOPA is co-administration with a DOPA decarboxylase inhibitor (carbidopa) -\> carbidopa cannot cross the BBB, so does not affect conversion of L-DOPA in the brain

Question 149

What is the problem of using L-DOPA as a treatment for Parkinson's Disease?

Answer 149

- lots of L-DOPA is converted to dopamine outside of the brain by DOPA decarboxylase, reducing the conc. of L-DOPA which can cross the brain - can't raise does or adverse effects of dopamine appear

Question 150

How are the problems with L-DOPA overcome for Parkinson's treatment?

Answer 150

- co-administrating a DOPA carboxylase inhibitor (carbidopa) - carbidopa cannot cross the BBB so enzymes instead the BBB aren't inhibited

Question 151

What is a modality?

Answer 151

- a type of stimulus -\> hot, cold, touch, etc - each modality has a specialised receptors which transmit information through specfic anatomical pathways to the brain

Question 152

What is registered by mechanoreceptors?

Answer 152

- touch, pressure, vibration - proprioception -\> joint position, muscle length, muscle tension

Question 153

What receptors sense temperature?

Answer 153

- thermoreceptors

Question 154

What is the receptor for pain?

Answer 154

- noiceptors

Question 155

What sensory information is carried by A-alpha fibres?

Answer 155

- proprioception of skeletal muscles

Question 156

What sensory information is carried by A-beta fibres?

Answer 156

- mechanoreception of skin

Question 157

What sensory information is carried by A-gamma fibres?

Answer 157

- pain - temperature

Question 158

What sensory information is carried by C fibres?

Answer 158

- temperature - pain - itch

Question 159

Define Sensory Receptor.

Answer 159

- transducers that convert energy from the environment into neuronal action potentials

Question 160

Define Absolute Threshold.

Answer 160

- the level of stimulus that produces a positive response of detection 50% of the time

Question 161

Describe thermoreceptors, including their activation.

Answer 161

- free nerve endings with high thermal sensitivity - changes in temperature activates a family of transient receptor potential ion channels

Question 162

What do Meissner's corpuscles detect?

Answer 162

- fine discriminative touch

Question 163

What do Merkel cells detect?

Answer 163

- light touch and superficial pressure

Question 164

What do Pacinian corpuscles detect?

Answer 164

- deep pressure, vibrations and tickling

Question 165

What do Ruffini endings detect?

Answer 165

- continuous pressure or touch and strech

Question 166

How sensitive are mechanoreceptors?

Answer 166

- very -\> have a very low threshold

Question 167

What are tonic receptors?

Answer 167

o detect continuous stimulus strength -\> transmit impulses to the brain as long the stimulus is present -\> keeps the brain constantly informed of the status of the body o slowly adapting - eg. merkel cells-\> slowly adapt allowing for superficial pressure and fine touch to be perceived

Question 168

What are phasic receptors?

Answer 168

o detect a change in stimulus strength -\> transmit an impulse at the start and the end of the stimulus o slowly adapting - e.g. pacinian receptor -\> sudden pressure excites receptor causing a signal, transmits a signal again when pressure is released

Question 169

Define Receptive Field.

Answer 169

- a region on the skin which causes activation of a single sensory neuron when activated

Question 170

What is the significance of the receptive fields, when talking about sensitivity?

Answer 170

- finger tips, lips, tongue have high density of innervation with very small receptive fields = more sensitive - the back has less densely packed innervation with larger receptive fields = less sensitive

Question 171

What is two point discrimination and how does it tie in with receptive fields?

Answer 171

o minimum distance at which two points are perceived as seperate - is related to the size of receptive fields -\> points can be closer on the hand than the back

Question 172

What is tranduction?

Answer 172

- sensory receptors generate a receptor potential, a change in their membrane potential, in response to approriate stimulation

Question 173

Where does the cuneate nucleus recieve input from?

Answer 173

- C1-T6 -\> via the cuneate tract

Question 174

What imputs into the gracile nuclues?

Answer 174

- T7-S4 -\> via the gracile tract

Question 175

In terms of sensory input, what is area 3b involved in?

Answer 175

- tactile discrimination

Question 176

In terms of sensory input, what is area 1 involved in?

Answer 176

- analysis of texture

Question 177

In terms of sensory input, what is area 2 involved in?

Answer 177

- stereognosis -\> ability to percieve the 3D shape of an object by touch - has input from muscles and joints and reciprocal connections with the motor cortex -\> may inform the motor cortex of sensory consequences of moving

Question 178

What inputs into the primary somatosensory cortex?

Answer 178

- input from a single type of receptor, and from a specfic location

Question 179

What inputs into the secondary somatosensory cortex?

Answer 179

- input from the thalamus and primary somatosensory cortex - many neurons in the SII have bilateral receptive fields -\> stimuli in corresponding regions on both sides of the body will evoke a response

Question 180

How is the secondary somatosensory cortex able to form a whole body perceptual experience?

Answer 180

- inputs from the contralateral body surface arise directly due to decussation (crossing over) of the medial lemniscus - inputs from the ipsilateral body surface enter secondary somatosensory cortex from the contralateral side via the corpus callosum - by integrating information from both sides the SII is the first stage in froming whole body perceptual experiences

Question 181

What are the roles of the secondary somatosensory cortex?

Answer 181

- enable tactile discrimination learned using one hand to be easily performed with the other -\> due to its input into the limbic cortex - important in controlling movement in the light of somatosensory input via its connections with the motor cortex

Question 182

Explain how we are not aware of the sensations caused by wearing clothes.

Answer 182

- the somatosensory cortex has reciprocal connections with all of the subcortical structures which relay sensory input to it - the descending pathway is made by the corticospinal (pyramidal) tract either directly or via its connections witht he brainstem reticular nuclei -\> these back projections have a somatotopic mapping precisely in register with the ascending dorsal column-medial lemniscal system -\> this is the vehicle which somatosensory input is filtered as an attention mechanism

Question 183

What is the difference between nocieptive and pathological pain?

Answer 183

- nociceptive (acute) has a protective role - pathological (clinical) is associated with disease and nervous system dysfunction

Question 184

What is the name given to the area of skin innervated by a dorsal root?

Answer 184

- dermatome

Question 185

What is conveyed by the anterolateral pathways?

Answer 185

- temperature - pain - crude touch sensation

Question 186

Name 4 characteristics of nociceptors.

Answer 186

- polymodal -\> different types of nociceptor respond to different types of stimuli - free nerve endings -\> in terms of structure they are much simpler than mechanoreceptors, usually just free axonal endings of sensory neurones - high threshold - higher activation threshold than touch receptors - slow Adapting -\> good because if there is a potentially harmful stimulus then you want to be constantly reminded of it so you do something about it

Question 187

What two sensroy fibres carry nociceptive information?

Answer 187

- A-delta - C neurone

Question 188

Describe A-delta fibres.

Answer 188

- large - fast adapting - produces pain fast -\> alerts you to the potential of some harmful scenario - fast conducting -\> still no where near as fast as touch neurones

Question 189

Describe C neurones.

Answer 189

- smaller than A-delta neurones - produces a dull, aching pain -\> the role of C neurone mediated nociception is to remind you of the injury so that you guard this part of the body - slow conducting -\> unmyelinated -\> ties in with its role/provides a constant reminder

Question 190

Where does input pass through as it goes from the peripheral to central nervous system?

Answer 190

o the dorsal root - dorsal root ganglion (body) - trigeminal ganglia (face)

Question 191

Where is the dorsal horn situated and how is it organised?

Answer 191

- part of the spinal cord - organised into rexed laminae (I-VII)

Question 192

Where exactly does innocuous mechanical stimuli input into the dorsal horn?

Answer 192

- A-beta fibres terminate in lamina III-VI -\> deep in the dorsal root

Question 193

Where exactly does pain and temperature stimuli input into the dorsal horn?

Answer 193

- A-delta and C-fibers terminate in lamina I-II -\> supericial

Question 194

What is the main excitatory neurotransmitter in the dorsal horn?

Answer 194

- glutamate

Question 195

How do interneurons connect?

Answer 195

- between different laminae and between adjacent peripheral inputs

Question 196

What is lateral inhibition used for?

Answer 196

- to detect the difference between adjacent inputs

Question 197

How can rubbing an injured area provide pain relief?

Answer 197

- rubbing the skin stimulates the A-beta fibres -\> inhibits stimulated pain fibres by interneuron inhibition

Question 198

What travels in the dorsal column system?

Answer 198

o innocuous mechanical stimuli - fine discriminative touch - vibration

Question 199

How do A-beta fibres enter the dorsal column pathways?

Answer 199

- through the dorsal horn

Question 200

Where are the gracile and cuneate nuclei postioned?

Answer 200

- in the medulla

Question 201

Where do 2nd order neurones of the dorsal column cross the in the medulla?

Answer 201

- caudal medulla -\> forms the contralateral medial lemniscus tract -\> travels and terminates in the ventral posterior lateral nucleus of the thalamus

Question 202

Where do 3rd order neurones of the dorsal column project to?

Answer 202

- somatosensory cortex -\> size of somatotopic areas in proportional to density of sensory receptors in that body region - somatosensory humunculus

Question 203

Where do 1st and 2nd order neurons of the spinothalamic tract terminate?

Answer 203

- 1st = dorsal horn - 2nd = decussate immediately in the spinal cord and form the spinothalamic tract and terminate in the ventral posterior lateral nucleus of the thalamus

Question 204

What is the spinoreticular tract?

Answer 204

- the pathway which links pain to the limbic cortex and tehrefore emotion

Question 205

What is the main cause of an anterior spinal cord lesion?

Answer 205

- blocked anterior spinal artery causes ischaemic damage to the anterior part of the spinal cord

Question 206

What are the symptoms of an anterior spinal cord lesion?

Answer 206

- bilateral loss of pain and temperature below the lesion -\> spinothalamic tract is damaged - retained light touch and vibration sensation -\> dorsal column is fine

Question 207

What is Electrical Perceptual Thresholds (EPT)?

Answer 207

- a technique in which an electronic pulse is passed to the skin - used to determine the type and location of a spinal cord injury

Question 208

Define pain.

Answer 208

- an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

Question 209

State the types of pain.

Answer 209

- nociceptive -\> tissue damage, typical ACUTE (e.g. cut skin) - muscle -\> lactic acidosis, ischaemia (e.g. strecthing, fibromyalgia) - somatic -\> well localised (e.g. inflammation, infection) - visceral -\> deep, poorly localised pain (e.g. stomach, colon, IBS) - referred -\> from an internal organ/structure (angina, appendicitis) - neuropathic -\> dysfunctional nervous system

Question 210

How long does pain last for before it would be counted as chronic?

Answer 210

- 6 months

Question 211

Define neuropathic pain.

Answer 211

- pain cuased by a lesion or disease of the somatosensory nervous system

Question 212

What does neurpathic pain feel like?

Answer 212

- sharp, burning, electric shock like

Question 213

How does neuropathic pain respond to opiates?

Answer 213

- poorly - anti-depressants are commonly used instead -\> particularly TCAs

Question 214

What is sciatica?

Answer 214

- pain caused in the sciatic nerve due to spinal nerves becoming compressed in the intervertebral foramen

Question 215

Name 5 examples of neurpoathic pain.

Answer 215

- sciatica - diabetic neuropathy - post-herpetic neuralgia - post-surgical pain - HIV-induced neuropathy - chemotherapy indcued neuropathy - complex regional pain syndrome

Question 216

Define Allodynia.

Answer 216

- pain due to to a stimulus that does not normal provoke pain

Question 217

Define Hyperalgesia.

Answer 217

- increased pain from a stimulus that normally provokes pain

Question 218

Define Sensitisation.

Answer 218

- increased responsiveness of nociceptive neurons to their normal input - a research driven phrase

Question 219

Define Hypoalgesia.

Answer 219

- a diminised pain in response to a normally painful stimulus

Question 220

Define Paraesthesia.

Answer 220

- abnormal sensation, whetehr spontaneous or evoked

Question 221

How is neuropathic pain diagnosed/assessed?

Answer 221

- questionnaires - simply examination techniques -\> cold/freezing pain, brus, pin prick

Question 222

What is mechanism behind a repeated painful stimulus becoming more painful when it is repeated?

Answer 222

- intiated by NMDA receptor activation - Ca²⁺ mediated synpatic plasticaity in dorsal horn neurons - increased synaptic strength - reduced inhibtory influences on dorsal neurons - persistant activation of NMDA receptors can result in the development of chronic pain

Question 223

What is the role of monoamines?

Answer 223

- inhibit spinal cord excitability

Question 224

What is the descending control of nociception with the PAG-RVM axis and locus cereleus?

Answer 224

- PAG-RVM = serotonin - locus cereleus = noradrenaline

Question 225

How might endogenous opiods affect peoples pain thresholds?

Answer 225

- endogenous opiods are contained within the PAG and RVM o they enhance the inhibition from the PAG-NVM axis -\> reduces the pain transmission in the dorsal horn by inhibitng glutamate release -\> activates spinothalamic neurons and therefore inhibition of pain - this mechanism works when placebos are given

Question 226

Name some pain relief drugs that work in the descending control systems?

Answer 226

- opiods - anti-depressants -\> TCA, SNRI, SSRI

Question 227

What is the mechanism of Serotonin and Norepinephrine Re-uptake Inhibitors (SNRIs) mechanism in descending noradrenaline inhibition?

Answer 227

- binds to the pre-synaptic (sometime post) terminal in the dorsal horn and therefore increases the amount of noradrenaline in the cleft - noradrenaline binds to alpha 2 receptors -\> inhibitory signalling in that neurone

Question 228

What are the 3 neuropathic pain 'clusters'?

Answer 228

- sensory loss - thermal hyperalgesia - mechanical hyperalgesia

Question 229

What is Functional Segregation?

Answer 229

- motor systems organised in a number of different areas that controls different aspects of movement

Question 230

What is meant by Hierarchical Organisation?

Answer 230

- high order areas are involved in more complex tasks -\> programme and decide on movements, coordinate muscle activity - lower level of the hierarchy performs lower level tasks -\> execution of movement

Question 231

Describe the Motor System Hierarchy.

Answer 231

o Level 1 = spinal cord -\> mainly involved in reflex movements o Level 2 = Brainstem -\> is the centre of integration of different inputs coming from the vestibular system, the vision system and the auditory system o Level 3 = Motor Cortex (consists of the: primary motor cortex, premotor cortex and supplementary motor area) -\> is where the movements are programmed and where the voluntary movements are initiated - Level 4 = Association Cortex (contains the parietal and frontal cortex) -\> not strictly part of the motor pathway, but it influences the planning and execution of movements

Question 232

What is the role of the basal ganglia and cerebellum in movement?

Answer 232

- basal ganglia and cerebellum fine tune the corse instruction from the primary motor cortex before it reaches the spinal cord

Question 233

What is the anatomical pathway which from wanting to move to movement?

Answer 233

Question 234

Where is the primary motor cortex located?

Answer 234

- precentral gyrus, anterior to the central sulcus

Question 235

What is the function of the primary motor cortex?

Answer 235

- controlled fine, discrete, precise voluntary movement - provides descending signals to execute movement

Question 236

What are the 3 parts of the motor cortex?

Answer 236

- Primary Motor Cortex or M1 - Broadmann's Area 4 - Premotor Cortex - Broadmann's Area 6 - Supplementary Motor Area - Broadmann's Area 6

Question 237

Where is the motor cortex located?

Answer 237

o all are anterior to the central sulcus

Question 238

How is the primary motor cortex arranged?

Answer 238

- somatotopic organisation

Question 239

What is the name of the descending motor pathway?

Answer 239

- lateral corticospinal pathway - anterior corticospinal pathway

Question 240

Where does motor pathways decussate, identifying which pathway is each?

Answer 240

- base of the medulla -\> POSTERIOR CORTICOSPINAL TRACT - 5-10% travel ipsilaterally until the spinal cord level -\> supply the trunk and the proximal parts of the limbs -\> ANTERIOR CORTICOSPINAL TRACT

Question 241

What are cerebral peduncles?

Answer 241

- structures at the front of the midbrain which arise from the front of the pons and contain the large ascending (sensory) and descending (motor) nerve tracts that run to and from the cerebrum from the pons

Question 242

What are the 2 parts of the descending/pyramidal system?

Answer 242

- corticobulbar tract -\> starts in the cortex, then exits and innervates the muscles in the face - corticospinal tract -\> starts in the cortex and innervates the muscles of the arms and legs

Question 243

What is the corticobulbar pathway?

Answer 243

- the descending linb which innervates the muscles of the face

Question 244

Where is the premotor cortex located?

Answer 244

- fronatl lobe anterior to the primary motor cortex

Question 245

What is the function of the premotor cortex?

Answer 245

- planning of movements - regulation of externally cued movements

Question 246

Where is the supplementary motor area located?

Answer 246

- fronatl lobe anterior and superior to the primary motor cortex

Question 247

What is the function of the supplemetary motor area?

Answer 247

- planning complex movements - programming sequencing of movements - regulates internally driven movements (e.g. speech) - SMA becomes active when thinking about a movement before executing that movement

Question 248

What is meant by associated cortex?

Answer 248

o brain areas not strictly motor areas as their activity does not correlate with motor output/act - posterior parietal cortex -\> ensures movements are targeted accurately to objects in external space - prefrontal cortex -\> involved in selection of appropriate movements for a particular course of action -\> think emotions as control of personality

Question 249

What are the lower motor neurons?

Answer 249

- spinal cord - brainstem

Question 250

What are the upper motor neurons?

Answer 250

- corticospinal - corticobulbar

Question 251

What is clincally called pyramidal?

Answer 251

- lateral corticospinal tract

Question 252

What is clincally known as the extrapyramidal?

Answer 252

- basal ganglia - cerebellum

Question 253

Define Paresis.

Answer 253

- graded weakness of movement

Question 254

What occurs with a upper motor neuron lesion?

Answer 254

o initially you get loss of function ('negative signs') -\> paresis (graded weakness of movement) or paralysis/plegia o after a few weeks of having this lesion you will get increased abnormal motor function ('positive signs') -\> due to the loss of inhibitory descending inputs - spasticity = increased muscle tone - hyperreflexia = exaggerated reflexes - clonus = abnormal oscillatory muscle contraction

Question 255

Define Spasticity.

Answer 255

- increased muscle tone

Question 256

Define Hyperreflexia.

Answer 256

- exaggerated reflexes

Question 257

Define Clonus.

Answer 257

- abnormal oscillatory muscle contraction

Question 258

Name the tell tale/important sign of upper motor neuron lesions.

Answer 258

- Babinski's Sign (aka extensor plantar response) - stroking the plantar side of the foot in a normal person causes the toes will flex, but after upper motor neurone lesions the toes will fan and the big toe will go up

Question 259

Do upper motor neuron lesions cause muscle atrophy?

Answer 259

o NO muscle atrophy - will have muscle disuse but this will only lead to partial atrophy -\> it's the lower motor neurones, exiting from the spinal cord that bring nutrients to the muscle

Question 260

What is Apraxia?

Answer 260

o a disorder in skilled movement NOT caused by weakness, abnormal tone or posture or movement disorders (tremors or chorea) - patients are NOT paretic (partial motor paralysis) but have lost information about how to perform skilled movements -\> not because they’ve lost motor command to the muscle but is instead because they have lost the information on how to perform the skilled movements

Question 261

What causes Apraxia?

Answer 261

o lesions of the inferior parietal lobe and the frontal lobe (premotor cortex and supplementary motor area) - any disease of these areas can cause Apraxia, but Stroke and Dementia are the most common causes

Question 262

Define Chorea.

Answer 262

- a movement disorder that causes involuntary, unpredictable body movements

Question 263

What are the signs of a lower motor neuron lesion?

Answer 263

- weakness - hypotonia (reduced muscle tone) - hyporeflexia (reduced reflexes) - muscle atrophy - the metabolic trophic support to the muscle is lost - fasciculations - damaged motor units produce spontaneous action potentials, resulting in a visible twitch - fibrillations - twitch of individual muscle fibres - these aren't visible to the naked eye but can be recorded if the patients have needle electromyography

Question 264

What is Motor Neuron Disease?

Answer 264

- progressive neurodegenerative disorder of the motor system - it is a spectrum of disorders - MND can affect only upper motor neurones, only lower motor neurones or both -\> when MND affects both upper AND lower motor neurones it is called Amyotrophic Lateral Sclerosis (ALS) (MND and ALS are used interchangeably in the UK)

Question 265

What is the most common cause of death in MND suffers?

Answer 265

- respiratory failure when they can no longer control their respiratory muscles

Question 266

What are the upper motor neuron signs of MND?

Answer 266

- increased muscle tone (spasticity of limbs and tongue) - brisk limbs and jaw reflexes - Babinski’s sign - loss of dexterity - dysarthria - dysphagia

Question 267

What are the lower motor neuron signs of MND?

Answer 267

- weakness - muscle wasting - tongue fasciculations and wasting - nasal speech - dysphagia

Question 268

What makes up the basal ganglia?

Answer 268

- caudate nucleus - lentiform nucleus (putamen + external globus pallidus) - subthalamic nucleus - substantia nigra - ventral pallidum - claustrum - nucleus accumbens - nucleus basalis of Meynert

Question 269

What are the functions of the basal ganglia?

Answer 269

- elaborating associated movements (e.g. swinging arms when walking) - moderating and coordinating movement (suppressing unwanted movements) - performing movements in order

Question 270

What is the consequence of of damage to the subthalamic nucleus?

Answer 270

- random, uncontrabble movement -\> commonly swinging of the arm - random movements in Parkinson's can sometimes be successfully treated by surgically inserting an electrode into the subthalamic nucleus

Question 271

What is a vertebral feature of Parkinson's?

Answer 271

- camptocormia -\> forwardly arched spine

Question 272

What is the neuropathology of Parkinson's?

Answer 272

- neurodegeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum

Question 273

What are the main motor sign of Parkinson's?

Answer 273

- bradykinesia -\> slowness of small movements (doing up buttons, handling a knife) - hypomimic face -\> expressionless, mask-like - akinesia -\> difficulty in the initiation of movements because cannot initiate movements internally - rigidity -\> muscle tone increase, causing resistance to externally imposed joint movements - tremor at rest -\> 4-7 Hz, starts in one hand (“pill-rolling tremor”); with time spreads to other parts of the body

Question 274

What is the genetic mechanism of Hungtington's?

Answer 274

- CAG repeats in the Huntington gene on chromosome 4 - autosomal dominant

Question 275

What is Huntington's and what are the pathological changes that occur?

Answer 275

- genetic neurodegenerative disorder - degeneration of GABAergic neurons in the striatum, cuadate and then the putamen -\> loss of cuadate nucleus leads to massively enlarged ventricles

Question 276

What are the motor signs of Huntington's Disease?

Answer 276

- chorea -\> starts with hands and face before progressing legs and rest of the body - speech impairment - difficulty swallowing - unsteady gait - later stages, cognitive decline and dementia

Question 277

What are the 3 layers of the cerebellum from the outside in?

Answer 277

- molecular - Purkinje - granular

Question 278

What is the name of the nucleus which reaches and inputs information to the cerebellum?

Answer 278

- central nucleus

Question 279

What are the 3 divisions of the cerebellum?

Answer 279

- vestibulocerebellum - spinocerebellum - cerebrocerebellum

Question 280

Where is the vestibulocerebellum?

Answer 280

- deep, inner section of the cerebellum

Question 281

Where is the spinocerebellum?

Answer 281

- medial section of the cerebellum

Question 282

Where is the cerebrocerebellum?

Answer 282

- lateral area of the cerebellum

Question 283

What is the role of the cerebrocerebellum?

Answer 283

- co-ordination of skilled movements - cognitive function -\> attention, processing of language - emotional control

Question 284

What is the role of the spinocerebellum?

Answer 284

- co-ordination of speech - adjustment of muscle tone - co-ordination of limb movements

Question 285

What is the role of the vestibulocerebellum?

Answer 285

- regulation of gait, posture and equilibrium - co-ordination of head movements with eye movements

Question 286

What is the major cause of damage to the vestibulocerebellum and its symptoms?

Answer 286

- tumour - gait ataxia, tendency to fall (even when sitting with eyes open) -\> similar to the symptoms of vestibular disease

Question 287

What is the major cause of damage to the spinocerebellum and what symptoms does it cause? Back

Answer 287

- chronic alcoholism - mainly affects the legs -\> causes abnormal gait and stance

Question 288

What are does damage to the cerebrocerebellum cause?

Answer 288

- mainly affects the arms, skilled co-ordinated movements and speech

Question 289

What are the main signs of cerebellar dysfunction?

Answer 289

- ataxia -\> general impairments in movement co-ordination and accuracy -\> disturbances of posture or gait: wide-based, staggering (“drunken”) gait - dysmetria -\> inappropriate force and distance for target-directed movements - intention tremor -\> increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking) - dysdiadochokinesia -\> inability to perform rapidly alternating movements, (rapidly pronating and supinating hands and forearms) - scanning speech -\> staccato, due to impaired coordination of speech muscles

Question 290

Describe what triggers transmission across synapses.

Answer 290

o membrane potential of the post synaptic neurone can be altered in two directions by inputs - can be made be made less negative -\> brought closer to the threshold for firing -\> excitatory post-synaptic potential (EPSP) or made more negative (hyperpolarised) -\> inhibitory post-synaptic potential (IPSP) o GRADED effects -\> post-synaptic neurone fire dependent on the summation of the various inputs

Question 291

Describe the neuromuscular junction.

Answer 291

- a specialised synapse between the motor neurone and the motor end plate on the muscle fibre cell membrane

Question 292

What neurotransmitter is used in neuromuscular junctions?

Answer 292

- acetylcholine

Question 293

What are miniature end plate potentials?

Answer 293

- when recording membrane potential across the muscle fibre, you can see that at any one point there are small changes in membrane potential - are NOT action potentials but rather just small changes in membrane potential that happens as vesicles are constantly dumping their contents into the synaptic cleft

Question 294

What are the 4 names for alpha motor neurones?

Answer 294

- alpha motor neurone - ventral horn cells - anterior horn cells - lower motor neurones

Question 295

Define intrafusal.

Answer 295

- skeletal muscle fibres that serve as specialised sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle

Question 296

Define extrafusal.

Answer 296

- standard skeletal muscle fibres that are innervated by alpha motor neurones and generate tension by contracting, thereby allowing for skeletal muscle movement

Question 297

What do alpha motor neurones innervate?

Answer 297

- extrafusal muscle fibres of the skeletal muscle -\> cause skeletal muscle contraction

Question 298

What are spindles?

Answer 298

- coiled, spring like sensory receptors in the muscle - when stretched they feedback to the CNS and allows an excitatory reflex to be generated -\> what you want when your patella ligament gets hit by a tendon hammer

Question 299

Define Motor Neurone Pool.

Answer 299

- collection of lower motor neurones that innervate a single muscle

Question 300

What is the arrangement of alpha motor neurones in the spinal cord?

Answer 300

- extensors = more anterior part of the ventral horn - flexors = more posterior part of the ventral horn - proximal = more central - distal = more lateral

Question 301

Define Motor Unit.

Answer 301

- a single motor neurone together with all the muscle fibres that it innervates, it is the smallest functional unit with which to produce force

Question 302

How many muscle fibres are innervated by a single aplha motor neurone?

Answer 302

- it depends on the complexity/control of the movement that is required -\> each alpha motor neurone can innervate several muscle fibres -\> each muscle fibre is only innervated by ONE ALPHA NEURONE o muscles in the eye have a low innervation ratio (number of fibres innervated by a single motor neurone) because this needs to be finely controlled o quadriceps do not need a low innervation ratio because you want power from this muscle rather than delicate control

Question 303

Under what circumstances can an axon sprout and innervate muscle fibres which are already being innervated?

Answer 303

- pathological ones e.g. when a nerve has been cut

Question 304

Name the types of motor units\>

Answer 304

- slow -\> smallest cell body diameter, dendritic trees, thinnest axons -\> slowest conduction velocity - fast, fatigue resistant -\> larger cell body diameter, dendritic trees, thicker axons -\> faster conduction velocity - fast, fatigable -\> largest cell body diameter, dendritic trees, thickest axons -\> fastest conduction velocity

Question 305

What are the functions of slow and fast motor units?

Answer 305

- slow = not much force but work for a long time -\> postural muscles e.g. soleus -\> standing all day - fast = lots of force but tire much faster -\> bicep

Question 306

How are different muscle fibre types distributed through muscle?

Answer 306

- evenly -\> produce even force and longetivity across the muscle

Question 307

How is the muscle force regulated?

Answer 307

o 2 mechanisms by which the brain regulates the force that a single muscle can produce - recruitment -\> recruiting more motor units -\> smaller units, generally slow twitch, are recruited first - rate coding -\> changing the frequency with which you send action potentials down the nerves

Question 308

What are Neurotrophic factors?

Answer 308

- factors that are produced within the nerve and transported throughout the nerve to maintain the nerves integrity and function -\> type of growth factor, prevent neuronal death, promote the growth of neurons after injury - CNS neurones don't regenerate after injury unlike peripheral nerve - the explanation is that in the CNS you have millions of axons as opposed to a few thousand so the consequences of rewiring incorrectly is not worth it

Question 309

Is it possible to switch from slow to fast muscle types?

Answer 309

- NO WAY of changing fast to slow or vice versa - slow to fast is only possible in cases of severe deconditioning or spinal cord injury - microgravity during spaceflight results in a shift from slow to fast muscle fibre types - ageing is associated with a loss of slow and fast muscle fibres but with preferential loss of fast fibres -\> leaves a large proportion of slow fibres in aged muscle -\> is called sarcopenia

Question 310

What are the corticospinal/pyramidal and extrapyramidal tracts?

Answer 310

- corticospinal/pyramidal tract = voluntary movement pathway - extrapyramidal tracts = automatic movements in response to stimuli

Question 311

Define reflex.

Answer 311

- automatic and often inborn response to a stimulus that involves a nerve impulse passing inward from a receptor to a nerve centre and then outward to an effector (as a muscle or gland) without reaching the level of consciousness

Question 312

What are the components of the reflex arc?

Answer 312

sensory receptor -\> sensory neuron -\> integrating system within the CNS -\> motor neuron -\> effector

Question 313

What is the Hoffman Reflex?

Answer 313

- a way in which the stimulus can be identical every time the reflex is tested -\> ensures that the stimulus has the same duration and amplitude so you know that any change in reflex size is NOT due to the input unlike with a tendon hammer - an electrical stimulus is delievered to a nerve -\> the impulse is carried along the sensory fibre to the spinal cord and via a reflex arc back to the muscle

Question 314

What will be seen in Hoffman Reflexes?

Answer 314

- direct motor response/twitch -\> going from the motor neurone that has been stimulated, directly to the muscle causing contraction -\> is the M wave (motor wave) - short time later you will see another response (in the EMG)/twicth -\> caused by the action potential in the sensory neurone going back to the spinal cord and exciting the motor neurone -\> is the H wave

Question 315

What is meant by flexion withdrawal and crossed extensor?

Answer 315

- lots of polysynaptic reflexes go up and down the spinal cord to innervate groups of muscle on the same side - are also reflexes that cross the spinal cord to the other side such that the other limbs do something to keep us upright -\> contract one leg if the other is picked up from stepping on something sharp

Question 316

What is the Jendrassik Manoeuvre?

Answer 316

- there is some descending control of reflexes from the brain from supraspinal centres - when testing the knee-jerk reflex on someone and you ask them to clench their teeth, the reflex you get when you tap their patellar tendon will be 2 or 3 times greater

Question 317

What are the cuases of hyper-reflexia and hypo-reflexia?

Answer 317

- hyper-reflexia = upper motor neurone lesions (e.g. strokes) -\> leads to clonus and Babinski's sign - hypo-reflexia = lower motor neurone lesions

Question 318

What are the main causes of hearing loss?

Answer 318

- loud traumatic sounds: military, industrial, clubs - 200 genetic conditions cause hearing problems - infections – meningitis or congenital (rubella or syphilis) - drugs -\> used for severe heart infections and chemotherapy - ageing o hearing loss affects about 10% of the population in the UK

Question 319

What is sound?

Answer 319

- changes in air pressure

Question 320

What determines pitch and volume?

Answer 320

- pitch = frequency - volume = intensity

Question 321

Describe the decibel scale.

Answer 321

- used to measure th eintensity of sound - logarithmic scal using base 10

Question 322

What is the Vestibular system?

Answer 322

- the organ/system which gives spacial orientation

Question 323

What are the 3 main inputs into the vestibular system?

Answer 323

- visual - rotation/gravity - pressure

Question 324

What are the outputs of the vestibular system?

Answer 324

- ocular reflexes - postural control - nausea -\> due to imbalance or mismatch of information

Question 325

What is the role of the outer ear?

Answer 325

- localises sound and channels it into the ear canal

Question 326

How are the sound waves turned into a noise we can hear and understand?

Answer 326

- sound reaches the tympanic membrane (ear drum) and causes it to vibrate - after the eardrum are 3 little bones (ossicles): the stapes, the incus and the malleus -\> these transmit the vibrations of the tympanic membrane onto the cochlea - the organ of hearing - after the cochlea, signals are transferred via the vestibulocochlear nerve (CN VIII) into the central pathways

Question 327

Describe the cochlea.

Answer 327

- organ of hearing - a snail-shaped organ filled with liquid - hair cells are the sensory receptors in the cochlea

Question 328

What is the exact role of the ossicles (little bones in the ear)?

Answer 328

- match the impedance and reduce the loss in energy as the vibration goes from the air to the cochlea - malleus and incus can have their positions adjusted by the tympanic and stapedius muscles to control the tension of the tympanic membrane -\> reduce noise going to cochlea to reduce damage

Question 329

What is Conductive Hearing Loss?

Answer 329

- hearing loss due to the ear being uncapable of transmitting the vibration of sound waves onto the cochlea

Question 330

Name some causes of conductive hearing loss.

Answer 330

- cerumen (ear wax) - infections (otitis) - tumours - fluid accumulation in the middle ear can occur due to cold -\> far more common in children - perforated tympanic membrane - otosclerosis – abnormal bone growth can obstruct ear canal - barotrauma -\> temporary form -\> driving down a hill fast or in take off

Question 331

Describe the contents of the cochlea.

Answer 331

- two liquid-filled chambers - the Organ of Corti -\> includes the basilar and tectorial membrane, hair cells and supporting cells

Question 332

Describe the function of the basilar membrane.

Answer 332

o an elastic structure with different mechanical properties at either end -\> it vibrates at different positions along its length in response to different frequencies -\> the base is narrow and tough while the apex is broad and floppy -\> higher the frequency the further along the membrane the sound will travel - breaks complex sounds down by distributing the energy of each component frequency along its length -\> hair cells (receptors) are present along the whole length of the basilar membrane in order to detect all frequencies

Question 333

What is the function of hair cells in the inner ear?

Answer 333

- receptors of the inner ear -\> motion of the basilar membrane deflects the hair bundles of the hair cells

Question 334

What is the mechanism of hair cells in the inner ear?

Answer 334

- bending of the sterocilia towards the tallest sterocilum due to themotion of the basilar membrane changes the internal voltage of the cell -\> ultimately produces an electric signal that travels towards the brain -\> is called Mechano-transduction - sterocilia are connected by filamentous linkages called tip links -\> work as small springs stretched by the sterocilia’s sliding

Question 335

Is the hair bundle process active or passive explain why it is?

Answer 335

o active -\> need for an active amplification is due to the large portion of energy that is lost in the viscous damping effects of the cochlear liquids - sensitivity and the sharp frequency selectivity of the cochlea cannot be explained solely by passive mechanical properties – basilar membrane (BM) impedance

Question 336

What are the 4 aspects of the active process of hair bundles in the inner ear?

Answer 336

- amplification - frequency tuning - compressive non-linearity - spontaneous otoacoustic emission

Question 337

What is the role of outer hair cells of the ear?

Answer 337

o electromobility - when efferent fibres are activated, frequency selectivity and sensitivity is enhanced -\> this could be due to OHCs -\> their cell bodies shorten and elongate when their internal voltage is changed -\> electromobility

Question 338

What causes electromobility?

Answer 338

- a change in outer hair cells internal voltage -\> happens at a rate of 80 kHz - is due to reorientation of the protein prestin - the spontaneous back and forth movement might be the cause of otoacoustic emissions

Question 339

What is the spiral ganglion?

Answer 339

- hair cells (mostly IHCs) form synapses with sensory neurones in the cochlear ganglion (spiral ganglion) - neurotransmitters are constantly released at rest but the rate changes in response to a change of the presynaptic voltage, due to MT ion channel gating - each ganglion cell nd corressponding axon responds best to stimulation at a particular frequency

Question 340

Why is each inner hair cell attached to multpile spiral ganglion cells?

Answer 340

- enable phase-locking -\> a collection of fibres can produce a phase-locked response when a single nerve fibre could not -\> if one/some fail you still hear the sound

Question 341

What is Sensorineural Hearing Loss?

Answer 341

- problem rooted in the sensory apparatus of the inner ear or the vestibulocochlear nerve (retrocochlear hearing loss) - the most widespread type of hearing loss

Question 342

Name some cuases of sensorineural hearing loss.

Answer 342

- loud noises – headphones at high volume (temporary or permanent hearing loss) -\> clubs are about 100 dB and concerts about 120 dB - Ménière's disease -\> excess fluid in the cochlea - genetic mutations affect the Organ of Corti - aminoglycoside antibiotics are toxic for hair cells -\> Streptomyocin - congenital diseases -\> rubella, toxoplasmosis - ageing (presbycusis)

Question 343

What is the treatment for sensorineural hearing loss?

Answer 343

- Cochlear Implants -\> most hearing loss is due to loss of hair cells -\> the implant bypasses the dead cells and directly stimulates the nerve fibres - do not work if the cochlear nerve is damaged

Question 344

Where does the cochlear nerve convey its information to?

Answer 344

- the cochlear nucleus of the brainstem -\> low frequency neurones are ventrally placed whie high frequency nerones are more dorsal

Question 345

What is the role of the dorsal cochlear nucleus?

Answer 345

- locates sounds in the vertical plane - sounds of high frequencies produce intensity differences between the two ears -\> high frequency sounds produce constructive and destructive interference - the ears detect and affect differently sounds coming from different directions due to their asymmetrical shape -\> called spectral cues

Question 346

What are the roles of the different cochlear nucleus neurones?

Answer 346

o T-Stellate Cells -\> encode sound frequency and intensity of narrowband stimuli -\> their tonotopic array represents sounds’ spectra o Bushy cells -\> produce more sharply but less temporally precise versions of the cochlear nerve fibres -\> provide the resolution required to encode the relative time of arrival of inputs to the two ears

Question 347

What is the role of the superior olivary complex?

Answer 347

- compare bilateral activity of the cochlear nuclei to determine the location of a sound

Question 348

How does the superior olivary complex function?

Answer 348

o medial superior olive computes the interaural time difference -\> sounds are detected at the nearest ear before they reach the other one -\> bushy cells carry information about the timing of inputs at every cycle so a map of interaural delay can be formed due to delay lines -\> used to locate sound in the horizontal plane o lateral superior olive detects differences in intensity between the two ears -\> neurones are excited by sound arising from the ear in the same side (ipsilaterally) while they are inhibited by opposite sounds (contralaterally) o SOC neurones feedback to the hair cells -\> feedback is used to balance the response from the two ears, but also to reduce the sensitivity of the cochlea

Question 349

What is the role of the inferior colliculus?

Question 350

What is the relevance of the superior colliculs?

Answer 350

- auditory and visual maps merge -\> neurones are tuned to respond to stimuli with specific sound directions -\> the auditory map here created is fundamental for reflexes in orienting the hear and eyes to acoustic stimuli

Question 351

What can be detected by the balance system?

Answer 351

- only acceleration - two types of acceleration -\> angular acceleration (turning) and linear acceleration (forward/backwards)

Question 352

What governs angular and linear acceleration?

Answer 352

- angular acceleration = 3 semi-circular canals -\> detect head motion - linear acceleration = 2 otolith organs (utricle and saccule) -\> detect linear acceleration

Question 353

What is the normal function of the vestibular system?

Answer 353

- subserve perception of movement in space and tilt with respect to gravity - provide reflex balance reactions to sudden instability of gait or posture ‘vestibulo-spinal reflexes - stabilise the eyes on earth fixed targets, preserving visual acuity during head movements -\> ‘vestibular-ocular reflexes’ - assist control of blood pressure and heart rate during rapid up-down tilts - assist synchronisation of respiration with body reorientations - provokes motion sickness when stimulated in unusual motion environments - provide a reference of absolute motion in space, which helps interpret the relativistic signals of the other senses in creating a perception of spatial orientation

Question 354

Name some disorders of the vestibular system.

Answer 354

 - false perception of movement in space -\> ‘vertigo’ (Vestibulo-cortical)  - instability of gait and posture -\> ‘vestibular ataxia’ (Vestibulo-spinal )  - inability to stabilise the eyes -\> ‘vestibular nystagmus’ in unilateral lesions; ‘oscillopsia’ during head movement in bilateral vestibular lesions (Vestibulo-ocular)  - slight impairment of orthostatic control in the acute phase of vestibular loss  - severe nausea and vomiting in the acute phase of unilateral vestibular loss  - loss of co-ordination on directional reorientation; motion intolerance, oversensitivity to visual motion in the environment

Question 355

Describe the vestibular labyrinth.

Answer 355

o bony labyrinth -\> bounded by petrous temporal bone filled with perilymph o membranous labyrinth -\> filled with endolymph contain the receptor cells - located within the utricle, saccule and semicircular canals

Question 356

Describe hair cells within the vestibular system.

Answer 356

o Type 1 - more in number - direct afferent and indirect efferent - chalice-like nerve endings form ribbon synapses o Type 2 - less in number - direct acting - simple nerve terminals

Question 357

What is the anatomy of the eye?

Answer 357

Question 358

What is the major functions of the tear film?

Answer 358

- protect the eye from drying out - aid the optical properties of the eye

Question 359

What are the three types of tears?

Answer 359

- basal tears - reflex tears due to irritation - emotional/crying tears

Question 360

What is the route that tears take?

Answer 360

- tears produced by the lacrimal gland -\> drains through the two puncta, opening on medial lid margin -\> flows through the superior and the inferior canaliculi -\> gather in the Tear Sac and then the Tear Duct -\> exit the Tear Duct through the tear duct into the nose cavity - is a valve where the canaliculi meet the Tear Sac which prevents reflux of tears back onto the surface of the eye

Question 361

What functions does the tear film play?

Answer 361

- maintain smooth cornea-air surface - oxygen supply to the cornea - removal of debris - bactericide

Question 362

What are the 3 layers of tear film?

Answer 362

- outer most = superficial oily layer -\> reduces tear film evaporation -\> produced by Meibomian Glands along lid margins - middle layer = aqueous tear film -\> produced by the tear glands - inner most = mucinous layer on the Corneal Surface to maintain surface wetting -\> produced by Goblet cells

Question 363

Which layer of the tear film protects the tear film from rapid evaporation? A) Lipid Layer B) Water Layer C) Mucinous Layer D) All Three Layers

Answer 363

- A

Question 364

Label the diagram.

Question 365

What is the conjunctiva?

Answer 365

- the thin, transparent tissue that covers the outer surface of the eye -\> begins at the outer edge of the cornea, covers the visible part of the eye, and lines the inside of the eyelids  - is nourished by tiny blood vessels that are nearly invisible to the naked eye -\> bleeding in the conjunctiva spreads around -\> results in blood shot eyes

Question 366

What are the 3 layers of the coat of the eye?

Answer 366

- sclera -\> hard, opaque connective tissue - choroid -\> pigmented and highly vascular -\> the eye is always functioning so requires a lot of energy - retina -\> neurosensory tissue

Question 367

Describe the sclera.

Answer 367

- high water content - tough, opaque tissue that serves as the eye's protective outer coat -\> helps maintain the shape - continuous with the cornea

Question 368

Describe the cornea.

Answer 368

- transparent, dome-shaped window (convex curvature) covering the front of the eye  - a powerful refracting surface -\> provides 2/3 of the eyes focusing power - acts as both a physical barrier and an infection barrier  - relies on tear film and aqueous fluid, for nutrients and oxygen supply  - low water content -\> dehydrated by the inner layer of the cornea - corneal endothelium

Question 369

What are the 5 layers of the cornea?

Answer 369

1. Epithelium -\> regenrates very quickly 2. Bowman’s Membrane 3. Stroma -\> thickest layer of the cornea -\> contributes towards transparency -\> corneal nerve endings provides sensation and nutrients for healthy tissue as no blood vessels are in normal cornea 4. Descemet’s Membrane 5. Endothelium -\> pumps fluid out of corneal and prevents corneal oedema -\> no regeneration power and the density decreases with age -\> endothelial cell dysfunction may result in corneal oedemaand corneal cloudiness

Question 370

What are the 3 parts of the uvea?

Answer 370

- the Iris - the ciliary body - the choroid

Question 371

Describe the choroid.

Answer 371

- posterior part of the uvea is the choroid - lies between the retina and sclera - is composed of layers of blood vessels that nourish the back of the eye

Question 372

Describe the iris.

Answer 372

- coloured part of the eye is called the iris - controls light levels inside the eye similar to the aperture on a camera - round opening in the centre of the iris is called the pupil - embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size

Question 373

Describe the structure of the lens.

Answer 373

- outer acellular capsule - regular inner elongated cell fibres -\> transparency - may loose transparency with age -\> cataract

Question 374

What are the functions of the lens?

Answer 374

- responsible for one third of the refractive power of the eye -\> higher refractive index than aqueous fluid and vitreous - accommodation -\> elasticity: muscles constrict -\> lens becomes smaller + thicker -\> short sight

Question 375

What is the lens suspended by?

Answer 375

- a fibrous ring known a lens zonules

Question 376

What issue occurs with the lens zonules with age?

Answer 376

- a problem with short-sightedness -\> the lens loses its elastic properties due to ageing of the lenz zonules muscles -\> when the muscle constricts, the lens remains wide and thin -\> short-sightedness

Question 377

What is the retina?

Answer 377

- retina is a very thin layer of tissue that lines the inner part of the eye -\> responsible for capturing the light rays that enter the eye -\> light impulses are then sent to the brain for processing, via the optic nerve

Question 378

What two features are prominent on the retina, when examined, when someone is looking straight ahead?

Answer 378

- optic nerve head/optic disc - macula

Question 379

Describe the macula.

Answer 379

- is located roughly in the centre of the retina, temporal (lateral) to the optic nerve - a small, highly sensitive part of the retina responsible for detailed central vision - the fovea is the very centre of the macula -\> allows us to appreciate detail and perform tasks that require central vision such reading

Question 380

What is glaucoma?

Answer 380

- optic neuropathy with characteristic structural damage to the optic nerve, associated with progressive retinal ganglion cell death, loss of nerve fibres and visual field loss

Question 381

What are the risk factors to glaucoma?

Answer 381

- age - family history - accidents - intraocular pressure (only modifiable risk factor à target)

Question 382

Where is aqueous fluid secreted from?

Answer 382

- the ciliary body into the anterior chamber

Question 383

What is the first line treatment for glaucoma?

Answer 383

- prostaglandns analogues -\> increased aqueous humour flow and therefore reabsorption

Question 384

What is the normal intraocular pressure?

Answer 384

- 12 -24 mmHg

Question 385

What are the 2 types of glaucoma?

Answer 385

- primary open angle glaucoma - close angle glaucoma

Question 386

What is the corresponding anatomical landmark for the physiological blind spot? a. macula b. fovea c. optic disc d. ora serrata

Answer 386

- b. fovea

Question 387

Describe central/macular vision.

Answer 387

- detail day and colour vision -\> fovea has the highest concentration of cone photoreceptors - used for reading, facial recognition and activities which require focus

Question 388

What test assesses central vision and what will its loss cause?

Answer 388

- assessed by Visual Acuity Assessment -\> loss of foveal vision results in poor visual acuity

Question 389

Describe peripheral vision.

Answer 389

- for detecting shape and movement in the environment and night vision - navigation vision -\> patients with loss of peripheral vision have problems navigating the world -\> extensive loss of visual field leads to the patient needing white stick even with perfect visual acuity

Question 390

Describe the retinal structure.

Answer 390

- Outer Layer -\> photoreceptors (1st Order Neuron) -\> detection of light - Middle Layer -\> bipolar cells (2nd Order Neurons) -\> local signal processing to improve contrast sensitivity, regulate sensitivity - Inner Layer -\> retinal ganglion cells (3rd Order Neurons) -\> transmission of signal from the eye to the brain

Question 391

What is the function of the retinal pigment epithelium?

Answer 391

- found in the outer thin layer - transports nutrients from the choroid to the photoreceptor cells and removes metabolic waste form the retina

Question 392

Describe Rod receptors.

Answer 392

- longer outer segment with photo-sensitive pigment - 100 times more sensitive to light and movement than cones - slow response to light - responsible for night vision (Scotopic Vision) - allow you to find your position in space and detect movement and judge distance - 120 million rods

Question 393

Describe Cone photoreceptors.

Answer 393

- less sensitive to light than rods - faster response than rods - responsible for day light fine vision and colour vision (Photopic Vision) - 6 million cones

Question 394

Where can one find the highest concentration of Rod Photoreceptors in the retina? a) Optic Disc b) Fovea c) 10-20 degrees away from Fovea d) 20-40 degrees away from Fovea

Answer 394

- d

Question 395

Describe the frequency spectrum of vision.

Answer 395

- rod vision has only one single peak light sensitivity,at 498 nano-meters wavelength - S-Cones: with photo-pigment sensitive to short wavelength -\> blue - M-Cones: with photo-pigment sensitive to medium wavelength -\> green - L-Cones: with photo-pigment sensitive to long wavelength -\> red

Question 396

What is the most common collur vision deficiency?

Answer 396

- deuteranomaly -\> redued sensitivity to red light

Question 397

How is colour blindness tested?

Answer 397

- ishihara test -\> used for red-green colour perception deficiencies -\> colour dotted circles with numbers in

Question 398

Describe light-dark adaptation of the eyes.

Answer 398

o dark adaptation - from light -\> dark) - retina increases its light sensitivity in dark -\> switches from photopic to scoptic vision - biphasic process - cone adaptation = 7 minutes - rod adaptation = 30 minutes -\> due to regeneration of rhodopsin o light adaptation (suppression of light sensitivity going into light) - occurs over 5 minutes - bleaching of photo-pigments mediates the process - neuro-adaptation: Inhibition of Rod/Cone function - pupil Adaptation (minor) constriction of pupil with light

Question 399

Which is the commonest form of colourvision deficiency in humans? a) absence of all cone photoreceptors b) absence of M-cone (green) photoreceptors c) abnormal L-cone (red) photoreceptors d) red-green confusion

Answer 399

- red-green confusion

Question 400

Define ametropia.

Answer 400

- refers to vision disorders characterized by the eyes inability to correctly focus the images of objects on the retina -\> forms include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism

Question 401

What is refraction?

Answer 401

- based on the idea that light is passing through one medium into another -\> as light goes from one medium to another, the velocity changes - ratio of two speeds can be compared:

Question 402

In order for light to reach the reina from air, what must light photons pass through?

Answer 402

- tear film -\> cornea -\> aqueous humour -\> lens -\> vitreous humour -\> retina

Question 403

What are the application of lenses?

Answer 403

- refraction

Question 404

What are the two basic types of lenses?

Answer 404

o convex lenses - light passes through the converging (convex) lens and rays converge towards a focal point - focal point is at a distance from the central plane of the lens – this distance is proportional to the thickness of the lens -\> used by short-sighted people in glasses o concave lenses - light disperses around because it is refracted in a divergent way -\> focal point is a virtual point -\> virtual focal point is in front of the lens

Question 405

Define emmetropia.

Answer 405

- an eye with a refractive power of 0 -\> no visiual defects

Question 406

Define ametropia.

Answer 406

- presense of a refractive error -\> mismatch between axial length and refractive power -\> parallel light rays don’t fall on the retina (no accommodation)

Question 407

What are the 4 types of ametropia?

Answer 407

- nearsightedness (myopia) - farsightedness (hyperopia) - astigmatism - presbyopia

Question 408

What is myopia?

Answer 408

- short-sightedness -\> parallel rays converge at a focal point anterior to the retina

Question 409

What are the causes of myopia?

Answer 409

- excessive long globe -\> axial myopia -\> more common - excessive refractive power -\> refractive myopia

Question 410

What are the symptoms of myopia?

Answer 410

- blurred distance vision - squint in an attempt to improve uncorrected visual acuity when gazing into the distance - headache

Question 411

What are the treatments for myopia?

Answer 411

- concave glasses -\> also achieved with contact lenses -\> both move focal point slightly backwards - surgical removal of the lens to reduce refractive power

Question 412

What is hyperopia?

Answer 412

- long-sightedness -\> parellel rays converge at a focal point posterior to the retina

Question 413

What are the causes of hyperopia?

Answer 413

- excessive short globe (axial hyperopia) -\> more common - insufficient refractive power (refractive hyperopia)

Question 414

State some symptoms of hyperopia.

Answer 414

- visual acuity at near tends to blur relatively early -\> usually more noticable if they are tired - asthenopic symptoms -\> eyepain, headache in frontal region, burning sensation in the eyes, blepharoconjunctivitis - amblyopia (lazy eye) -\> uncorrected hyperopia in one eye leads the brain favouring the other eye -\> 5D

Question 415

What is the treatment for hyperopia?

Answer 415

- convex lenses in glasses of contact lens - surgical intervention

Question 416

What is astigmatism?

Answer 416

- caused by a refractive media that is not spherical -\> more elliptical -\> the cornea is not evenly shaped in terms of the radius - light refracts differently along one meridian than along meridian perpendicular to it -\> results in 2 focal points (punctiform object is represent as 2 sharply defined lines)

Question 417

What are the symptoms of astigmatism?

Answer 417

- asthenopic symptoms (headache , eyepain) - blurred vision - distortion of vision - head tilting and turning

Question 418

What is the treatment for astigmatism?

Answer 418

- regular astigmatism -\> cylinder lenses with or without spherical lenses (convex or concave) - irregular astigmatism -\> rigid CL or surgery

Question 419

Describe presbyopia.

Answer 419

- naturally occurring loss of accommodation (focus for near objects) -\> onset from age 40 years due to natural loss of lens elasticity - distant vision intact - corrected by reading glasses (convex lenses) to increase refractive power of the eye

Question 420

Which statement is false for Myopia? a) may be associated with large globe b) light ray converges behind the retina c) may be associated with increased corneal curvature d) unable to see objects clearly at distance without glasses or other optical correction

Answer 420

- b -\> converges infront of the retina

Question 421

In accommodation, which one of the following events does not take place? a) relaxation of Circular Ciliary Muscle b) relaxation of Zonules c) thickening of Lens d) increase of Lens Refractive Power

Answer 421

- a

Question 422

What is the pathway down which signals are transmitted in the visual pathway?

Answer 422

- eye -\> optic nerve -\> optic chiasm -\> optic tract -\> lateral geniculate nucleus -\> optic radiation -\> primary visual cortex or striate cortes

Question 423

WHat perecentage of ganglionic fibres cross at the optic chiasm?

Answer 423

- 53% ganglion fibres cross at optic chiasm - crossed fibres -\> originate from nasal retina -\> responsible for temporal visual field - uncrossed fibres -\> originate from temporal retina -\> responsible for nasal visual field

Question 424

What are the results of lesions at the optic chaism and posterior to the optic chiasm?

Answer 424

- Temporal Field Deficit in Both Eyes -\> Bitemporal Hemianopia - Right sided lesion -\> Left Homonymous Hemianopia in Both Eyes - Left sided lesion -\> Right Homonymous Hemianopia in Both Eyes

Question 425

What is the typical cause of bitemporal hemianopia?

Answer 425

- enlargement of the pituitary gland

Question 426

Describe the primary visual cortex.

Answer 426

- located along the Calcarine Sulcus within the Occipital Lobe (aka the Striate Cortex) - specializes in processing visual information of static and moving objects - organised as columns of information from the left and right which are interspersed -\> helps judge depth - a disproportionately large area representing the macular central vision within the PVC - area above the Calcarine Fissure represents the inferior visual field and below the Calcarine Fissure represents the superior visual field

Question 427

Describe how a stroke can lead to macular sparing homonymous hemianopia.

Answer 427

- leads to Contralateral Homonymous Hemianopia with Macula Sparing -\> area representing the Macula receives dual blood supply from Posterior Cerebral Arteries from both sides

Question 428

What is the extrastriate cortex?

Answer 428

- area around PVC within the Occipital Lobe - converts basic visual information, orientation and position into complex information

Question 429

What causes pupil dilation and constriction?

Answer 429

- constriction = iris muscle contracts to constrict the pupillary aperture - dilation = radial muscle contracts

Question 430

Describe the pathway of the pupilary reflex.

Answer 430

o Afferent pathway (Red & Green) - Rod and Cone Photoreceptors synapsing on Bipolar Cells synapsing on Retinal Ganglion Cells - Pupil-specific ganglion cells exits at posterior third of optic tract before entering the LGN -\> synapses at the Brain Stem (Pretectal Nucleus) -\> afferent (incoming) pathway from each eye synapses on Edinger-Westphal Nuclei on both sides in the brainstem o Efferent pathway (Blue) - Edinger-Westphal Nucleus -\> Oculomotor Nerve Efferent -\> synapses at Ciliary ganglion · Short Posterior Ciliary Nerve à Pupillary Sphincter No action Mouse Gestures ![]() ![]() Back ![]() Forward ![]() Scroll up ![]() Scroll down ![]() Switch to previous tab ![]() Switch to next tab ![]() Close all tabs except current ![]() Close current tab ![]() Open new tab ![]() Close all tabs ![]() Refresh current tab ![]() Stop loading ![]() Scroll to bottom ![]() Scroll to top ![]() Reopen closed tab ![]() Go to home page

Question 431

What pupillary response would occur in someone with a right afferent defect?

Answer 431

- no pupil constriction in either eye when right eye is stimulated

Question 432

What pupillary response would occur in someone with a right efferent defect?

Answer 432

- no right pupil constriction when either eye is stumlated with light

Question 433

What pupillary response would occur in someone with a unilateral afferent defect?

Answer 433

- different response depending on which eye is stimulated

Question 434

What pupillary response would occur in someone with a unilateral efferent defect?

Answer 434

- same unequal response between left and right eye irrespective which eye is stimulated

Question 435

Define duction, in terms of the eye.

Answer 435

- eye movement in one eye, without making any reference to the movement of the fellow eye

Question 436

Define version, in terms of eye movement.

Answer 436

o movement of both eyes in the same direction - gazing to the right = dextroversion - gazing to the left: levoversion

Question 437

Define vergence, in terms of eye movements.

Answer 437

- movement of both eyes in opposite directions simultaneously

Question 438

Define convergence, in terms of movements of th eye.

Answer 438

- simultaneous adduction (inward) movement in both eyes when viewing a near object

Question 439

What is saccade and state the 5 different saccades?

Answer 439

o short fast burst -\> up to 900deg/sec - reflexive saccade to external stimuli - scanning saccade - predictive saccade to track objects - memory-guided saccade

Question 440

What is smooth pursuit?

Answer 440

- slow sustained movement -\> up to 60 degrees per second - driven by motion of a moving target across the retina

Question 441

What are the 6 extraocular muscles?

Answer 441

- superior rectus - inferior rectus - lateral rectus - medial rectus - superior oblique - inferior oblique

Question 442

Where is the superior rectus attached and what is its function?

Answer 442

- attached at 12 o'clock - moves the eye up

Question 443

Where is the inferior rectus attached and what is its function?

Answer 443

- attached at 6 o'clock - moves the eye down

Question 444

Where is the lateral rectus attached and what is its function?

Answer 444

- attached to the temporal side of the eye - moves the eye towards the temple

Question 445

Where is the medial rectus attached and what is its function?

Answer 445

- attached on the nasal side of the eye - moves the eye towards the nose

Question 446

Where is the superior oblique muscle attached and what is its function?

Answer 446

- attached high on the temporal side of the eye -\> passes under the superior rectus - moves the eye in a diagonal pattern -\> down and in

Question 447

Where is the inferior oblique muscle attached and what is its function?

Answer 447

- attached low on the nasal side of the eye -\> passes over the inferior rectus - moves the eye in a diagonal pattern -\> up and out

Question 448

What eye muscles are innervated by the superior branch of the third cranial nerve?

Answer 448

o Superior Rectus – elevates eye o Lid Levator – raises eyelid

Question 449

What eye muscles are innervated by the inferior branch of the third cranial nerve?

Answer 449

o Inferior Rectus -\> depresses eye o Medial Rectus -\> adducts eye o Inferior Oblique -\> elevates eye o Parasympathetic Nerve -\> constricts pupil

Question 450

What eye muscle is innervated by the fourth cranial nerve?

Answer 450

- superior oblique -\> depresses the eye

Question 451

What eye muscle is innervated by the sixth cranial nerve?

Answer 451

- lateral rectus -\> abducts the eye

Question 452

Define supra- and intra version.

Answer 452

- supraversion = elevation of both eyes -\> namely simultaneous right and left eye supraduction - infraversion = depression of both eyes -\> namely simultaneous right and left eye infraduction

Question 453

What occurs in third nerve palsy?

Answer 453

- only muscles not innervated by CN III in the affected eye are working -\> lateral rectus muscle and superior oblique muscle - affected eye down and out with a droopy eyelid (ptosis)

Question 454

What occurs in sixth nerve palsy?

Answer 454

- sixth nerve palsy presents with deficit in abduction in the affected eye -\> made apparent when the patient is asked to abduct the affected eye - affected eye deviates inwards (unable to abduct) - double vision worsen on gazing to the side of affected eye

Question 455

What is mystagmus?

Answer 455

- oscillatory eye movement -\> can be physiological or pathological

Question 456

When is the optokinetic nystagmus reflex clinically useful?

Answer 456

- in testing visual acuity in pre-verbal children by observing the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies

Question 457

What does oscillopsia indicate?

Answer 457

- nystagmus

Question 458

What is nystagmus?

Answer 458

- a condition involving involuntay eye movements

Question 459

What is the most common cause of vertigo?

Answer 459

- benign paroxysmal positional vertigo (BPPV)

Question 460

What are the red flags for vertigo?

Answer 460

- headache - gait problems - hyperacute onset - hearing loss - prolonged symptoms -\> for more than 4 days

Question 461

A 65 year old artist with hypertension has a 4 year history of recurrent attacks of violent spinning dizziness with sweating, a sensation of impending doom and nausea. He feels unwell for about an hour afterwards. The attacks occur on looking up. On direct questioning the attacks also occur in bed. What one test would you perform to do to confirm the diagnosis? 1. MRI brain scan 2. MRI of the internal acoustic meati 3. Hallpike manouevre 4. Cardiac monitoring 5. Bithermal caloric irrigation

Answer 461

3. Hallpike manouevre

Question 462

A previously well 44 year old businesswoman has a 1 year history of episodic rocking-type dizziness lasting 30-60 minutes. During these episodes she notices that she prefers to lie down in a quiet dark room until the dizziness abates. She has mild asthma, suffered from severe headaches in her 20’s but now only gets the occasional headache (x 1/month). The examination is normal although there was a 10mm postural drop in systolic blood pressure. What is the likely diagnosis? 1. Vertebro-basilar insufficiency 2. Postural hypotension 3. Benign paroxysmal positional vertigo 4. Vestibular migraine 5. Cardiac dysrrhythmia

Answer 462

4. Vestibular migraine

Question 463

A previously well 34 year old lawyer developed severe and sudden onset spinning dizziness one evening whilst working out in the gym with weights. The dizziness was associated with nausea, vomiting and headache even though he had no previous headache history. He staggered home and went to bed. The next day he was still the same and vomited whenever he got up to move around. He went to his GP practice and was seen by the nurse who prescribed stemetil for an ear problem. Along with migraine, what is the most likely differential diagnosis? 1. BPPV 2. Cerebellar stroke 3. Meniere’s Disease 4. Meningitis 5. Vestibular neuritis

Answer 463

2. Cerebellar stroke - very fast onset

Question 464

Briefly summarise grey and white matter in the brain.

Answer 464

- grey matter- \> on the surface of the brain -\> contains nerve cell bodies - white matter -\> the circuitry -\> axons and connections

Question 465

What is diffusion tensor imaging?

Answer 465

- a MR modality that looks for alignment of water molecules, and coincident activity -\> it is a good way of looking at functional connectivity

Question 466

What are the 3 types of white matter fibres?

Answer 466

1. association fibres 2. commissural fibres 3. projection fibres

Question 467

Describe association fibres.

Question 468

What are commissural fibres?

Answer 468

- connections between the two hemisphere to integrate information from different areas -\> main one being the corpus callosum

Question 469

Describe projection fibres.

Answer 469

- long pathways that connect the cortex with the lower brain structures (e.g. thalamus), brainstem and spinal cord

Question 470

Describe the cortical layers of the grey matter.

Answer 470

o the neocortex (most of the cortex) has a 6-layer structure -\> the archicortex has 3 cortical layers - layer I contains mainly neuropil - layer II contains generally smaller pyramidal neurons with primarily corticocortical connections - layer IV is typically rich in stellate neurons with locally ramifying axons; in the primary sensory cortices -\> these neurons receive input from the thalamus, the major sensory relay from the periphery - layer V, and to a lesser degree layer VI, contain pyramidal neurons whose axons typically leave the cortex (output)

Question 471

Describe columnar distribution in the cortex.

Answer 471

- we have cortical columns - the neocortex is arranged in layers (lamina structure) and columns there are more dense vertical connections -\> these columns are the basis for topographical organization - neurons with similar properties are connected in the same column

Question 472

Define primary and association cortices.

Answer 472

- primary cortices: function is predictable, organised topographically, left-right symmetry - association cortices: function less predictable, not organised topographically, left-right symmetry weak/absent

Question 473

What functions occur in the occipital lobe?

Answer 473

o primary visual cortex in the occipital lobe - visual association cortex analyses different attributes of visual image in different places -\> form and colour is analysed along the ventral pathway, spatial relationships and movement along dorsal pathway

Question 474

What processes occur in the parietal lobe?

Answer 474

o primary somatosensory cortex in the post-central gyrus in the parietal lobe - posterior parietal association cortex creates spatial map of body in surroundings, from multi-modality information

Question 475

What are the functions of the temporal lobe?

Answer 475

o auditory cortex in the superior temporal gyrus in the temporal lobe - language, object recognition, memory, emotion

Question 476

What processes occur in the frontal lobe?

Answer 476

- primary motor cortex (PMC) part of the pre-central gyrus in the frontal lobe - judgement, foresight, personality, appreciation of self in relation to world -\> personalities

Question 477

What kind of stroke is most likely to cause language deficits?

Answer 477

- left sided - Broca's and Wernicke's areas are both lateralised to the left hemisphere

Question 478

What is the consequence of a lesion in the fusiform gyrus?

Answer 478

- prosopagnosia -\> face blindness

Question 479

What are the consequences to having a lesion in the occipital cortex?

Answer 479

- lesions affect specific aspects of vision perception

Question 480

What are the consequences of an injury to the parietal lobe?

Answer 480

- injury may cause disorientation, inability to read map or understand spatial relationships, apraxia, hemispatial neglect

Question 481

What does injury to the temporal lobe lead to?

Answer 481

- injury leads to agnosia, receptive aphasia

Question 482

What happens as a result of injury to the frontal lobe?

Answer 482

- injury leads to deficits in planning and inappropriate behaviour

Question 483

What happens in someone who has no corpus callosum?

Answer 483

- left hemisphere is language dominant while right is is for spatial processing - in an experiment, a word is flashed briefly to the right field and the patient is asked what they saw -\> they will be able to, because the left hemisphere is dominant for verbal processing - if you flash the word briefly to the left field, the patient doesn’t see anything -\> however, they will be able to draw what the word says o due to dominant activities of the hemispheres on either side, a split callosum is problematic

Question 484

Why might a patient have their corpus callosum surgically cut?

Answer 484

- severely epileptic -\> prevent a global seizure that initiates in one hemisphere

Question 485

What is the use of functional MRI?

Answer 485

- get information in vivo about connectivity -\> particularly in CNS conditions - usually about monitoring blood flow and glucose metabolism -\> glucose use is probably related to functional activity of the brain -\> where there is more glucose and more blood flow, there is probably higher activity

Question 486

Where are the primary olfactory neurones and olfactory bulbs located?

Answer 486

- neurones = mucosa at the top of the nose - bulbs = inferior surface of the frontal lobes

Question 487

What is loss of olfaction due to?

Answer 487

- trauma to the ethmoid bone which damage the olfactory neurones - early sign of Parkinson's and Alzhemeir's - old age

Question 488

Describe, to the best of current knowledge, how a certain smell is detected?

Answer 488

- the cribriform plate is a very fine layer with small holes making up part of the ethmoid bone -\> projecting through the holes are the olfactory receptor cells with a bipolar morphology - olfactory neurones project into the olfactory bulb, and form glomerular like structures in their interaction with second order olfactory neurones -\> cells in the olfactory bulb (second order) are called mitral cells - second order neurones then project back to the olfactory processing centres -\> olfactory tract lies on the inferior surface of the frontal lobe -\> mitral cells project back to the olfactory tract, and they split into medial and lateral olfactory stria - neurones project to two cortical olfactory processing areas -\> piriform cortex of the temporal lobe and the orbitofrontal cortex - connections of olfactory neurones to the brainstem evoke and promote autonomic responses -\> e.g. if you smell something you want to eat, you will start salivating

Question 489

Name 2 clinical defects of smell.

Answer 489

- anosmia = complete loss of smell - prodromal aura = in temporal lobe epilepsy, the electrical activity before a seizure may provoke a prodromal aura -\> in some people this may be a smell -\> they smell something and know they will have a seizure

Question 490

What processes is the limbic system responsible for?

Answer 490

o processes aimed at survival of the individual - maintenance of homeostasis (hypothalamic function) via activation of visceral effector mechanisms -\> modulation of pituitary hormone release and initiation of feeding and drinking - agonistic behaviour (fight or flight) - sexual and reproductive behaviour - memory -\> vital in terms of emotional response to stimuli in the environment

Question 491

What areas are in the limbic system?

Answer 491

- frontal lobe - thalamus - hippocampus - amygdala - hypothalamus - olfactory bulb - cingulate cortex

Question 492

Describe the Papez circuit.

Answer 492

- main output pathway of the hippocampus is the fornix, which comes out of the inferior horn of the lateral ventricle (the hippocampus sits in the ventricle floor) -\> fibres go up, forward and down into the mammillary bodies of the hypothalamus -\> a connection to the anterior nucleus of the thalamus via the mamillo-thalamic tract -\> projections from the thalamus to the cingulate cortex (just above the corpus callosum) -\> to complete the circuit, there are fibres running from the cingulate cortex to the hippocampus (via the cingulum bundle

Question 493

What is the role of the neocortex?

Answer 493

- information is received from the outside, and integrated at the hippocampus - provokes a response, which stimulates the hypothalamus to change normal homeostatic activity - reactions you have are influenced by memories and previous experiences

Question 494

Where is long term memories stored?

Answer 494

- within the parietal cortex

Question 495

What are the afferent and efferent inputs into the hippocampus?

Answer 495

- afferent = perforant pathway - efferent = fimbria/fornix

Question 496

What are the functions of the hippocampus?

Answer 496

- short-term memory - learning

Question 497

Name 2 diseases which have clinical links to the hippocampus.

Answer 497

- Alzheimer's -\> localised atrophy to the hippocampus - epilepsy

Question 498

Where is the hippocampus?

Answer 498

- sits in the floor of the ventricle - the fimbria and fornix can be seen projecting into the mammillary bodies at the base of the diencephalon - the amygdala is a nucleus buried in the white matter, in the anterior part of the temporal lobe

Question 499

Describe the cortical atrophy is Alzheimer's.

Answer 499

- temporal lobe atrophy (shrinkage) - gyri get thinner and the sulci become wider -\> there is less brain substance - in later stages of Alzheimer’s, the frontal lobe also starts to undergo atrophy - primary motor cortex, primary sensory cortex and occipital lobe are largely unaffected

Question 500

Describe plaques and tangles in Alzheimer's.

Answer 500

- pathology at a cellular level is tangles -\> abnormal cytoskeletal proteins - cytoskeleton breaks down and neuronal cell function breaks down -\> differential susceptibility of the cells (some neurones will not be affected) - senile plaques are observed -\> protein is laid down in the hippocampus -\> disturbing normal memory function.

Question 501

Describe the anatomical progression of Alzheimer's.

Answer 501

- early = hippocampus and entorhinal cortex -\> short-term memory problems - moderate = parietal lobe -\> dressing apraxia - late = fronatl lobe -\> loss of executive skills and personality

Question 502

Where is the amygdola located?

Answer 502

- a nucleus buried in the white matter of the anterior part of the temporal lobe

Question 503

How is the amygdola connected?

Answer 503

o is highly interconnected with everything else; - afferent = olfactory cortex, septum, temporal neocortex, hippocampus, brainstem - efferent = stria terminalis

Question 504

What is the function of the amygdola?

Answer 504

- fear and anxiety - fight or flight

Question 505

What is Kluver-Bucy syndrome?

Answer 505

- a reversion to the basis survival instincts, and exploration of the environment -\> YOU BECOME COMPLETELY FEARLESS - results from localised bilateral lesions in the anterior temporal lobe -\> often due to trauma but still incredibly rare

Question 506

What are the symptoms of Kluver-Bucy syndrome?

Answer 506

- hyperorality - loss of fear - visual agnosia - hypersexuality o very rare for more than two symptoms to be shown in the same patient

Question 507

What structures are associated with aggression?

Answer 507

- anterior parts of the hypothalamus - brainstem - amygdola - NT- system -\> has a role in serotonin in the raphe nuclei

Question 508

What is the septum?

Answer 508

· - the membrane between the two lateral ventricles anteriorly, at its base is the septal nuclei

Question 509

What in the inputs and outputs of the septal nuclei?

Answer 509

- afferent = amygdala, olfactory tract, hippocampus, brainstem - efferent = stria medularis thalami, hippocampus, hypothalamus

Question 510

What is the function of the septal nuclei?

Answer 510

- reward - reinforcement

Question 511

What is the drug dependency pathway?

Answer 511

- mesolimbic pathway - dopaminergic neurones are in the midbrain -\> fibres project via the median forebrain bundle to the cortex, nucleus accumbens (obssession, compulsion and reward) )and amygdola (reward)

Question 512

What is the nucleus accumbens involved in?

Answer 512

- obsessive compulsion - reward

Question 513

What must be considered when prescribing a Parkinson's patient dopamine agonsits?

Answer 513

- family must watch for compulsie reward-based behaviour -\> may become compulsive gamblers - stimulation of the mesolimbic pathway causes this effect

Question 514

What system acts as the control/gateway of consciousness?

Answer 514

- reticular activating system -\> starts in the brainstem and influences the activity of the cerebral cortex -\> can be direct or indirectly though the intralaminar nuclei in the thalamus - high activity in this system leads to higher level of arousal

Question 515

What nuclei and bodies are linked in with the RAS system and therefore aid the ability to fall asleep?

Answer 515

- lateral hypothalamus -\> promotes wakefulness via the orexin system - ventrolateral preoptic nucleus -\> promotes sleep from within the naterior hypothalamus - suprachiasmatic nucleus -\> synchronises sleep with falling light -\> provides the body with circadian rhythm

Question 516

What are the effects of sleep depreivation?

Answer 516

o psychiatric -\> sleepiness, irritability, stress, mood fluctuations, depression, impulsivity, hallucinations o neurological -\> impaired attention, memory, executive function, risk of errors and accidents - neurodegeneration -\> sleep problems can be a warning sign for neurodegenerative disease o somatic -\> CAN LEAD TO DEATH - glucose intolerance - reduced leptin/increased appetite à obesity - impaired immunity - increased risk of cardiovascular disease and cancer

Question 517

How is sleep altered/regulated after sleep loss?

Answer 517

- reduced latency to sleep onset - increase of slow wave sleep (NREM) - increase of REM sleep (after selective REM sleep deprivation)

Question 518

What is the function of sleep?

Answer 518

- restoration and recovery -\> but active individuals do not sleep more - energy conservation -\> 10% drop in BMR -\> but lying still is just as effective - predator avoidance by staying still -\> doesn’t explain why sleep is so complex o specific brain functions -\> MEMORY CONSOLIDATION

Question 519

Describe dreams.

Answer 519

- can occur in REM and NREM sleep -\> most frequent in REM sleep -\> more easily recalled in REM sleep - contents of dreams are more emotional than ‘real life’

Question 520

Describe the brain activity during a time of dreams.

Answer 520

- brain activity in the limbic system is higher than in frontal lobe during dreams -\> suggests emotion/memory

Question 521

What are the potential function of sleep?

Answer 521

o no-one really knows but there are some theories - afety valve for antisocial emotions - disposal of unwanted memories - memory consolidation

Question 522

Name some causes of chronic insomnia.

Answer 522

- physiological -\> sleep apnoea (obstructive and central), chronic pain - brain dysfunction -\> depression, fatal familial insomnia, night working

Question 523

What treatments are available for insomnia?

Answer 523

- treat the cause if possible - improved sleep hygiene - sleep cognitive behavioural therapy - hypnotics (sleeping tablets) -\> enhance GABAergic circuits -\> inhibitory mechanisms on brain activity

Question 524

What is narcolepsy?

Answer 524

- falling alseep repeatedly during the day and disturbed sleep during the night

Question 525

What condition is often linked with narcolepsy?

Answer 525

- ccataplexy -\> sudden, brief loss of voluntary muscle tone, often triggered by strong emotions e.g. laughter

Question 526

What is Lewy-Body disease?

Answer 526

- a type of dementia - in lewy-body dementia, patients can act out their dreams, often in a very violent way - sufferes partners will recall being punched in the middle of the night, as the patient is acting out the dream - Lewy-body disease can often pre-date the onset of other kinds of obvious dementia symptoms by years

Question 527

What is vigilance?

Answer 527

- wakefulness -\> the level of consciousness in terms of how much your RAS is working

Question 528

Define awareness.

Answer 528

- level and content of consciousness

Question 529

Describe a graph showing awareness against vigilance.

Answer 529

Question 530

What is the default-mode network?

Answer 530

- a pathway which is more active at rest/inbetween tasks

Question 531

What is the pertubational complexity index?

Answer 531

- a method of quantifying brain complexity using transcranial magnetic stimulation and EEG - a transcranial magnetic stimulator sends a pulse to the brain -\> causes reverberation of activity -\> this reverberation (activity around the brain) can be measured using EEG - in patients who have disorders of consciousness (or are asleep/anaesthetised), their response is NOT AS DIVERSE -\> measurea/tracks conscious levela

Question 532

Define a coma.

Answer 532

Question 533

Define vegetative state.

Answer 533

Question 534

Define minimally active state.

Question 535

What is the difference between homonymous hemianopia and visual neglect?

Answer 535

o homonymous hemianopia = loss of half of the visual field, common after stroke o visual neglect = a higher order problem -\> lose conscious awareness of one side. - if the neglect is on the left side, the patient won’t attend at all to anything on the right side -\> if much high order problem -\> the patient has completely lost awareness of that side

Question 536

Describe the glasgow coma scale.

Answer 536

- a clinical means of assessing something about conscious level - ranges between 3 and 15 -\> the lower the score, the higher the severity - eyes =4, voice = 5 and motor = 6

Question 537

What are the paramater/scoring systems for the glasgow coma scale?

Question 538

What are the 4 main categories of causes of coma?

Answer 538

- metabolic - diffuse intracranial - hemisphere lesion - brainstem

Question 539

What are the metabolic causes of a coma?

Answer 539

- drug overdose - hypoglycaemia - diabetes - 'the failures’ -\> renal, liver etc. - hypercalcaemia

Question 540

What are the cause of coma that are classified as diffuse intracanial?

Answer 540

- head injury (trauma) - meningitis - SAH - encephalitis - epilepsy - hypoxic brain injury

Question 541

What are the hemisphere lesional causes of coma?

Answer 541

- cerebral infarct - cerebral haemorrhage -\> subdural or extradural - abscess - tumour

Question 542

What are the brainstem causes of coma?

Answer 542

- brainstem infarct - tumour - abscess - cerebellar haemorrhage - cerebella infarct

Question 543

What is shown on this scan?

Answer 543

- extradural haemorrhage

Question 544

What is shown on this scan?

Answer 544

- subdural haemorrhage

Question 545

What is shown on this scan?

Answer 545

- diffuse axonal injury

Question 546

What is shown on this scan?

Answer 546

- posterior fossa lesions -\> compresses the brain stem

Question 547

What is shown on this scan?

Answer 547

- bilateral medial thalamic infarcts

Question 548

How far can neural crest derived cell migrate?

Answer 548

- capable of migrating over quite large distances

Question 549

Answer 549

Question 550

Where do you find the pineal gland?

Answer 550

- in the brainstem on the midline -\> unusual as it is not bilateral like the rest of the braintem

Question 551

What cranial nerves emerge from the midbrain?

Answer 551

- optic nerve - oculomotor

Question 552

Which cranial nerve emerges out of the lateral part of the pons?

Answer 552

- trigeminal (V)

Question 553

What 3 cranial nerves emerge at the ponto-medullary junction?

Answer 553

- most medially = abducens (VI) - facial (VII) - most laterally = vestibulocochlear (VIII)

Question 554

What is Bell's palsy?

Answer 554

- dysfunction of the facial nerve causes a loss of facial muscle tone -\> can lead to drooping of one side of the mouth and therefore drowl - nearly almost resolves itself

Question 555

What 4 cranial nerves emerge from the medulla?

Answer 555

- glossopharyngeal (IX) - lateral - vagus (X) - lateral - accessory (XI) - lateral - hypoglossal nerve (XII) - seperate from the others

Question 556

What is the pyramidal decussation?

Answer 556

- the point of the medulla at which 90-95% of fibres cross over

Question 557

What is the function of the oculomotor (III) nerve?

Answer 557

- movement of the eye

Question 558

What is the function of the trigeminal (V) nerve?

Answer 558

- touch and sensation throughout the head and neck through its 3 divisions -\> opthalmic, maxillary and mandibular - is a small root next to the main larger one because the trigeminal also has motor function in mastication

Question 559

What is the function of the abducens (VI) nerve?

Answer 559

- supplies the lateral rectus -\> cause abduction from the midline

Question 560

What is the function of the facial (VII) nerve?

Answer 560

- innervates facial muscles -\> involved in movement of the face

Question 561

What is the function of the vestibulocochlear (VIII) nerve?

Answer 561

- innervates the inner ear -\> involved in balance and hearing

Question 562

What is the function of the glossopharyngeal (IX) nerve?

Answer 562

- sensory and motor innervation of the tongue and pharynx

Question 563

What is the function of the vagus (X) nerve?

Answer 563

- main parasympathetic nerve -\> projects down into the viscera

Question 564

What is the function of the accessory (XI) nerve?

Answer 564

- supplies the sternocleidomastoid and trapezius -\> turning of the head and shrugging of shoulders

Question 565

What is the function of the hypoglossal (XII) nerve?

Answer 565

- supplies the musculature of the tongue

Question 566

Touch sensation from the skin on the forehead is of what functional classification? a. general viseral afferent b. general visceral efferent c. general somatic afferent d. general somatic efferent e. special somatic efferent

Answer 566

a. general somatic afferent

Question 567

What is the role of the general somatic afferent nerves?

Answer 567

- sensation from skin and mucous membranes

Question 568

What is the role of the general somatic efferent nerves?

Answer 568

- muscles for eye and tongue movements

Question 569

What is the role of the general visceral efferent nerves?

Answer 569

- preganglionic parasympathetic -\> mainly the vagus

Question 570

What is the role of the general visceral afferent nerves?

Answer 570

- sensation from the GI tract, heart, lungs and other deep organs

Question 571

What does a pale substantia nigra suggest?

Answer 571

- Parkinson's disease -\> the neurones have been loss so there is no black from the build up of neuromelanin

Question 572

Which of these cranial nerve nuclei recieves sensory information concerning taste? a. Edinger-Westphal b. facial c. nucleus ambiguus d. nucleus solitarius e. pontine trigeminal nucleus

Answer 572

d. nucleus solitarius

Question 573

Which of the following arteries of the circle of Willis is unpaired? a. anterior cerebral b. anterior communicating c. middle cerebral d. posterior cerebral e. posterior communicating

Answer 573

- anterior communicating artery

Question 574

What are the areas of the brain involved in understanding language?

Answer 574

- Wernicke's Area

Question 575

Describe a subarachnoid haemorrhage.

Answer 575

- blood ciculates (often after an aneurysm has ruptured) in the subarachnoid space where CSF usually is - is an emergency -\> quite often it is fatal

Question 576

Which of these vascular problems is most likely to require rapid neurosurgical intervention? a. extradural haemorrhage b. lacunar infarct c. parenchymal infarct d. sudural haemorrhage e. transient ischaemic attack

Answer 576

a. extradural haemorrhage

Question 577

How many spinal nerve pairing are there?

Answer 577

o 31 pairs of spinal nerves - 8 cervical - 12 thoracic - 5 lumbar - 5 sacral - 1 coccygeal

Question 578

Where do the spinal nerves leave the vertebral column?

Answer 578

- through the intervertebral foramina

Question 579

What are the two enlargements of the spinal cord?

Answer 579

- cervical enlargement -\> has extra motor neurones that go to the muscles of the upper limb - lumbarsacral enlargement -\> has extra motor neurones that go to the muscles of the lower limb

Question 580

Lesion(s) in what area would cause a loss of the ability to breath?

Answer 580

- C3-C5 -\> C3,4,5 keep the diaphragm alive

Question 581

What area is used to sample the CSF?

Answer 581

- lumbar cistern

Question 582

Describe the main sensory pathways.

Answer 582

o neuron has cell body in dorsal root ganglion -\> neuron either in spinal cord or in medulla, dependent on type of pathway (second order neurons cross from one side to the other) o third neuron is from thalamus to the cortex o crossing over: touch = medulla (dorsal column) and pain = spinal cord (spinothalamic tract)

Question 583

Describe the patella tendon test.

Answer 583

o reflex test - hitting patella tendon causes muscle to stretch - stretch signal sent to spinal cord – via muscle spindals - causes motor neurone to contract muscle

Question 584

What spinal segmenst have sympathetic outflow from them?

Answer 584

- T1 to L2

Question 585

What is syncope?

Answer 585

- fainting

Question 586

What happens if the arterial blood flow falls below 60mmHg?

Answer 586

- comprimised brain function and then possible irreversible brain damage and death

Question 587

Explain how sympathetic nerve stimulation can alter cerebral blood flow.

Answer 587

- by producing vasoconstriction in the main cerebral arteries -\> probably only active when the arterial blood pressure is high

Question 588

Explain how parasympathetic nerve stimulation can alter cerebral blood flow.

Answer 588

- don’t normally associate the parasympathetic NS with vasculature, however facial nerve fibres are innervated by parasympathetic fibres can cause slight vasodilation

Question 589

Explain how central cortical neurones can alter cerebral blood flow.

Answer 589

- neurones within the brain itself release a variety of vasoconstrictor neurotransmitters, such as catecholamines -\> vasoconstriction

Question 590

Describe the structure of the blood-brain barrier.

Answer 590

- endothelial cells that line the capillaries in the brain have very tight junctions (non-fenestrated) -\> a lot of molecules can't pass readily through the BBB - capillaries are also surrounded by pericytes (far more heavily than in periphoral capillaries) that have end-feet that run along the capillary wall -\> pericytes contraction makes it more likely for molecules to escape the capillary - overall it’s mainly the tight junctions between endothelial cells forming the BBB but also pericytes

Question 591

What is the relationship between anti-histamines and the blood-brain barrier?

Answer 591

- old-fashioned H1 blockers are hydrophobic and could cross the BBB -\> since histamine is important in wakefulness and alertness, these antihistamines made people drowsy -\> lots of over-the-counter sleeping tablets are old-fashioned anti-hisatmines - second-generation anti-histamines are polar, therefore don’t readily cross the BBB -\> no drowsiness

Question 592

Label this diagram.

Answer 592