Neuro Physiology Flashcards
(333 cards)
1
Q
What is refraction?
A
The bending of light when it passes from one optical medium to another
2
Q
Where in the eye do light rays bend?
A
At the cornea and again at the Lens
3
Q
Which part of the eye can change to focus on different distances and how does it do so?
A
Lens- thickens to focus on closer objects
4
Q
What is accommodation?
A
The process of the eyes changing to focus on closer objects
5
Q
What three processes allow accommodation to occur?
A
Lens becomes thicker and more spherical
Pupils constrict
Eyes converge
6
Q
What muscles control each of the processes behind accommodation?
A
Lens thickening- contraction of ciliary body
Pupil constriction- constrictor pupillae
Convergence of eyes- medial recti
7
Q
What is the meaning of the term myopia?
A
Short-sightedness
8
Q
What is the meaning of the term hyperopia?
A
Long-sightedness
9
Q
What is the meaning of the term astigmatism?
A
A non-spherical curvature of the cornea/lens
10
Q
What is the meaning of the term presbyopia?
A
Long-sightedness of old age
11
Q
What is the cause of myopia?
A
Most commonly caused by the eyeballs being too long, causing the image to form in front of the retina so close objects can be seen but far away objects appear blurry
12
Q
What type of lenses correct myopia?
A
Biconcave lenses
13
Q
What is the cause of hyperopia?
A
The eyeballs being too short, or the cornea and lens being too flat so the image is formed behind the retina. Accommodative power is used to make the image form on the retina and so far away objects can be seen but close objects cannot
14
Q
What type of lenses correct hyperopia?
A
Biconcave lenses
15
Q
What is the cause of astigmatism?
A
The eyeball has different curves in different meridians so images will be hazy regardless of distance
16
Q
How is astigmatism corrected?
A
Cylindrical glasses- only curved in one axis
Laser eye surgery
17
Q
What is the cause of presbyopia?
A
With age, the lens becomes less elastic and so when the ciliary body contracts, it is less capable of changing shape and so long-sightedness develops
18
Q
How is presbyopia corrected?
A
Biconvex lenses
19
Q
What cells in the eye are stimulated by light energy and where are they found?
A
Photoreceptors(rods and cones) on the retina
20
Q
What does the term “phototransduction” mean?
A
The conversion of light energy to an electrochemical response by photoreceptors
21
Q
What do the rods and cones do once they have been phototransduced?
A
They activate optic nerve neurons
22
Q
What happens when light falls on 11-cis retinal?
A
It isomerises to all-trans retinal, which cannot fit into the opsin and so rhodopsin splits, resulting in bleaching of the colour purple. This results in phototransudction via a phototransduction cascade
23
Q
What is responsible for visual pigment regeneration?
A
Vitamin A
24
Q
What is the definition of the visual field?
A
Everything you can see with one eye, including peripheries
25
How are images formed in the optic field?
They are formed upside down and inverted on the retina
26
Describe the passage of fibres from the eye to the primary visual cortex
FIbres from the eye pass through the optic nerve to the optic chiasm, where the nasal fibres cross to the opposite sides. Fibres from the optic tract then synapse at the LGB of the thalamus, from where the optic radiation passes behind the internal capsule to reach the primary visual cortex in the occipital lobe.
27
What is the result of optic nerve damage?
Blindness in ipsilateral side
28
What is the result of damage to the optic chiasm?
Bitemporal hemianopia
29
What is the result of optic tract damage?
Contralateral homonymous hemianopia
30
What is the result of damage to the optic radiation?
Contralateral homonymous hemianopia
31
What is the conjunctiva?
A thin, vascular membrane that covers the inner surface of the eyelids and loops back over the sclera without covering the cornea
32
What is conjunctivitis?
A self-limiting bacterial or viral infection of the conjunctiva
33
What are the characteristics of conjunctivitis?
Red, watering eyes with possible discharge
| Should be no loss of vision unless spread to cornea
34
What is affected by internal and external styes?
Internal- Meibomian glands
| External- Sebaceous gland of an eyelash
35
What kind of epithelium makes up the cornea?
Stratified, squamous, non-keratinised epithelium
36
What lies between the cornea and the stroma?
Bowman's membrane
37
What makes up the stroma?
A thick layer of regularly arranged collagen with no blood vessels
38
What lies just superior to the aqueous humor?
A single layer of endothelium
39
What is the common complication of a corneal pathology and how is this repaired?
Opacification of the cornea- requiring a corneal transplant to repair
40
What are the possible causes of corneal ulcers?
Infection
Trauma
Corneal degenerations
Dystrophy
41
What are the possible complications of corneal ulcers?
Spread
| Scarring
42
What are the characteristics of dystrophies/degenerations?
A group of diseases that are bilateral, opacifying, non-inflammtory and mostly genetic in aetiology
Usual clinical presentation is in first to fourth decade with decreased vision
43
What characteristic of the cornea makes it relatively easy to transplant and why?
The avascularity-lesser chance of foreign antibodies being rejected so less chance of a graft rejection
44
Why does cataracts develop?
Older embryological fibres of the lens are never shed, they just converge in the middle. These absorb harmful UV rays and prevent them from harming the retina, but are harmed themselves. The damaged lens fibres become opaque and cause cataracts
45
What is the cause of glaucoma?
A raised intraocular pressure
46
Why does a raised introcular pressure cause glaucoma?
The pressure of raised IOP on nerve fibres on the retinal surface causes them to die out and cause visual field defects. Pressure builds on the optic nerve head as nerve fibres die, altering the field of vision. Eventually all fibres are lost, resulting in blindness
47
What are the triad of signs of glaucoma?
Raise IOP
Visual field defects
Optic disc changes on opthalmoscopy
48
What are the possible treatments of glaucoma?
Eye drops to decrease IOP (can be prostaglandin analogues, beta-blockers or carbonic anhydrase inhibitors)
Laser trabeculoplasty
Laser trabeculectomy
49
How does angle closure glaucoma present?
Sudden onset painful eyes with lost or blurred vision and headaches
50
What can cause angle closure glaucoma?
A functional blockage such as a large lens
A mid-dilated pupil periphery of the iris can crowd around the angle
Iris can stick to pupillary border which prevents humor reaching the anterior chamber, so iris balloons anteriorly and obstructs the angle
51
What is uveitis?
Inflammation of the uvea
52
What are the three kinds of uveitis and how are each differentiated?
Anterior uveitis- inflammation of iris with or without ciliary body
Intermediate uveitis- ciliary body inflamed
Posterior uveitis- choroid inflamed
53
What are the causes of uveitis?
Autoimmune disorders
Infection
Systemic disease
Idiopathic
54
What leaks from the iris in anterior uveitis and what does this cause?
Plasma and white blood cells into the aqeuous humor
| Causes the eye to be red and painful with visual loss
55
What leaks from the ciliary body in intermediate uveitis and what does this cause?
Leaks cells and proteins
| Causes a hazy vitreous humor, with patients often complaining of "floaters" in their vision or of hazy vision
56
What are the possible complications of posterior uveitis?
Inflammation can spread from choroid to retina and cause blurred vision
57
What is the function of the vestibular system?
The control of posture and balance
58
What are the labyrinths and where are they found?
A series of fluid-filled membrane tubes that are embedded within the temporal bone
59
What makes up the vestibular apparatus?
Three semicircular canals
The utricle
The saccule
60
What are the anatomical relations of the semicircular canals, the utricle and the saccule?
The three semicircular canals lie at right angles to each other and are connected to the saccule by the utricle
61
What are the ampulla and what is found within them?
Swellings at the base of the semicircular canals that contain sensory hair cells
62
What are the otolith organs?
The utricle and the saccule
63
What movements do the utricle detect?
Back/front tilt
64
What movements do the saccule detect?
Vertical movement
65
What movements do the semicircular canals detect?
Rotational acceleration
66
What are the cristae and where are they found?
Sensory receptors found within the ampulla of the semicircular canals
67
What is the cupula, where is it found and what is its function?
A flexible, gelatinous structure found within the ampulla of the semicircular canals as part of the cristae that stretches across the width of the ampulla and responds to the movement of the endolymph fluid within the canals
68
How do the ampulla communicate with the brain?
Within the ampullae are the cilia of the hair cells that synapse directly with the sensory nerves of the vestibulococchlear nerve
69
What do the cilia detect and how?
Rotational acceleration
As the skull is rotated, the endolymph does not initially move due to inertia but the ampullae do move instantly because they are embedded within the skull. The inertia of the endolymph causes drag, bending the cupula and the cilia in the opposite direction to movement.
70
What do the cilia of the hair cells consist of?
A single large kinocilium followed by a series of smaller stereocilia
71
What is the result of distortion of the cilia in the direction of the kinocilium?
Distortion of the cells in the direction of the kinocilium causes depolarisation and increased discharge of action potentials in the vestibular nerve
72
What is the result of distortion of the cilia away from the direction of the kinocilium?
Distortion of the cilia away from the kinocilium causes hyperpolarization and decreased discharge of action potentials in the vestibular nerve
73
Why are the oreintations of the cupulae all slightly different?
It allows the brain to build a 3D image of the body positioning using the pattern of firing and inhibition received.
74
Where does integration of the information received from the cupulae take place?
In the cerebellum
75
What are the sensory apparatus of the otolith organs?
The maculae
76
How are the maculae orientated in the saccules and utricles?
Utricles- horizontally
| Saccules- vertically
77
How are the cilia organised in the maculae?
Similarly to as in the crista, but they protrude into the otolith membrane
78
What is the otolith membrane and what is embedded within it?
A gelatinous mass with CaCO3 crystals embedded within it known as otoliths
79
How are the otoliths involved in proprioception?
The otoliths have a greater density than the endolymph, and so are more affected by gravity. Tilting the head moves the otoliths and the otolith membrane, distorting the jelly and moving the otoliths. The otoliths move the kinocilium and cause depolarisation/hyperpolarisation
80
How is backwards tilt detected in the maculae?
Backwards tilt moves the otoliths in the direction of the kinocilium, causing depolarisation and increasing discharge of action potentials
81
How is forwards tilt detected in the maculae?
Forwards tilt moves the otoliths away from the kinocilum, causing hyperpolarisation and decreasing discharge of action potentials
82
What is the role of the maculae in the saccule?
They respond to vertical forces and provide information on the orientation of the head when lying down
83
Where do the sensory afferents of the vestibular nerves terminate?
In the vestibular centres of the medulla
84
Where does coordination of postural muscles occur?
In the cerebellar centres
85
How are the vestibular centres of the medulla and the cerebellar centres associated and why?
Need associations as interpretation of information from vestibular nerves occurs in medulla and postural muscles controlled by cerebellum
Associated through:
1. Projection fibres from the vestibular nuclei project in every direction to descending motor pathways
2. Vestibular nuclei receive input from proprioceptors signalling limb and body position
3. Vestibular nuclei project via the thalamus to the cerebral cortex allowing for perception of movement and body position
86
How is the axis of the head kept constant with the rest of the body?
The tonic labyrinthine reflexes keep the axis consistent by using information from the maculae and the neck proprioceptors
87
What is the function of the dynamic righting reflexes?
To stop you falling when you trip
88
What reflex stops you falling when you trip?
The dynamic righting reflexes
89
How are the semicircular canals linked to eye movements?
Afferents from the semicircular canals connect to afferent fibres travelling to the extraocular nuclei
90
What is the static reflex?
The static reflex occurs when you tilt your head and the eyes intort/extort to compensate
91
What is dynamic vestibular nystagmus?
A series of saccadic eye movements that rotate the eye against rotation of rotation of the head. When the extent of eye movement is reached, the eyeball rapidly flicks back to straight ahead
92
What is considered to be the direction of nystagmus?
The direction of the flick back
93
What spinal tracts are involves in the vestibular system reflexes?
The vestibulocortical and vestibulospinal tracts
94
How can nystagmus be tested in clinic?
THe outer ear is washed with either cold or warm water and the temperature difference away from core body temperature carries through the thin temporal bone and sets up convection currents affecting the endolymph. Warm water causes nystagmus towards the affected side, cold water away from the affected side (COWS)
95
When does motion sickness occur?
When visual and vestibular signals to the cerebellum are in conflict
96
What is the white matter of the brain made up of?
Myelinated axons
97
What is the grey matter of the brain made up of?
Neuronal cell bodies
98
What are neuronal cell body collections known as within and outside of the central nervous system?
In CNS- neuron
| Outside CNS- ganglion
99
What are the ventricles of the brain and where is each found?
Ventricles are spaces in the brain
Lateral ventricles- cerebreal hemispheres
Third ventricle- diencephalon
Cerebral aqueduct- midbrain
Fourth ventricle- between pons, medulla and cerebellum
100
Where is cereberospinal fluid found?
In the ventricles and between the arachnoid and pia mater
101
What produces and absorbs cerebrospinal fluid?
Produced by choroid plexus of each ventricle
| Absorbed by arachnoid villi into the sagittal sinus
102
What arteries supply the brain and where do they enter the skull?
The two internal carotid arteries enter through the carotid canal.
Two vertebral arteries join with the posterior cerebral arteries to form circle of Willis
103
Why are the arteries supplying the brain arranged in a circle?
Protective feature to minimise effects of vasco-occlusion on the brain
104
What branches do the internal carotid arteries give off in the brain?
The anterior, middle and posterior cerebral arteries
105
What areas of the brain does the anterior cerebral artery supply?
The medial aspect of the cerebral hemispheres excluding the occipital lobes
106
What areas of the brain does the middle cerebral artery supply?
The lateral aspects of the cerebral hemispheres
107
What areas of the brain does the posterior cerebral artery supply?
The inferior aspect of the cerebral hemispheres and the occipital lobe
108
What areas of the brain do the branches of the vertebro-basilar system supply?
The brainstem and the cerebellum
109
How is the venous drainage of the brain organised?
The superficial and deep veins of the brain drain into two venous sinuses which lie between two layers of the dura mater. The dural venous sinuses join together to drain into the internal jugular veins
110
What are the basic functions of the cerebrum, the cerebellum and the brainstem?
Cerebrum- seat of consciousness
Cerebellum- balance and coordination
Brainstem- responsible for vital centres and acts as a pathway for fibre tracts
111
What are the surface features of the medulla?
Pyramids and their decussation
Olives (laterally)
Cranial nerves 9-12 projecting from its surface
Cerebellar peduncles
112
What are the surface features of the pons?
Middle cerebellar peduncle
| Origins of cranial nerves 5-8
113
What are the surface features of the midbrain?
Cerebral peduncle
Superior cerebellar peduncle
Corpora quadrigemina (colliculi)
Origins of cranial nerves three and four
114
What are the lobes present on each cerebellar hemisphere?
The anterior, posterior and flocculonodular lobes
115
What seperates the two cerebellar hemispheres?
The vermis
116
What are present on the surface of the cerebellum?
Sulci and folia
117
How is the cerebellum connected to the brainstem?
Through three cerebellar peduncles
118
Where does the cerebellum receive information from?
The pyramidal tracts
Ipsilateral proprioceptors from the peripheries
Vestibular nuclei
119
What does the cerebellum do with the information it receives and where does it send it onto?
It calculates the best way to coordinate force, direction and extent of muscle contraction to maintain posture, prevent overshoot and ensure coordinated muscle action
Sends this information to the cerebral cortex via the superior cerebellar peduncle
120
What are the component parts of the diencephalon?
Thalamus
Hypothalamus
Epithalamus/pineal gland
121
What separates the thalamus and the hypothalamus?
The hypothalamic sulcus
122
What are the groups of nuclei within the thalamus called?
The anterior, middle and lateral groups
123
What is the role of the thalamus and the hypothalamus?
Thalamus- sensory relay centre
| Hypothalamus- main visceral control centre and maintenance of homeostasis
124
How is the white and grey matter arranged in the cerebral hemispheres?
A surface made of grey matter with a white matter centre
125
Which parts of the cerebrum is sensory and which part motor?
Anterior part is motor
| Posterior part is sensory
126
Where is the primary motor cortex?
The precentral gyrus of the frontal lobe
127
Where is Broca's area of motor speech?
Inferior frontal gyrus of the frontal lobe
128
What is the role of the prefrontal cortex?
Responsible for cognitive functions of higher order
129
Where is the primary sensory area?
The postcentral gyrus of the parietal lobes
130
Where does interpretation of sensory information occur?
The superior parietal lobule
131
Where does the interface between the somatosensory cortex and the visual and auditory association areas occur?
In the inferior parietal lobule
132
Where is the primary auditory cortex?
The superior temporal gyrus of the temporal lobe
133
Which lobe are the auditory association/Wernicke's areas a part of?
The temporal lobe
134
What part of the brain receives fibres from the olfactory tract and so is responsible for conscious appreciation of smell?
The inferior surface of the temporal lobes
135
Where is the primary visual cortex?
On the medial surface of the occipital lobe on either side of the calcarine sulcus
136
What makes up the bulk of the occipital lobe?
The visual association cortex
137
Where is the limbic lobe?
On the medial surface of the cerebral hemisphere
138
What is the function of the limbic lobe?
Involved in memory and emotional aspects of behaviour
139
What are the component parts of the limbic lobe?
Cingulate gyrus
Hippocampus
Parahippocampal gyrus
Amygdala
140
How does Broca's aphasia present?
Someone who understands speech but misses small words and is aware they are doing so
141
What causes Broca's aphasia?
Damage to the frontal lobe
142
How does Wernicke's aphasia present?
Somebody with fluent speech but with meaningless words
| Also can't understand speech and are not aware of their difficulties
143
What causes Wernicke's aphasia
Damage to the temporal lobe
144
What potential paralysis does Broca's and Wernicke's aphasia present with?
Broca's- might have weakness/paralysis on one side of the body
Wernicke's- no paralysis
145
What are the three types of myelinated axons that are bundled into tracts in the white matter and what is each's role?
Commisural fibres- connects corresponding areas of the two cerebral hemispheres
Association fibres- connect one part of the cortex with another
Projection fibres- runs between cerebral cortex and subcortical centres
146
What fibres make up the internal capsule?
Projection fibres passing to and from the cerebral cortex
147
What structures does the internal capsule lie between?
Thalamus and caudate nucleus medially
| Lentiform nucleus laterally
148
What artery supplies the internal capsule?
The middle cerebral artery
149
What are the component parts of the basal ganglia?
Caudate nucleus
Putamen
Globus pallidus
Substantia nigra (functionally but not anatomically)
150
What are the anatomical relations of the caudate nucleus?
Starts as a head medial to the internal capsule then continues as a neck and body that follow the curves of the lateral ventricles. Lateral to the caudate nucleus is the lentiform nucleus
151
What are the component parts of the lentiform nucleus and which part is more medial/lateral?
Putamen (lateral) and globus pallidus (medial)
152
Where do the caudate nucleus and the putamen receive information from?
Motor cortex
Premotor cortex
Thalamus
153
What are the input and output regions of the basal ganglia?
Input regions- caudate nucleus and putamen
| Output regions- Globus pallidus and substantia nigra
154
Where does the globus pallidus project to?
The thalamus, which in turn sends fibres to the motor areas of the cortex
155
What is the major function of the basal ganglia?
Regulate the initiation and termination of movements
156
How is the white and grey matter arranged in the spinal cord?
Grey matter centre surrounded by white matter. Grey matter has a dorsal and a ventral horn on each side
157
Where do sensory fibres enter and motor fibres leave the spinal cord?
Sensory fibres enter through the dorsal horn
| Motor fibre leave out the ventral horn
158
Where are the cell bodies of the motor neurons found within the spinal cord?
Within the ventral horn
159
What are the names of the columns that the white matter of the spinal cord is arranged into?
Lateral, anterior and posterior columns
160
What is the function of the corticospinal/pyramidal tract?
Carries motor impulses from the motor cortex to the skeletal muscle
161
What is the function of the posterior/dorsal column?
Carries touch, tactile localisation, vibration sense and proprioception
162
What is the function of the lateral spinothalamic tract?
Carries pain and temperature
163
How is voluntary movement transmitted?
Transmitted by corticospinal tract
Pathway starts in motor cortex and travels through the posterior limb of the internal capsule. Corticobulbular fibres go to the contralateral cranial nerve nuclei and corticospinal fibres cross over at the decussation of the pyramids. Upper motor neuron synapses in the spinal cord. Lower motor neuron travels from spinal cord to skeletal muscle.
164
How many neurons do the ascending spinal tracts have between the peripheral receptor and the cortex?
Three
165
What type of spinal tract has dorsal root ganglion?
Sensory/ascending
166
Where do ascending spinal tracts decussate?
In the spinal cord or the medulla
167
Where is the synapse between the first and second order cells of the dorsal column found?
The lower part of the medulla
168
Which neuron of the dorsal column decussates?
The second neurons
169
What is the dorsal column called after it decussates?
The medial lemniscus
170
Where do the third order neurons of the dorsal column start?
In the thalamus
171
What is the pathway of the third order neurons of the dorsal columns?
Start in the thalamus and the axons pass through the internal capsule and radiate to the postcentral gyrus
172
Where does the first order neuron of the spinothalamic tract end?
In the grey matter at the level of entry
173
What is the pathway of the second order neuron in the spinothalamic tract?
Second order neuron crosses over to reach lateral column and becomes lateral spinothalamic tract. Second order neuron ends in thalamus
174
What is the pathway of the third order neuron of the lateral spinothalamic tract?
Starts in the thalamus, passes through the internal capsule then radiates to the postcentral gyrus
175
Describe the pathway of the stretch reflex
1. Tendon is stretched
2. Intrafusal muscle fibres stimulated
3. Sensory neuron activated
4. Monosynaptic reflex arc activated. Polysynaptic reflex arc to inhibitory interneuron then activated
5. Muscle then contracts and reciprocal innervation is activated
176
Describe the pathway of the flexor or crossed extensor reflec
1. Pain stimulus present
2. Sensory neuron activated
3. Polysynaptic reflex arc activated
4. Flexion and withdrawal from noxious stimuli
5. Crossed extensor response is replicated in contralateral limb, but only in weight bearing limbs
177
What is the purpose of the flexor reflex?
To help protect the body from painful stimuli
178
What neurons control reflexes?
Lower motor neurons
179
Which motor neurone lesions cause flaccidity and which cause spasticity?
Lower motor neuron lesions cause flaccidity
| Upper motor neuron lesions cause spasticity
180
What are the characteristics of a left UMN lesion at the internal capsule?
Right-sided paralysis
Hyper-reflexia
Increased tone
181
What are the characteristics of a left UMN lesion at the upper cervical spinal cord?
Left-sided paralysis
Hyper-reflexia
Increased tone
182
What are the characteristics of a left LMN lesion?
Left-sided paralysis
Absent reflexes
Flaccid tone
183
What are the characteristics of a UMN lesion above the decussation?
Contralateral spastic paralysis
| Hyper-reflexia
184
What are the characteristics of a UMN lesion below the decussation?
Ipsilateral spastic paralysis
| Hyper-reflexia
185
What are the characteristics of a LMN lesion?
Ipsilateral flaccid paralysis
| Areflexia
186
What part of the spinal cord is affected by motor neurone disease and how does this manifest?
Affects the lower motor neuron in the ventral horn of the spinal cause causing atrophy of the supplied muscle
187
How does sleep occur?
Due to active inhibitory processes that originate in the pons
188
How can consciousness level be assessed?
Behaviour, general alertness AVPU etc
| Record brain activity using EEG
189
How can EEG waves be analysed?
By looking at amplitude or frequency
190
When are alpha waves observed and how are they characterised?
When awake and relaxed
| Characterised by high frequency, high amplitude waves
191
When are beta waves observed and how are they characterised?
When awake and alert
| Characterised high frequency, low amplitude waves
192
When are theta waves observed and how are they characterised?
In childhood and in times of stress/frustration in adults
| Characterised by varying amplitude, low frequency waves
193
When are delta waves observed and how are they characterised?
During deep sleep
| Characterised by low frequency, high amplitude waves
194
How are the five stages of sleep characterised?
Stage 1- slow wave S-sleep with slow eye movements, light sleep that is easily roused with theta waves
Stage 2- eye movements stop, frequency slows down but EEG shows bursts of rapid waves (sleep spindles)
Stage 3- high amplitude, low frequency waves that are interspersed with short episodes of faster waves. Spindle activity declines
Stage 4- exclusively theta waves
REM sleep- rapid eye movements, fast waves that are very similar to those in awake state
195
What stages of sleep are referred to as deep sleep?
Stages 3 and 4
196
During what stage of sleep do dreams occur?
REM
197
What stages of sleep are known as slow wave sleep?
Stages 1-4
198
How much of sleep does REM take up?
25%
199
What is the most restful kind of sleep and when does it occur?
Deep, slow wave sleep that occurs in the first few hours of sleep
200
How does REM sleep occur through a sleep cycle?
Lasts for 5-30 minutes of every 90 minutes of sleep, becoming more recurrent as the night progresses
201
What characteristics do sleep deprived people display?
Irritability
Sluggishness
Impairment of cognitive function
Impairment of physical ability
202
What does sleep support?
```
Neuronal plasticity
Learning and memory
Cognition
Clearance of waste products from CNS
Conservation of whole body energy
Immune function
```
203
What aspects of sleep decrease during childhood and adolescence?
Total sleep time
| Percentage of sleep spent in REM
204
What is the definition of insomnia?
The chronic inability to obtain the necessary amount or quality of sleep to maintain adequate daytime behaviour
205
What stage of sleep do night terrors occur during and what age are they most common in?
During deep sleep (stage 3-4)
| Most common in those aged 3-8
206
What stage of sleep does somnambulism occur during?
Exclusively non-REM
207
What stage of sleep do patients with narcolepsy enter into?
REM
208
Where is the "master clock" of the circadian rhythm found?
In the suprachiasmatic nucleus of the hypothalamus
209
What neurones does vountary control of muscles occur via?
alpha motoneurones in the spinal cord
210
Where do brainstem nuclei receive control inputs about voluntary movement from?
Higher centres- cerberal cortex, basal ganglia and cerebellum
211
What are the four systems that control movement?
Descending control pathways, basal ganglia, cerebellum and local spinal cord/brainstem circuits
212
How is the spatial map of the body musculature in the spinal cord arranged?
Proximal structures mapped to medial motoneurones, distal structures mapped to lateral motoneurones
213
What inputs regarding voluntary movement do the spinal cord receive?
Descending input via the brainstem
| Direct cortical input via corticospinal tract
214
Where does sensory input enter the motor system?
At the spinal cord in the form of proprioceptors
At the brainstem from the vestibular system giving information about balance
At the cortical level, where we make movements in response to a number of stimuli
215
What muscles is the stretch reflex found in?
ALL muscles
216
What are the three types of connections made in response to a sharp tap to an inelastic tendon?
1. Directly activate the alpha-motoneurones to the stretcged muscle causing rapid contraction of afferent muscle (monosynaptic reflex- no interneurones)
2. Sensory fibres from stretched spindle also connect indirectly with antagonist muscle and relaxes antagonist as agonist contracts- spindle afferents activate inhibitory interneurones that decreases activation of alpha-motoneurones to antagonist muscle
3. Spindle afferent information also ascends in the dorsal columns and makes connections in somatosensory cortex to tell brain about length of muscles
217
How can the stretch reflex be considered a negative feedback loop?
The muscles stretches, which stimulates muscles spindles and causes a reflex muscle contraction resulting in the muscle shortening to previous length
218
Describe the pathway of the inverse stretch/Golgi tendon organ reflex
Muscle contracts, pulling on the tendon and 1b sensory nerves from the GTOs causing increased firing of action potentials. This causes activation of inhibitory interneurones to the agonist muscle and excitatory interneurones to the antagonist muscles
219
How does information about muscle tension ascend?
Through the dorsal columns to the somatosensory cortex
220
What is the function of the inverse stretch reflex?
Protective- prevents muscles from contracting so hard that the tendon insertion is torn away from the bone
221
What receptors does the flexor/withdrawal reflex receive information from?
Nociceptors
222
What is the function of the flexor reflex?
Protective- withdraw part of the body away from a painful stimulus and towards the body
223
Describe the pathway of the flexor reflex
Increased sensory APs from nociceptors cause an increased activity in the flexor muscles of the affected part via excitatory interneurones and the antagonistic extensors are inhibited by excitatory and inhibitory interneurones
224
What fibres allow the flexor reflex to operate?
Small diameter A delta nociceptive fibres triggering pain entering the cord and activating interneurones in several spinal segments which activates alpha motoneurones controlling all the flexor muscles of the affected limb
225
How does the contralateral limb allow for the flexor reflex to avoid falling over?
Occurs via several excitatory interneurones that cross the spinal cord exciting the contralateral extensors and at the same time there is inhibition of the contralateral flexors via several interneurones.
226
Which is the fastest of the reflexes?
The stretch reflex
227
How can the GTO reflex be overridden?
Descending voluntary excitation of alpha motoneurones can override the inhibition from the GTOs and maintain contraction
228
How can the stretch reflex be overridden?
Descending inhibition hyperpolarizing alpha-motoneurones and so the stretch reflex cannot be evoked
229
What are the three functional levels involved in motor control?
Strategy, tactics and execution
230
What brain structures are involved in strategy motor control and what is the goal?
Association cortex and basal ganglia
| Focuses on the goal and the movement strategy to best achieve this goal
231
What brain structures are involved in tactics motor control and what is the goal?
Motor cortex and cerebellum
| Controls the sequence of spatiotemporal muscle contractions to achieve a goal smoothly/accurately
232
What brain structures are involved in execution motor control and what is the goal?
Brainstem and spinal cord
| Focuses on activation of motor neuron and interneuron pools to generate goal-directed movement
233
What do the ventromedial pathways control?
Posture and locomotion under brain stem control
234
What do the lateral pathways control?
Voluntary movements of distal muscles under direct cortical control
235
Describe the pathway of the corticospinal tract
Most of the pathway originates in areas 4 and six of the frontal motor cortex before dessucating at the medulla/spinal cord junction. CST axons synapse on the ventral horn motor neurones and interneurones to control muscles
236
Where does the rubrospinal tract receive input from?
Starts in the red nucleus of the midbrain and receives input from areas four and six of the frontal motor cortex
237
How do lesions of the corticospinal and rubrospinal tracts present?
As loss of fine movements of the arms and hands. After a few months these functions reappear in corticospinal tract lesions only as these functions are taken over by the rubrospinal tract
238
Which pathway plays a larger part in controlling voluntary movements: CST or RST?
Cerebrospinal tract
239
How do large pyramidal neurones from the motor cortex project and what is their function?
They project via the cerebrospinal tract and monosynaptically excite pools of agonist motoneurones.
Also branch and inhibit pools of antagonist motoneurones via interneurones
240
Which two ventromedial pathways control posture and locomotion?
The vestibulospinal and tectospinal tracts
241
What is the function of the vestibulospinal tract?
To stabilise the head and neck
242
What is the function of the tectospinal tract?
To ensure the eyes remain stable as the body moves
243
What information do the pontine and medullary reiculospinal tracts use and what is their function?
Use sensory information about balance, body position and vision to reflexly maintain balance and body position
244
What do the pontine and medullary reiculospinal tracts innervate?
Trunk and antigravity muscles in limbs
245
How can the motor cortex activate spinal motoneurons?
Directly
| Free them from reflex control by communicating with the nuclei of the ventromedial pathways
246
Where are movements planned and controlled?
In the primary motor cortex and pre-motor areas
247
How are lower motor neurons distributed in the spinal cord?
Somtatotopically- medial ones control axial/proximal limbs, lateral LMNs innervate distal limbs
248
What do medial white matter tracts from the brainstem control?
Posture, balance and orienting mechanisms
249
What do lateral white matter tracts from the cortex control?
Precise skilled voluntary movements
250
Where are the somatotopic maps of the body in the brain?
In the cortex
251
From medial to lateral, what is the order of the motor homunculus?
```
Genitals
Toes Feet Legs Hip
Trunk Neck Head
Shoulder Arm Elbow Forearm Wrist Hand Fingers (Little to thumb)
Eye Nose Face Lips
Teeth, gums and jaw
Tongue
Pharynx
```
252
How is a mental image of the body in space formed?
By somatosensory, proprioceptive and visual inputs to the posterior parietal cortex
253
Where are decisions made in the brain?
The prefrontal and parietal cortexes
254
How are decisions converted into actions?
Axons from the prefrontal and parietal cortexes converge on area 6, where signals encoding desired actions are converted into how to carry them out
255
When do decision making neurones in area 6 fire?
Before a movement
256
When do "mirror neurones" fire and where do they fire from?
They fire when self or others perform specific actions from the primary motor cortex
257
What is the function of mirror neurones?
To understand the actions of others
| May underpin emotions and empathy
258
How are command to perform precise movements encoded?
Encoded in the integrated activity of large populations of neurones
259
What kind of mechanisms control movement?
Feedback and feedforward
260
How does the brain respond to a change in body position?
Brain initiates rapid compensatory feedback messages from brainstem vestibular nuclei to spinal cord motor neurones to correct postural instability
261
What changes does the brain make before a movement begins?
Brainstem reticular formation nuclei initiate feedforward anticipatory adjustments to stabilise posture.
262
What motor symptoms does cortical damage cause?
Immediate flaccidity of contralateral muscles
263
What is initial hypotonia indicative of?
That the spinal circuits are deprived of cortical input
264
Where does the major subcortical input to area 6 come from?
The ventral lateral nucleus in the dorsal thalamus
265
Where does input to the ventral lateral nucleus come from?
The basal ganglia
266
How do the basal ganglia receive information?
Medium spiny neurones in the putamen and caudate receive excitatory cortical inputs on dendrites
267
What inputs do the putamen and caudate nuclei integrate?
Somatosensory, premotor and motor cortical inputs
268
Where do the cortical axons project to from the putamen and caudate?
The globus pallidus and the substantia nigra
269
When do the putamen and caudate nuclei fire?
Putamen- before limb and trunk movements
| Caudate- before eye movements
270
What are the component parts of the motor loop?
The cortex and the basal ganglia
271
```
Which of the following pathways are inhibitory and which excitatory?
Cortex to putamen
Putamen to globus pallidus
Globus pallidus to VLo neurones
VLo to supplementary motor area
```
Cortex to putamen- excitatory
Putamen to globus pallidus- inhibitory
Globus pallidus to VLo neurones- inhibitory
VLo to supplementary motor area- excitatory
272
How does cortical activation of the putamen boost cortical excitation?
The globus pallidus neurones are spontaneously active at rest and inhibit VLo. Cortical excitation excites putamen which inhibits the inhibitory globus pallidus, which releases cells in the VLo from inhibition so activity in VLo boosts SMA activity
273
How does the gating operation of the basal ganglia function?
A chain of neurones are arranged in a disinhibitory circuit. At rest, little cortical input so UMNs in supplementary motor are not excited. When excited, there is a lot of cortical input to the globus pallidus, which is inhibited. Thus the thalamus is disinhbited and so excites the UMNs in the SMA
274
What is the function of the direct pathway of cortical input in the basal ganglia?
Acts as a positive feedback loop signal to the SMA in the cortex and enhances initiation of movements by the SMA.
275
What is the result of globus pallidus neurones being active at rest?
They tonically inhibit the ventral lateral thalamus
276
How is inhibition of the ventral lateral thalamus released?
Through inputs from the cortex
277
What is the function of the indirect pathway of cortical input in the basal ganglia and how does it achieve this function?
Antagonises the direct route
Striatum inhibits the globus pallidus external, inhibiting the globus pallidus internal and the subthalamic nuclei. Cortex excites the subthalamic nuclei, which excites the globus pallidus internal, which excites the thalamus
278
What is the product of cerebellar lesions?
Uncoordinated and inaccurate movements
279
How is the cerebellum connected to the cortex?
Via the ventrolateral thalamus
280
What is motor learning within the cerebellum based on?
Predictions
Calculations
Experience
281
What is the receptive field?
The specific area that a receptor responds to stimuli within
282
How is the intensity of a stimulus initially encoded?
Size of the receptor potential
283
What do the receptor potentials trigger?
Firing of action potentials for long distance transmission.
284
How is the intensity of a stimulus encoded after firing of action potentials?
The frequency of the action potentials
285
How are locations of stimuli encoded in signals?
By the receptive field
286
What information is given to the brain about a stimulus?
Modality
Intensity
Location
287
What are the three different types of primary afferent fibres that mediate cutaneous sensation?
A beta
A delta
C
288
What are the characteristics of A beta fibres?
Large myelinated axons carrying touch, pressure and vibration
289
What are the characteristics of A delta fibres?
Small myelinated axons carrying cold, "fast" pain and pressure
290
What are the characteristics of C fibres?
Unmyelinated fibres carrying warmth and "slow" pain
291
What primary afferent fibres mediate proprioception?
A alpha and A beta
292
Where do afferent sensory fibres enter the spinal cord?
Via the dorsal root ganglion or the cranial nerve ganglia inside the head
293
Describe the pathway of mechanoreceptive fibres
A alpha and A beta fibres project straight up through the ipsilateral dorsal columns and synapse in the cuneate and gracile nuclei. 2nd order fibres decussate in the brainstem and project to the reticular formation, thalamus and cortex
294
Describe the pathway of thermoreceptive fibres
A delta and C fibres synapse in the dorsal horn with the 2nd order fibres crossing over the midline in the spinal cord. They project up through the contralateral spinothalamic tract to the reticular formation, thalamus and cortex
295
Describe the pathway of nociceptive fibres
A delta and C fibres synapse in the dorsal horn with the 2nd order fibres crossing over the midline in the spinal cord. They project up through the contralateral spinothalamic tract to the reticular formation, thalamus and cortex
296
What is the result of damage to the dorsal columns?
Loss of touch, vibration sense and proprioception sense below the lesion on the ipsilateral side
297
What is the result of damage to the anterolateral qudrant?
Loss of nociceptive and temperature below the lesion on the contralateral side
298
Where does sensory information terminate?
In the somatosensory cortex of the postcentral gyrus
299
From medial to lateral, what is the order of the sensory gyrus?
```
Genitals
Toes Foot Leg Hip Trunk
Neck Head
Shoulders Arm Elbow Forearm Wrist Hand Fingers (from little to thumb)
Eye Nose Face Lips Gum/Jaw
Tongue Pharynx Intraabdominal
```
300
What does processing in sensory pathways involve?
Adaptation
Convergence
Lateral inhibition
Perception
301
How does adaptation aid processing in sensory pathways?
Avoids excessive repeat firing of action potentials in response to the same stimuli
302
How does convergence aid processing in sensory pathways?
Saves on neurones (but reduces acuity)
303
How does lateral inhibition aid processing in sensory pathways?
Activation of one sensory input causes synaptic inhibition of its neighbours giving a better definition of the boundaries of a stimulus and cleans up sensory information
304
What can activate signal transduction in nociceptors?
Low pH
Heat
Local chemical mediators
305
Describe the pathway of signal transduction in nociceptors
Activity in A alpha/beta fibres activates inhibitory interneurones, releasing opioid peptides (endorphins) that inhibit transmitter release from A delta or C fibres- closing the gate. Same interneurones also activated by descending pathways from the peri-aqueductal grey matter and the nucleus raphe magnus
306
How do NSAIDs give analgesia?
Prostaglandins sensitise the nociceptors to bradykinin by inhibiting cyclo-oxygenase which converts arachidonic acid to prostaglandins
307
How do local anaesthetics give analgesia?
They block the sodium action potential and therefore all axonal transmission
308
How do opiates give analgesia?
Reduce the sensitivity of nociceptors, block the release of transmitters from the dorsal horn and activate descending inhibitory pathways
309
What does cognition relate to?
Behaviour that deals with thought processing
310
How does learning occur?
Changes in neuronal plasticity or the ability of the central neurons to adapt their neuronal connections in responses to learning experiences
311
What is the role of association areas and where are they found?
To integrate information from multiple sources
| Found in the cerebrum
312
What parts of the brain are involved in learning and memory and what are the specific roles of each?
Hippocampus- forms memories
Cortex- store memories
Thalamus- searches and accesses memories
Limbic system- gives events emotional significance
313
What are the component parts of the limbic system?
Hypothalamus
Hippocampus
Cingulate gyrus
Amygdala
314
What is the limbic system responsible for?
Instinctive behaviours- fighting, fleeing, feeding and mating
Emotive behaviours
315
What drives emotive behaviours?
Seeking reward or avoiding punishment
316
How does bilateral hippocampal damage affect memory?
Patients have immediate, short term and intact long-term memory but are incapable of forming new long-term memories
317
What are the subsets of memory and what are the characteristics of each?
Immediate/sensory memory- hols memory in mind for a few seconds
Short-term memory- memory lasting seconds to hours
Intermediate long-term memory- memory lasting from hours to weeks, associated with chemical adaptation of the presynaptic terminal
Long-term memory- can be lifelong, associated with structural changes in synaptic connections
318
Do visual or auditory memories decay faster?
Visual memories decay faster
319
How are short-term memories formed?
Electrical phenomenon depending on maintained excitation from reverberating circuits
320
What are the two types of amnesia and how is each characterised?
Anterograde- can't form new memories
| Retrograde- can't access old memories
321
How are intermediate long-term memories formed?
Increasing calcium ion entry to presynaptic terminals increases neurotransmitter release
322
How are long-term memories formed?
Structural changes at the synapses as follows:
Increase in neurotransmitter release sites on presynaptic membrane
Increase in number of neurotransmitter vesicles stored and released
Increase in number of presynaptic terminals
323
What is often observed during the synaptic changes involved with long-term memory?
Increased amplitude in graded membrane potential in the post-synaptic cell
324
What is the increased amplitude in graded membrane potential in the post-synaptic cell known as and what is its function?
Potentiation- forms the basis of learnind and memory
325
What are the two kinds of long-term memory and what are the characteristics of each?
Declarative/explicit memory- abstract memory for events and words, relies heavily on hippocampus
Procedural/reflexive/implicit memory- acquired through repetition, involves motor memory and rules based learning. Based mainly in cerebellum
326
How is short-term memory converted to long-term memory?
Through consolidation- selective strengthening of synaptic connections through repetition. Takes hours-days, during which time memory is vulnerable to being wiped out
327
What does memory recall depend on?
The significance of the event
328
What parts of the brain assess the significance of events and when does this occur?
The frontal cortex and its association with the limbic system
Occurs during short term memory
329
Where are new memories stored?
In the sensory and association areas of the cortex
330
How are new memories stored?
Coding results in new memories being stored near existing memories that the brain deems similar
331
What parts of the brain make up the Papez circuit?
Hippocampus
Mammillary bodies
Anterior thalamus
Cingulate gyrus
332
What occurs if the brain deems an experience as useful?
The frontal cortex gates the Papez circuit, with reverberating activity occuring between the Papez circuit, the frontal cortex and the sensory and association areas until consolidation is complete
333
What is the result of different components of the same memory being laid down in different parts of the cortex?
Recall can be evoked by multiple associations
