Orientation Week Flashcards
1
Q
How does information arrive at the cell body of an excitable cell?
A
Via dendrites
2
Q
What happens to the information that arrives at the cell body of an excitable cell?
A
Its assimilated and processed
3
Q
What happens to the processed information in the cell body?
A
Digitised into action potentials which are transmitted along the axon
4
Q
The larger the diameter of the axon, the ______ the resistance is. And so larger axons have faster _______ charge movement?
A
- Lower
- Passive
5
Q
The more surface area there is on an axon, the _____ its capacity to store charge across its membrane?
A
Higher
6
Q
What is the fastest speed a libra can carry a signal at?
A
250 mph
7
Q
What does the voltage dependent Na channel help to set up?
A
Refractory period of action potential
8
Q
Where are Schwann cells found?
A
Peripheral nervous system
9
Q
Where are Oligodendrocytes found?
A
Central nervous system
10
Q
Describe local currents in a myelinated axon?
A
Saltatory (jumping) conduction
11
Q
In a myelinated axon where is the only place an action potential can occur?
A
Node of Ranvier
12
Q
What approximate size is the synaptic gap?
A
20nm
13
Q
What helps the binding of the vesicle and cell membrane at the bouton?
A
SNARE proteins
14
Q
What catalyses membrane fusion at the bouton?
A
Ca2+-bound synaptotagmin
15
Q
What 3 things can happen to inactivate neurotransmitters?
A
- Diffusion
- Re-uptake
- Enzymal inactivation
16
Q
What are the 2 different types of receptors?
A
- Ionotropic (directly gate ion flow)
2. Metabotropic (indirectly gate ion flow or active other pathways)
17
Q
How do most receptors code the duration and magnitude of external signals?
A
Using a generator potential
18
Q
What does stronger external signals sent to receptors result in?
A
Higher frequency of action potentials in the axon
19
Q
What are stretch reflexes mediated by?
A
Sense organs within muscles known as muscle spindles
20
Q
Describe the 3 parts of the spindle fibre mechanism?
A
- Contractile (gamma MN’s) & elastic portion
- Less elastic/contractive sensory portion
- Contractile (gamma MN’s) & elastic portion
21
Q
In peripheral spinal nerves what does rootles converge to become?
A
Roots
22
Q
In peripheral spinal nerves what does the ventral & dorsal roots converge to become?
A
Spinal nerve (mixed, motor & sensory)
23
Q
Is a ventral root sensory or motor?
A
Motor (efferent)
24
Q
In peripheral spinal nerves what does the spinal nerve divide into?
A
Ventral & dorsal rami (mixed, motor & sensory nerve fibres)
25
What are the 5 steps to withdrawal when a lit match is help to a bare foot?
1. Aδ & C fibres in skin detect noxious stimulus
2. Aδ & C fibres synapse with inhibitor interneurons
3. Aδ & C synapse with α-motor neurons for flexor muscles
4. α-motor neurons to the extensor muscle are inhibited
5. α-motor neurons to the flexor muscles are excited & flexors contract, resulting in withdrawal
26
List the 4 different neurons in the spinal nerve from posterior to anterior?
1. Somatic sensory neuron
2. Visceral sensory neuron
3. Visceral motor neuron
4. Somatic motor neuron
27
What resides in the grey matter of the spinal cord?
Cell bodies
28
What resides in the white matter of the spinal cord?
Axons
29
What resides in the ventral horn (grey matter) of the spinal cord?
Somatic motor cell bodies
30
What resides in the lateral horn (T1-L2, grey matter) of the spinal cord?
Visceral cell bodies
31
What resides in the dorsal horn (grey matter) of the spinal cord?
Somatic sensory nerves/interneurons (cell bodies in dorsal root ganglion)
32
What is the terminology for the collection of nerve fibres (white matter) in PNS & spinal cord?
- Fascicle/bundle (nerve)
| - Tract
33
What is the terminology for the collection of cell bodies (grey matter) in PNS & spinal cord?
- Ganglia
| - Horns
34
What are the different vascular supplies of the spinal cord?
- 2 posterior spinal arteries (with veins)
- 1 anterior spinal artery (with veins)
- Segmental medullary arteries "supporting" the spinal arteries
- Internal vertebral venous plexus (extradural/epidural space)
35
Whats the clinical problem with the spinal cord venous system?
They do not have valves & pressure gradients permit blood flow which increases infection & metastasis spread
36
Whats the role of the anterior white commissure in the spinal cord?
- Pain & temp fibres cross
| - Anterior corticospinal tract fibres cross
37
Whats the role of the fasciculus gracilis in the spinal cord?
Sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
38
Whats the role of the fascicles cuneatus in the spinal cord?
Sensory (fine touch, vibration, proprioception) from ipsilateral upper limb
39
Whats the role of spinocerebellar tract in the spinal cord?
Proprioception from limbs to cerebellum
40
Whats the role of the lateral corticospinal tract in the spinal cord?
Motor to ipsilateral anterior horn
41
Whats the role of the spinothalamic tract in the spinal cord?
Pain & temp from contralateral side of the body
42
Whats the role of the anterior corticospinal tract in the spinal cord?
Motor to ipsilateral & contralateral anterior horn
43
What do peripheral nerves do?
Link spinal cord & brain to peripheral tissue
44
What is the arterial anastomosis in the spinal cord?
Extra & intervertebral arteries
45
What is the main arterial supply in the brain?
Intracranial arteries
46
What is the difference between the venous system in the spinal cord & in the brain?
- Spinal cord: venous plexus
| - Brain: venous sinuses
47
What sign/s does a spinal cord pathology cause?
Lower motor neuron & Upper motor neuron signs
48
What sign/s does a intracranial pathology cause?
Only Upper motor neuron signs
49
Describe the location of an Upper motor neuron?
Above ventral horn/cranial nuclei, brain, brainstem & spinal cord
50
Describe the location of a lower motor neuron?
Ventral horn & below. Cranial or spinal nerve, roots, rami, plexus
51
What are typical signs of upper motor neuron lesions?
- Increased muscle tone (spasticity)
- Muscle weakness, but no wasting
- Hyperreflexia
- No fasciculations
- Extensor plantar response (+ babinski)
- Clonus
52
What are typical signs of lower motor neuron lesions?
- Decreased muscle tone
- Muscle weakness & wasting (atrophy)
- Hyporeflexia/areflexia
- Fasciculations
- No pathological plantar response
53
What does the Central Nervous system do?
Processes/integrates/learns and sends information
54
What are neurons?
Separate cells that communicate by releasing chemicals by secretion at the ends of cell processes
55
What is the purpose of microtubules in the axon?
Vesicle transport
56
Describe the different parts of an axon from top to bottom?
- Dendrites
- Cell body
- Nucleus (+ nucleolus)
- Axon hillock
- Axon
57
What does repeated stimulation of neuronal pathways modify?
Function of dendritic spines (long term potentiation)
58
Where does processing occur in the brain & spinal cord?
Grey matter
59
Where does communication occur in the brain & spinal cord?
White matter
60
What is horizontal plane also known as in imaging (CT & MRI)?
Axial
61
What makes up the central nervous system?
Brain & Spinal cord
62
What does diencephalon stand for?
"Between brain"
63
What are the 4 lobes of the brain?
1. Frontal
2. Parietal
3. Occipital
4. Temporal
64
What lies on the floor of the lateral fissure of the brain?
Insula
65
What does the central sulcus in the brain separate?
Precentral gyrus & postcentral gyrus
66
What is another name for cerebral hemispheres?
Telencephalon
67
What lies within the diencephalon?
Thalamus & Hypothalamus etc.
68
What are the 3 parts of the brain stem?
1. Midbrain
2. Pons
3. Medulla
69
What are the 5 fluid filled ventricles inside the brain?
1. Lateral (x2)
2. Interventricular foramen
3. Third (head)
4. Fourth (body)
5. Cerebral aqueduct (neck)
70
What lies directly above the corpus callosum?
Cingulate gyrus
71
What is the largest bundle of white matter?
Corpus callosum
72
How many cranial nerves are there?
12 (most exit ventrally)
73
What 2 joints in the skull allow some form of movement ?
- Temporomandibular joint
| - Atlanto-occipital joint
74
What 3 different types of bones make up the skull?
1. Flat
2. Irregular
3. Pneumatised
75
What is a Pneumatised bone?
Bones with air spaces such as the frontal, temporal, sphenoid & ethmoid
76
What are the 4 functions of the skull?
1. Protection
2. Attachment for muscles
3. Framework for the head
4. Gives our identity
77
What are the 3 divisions of the skull?
1. Neurocranium
2. Viscerocranium (facial skeleton)
3. Mandible
78
How many bones are there in an adult skull?
22
79
What is the neurocranium?
Bony case of brain including cranial meninges with a dome-like roof (calvaria) & floor (cranial base)
80
What is the viscerocranium?
Anterior part of the cranium that consists of bones surrounding the oral cavity, nasal cavity & most of the orbit
81
What 6 bones make up the Neurocranium?
| 4 singular midline & 2 bilateral paired bones
1. Frontal
2. Parietal (x2)
3. Occipital
4. Sphenoid
5. Temporal (x2)
6. Ethmoid
82
What 9 bones make up the Viscerocranium?
| 15 irregular, 3 singular midline & 6 bilateral paired bones
1. Ethmoid
2. Palatine (x2)
3. Lacrimal (x2)
4. Nasal (x2)
5. Zygomatic (x2)
6. Vomer
7. Inferior nasal concha (x2)
8. Maxilla (x2)
9. Mandible
83
What are the 3 main features of the Viscerocranium?
1. Zygomatic arch
2. Mandible
3. Infratemporal fossa
84
What are the 4 main features of the Neurocranium?
1. External acoustic meatus
2. Styloid process
3. Mastoid process
4. Temporal fossa
85
What are the borders of the temporal fossa?
1. Sup & Post- sup & inf temporal lines
2. Ant- frontal process of zygomatic bone
3. Inf- infratemporal crest deep to zygomatic arch
4. Floor- pterion
86
What is the Pterion?
H-shaped junction of sutures (frontal, parietal, temporal, sphenoid) which is structurally weak & vulnerable to injury
87
What does the Pterion overlie?
Anterior branch of middle meningeal artery
88
What can trauma to the Pterion lead to?
Extradural/epidural haematoma
89
What are the 4 flat bones of the calavaria fused by?
Coronal, sagittal & lambdoid sutures
90
Describe Fontanelles?
- Space between the bones of the skull in infant/fetus, where ossification is not complete & sutures not fully formed
- Main one is between the frontal & parietal bones (anterior fontanelle)
91
When do corners of frontal & parietal bones fuse?
By 18months
92
Describe the suture joint?
- Fibrous
| - Limited or no movement (synarthrosis)
93
What 3 foramen's in the anterior skull are involved in the divisions of the trigeminal nerve (CN V)?
1. Supra-orbital notch
2. Infra-orbital foramen
3. Mental foramen
94
What are the 8 important craniometric points from posterior to anterior of the skull?
1. Asterion
2. Inion (protrude)
3. Lambda
4. Vertex
5. Bregma
6. Pterion
7. Glabella (protrude)
8. Nasion
95
What are the 7 foramen's in the inferior external view of the cranial base?
1. Foramen magnum
2. Jugular foramen
3. Carotid canal
4. Foramen lacerum
5. Foramen ovale
6. Foramen spinosum
7. Hypoglossal canal
96
What are the borders of the Infratemporal fossa?
- Lat: ramus of mandible
- Med: lat pterygoid plate of sphenoid
- Ant: post maxilla
- Post: Tympanic plate, mastoid & styloid processes
- Sup: infratemporal crest of sphenoid
- Inf: angle of mandible
97
What is the shallowest part of the cranial base?
Anterior cranial fossa
98
How do olfactory bulbs (CN I) receive nerve fibres from the nasal cavity?
Foramina of cribriform plate (olfaction)
99
How can cribriform fractures present?
CSF rhinorrhoea
100
What 3 bones make up the anterior cranial fossa?
1. Frontal
2. Ethmoid
3. Sphenoid
101
What 2 bones make up the middle cranial fossa?
1. Sphenoid
| 2. Temporal
102
Where does the pituitary gland lie?
Hypophyseal (pituitary) fossa
103
What 3 bones make up the posterior cranial fossa?
1. Sphenoid
2. Occipital
3. Temporal
104
Describe the temporomandibular joint?
- Glenoid fossa of temporal & condylar process of mandible
- Synovial joint
- Fibrocartilage cover
105
Whats the most common clinical problem with the temporomandibular joint?
Anterior dislocation
106
What are the 2 ligaments in the temporomandibular joint?
1. Sphenomandibular ligament
| 2. Lateral ligament (prevents post dislocation)
107
When is the temporomandibular most unstable?
During depression
108
What are the 4 assessment tools for cognitive assessment?
1. 4AT
2. Mini Mental state examination (MMSE)
3. Montreal cognitive assessment (MOCA)
4. Addenbrookes cognitive examination (ACE III)
109
What is the 4 "A"s test?
Initial assessment for delirium & severe cognitive impairment
110
What are the 4 "A"s?
1. Alertness
2. AMT 4
3. Attention
4. Acute change or fluctuating course
111
What is delirium?
Mental confusion that can happen if someone becomes medically unwell (common 1:10 hospital patients)
112
Describe the Montreal Cognitive Assessment (MoCA)?
- Better identifying mild levels of impairment
| - Less bias ethnicity/age/education
113
What are the 5 cognitive domains of ACE II test?
1. Attention
2. Memory
3. Verbal fluency
4. Language
5. Visuospatial abilities
114
What is confabulation?
Presenting false information with no intent to deceive
115
Give 2 illnesses in which confabulation occurs?
1. Korsakoff's syndrome
| 2. Alzheimer's dementia
116
What are the 7 skills in neuro history taking?
1. Clarifying
2. Being curious
3. Sifting & sorting
4. Analysing info
5. Recognising value of negatives
6. Observing how things are said, not just listening
7. Succinctly documenting story
117
What are some questions you can ask a patient when taking a neuro history?
- Have you noticed any changes in your writing?
- Any differences in the way you walk?
- Increased difficulty doing up buttons?
118
How common are medically unexplained symptoms in neuro history taking?
30%
119
What are 6 common neurological presentations?
1. Altered cognitive ability
2. Fits, faints, funny turns
3. Headache
4. Weakness or movement disorders
5. Numbness or sensory disorders
6. Visual impairments
120
What are some questions you could ask a patient for them to describe the most recent episode?
- What was happening before?
- What factors might have lowered the seizure threshold?
- What position was the patient in?
- Any prodromal symptoms?
- What happened during the episode and after?
121
What can focal weakness suggest?
Neurological origin
122
What are 2 examples of proximal muscle weakness?
- Rising from sitting
| - Drying hair
123
What are 2 examples of distal muscle weakness?
- Standing on tip toes
| - Fine finger movements
124
Give an example of an illness in which there is too little movement?
Parkinson's disease (stiffness)
125
Give an example of an illness in which there is too much movement?
- Chorea ("fidgety jerks")
| - Choreoathetosis (decreased tone, rapid)
126
What does ADLs stand for?
Activities of Daily Living
127
When should a child be able to walk & talk?
1 to walk, 2 to talk
128
What systems enquiry would you go through in a neuro history?
- Psychological (depressed)
- ANS (bowel, bladder, sexual, light headaches)
- Infection
129
What are 6 cranial nerve screening questions?
1. Change in your sense of smell?
2. Vision? Double vision?
3. Dry eyes? Dry mouth? Change in taste?
4. Hearing? Dizziness?
5. Change in voice?
6. Articulation?
130
Is it ectoderm, endoderm or mesoderm which makes the CNS?
Ectoderm
131
Describe the steps of the early development of the CNS?
- The plate will make a tube (neurulation)
- Day 19+ midline groove apparent
- Neurulation induced by the bar shaped tissue (notochord)
132
What happens to the CNS development in 20-21days (end of 3rd week)?
Cells on plate edge thicken forming folds and a groove
133
What happens to the CNS development into the 4th week?
Plate edges roll over and the cells fuse to make a tunnel
134
When does the rostral neuropore close?
25 days
135
When does the caudal neuropore close?
27 days
136
Describe Anencephaly?
- Failure of rostral neuropore to close
- Born without forebrain
- Unreactive to light & sound
- Stillborn
- May have respiration & respond to touch & sound
137
What are some risk factors for neural tube defects?
- Previous anencephaly
- Diabetes
- Epilepsy drugs
138
Give a birth defect caused by failure of caudal neuropore to close?
Spina bifida
139
What maternal supplement can reduce risk of neural tube defect?
Folate
140
What 2 things are associated with Spina bifida?
1. Displaced cerebellum
| 2. Hydrocephalus
141
What 3 types of diseases can Alpha fetoprotein (AFP) detect?
- Neural tube defects
- Some cancers
- Liver disease
142
What neural tube swelling (vesicle) forms the forebrain?
Prosencephalon
143
What neural tube swelling (vesicle) forms the midbrain?
Mesencephalon
144
What neural tube swelling (vesicle) forms the hindbrain?
Rhombencephalon
145
Describe the growth of the forebrain?
Grows 2 lateral expansions connected to a central slit like space
146
Describe the growth of the midbrain?
Slower than forebrain, remains as single central tube
147
Describe the growth of the hindbrain?
Develops into (rest of) brainstem & cerebellum with a central ventricle expanding
148
What are the different lumens formed in the fore, mid and hindbrain?
- FOREBRAIN: 2 lateral ventricles, 3rd ventricle
- MIDBRAIN: cerebral aqueduct
- HINDBRAIN: 4th ventricle
149
Describe the walls of the forebrain?
- Telencephalon (endbrain) cerebral hemispheres x2
| - Diencephalon ("between brain") includes thalamus
150
Describe the walls of the hindbrain?
- Metencephalon (pons, cerebellum)
| - Myelencephalon (medulla)
151
What are the different grooves in the brain?
- Lateral fissure
- Central sulcus
- Pre-occipital notch
- Parieto-occipital sulcus
152
Where does the insula lie?
Floor of the lateral fissure
153
What is the purpose of the gyri in the brain?
Increase surface & volume of grey matter
154
What 4 structures lie within the C-shaped lateral ventricles?
1. Corpus callosum
2. Fornix
3. Interventricular foramen (fluid filled)
4. Hippocampus
155
What is the purpose of the Hippocampus?
Memory
156
What is the purpose of the fornix?
Connects hippocampus with anterior structures
157
What does the internal capsule do?
Basal ganglia split by ascending & descending bundle (lies between caudate nucleus & lentiform nucleus)
158
Where is the sensory grey matter before & after the 4th ventricle forms?
- BEFORE: in dorsal position
| - AFTER: more lateral
159
Where does the cerebellum develop?
Dorsal wall of neural tube
160
How many cranial nerves are there?
12 (most exit ventrally)
161
What does the caudal neural tube become?
Spinal cord
162
What are the 3 layers of the caudal neural tube?
1. VENTRICULAR: progenitor cells- neurons/glia
2. MANTLE: neutron bodies/glia
3. MARGINAL: processes of neurons
163
What are the 3 regions of the developing spinal cord?
1. Sulcus limitans
2. Alar lamina (posterior basal lamina)
3. Basal lamina (anterior basal lamina)
164
How does the CNS connect to the PNS?
- Ingrowth of neurites from DRG forms dorsal root
| - Outgrowth from neurons motor grey forms ventral root
165
What induces the neural plate?
Notochord
166
What does Bone morphogenetic protein (BMP) do?
Inhibits neural ectoderm, promoting skin
167
What 3 things blocks bone morphogenetic protein?
1. Noggin
2. Chordin
3. Follistatin
(all produced in the notochord)
168
Where do the neural crest cells go?
Migrate from the neural tube epithelium and into mesoderm
169
What 3 things can neural crest cells produce?
1. Skull (bone)
2. Sensory & ANS
3. Pigment cells
170
What are 2 autosomal dominant syndromes caused by a defect in neural crest development?
1. Waardenburg's syndrome
| 2. Treacher Collins syndrome
171
Describe Waardenburg's syndrome?
- Some have Pax-3 gene deletion
- Pigment abnormalities
- Deafness
- Constipation
- Heterochromia of eyes
- Telecanthus
172
Describe Treacher Collins syndrome?
- Treacle (TCOF1 gene) defect
- Failure of formation/apoptosis of neural crest cells
- Abnormal eye shape
- Micrognathia
- Conductive hearing loss
- Underdeveloped zygoma
- Malformed ears
173
What are the 3 stages to corporal senses?
1. Detection of a stimulus
2. Transmission of stimulus information to brain
3. Recognition (conscious/unconscious) of nature, location, intensity & duration of stimulus
174
What 4 things do the cutaneous receptors detect?
1. Temperature
2. Nociception
3. Pressure
4. Vibration
175
What are the 5 special senses?
1. Sight
2. Hearing
3. Taste
4. Balance & movement
5. Olfaction
176
What happens to the degree of myelination when the speed of saltatory transmission increases?
Myelination Increases
177
Describe Free nerve endings (specialised cutaneous receptor)?
- C & Aδ fibres
- Detect Pain
- All skin types
- Slowly adapting with high activation threshold
178
Describe Merkel's disks (specialised cutaneous receptor)?
- Aβ fibres
- Non-encapsulated
- Static touch & pressure
- All skin types
- Slowly adapting with low activation threshold
179
Describe Meissner's corpuscles (specialised cutaneous receptor)?
- Aβ fibres
- Encapsulated
- Changes in touch & pressure
- Glabrous skin
- Rapidly adapting with low activation threshold
180
Describe Pacini's corpuscles (specialised cutaneous receptor)?
- Aβ fibres
- Encapsulated
- Vibration
- All skin types
- Rapidly adapting with low activation threshold
181
Describe Ruffini corpuscles (hair follicle receptor)?
- Entangled in collagen
- Skin stretch & direction
- Slow adaptation & widely distributed
182
What is the purpose of muscle spindles?
- Measure changes in length of muscle
| - Regulates length via gamma reflex loop
183
How does the gamma reflex loop work in muscle spindles?
When intrafusal fibres are stretched (length increases) afferent fibres stimulate contraction of extrafusal fibres via alpha motor neurons
184
What is the purpose of the golgi tendon organs?
- Detect tension in muscle via type 1b sensory nerve endings which innervate a collagen matrix in the tendon
- Tendon stretch --> ending depolarise & send afferent info to CNS
185
What pattern do most conscious sensory tracts follow?
General somatosensory system (1st, 2nd, 3rd order neurons)
186
What is the arrangement of the primary somatosensory cortex?
Topographical
187
What happens to the sensory information on route to the somatosensory cortex?
Passes through the thalamus
188
What is the purpose of the thalamus?
Has reciprocal connections (peduncles) to all cortical regions & can relay information, receive feedback & modulate cortical activity
189
What does the grey matter in the spinal cord divide into?
Lamina (rexed) and these represent targets for afferent information
190
What does the white matter in the spinal cord divide into?
Tracts of axons carrying typified information
191
What does fasciculus gracilis carry?
Information from lower body extremities
192
What does fasciculus cuneatus carry?
Information from the upper body extremities
193
What does the dorsal & ventral spinocerebellar tracts carry?
Proprioceptive information from muscle spindles (dorsal) & golgi organs (ventral)
194
What are the 4 principle ascending pathway systems in the spinal cord?
1. Dorsal column medial lemniscus pathway
2. Anterolateral pathways
3. Spinocerebellar pathway
4, Trigeminal pathway (thalamus & brainstem)
195
Describe the dorsal column medial lemniscal pathway?
- Large diameter fast Aβ fibres
- 1st order neuron ascend ipsilaterally in fasciculus gracilis & cuneatus & synapse with 2nd order neuron at brainstem nuclei
- Then decussate, form part of medial lemniscus & project to ventral posterolateral lobe of thalamus --> cortex
196
What does lateral inhibition rely on?
Reciprocal inhibition between 2 adjacent neurons where extent of inhibition from each 1 is linked to stimulus point on neuronal receptive field overlap
197
What can lesions of gracile fasciculus cause and why?
Gait ataxia as brain is deprived of information about position of the feet
198
What can lesions of the cervical cord cause?
Upper extremity ataxia and often patient is able to compensate with vision minimising sensory ataxia
199
What is a classic sign of gait/sensory ataxia?
"Stamp & Stick"- Patient stamps down feet to enhance sensory input & maintains broad based stance
200
What can dorsal column disease also cause?
Paraesthesia (tingling, numbness, crawling, deadness) in distal parts of extremities
201
How can dorsal column function impairment be concluded?
Testing ability of proprioception
202
Proprioception is NOT lost until about ___ of posterior column axons have ceased to function?
75%
203
What 3 diseases can Romberg's sign show?
1. Dorsal column disease/lesion
2. Vestibular disease
3. Cerebellar disorders
204
What are the dorsal column medial lemniscal pathways 2 cortical functions?
1. Determine the shape by fine discriminating touch & proprioception of an object without sight
2. Determine texture by vibration & slip receptors of an object without sight
205
What is required for the dorsal column medial lemniscal cortical functions?
Somatosensory association area in parietal lobe functioning normally
206
What can lesions of one of the somatosensory associated cortex cause?
Amorphosynthesis- unable to recognise complex object by feel on the opposite side to the lesion
207
What are the 2 principle cell types in nervous tissue?
1. Neurons
| 2. Supporting cells (neuroglia)
208
What is the structural & functional unit of the nervous system?
Neuron
209
What are the 3 different types of neurons?
1. Multipolar
2. (Pseudo)unipolar
3. Bilpolar
210
What is Nissl stain used for?
- Stains rough endoplasmic reticulum & polyribosomes
| - Important in protein synthesis
211
Where is there a lack of Nissl substance usually when dying neuron?
Axon
212
List the 6 layers of the cerebral cortex (neocortex) from top to bottom?
1. Molecular
2. External granular
3. External pyramidal
4. Internal granular
5. Internal pyramidal
6. Multiform
213
Are pyramidal & granule neurons unique to the cortex?
NO
214
List the 3 layers of the cerebellar cortex from top to bottom?
1. Molecular
2. Purkinje
3. Granule
215
What cells lie within each (3 layers) layer of the cerebellar cortex?
1. Molecular: basket cells, stellate cells, fibres
2. Purkinje: Purkinje cells
3. Granule: granule cells, golgi cells
216
Describe the Purkinje neurons in the cerebellum?
- Multipolar
- Largest cell in cerebellum
- Pear-shaped cell bodies
- Dendritic tree expands into molecular layer
- Receive afferent info from other areas of CNS
217
What is the function of Neuroglia cells?
Metabolism & support of neurons
218
What are the neuroglia cells in the CNS?
- Astrocytes
- Oligodendroglia
- Ependymal cells
- Microglia
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What are the neuroglia cells in the PNS?
- Schwann cells
| - Satellite cells
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What are the 4 different types & location of Astrocytes in the CNS?
1. Fibrous (white matter)
2. Protoplasmic (grey matter)
3. Müller glia (retina)
4. Radial glia (specialised)
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What size of solutes are not allowed to pass the blood-brain barrier?
>500daltons MW
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What is the integrity of the blood-brain barrier highly dependent on?
Astrocyte "end feet"
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What are Ependymal cells?
Ciliated cuboidal epithelial cells which line ventricle as part of plexus & secrete CSF
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What is Cerebrospinal fluid (CSF)?
Clear, cell-free fluid produced in choroid plexus
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What is the purpose of Microglia?
- Immune function within CNS
- Phagocytose debris in response to injury
- Release cytokines
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What are 2 diseases which can affect oligodendrocytes in the CNS?
1. Multiple sclerosis
| 2. Leukodystrophies
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What % of lipid does myelin consist of?
~80%
228
Describe the action potentials in unmyelinated axons?
"Continuous conduction" of action potentials due to passive current flow (low conduction)
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What are examples of unmyelinated axons?
Sensory fibres carrying pain, temp, itch
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What are individual ganglion cells surrounded by?
Layer of flattened satellite (fibroblast) cells
231
What are ganglia?
Aggregations of nerve cells outside the CNS
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Describe the arrangement of Peripheral nerve?
Numerous nerve fibres collected into bundles
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Peripheral nerve bundles surrounded by thick sheath of _______, each bundle then surrounded by _______, each nerve fibre surrounded by _______?
1. Epineurium
2. Perineurium
3. Endoneurium
234
Describe the histology of cell bodies of multipolar motor neurons?
- Large
- In ventral horn of spinal cord
- Pale staining nucleus & prominent nucleolus & nissl bodies
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Can peripheral nerve be repaired after injury?
YES- large degree of regeneration due to intrinsic capabilities
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Can CNS axons be repaired after injury?
NO
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What process exists in both CNS & PNS following trauma?
Wallerian degeneration
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What is Wallerian degeneration?
- Clears debris & lays foundation for regrowing nerve fibres
- Not efficient in CNS resulting in failed repair
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Describe the 5 steps of Wallerian Degeneratin in the PNS?
1. Schwann cells become reactive, proliferate due to injury
2. Macrophages (& Schwann) phagocytose debris
3. Schwann cells express/secrete growth factors & form Bands of Büngner
4. Nerve fibres grow towards & through the Bands
5. Nerve fibres reconnect with end organs & are remyelinated by Schwann cells
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Describe the 5 stops of Wallerian Degeneration in the CNS?
1. Microglia & astrocytes become active due to injury
2. Inflammation
3. Macrophages remove debris (not completely)
4. Glial scar formed by reactive astrocytes
5. Regeneration fails as growth of transected axons is inhibited by persistent myelin debris & glial scar
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What happens to Reactive astrocytes during CNS Wallerian Degeneration after injury?
- Become hypertrophic
- Express/secrete inhibitory molecules like chondroitin sulfate proteoglycans (CSPGs)
- Increase expression of normal molecules (GFAP)
- Resulting in glial scar
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What does Glial scar + Myelin debris equal?
Area which growing axons cannot pass through
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What is the histological end result of failed CNS regeneration?
Growing axons turning away from the lesion &/or having reactive "end bulbs" (swellings of accumulated organelles) at their tips
244
What do oligodendrocytes in the CNS do during repair?
Contribute to myelin debris & failed repair
245
Where are glial cells of CNS & PNS segregated?
Glial limiting membrane at the dorsal root entry zone
