Neuro Flashcards
1
Q
what part of the brain encompasses the rhombencephalon
A
hindbrain = medulla oblongata/pons/cerebellum
2
Q
what is white matter
A
a collection of nerve fibres with few/no neural cell bodies = forms deeper parts of brain = myelinated
3
Q
what is grey matter
A
aggregations of neuronal cell bodies and local processes = forms surface of cerebral hemispheres = non-myelinated
4
Q
what is the neuropil
A
space between neuronal cell bodies in grey matter
5
Q
which parietal lobe is normally dominant
A
left
6
Q
where is the primary sensory area located
A
post central gyrus
7
Q
what is the parietal lobe responsible for (4)
A
perception
interpretation of sensory info
complex, meaningful motor response
language
8
Q
what is the non dominant parietal lobe responsible for
A
visuospatial functions
9
Q
what is the frontal lobe responsible for (5)
A
higher intellect mood personality social conduct language
10
Q
what is the temporal lobe responsible for (4)
A
short term memory
equilibrium
emotion
primary auditory cortex
11
Q
what is wernicke’s area responsible for
A
understanding spoken word
12
Q
what is the occipital lobe responsible for
A
vision = contains primary visual/visual association cortex
13
Q
what is the limbic system involved in (4)
A
emotion
memory
behavior
olfaction (smell)
14
Q
name 2 systems that the limbic system influences
A
endocrine system
autonomic NS
15
Q
name the 3 layers of the cranial meninges
A
dura mater
arachnoid mater
pia mater
16
Q
what are the 2 layers of the dura mater
A
inner meningeal layer
outer endosteal layer
17
Q
what are the falx cerebri
A
the dura mater between 2 cerebral hemispheres
18
Q
what are the falx cerebelli
A
the dura mater between the cerebellar lobes
19
Q
what are the sinuses
A
non-fused spaces between 2 layers of dura mater
20
Q
what does the subarachnoid space contain
A
CSF
blood vessels
21
Q
what are the zonula occludentes
A
tight junctions linking cells of the arachnoid mater together
22
Q
what binds the pia mater to the brain
A
astrocytes
23
Q
where is the motor cortex located
A
posterior precentral gyrus
24
Q
where is the foramen of Lushka
A
lateral sides of 4th ventricle = pontine cisterna
25
where is the foramen of Magendie
medial side of 4th ventricle = cerebellomedullary cisterna
26
where do external cerebral veins drain
into sagittal sinus and down into jugular vein
27
what structures does the cavernous sinus contain
```
O TOM CAT
oculomotor nerve
trigeminal - opthalmic, maxillary
internal Carotid artery
abducens nerve
trochlea nerve
```
28
what is CSF formed by
choroid plexus by ependymal cells
29
where is CSF reabsorbed
arachnoid villi mainly along sagittal sinus
30
what are arachnoid granulations
arachnoid villi become calcified and form granules
31
what is the role of CSF
1. cushioning/protection
2. removes toxins
3. creates CSF/blood barrier at choroid plexus to prevent contact of external things with ventricles
4. buoyancy = suspends brain
32
where does the CSF lie in the brain
between pia and arachnoid mater
33
what is Broca's area responsible for
language production
34
what is the corpus callosum
large bundle of white matter connecting 2 cerebral hemispheres
35
what is the fornix
white matter connecting hippocampus with diencephalon and precommisural septum
36
what 3 things make up the midbrain
tegmentum
tectum
cerebral peduncles
37
what are the superior colliculi associated with
visal system
38
what are the inferior colliculi associated with
auditory system
39
where are the colliculi located
directly inferior to the pineal gland
40
what structure separates the colliculi of the midbrain
cruciform sulcus
41
what structure separates the cerebral peduncles
interpeduncular fossa
42
what do the superior cerebellar peduncles do
connect cerebellum to midbrain
43
what do middle cerebellar peduncles do
connect cerebellum to pons
44
what to inferior cerebellar peduncles do
connect cerebellum to medulla
45
what 3 layers make up the blood-brain barrier
1. endothelial cells
2. pericytes
3. astrocytes
46
name 5 features of the blood brain barrier
1. endothelial tight junctions
2. astrocyte end feet
3. pericytes
4. continuous basement membrane lacking fenestrations
5. requires specific transporters for glucose
47
what does the vertebral artery supply
= 20%
posterior cerebrum
contents of posterior cranial fossa
48
what does the internal carotid artery
=80%
anterior cerebrum
middle cerebrum
diencephalon
49
what is the blood supply of the frontal lobe
anterior cerebral artery
| middle cerebral artery
50
what level does the common carotid artery bifurcate
c4
51
what is the blood supply of the parietal lobe
anterior cerebral artery
| middle cerebral artery
52
what is the blood supply of the temporal lobe
middle cerebral artery
| posterior cerebral artery inferior portion
53
what is the blood supply of the occipital lobe
posterior cerebral artery
54
what is a berry aneurysm
congenital sac-like out pouching of an inter-cranial artery progressively enlarging until rupture
55
what does a rupture of a berry aneurism cause
subarachnoid or intracerebral haemorrhage
56
where does a berry aneurysm most commonly occur
around circle of willis commonly anterior communicating artery
57
what is a stroke
ischaemic or haemorrhagic leading to intracerebral/subarachnoid haemorrhage = 3rd most common cause of death worldwide
58
where does the superior brachium nerve pathway do
conveys visual information from lateral geniculate body to superior colliculi
59
what does the inferior brachium nerve pathway do
conveys auditory information from medial geniculate body to inferior colliculi
60
which 2 cranial nerves originate from the cerebrum
olfactory and optic
61
how do you test the occulomotor III, trochlear IV and abducens nerve VI
tested together = external occular muscles
make patient follow your finger and make H shape
each eye separately then both together
62
how do you test the trigeminal nerve V
```
sensory = all sensory modalities of 3 main branches
motor = ask patient to clench teeth = temporal and masseter muscles
```
63
how do you test the facial nerve VII
```
shut eyes as tight as possible
raise eyebrows
smile
whistle
taste sensation anterior 3rd tongue
```
64
how do you test the vestibulocochlear nerve VIII
whisper in each ear then ask patient to repeat
| tuning fork
65
how do you test for the glossopharyngeal nerve IX and vagus nerve X
tickle back of pharynx = IX sensory
| note if reflex contraction occurs = X motor branch
66
how do you test the accessory nerve XI
test function of trapezius by asking patient to shrug shoulders against resistance
test sternocleidomastoid by asking patient to turn head on each side against resistance
67
how do you test the hypoglossal nerve XII
ask patient to push tongue out as far as possible = straight or one side
68
which spinal vertebrae have foramen transversium
cervical
69
what is the upper most palpable spinous process
c7
70
at what level is the highest point of the iliac crest
in line with L3-L4
71
what movements do cervical vertebrae provide
flexion
extension
lateral flexion
rotation
72
what movements do thoracic vertebrae provide
small amount forward flexion
lateral flexion
rotation = MOST ROTATION OF ALL
73
what movements do lumbar vertebrae provide
flexion
extension
lateral bending
rotation
74
what is the nucleus pulposus made of
well hydrated gel protoglycan/collagen
75
what is the annulus fibrosus made of
10-12 concentric layers of collagen
76
where is the epidural space
space between vertabrae and dura mater of spinal cord
77
how many vertebrae does each spinal section have
```
cervical = 7
thoracic = 12
lumbar = 5
sacrum = 5 fused
coccyx = 4 fused
```
78
what fibres do the dorsal roots carry
sensory = afferent
79
what fibres do the ventral roots carry
motor = efferent
80
where does the spinal cord end
between L1 and L2
81
what is the conus medullaris
tapering end of spinal cord
82
what is the filum terminale
fibrous strand extending from conus medullaris to coccyx
83
what is the cauda equina
formed from lumbar and sacral nerve roots hanging obliquely down from below conus medullaris
84
describe the interaction between c1 and c2
c1 = atlas
c2 = axis
odontoid peg of c2 becomes vertebral body for c1
85
name the conscious tracts
dorsal column-medial lemniscal pathway
| anterolateral system
86
name the unconscious tracts
spinocerebellar tracts
87
where do the spinal nerves leave the cervical vertebrae
1 vertebra higher than corresponding vertebra except c8 below by 1 vertebra
88
where do spinal nerves leave the thoracic, lumbar, sacral vertebrae
below the corresponding vertebrae
89
name the dorsal/medial lemniscal columns in the brainstem and in the spinal cord
cuneate and gracile nucleus in brainstem
| cuneate and gracile fasciculus in spinal cord
90
the cuneate fasiculus carries information from where
upper body ascending in lateral tract
91
the gracile fasciculus carries information from where
lower body ascending in medial tract
92
describe the path of the dorsal column medial lemniscal pathway
1. first order from limbs to medulla through dorsal column
2. second order in gracile/cuneate nucleus in medulla decussate then travel in medial lemniscus to contralateral thalamus
3. third order from thalamus to internal capsule to sensory cortex
93
what information does the dorsal/medial lemniscal columns carry
fine touch
vibration
proprioception
94
name the corticospinal tracts and what direction are they
descending
| lateral/anterior
95
describe the pathway of corticospinal tract
originate from motor/premotor cortex
descend through internal capsule
pass through crus cerebri to pons to medulla
96
describe the lateral corticospinal tract
decussate in the medullary pyramids - contralateral innervation 85%
descend to spinal cord
terminate in ventral horn for LMN
motor innervation for limbs/digits
97
describe the anterior corticospinal tract
remains ipsilateral - 15%
decussate at spinal cord level of innervation
terminate in ventral horn for LMN
motor innervation of trunk
98
what information do corticospinal tracts carry
motor control of voluntary muscles
lateral = limbs
anterior = axial
99
name the spinothalamic tracts, which direction they travel and what information they carry
ascending
anterior = crude touch/pressure
lateral = pain/temperature
100
describe the path of the spinothalamic tract
1. first order neurons from peripheral nerves to synapse in substantia gelatinosia
2. second order decussate in spinal cord then travel up via lateral/anterior spinothalamic tract to thalamus
3. third order neurons from thalamus to internal capsule to sensory cortex
101
what are the pyramidal tracts responsible for
```
corticospinal = musculature of body
corticobulbar = musculature of head/neck
```
102
name the extra-pyramidal tracts
```
= all descending
tectospinal
rubrospinal = non decussating
vestibulospinal
reticulospinal
```
103
name the 3 neurones in the dorsal column medial lemniscus pathway
1. dorsal root ganglion
2. cuneate and gracile nuclei
3. ventral posterolateral nucleus of thalamus
104
where does the spinothalamic tract decussate
anterior white commisure
105
where do the lateral and medial spinothalamic tracts merge
medulla = forms spinal lemniscus
106
what is brown sequard syndrome
rare condition where lesion on spinal cord results in weakness on one side of body and loss of sensation of other
107
what is the tectospinal tract responsible for
contralateral
| head movement to visual stimuli
108
what is the rubrospinal tract responsible for
contralateral from red nucleus
| fine hand motor
109
what is the vestibulospinal tract responsible for
from vestibular nuclei
| ipsilateral balance and posture
110
what is the reticulospinal tract responsible for
ipsilateral voluntary movement
111
which side will experience weakness in brown sequard syndrome
ipsilateral weakness below lesion due to damage to descending motor tract
112
which side will experience less of sensation in brown sequard syndrome
ipsilateral loss of dorsal column proprioception below lesion as ascending tract damaged before can reach medulla
contralateral loss of pain/temp below as spinothalamic decussate at vertebral level
113
what are the overall consequences of brown sequard syndrome
ipsilateral loss of proprioception, motor, fine touch
| contralateral loss of pain, temp, crude touch
114
what is neurulation
process of formation of embryonic nervous system
115
which cranial nerves are parasympathetic
```
3 occulomotor
7 facial
9 glossopharyngeal
10 vagus
1973
```
116
when does neurulation begin
3rd week
117
describe the process of neurulation in the 3rd week
1. ectoderm thickens in midline = becomes neural plate
| 2. neural plate bends dorsally and borders meet = become neural crest
118
describe the process of neurulation in the 4th week
1. neural tube closes = disconnect neural crest from ectoderm
2. layer of neural crest cells
3. notochord degenerates and mesoderm differentiate into somites
119
what develops from neural crest cells
```
forms most of peripheral NS
sensory dorsal rot ganglia of spinal chord
cranial nerves 5, 7, 9, 10
schwann cells
meninges
dermis
```
120
what does the neural tube develop into
brain and spinal chord
121
what 3 primary brain vesicles have formed by week 5 and what do they represent
```
prosencephalon = forebrain
mesencephalon = midbrain
rhombencephalon = hindbrain
```
122
what does the mesencephalon further develop into to
corpora quadrigemina
tegmentum = colliculi
cerebral peduncles
aquaduct
123
what does the rhombencephalon differentiate into and what does it further develop into
1. metencephalon = pons, cerebellum
| 2. myelencephalon = medulla oblongata
124
what is the 4th ventricle derived from
upper part = metencephalon
| lower part = myelencephalon
125
what causes anencephalus
failure of neural tube closure in brain
126
what week does eye formation occur
3 weeks
127
what occurs embryologically at 3, 5, 7, 9 months
```
3 = basic structures
5 = myelination begun
7 = lobes cerebrum formed
9 = gyri/sulci formed
```
128
when do CNS disorders generally occur
2nd trimester
129
when is noxious (painful) stimuli first felt
19+ weeks as c-fibre connections are made
130
where is working memory stored
prefrontal cortex
131
what is involved in laying down new memories
mamillary bodies
132
what are the 2 types of long term memory
1. explicit = conscious e.g. remembering appointments
| 2. implicit = unconscious e.g. motor skills
133
describe the 3 types of implicit memory and what area of the brain is responsible for it
1. skills/habits = cerebellum/basal ganglia
2. conditioned reflexes = cerebellum et al
3. emotional = amygdala
134
what is the amygdala responsible for
produces instinctive emotional output
| responsible for emotional memory and fear
135
how is the resting potential maintained
```
membrane is semi-permeable
Cl-/K+ move easily
Na+ low permeability
Na+/K+ATPase pump = 3Na+ out 2K+ in
K+ diffuses out via channels
= negative internal
```
136
describe repolarisation and hyperpolarisation
1. potential reaches around +30mv then Na+ voltage gated channels shut
2. K+ channels open = K+ out of neuron = repolarisation
3. K+ channels close slowly so continued outflow causes hyperpolarisation
4. K+ channels all close = resting potential restored
137
what is saltatory conduction
action potential jumps from node of ranvier to node as propagation occurs along axon
138
name the 2 types of synaptic transmission
electrical
| chemical = majority
139
what is the effect of a higher concentration of neurotransmitter
= more likely binding will occur = action potential propogation
140
how does myelin improve conduction
increase insulation = faster
| nodes of ranvier = saltatory = faster
141
what is multiple sclerosis
chronic autoimmune disorder = results in demyelination, gliosis, neuronal damage
142
what are excitatory neurotransmitters
depolarise cell membrane increasing probability of action potential = causing an excitatory post synaptic potential EPSP = many Na+ leave and few K+ enter
143
what are inhibitory neurotransmitters
hyperpolarise cell membrane = decrease probability of action potential = causing an inhibitory post synaptic potential IPSP = many K+ leave or many Cl- enter
144
name the 3 types of synapses and give examples for each
```
excitatory = glutamate
inhibitory = GABA
modulatory = associated with longer term changes in synaptic membrane = dopamine
```
145
what is spatial summation
2 inputs occur at different locations in postsynaptic neuron
146
what are the 5 processes of synaptic transmission
1. manufacture
2. storage = vesicles
3. release = action potential
4. interact with post-synaptic receptors
5. inactivation = breakdown/reuptake
147
what is the definition of pain
unpleasant sensory and emotional experience associated with actual potential tissue damage or described in terms of such damage
148
what is acute pain
short term pain of less than 12 weeks
149
what is chronic pain
continuous long term pain more than 12 weeks or persistent pain after trauma = cancerous or non-cancerous
150
what is nociceptive pain
pain arising from actual/threatened damage to non-neuronal tissue
= due to activation . of nociceptors
151
what is neuropathic pain
pain initiated/caused by primary lesion/dysfunction of nervous system
152
what is analgesia
selective suppression of pain without effects on consciousness/other sensations
153
what is anaesthesia
uniform suppression of pain = no pain felt at all sometimes loss of consciousness
154
what is the melzack-wall pain gate
states that non-painful input closes the 'gate' to painful input = preventing pain sensation from travelling to somatosensory cortex to be perceived/felt
155
what are nociceptors
sensory neurons in any area of body that sense pain:
externally = skin/cornea/mucosa
internally = viscera/joints/muscles
156
where are the cell bodies of nociceptors found
body = dorsal root ganglion
| head and neck = trigeminal ganglion
157
what does it mean that most nociceptors are 'poly-modal'
can detect thermal/chemical/mechanical pain
158
name the afferent pain fibres
alpha delta fibres
| c fibres
159
describe alpha delta fibres characteristics
small diameter
thinly myelinated
carry touch/pressure/temperature/FAST PAIN
medium conduction speed
160
describe c fibres characteristics
smallest diameter
unmyelinated
carries slow pain/temperature/touch/pressure/itch
slowest conduction speed
161
what do c fibres respond to
thermal/mechanical/chemical stimuli
162
what do a delta fibres respond to
mechanical stimuli over certain intensity
163
what is the pain quality produced by c fibres
dull
aching
slow
burning
164
what pain quality is produced by a delta fibres
well localised
sharp
stinging
fast
165
describe the mechanism of pain
1. noxious stimuli = damaged cells release substance P
2. nociceptors activated on alpha delta/c fibres = lower threshold
3. action potential generated in pain fibres = synapse in substantia gelitanosa
4. 2nd order neurones to lateral spinothalamic tract to thalamus
166
what neurotransmitters do a delta fibres release
glutamate
167
what neurotransmitters do c fibres release
glutamate and substance p
168
what is substance p
slow acting = involved in mediation of dull/aching pain
169
what is the role of prostaglandin
do not cause pain
| lower threshold of C fibre nociceptors = lower conc of bradykinin/histamine required to activate nociceptor
170
what is the role of the thalamus in pain
all sensation except olfaction pass through
| contains multiple nuclei for relay/association function
171
what is the role of the insula in pain
where degree of pain is judged = subjective aspect of pain perception
172
what is the role of the cingulate gyrus in pain
linked with limbic system = emotional response to pain
173
where is periaquaductal grey found
grey matter located around cerebral aquaduct
174
how does periaquaductal grey lead to reduced pain sensation
contains high concentration of opioid receptors/endogenous opioids
when activated =
inhibits nociceptive impulses reaching thalamus
inhibits presynaptic calcium movement
potassium release = hyperpolarise
175
describe the descending pain pathway
somatosensory cortex to periaquaductal grey in midbrain
| same as spinothalamic but descending
176
how do opioids work
mimic effect of endogenous opioids = bind to opioid receptors in periaquaductal grey = profound analgesia
177
what role does the anterior cingulate gyrus have in registering pain
registers physical pain
| emotional reaction to pain
178
what is acetylcholinesterase
enzyme found on pre/postsynaptic membrane
| destroys ACh = release choline and acetate
179
what is the motor end plate
connection between muscle fibre and synapse
180
where is ACh found in the neuromuscular junction
in vesicles in the axon terminals of the motor neuron
181
what is a neuromuscular junction
junction of axon terminal and motor end plate
182
describe neuromuscular transmission 3 steps
1. ACh released from presynaptic terminal = diffuse towards muscle
2. ACh binds to cholinergic nicotinic receptors on sarcolemma
3. depolarisation of sarcolemma = Ca2+ released from sarcoplasmic reticulum (for muscle contraction)
183
why is an EPP larger than an EPSP
neurotransmitter released over larger surface area = more binding to receptors
184
what is a motor unit
an alpha motor neuron and all the extrafusal skeletal muscle fibres it innervates
185
what happens when an alpha motor neuron is depolarised
causes contraction in all of the muscle fibres in that unit then spreads throughout muscle = more contraction
186
what type of synapse are neuromuscular junctions
all excitatory releasing ACh
187
the less fibres a single motor unit innervates =
greater degree of movement e.g. fingertips/tongue
188
what is the sarcolemma
cell membrane of muscle fibre
189
what is a muscle spindle
intrafusal fibres innervated by gamma motor neurons
| detect muscle stretch regardless of current length
190
what is the role of stretch receptors
monitor muscle length and change of muscle length
191
what are intrafusal fibres
modified muscle fibres within the muscle spindle
192
what are intrafusal fibres innervated by
gamma motor neurons prevent spindle going slack during muscle contraction
= keep intrafusal fibres at set length to optimise muscle stretch detection
193
what are the 2 types of stretch receptor and what is their role
1. nuclear chain fibres = respond to how much muscle is stretched
2. nuclear bag fibres = respond to magnitude and speed of stretch
194
what are type 1a afferent sensory nerves
fast nerves innervating middle third of muscle spindle
195
what are type 2 afferent sensory nerves
slower conducting nerves innervating superior and inferior thirds of muscle spindle
196
what occurs in the muscle spindle when extrafusal fibres contract
muscle shortens = spindles go slack = cannot send signals via afferent sensory nerves
gamma motor neurons with alpha MN prevent spindle going slack
197
what does muscle tension depend on
muscle length
load on muscles
degree of muscles fatigue
198
what is the golgi tendon organ
collagen fibres in tendon innervated by afferent fibres
| detect tension
199
what are the sensory fibres of the golgi tendon organ
1b afferent fibres = run to anterior horn of spinal cord = slower than muscle spindle fibres
200
how are golgi tendon organs activated
when muscle is stretched = extrafusal muscle fibres contract = tension exerted on tendon = collagen bundles are straightened = distorts GTO receptor endings
201
how does the GTO regulate muscle tension
muscle generates too much force = activate GTO
| 1b afferent sensory neuron = inhibits/reduces activity of alpha motor neurons = decrease muscle contraction/force
202
describe the knee jerk reflex
1. strike patella = tendon pushed down = quadricep stretched
2. muscle spindle detects stretch in muscle = activate afferent fibres
3. afferent fibres stimulate alpha motor neurons
4. alpha motor neurons innervate extrafusal fibres = quadricep contract
203
describe a withdrawal reflex (step on pin)
1. pain on skin = nociceptors activated
2. sensory neuron synapse with interneuron then motor neuron
3. motor neuron carry impulse to extrafusal fibres of muscles = activates flexor and inhibit extensor of muscle on ipsilateral leg = body moves away from painful stimuli
204
what is an example of inverse stretch reflex
action of golgi tendon organ
205
what causes the clasp knife reflex
1b afferent fibres from GTO inhibit alpha MN when GTO detects tension = inverse stretch reflex
206
what is a clasp knife reflex
period of give after a time of resistance e.g. when a limb is flexed there is resistance and then resistance falls dramatically
207
what area is responsible for voluntary movement
pyramidal tracts in the motor cortex = pre-central gyrus
208
what pathways are responsible for voluntary movement
corticospinal tract
| corticobulbar tract
209
what part of voluntary movement involves the pre-motor cortex
planning of movement
| incorporation of sensory info to movement
210
what part of voluntary movement involves the primary motor cortex
execution of movement
211
what pathways are involved in involuntary movement
tectospinal
vestibulospinal
reticulospinal
rubrospinal
212
what are the upper motor neurons
descending pathways and neurons of motor cortex
213
what problems are associated with a upper motor neuron lesion
weakness
altered muscle tone
fast twitching
214
what are lower motor neurons
motor neurons of spinal cord and brainstem e.g. alpha/gamma
215
what problems are associated with a lower motor neuron lesion
paralysis
| decreased muscle tone
216
name the 3 layers of the eye
fibrous outer
vascular
inner
217
what makes up the fibrous layer of the eye
cornea
| sclera
218
what makes up the vascular layer of the eye
choroid
ciliary body
iris
lens
219
what makes up the inner layer of the eye
retina = neural layer/pigmented layer
| vitreous humour
220
where is the primary visual cortex located
medial surface of hemisphere in region above and below calcarine sulcus = occipital lobe
221
name the 3 layers of the retina and what they do
1. photoreceptors = rods and cones for vision
2. bipolar neurons = transmit impulse
3. retinal ganglion cells = axons converge to form optic nerve
222
what occular muscles does the occulomotor nerve superior branch supply
superior rectus
| inferior rectus
223
what occular muscles does the occulomotor nerve inferior branch supply
medial rectus
| inferior obique
224
what occular muscle does the abducens nerve supply
lateral rectus
225
what occular muscle does the trochlear nerve supply
superior oblique
226
what is the optic path of temporal axons
remain ipsilateral
227
what is the optic path of nasal axons
cross at optic chiasm
228
where do the axons of the visual pathway synapse
lateral geniculate body of thalamus
| some = superior colliculus of midbrain
229
what is the path of superior hemiretinae fibres from the lateral geniculate nucleus
pass superiorly through parietal lobe as baum's loop
230
what is the path of inferior hemiretinae fibres from the lateral geniculate nucleus
pass inferiorly through temporal lobe as meyer's loop
231
where do axons of visual pathway terminate
primary visual cortex = calcarine fissure
232
what is the role of the outer ear
collect sound
233
what is the role of the middle ear
transmission of sound
234
what is the role of the inner ear
conversion of sounds to neural impulses
235
describe the path of sound in the outer ear
pinna = directs sound
sound enters via external auditory canal
waves vibrate tympanic membrane
slow waves = low frequency and vice versa
236
what nerve supplies the middle ear sensation
glossopharyngeal nerve
237
name the 3 bones of the middle ear = ossicles and what is their role
malleus
incus
stapes
= transmit sound from tympanic membrane to oval window in inner ear
238
name the 2 skeletal muscles of the middle ear and what is their role
tensor tympani = attached to malleus
stapedius = attached to stapes
= decrease movement of ossicles by contraction = protection
239
what is the role of the eustacian tube
connects middle ear to pharynx
| controls pressure = opens to equalise pressure at high altitudes/aeroplanes
240
how do the skeletal muscles protect the ear
muscles act reflexively to continuous loud noise but cannot protect from sudden intermittent loud sounds
241
what makes up the inner ear
cochlear
| semi-circular canals
242
describe the cochlear
spiral fluid filled space
divided by cochlear duct which is surrounded by fluid
scala vestibuli from oval window = runs above duct
scala tympani from round window runs below duct
243
describe the fluid in the cochlear
cochlear duct filled with endolymph = high K+ low Na+
surrounded by perilymph = high Na+ low K+
Na+/K+ATPase powers auditory system
244
where do the scala vestibuli and scala tympani connect
helicotrema
245
describe the pathway of sound in the inner ear
sound waves = move tympanic membrane = transmit to ossicles = transmit to oval window = oval window moves in/out of scala vestibuli = creates waves of pressure across cochlear duct/some to helicotrema to be relieved by round window
246
where is the organ of corti located
on basilar membrane = side of cochlear duct closest to scala tympani
247
how are high and low pitch tones interpreted by the inner ear
nearest to middle ear = basilar membrane narrow and stiff = low frequency
closer to helicotrema = wider less stiff = high pitch
248
describe the organ of corti
has receptor cells = mechanoreceptors with hairlike stereocilia
249
describe the hair cells of the organ of corti
single row of inner hair cells = protrude into endolymph to convert movement into receptor potentials
3-5 rows outer hair cells = embedded in tectorial membrane = fine tuning
250
describe auditory conduction
1. pressure waves displace basement membrane = stereocilia bens
2. K+ channels open = K+ in from endolymph = depolarisation
3. Ca2+ channels open on basement membrane = Glutamate released
4. stimulates cochlear branch of vestibulocochlear nerve VIII
5. to superior ollivary body to medial geniculate nucleus in thalamus to auditory cortex
251
what is bell's palsy and what effect does it have
acute unilateral inflammation of facial nerve
= pain behind ear
= paralysis of facial muscles
= failure to close eye
252
what are the vestibular apparatus
connected series of endolymph filled membranous tubes that also connect with cochlear duct = contain hair cells
= 3 membranous semi-circular canals
= 2 saclike swellings = utricle/saccule
253
what is the role of the hair cells of the vestibular system
detect changes in motion and position of head
| only acceleration/deceleration
254
how do the semi-circular canals detect motion in the head
1. movements = semicircular canals move, endolymph does not
2. moving cupula pushes against endolymph
3. stereocilia on cupula bend = iron channels open
4. glutamate released = vestibular branch of CNVIII
255
what does the utricle respond to
tipping head away from horizontal plane e.g. tying shoelace
256
what does the saccule respond to
from lying to standing/vertical acceleration
257
what is the central auditory pathway
```
cochlear nuclei
to superior olivary nucleus
to inferior colliculus
to medial geniculate body of thalamus via inferior brachium nerve
to primary auditory cortex
```
258
what is the role of the superior olivary nucleus
has fibres that leave brainstem in vestibulocochlear nerve and end in tympanic membrane = inhibitory function
259
what does I'MAuditory mean
inferior colliculus to medial geniculate body = auditory information
SO
superior colliculus to lateral geniculate body = visual information
