Anatomy CN 8 Flashcards
1
Q
What is the auricle (pinna)?
A
outer ear structure a part of the external ear
2
Q
What is the external auditory canal?
A
- part of the external ear
- tube connecting auricle to ear drum
3
Q
What is the ear drum? What 3 things is it composed of?
A
- Tympanic membrane
- sheet across the external auditory canal composed of epidermis, epithelium and CT fibers (elastic)
4
Q
What is the middle ear filled with?
A
Small air filled cavity
5
Q
What are the smallest bones of the body?
A
Auditory ossicles
- Malleus
- Incus
- Stapes
6
Q
What two things does the malleus (hammer) connect?
A
Hammer connects ear drum to anvil (incus)
7
Q
What two things does the incus (anvil) connect?
A
Hammer (malleus) to stirrup (stapes)
8
Q
What two things does the stapes (stirrup) connect?
A
Anvil (incus) to the oval window
9
Q
What is the oval window?
A
Membrane covered opening into perilymph of cochlea
10
Q
What is the membrane covered opening into perilymph at the other end of cochlea?
A
Round window
11
Q
What two muscles (and what are they innervated by) contract to prevent damage to middle ear structures by loud noise?
A
tensor tympani (CN V3) stapedius (CN 7)
12
Q
What connects the middle ear chamber to nasopharynx (upper throat)?
A
opening to the auditory tube (eustachian tube)
13
Q
What does the auditory tube (eustachian tube) do to the middle ear?
A
Equilibrate pressure
14
Q
What is another name for the inner ear?
A
Labrynth
15
Q
The bony labyrinth is lined by _____ and contains _____
A
Periosteum and contains parilymph
16
Q
The semicircular canals of the inner ear contain what type of sensory receptors?
What is their purpose?
A
Crista ampullaris For equilibrium (angular)
17
Q
T/F The semicircular canals lie at right angles to each other in 2 geometric planes
A
False, 3 geometric planes
18
Q
The vestibule of the inner ear contains what type of sensory receptors?
What are their purpose?
A
Contain macula for equilibrium (linear)
19
Q
The cochlea of the inner ear contain what type of sensory receptors?
A
Spiral organ of corti for hearing
20
Q
What are the sacs and tubes inside the bony labyrinth that have the same shape as the inside of the bony labyrinth?
What is it filled with?
A
Membranous labyrinth filled with endolymph
21
Q
What is the membranous sac in the vestibule that is connected to semicircular canals?
A
Utricle
22
Q
What is the membranous sac in the vestibule that is connected to the utricle?
A
Saccule
23
Q
What is the purpose of the cochlear duct in the inner membranous labyrinth?
A
For hearing
24
Q
CN8 special sensory innervation of what two organs and for what function?
A
- vestibular and semicircular canal organs to function in equilibrium
- cochlear organ to function in hearing
25
The vestibular branch of CN 8 travels through what ganglion?
Superior and inferior vestibular ganglion
26
The cochlear branch of CN 8 travels through what ganglion?
spiral ganglion
27
The auditory apparatus the spiral organ of corti do what?
Sensory/receptor for hearing
28
The hair cells of the ear are stereocilia embedded in what matrix?
Tectoral membrane which is stationary
29
The base of hair cells are attached to the basilar membrane which is the floor of what?
Separate what two things?
Floor of the cochlear duct separating endolymph (inner tube = membranous labyrinth) from perilymph in cochlea bony labyrinth which ends at the oval and round membranes
30
T/F Basilar membrane/hair cells move in response to sound
True
31
T/F The auditory apparatus does not have support cells
False, it does
32
What is the spiral core of the cochlear bony labyrinth?
Modiolus
33
The spiral organ of Corti consists of hair cell layer on basilar membrane arranged around modiolus embedded in tectoral membrane the (move/do not move)?
Do not move
34
Pitch is the _____ of sound waves
Frequency
35
amplitude is the ______ of sound waves
Loudness
36
Pitch plus amplitude =
Tone
37
How are sound waves from a vibrating object directed to eardrum?
By auricle and external auditory canal
38
T/F Sound waves cause eardrum to vibrate
True
39
How is the amplified vibration transmitted to the oval window?
By the auditory ossicles ear drum -> malleus -> incus -> stapes -> oval window
40
Pressure waves travel in what two lymphs?
peri and endolymph
41
Frequency + amplitude = tone result from discriminative movement of spiral organ of corti/basilar membrane and bends what?
Bends stero-cilia/kinocilium of hair cells embedded in tectoral membrane which does not vibrate
42
If the stereo-cilia/kinocilium of hair cells bend laterally -
depolarization -> release chemical messenger -> stimulate peripheral process of auditory sensory neuron
43
If the stereo-cilia/kinocilium of hair cells bend medial -
Hyperpolarization -> inhibition
44
T/F The entire spiral organ of Corti is stimulated by sounds of different pitch
False, different areas of spiral organ of Corti are stimulated by sounds of different pitch
45
What type of neuron in the spiral ganglia (in center, modiolus, of cochlea) of auditory pathway?
Bipolar Neuron
46
The auditory nerve pathway signal travels on what nerve?
Cochlear nerve
47
How does the cochlear nerve enter the skull?
Travels through the petrous portion of temporal bone exiting internal auditory meatus
48
How does the cochlear nerve enter the brain stem and what nuclei does it synapse with?
Enters brainstem at junction of pons and medulla and synapses with dorsal/ventral cochlear nuclei in tonotopic manner
49
The cochlear nuclei ascend to what three things?
1. Bilateral direct connections through superior olivary complex (cross over at trapezoid body)
2. Contralateral indirect connections to inferior colliculus via the lateral lemniscus
3. Reticular formation
50
After the inferior colliculus, the signal travels to what 3 places?
1. Medial geniculate body of thalamus -> auditory cortex (superior medial temporal lobe)
2. Tectospinal head turning reflex
3. Reticular formation
51
The bilateral projection of auditory signals to cortex allows for what?
Discrimination of sound differences in each ear
52
What is linear acceleration? Angular?
Linear - change in velocity when traveling in one direction
| Angular - change in velocity when rotating
53
What is the organ of equilibrium?
Vestibular apparatus
54
What is the Macula and what does it do?
2 thickened regions in walls of utricle and saccule- sensory receptor for linear acceleration
55
The hair cells of the macula are what?
stereo-cilia (microvilli)
56
What is the otolithic membrane?
- Extracellular matrix of gelatinous material secreted by supporting cells
- Has calcium carbonate crystals called otoliths
- Stereo-cilia and cilia of the hair cells are embedded in the otolithic membrane
57
How are the macula of the utricle and saccule arranged to each other?
Arranged at right angles
58
Body movement causes the otolithic membrane to move and bend the stereocilia of the hair cells resulting in what two possibilities?
1. membrane depolarization = generate AP in vestibulochoclear nerve
2. Hyperpolarization = inhibit AP
59
What is the organ for angular acceleration?
Crista ampularis - elevations in lumen of each semicircular canal
60
The hair cells of the crista ampularis contain what two thigns?
1. Stereocilia
| 2. Kinocilia
61
What matrix is the stereocilia of the hair cells of the crista ampularis embedded in?
Cupula gelatinous extracellular matrix
62
When the head rotates, the stereocilia of hair cells in crista ampularis will do what two things?
1. Membrane depolarization to generate AP in vestibular nerve on one side
2. Membrane hyperpolarization to inhibit signaling of vestibular n on the other side
63
What begins equilibrium pathway?
Bending stereocilia of hair cell
64
The equilibrium pathway change in pattern travels on what type of neuron through what ganglia?
Peripheral axon = bipolar neuron in vestibular ganglia
65
The central axon of the equilibrium pathway forms what?
Vestibular branch of vestibulocochlear nerve
66
Equilibrium pathway fibers from these areas go where?
Semicircular canal ->
Utricle maculae ->
Saccule maculae ->
Semicircular canal -> superior and medial vestibular nuclei
Utricle maculae -> lateral vestibular nucleus
Saccule maculae -> lateral and inferior vestibular nuclei
67
The vestibular nuclei of the equilibrium pathway project to what 5 areas:
1. Cerebellum flocculonodular lobe
2. Cervical spinal cord head turning muscles (medial vestibulospinal tract)
3. Both cervical and lumbar spinal cord extensor m (lateral vestibulospinal tract)
4. CN 3, 4, 6 nuclei (MLF)
5. MLF -> bilateral ventro-basal complex of the thalamus -> premotor and other regions of cerebral cortex = postcentral and adjacent associative cortex dealing with head proprioception
68
How does the cerebellum project back to vestibular nuclei in the equilibrium pathway?
fastigial nucleus
69
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Basal nucleus (ganglia) components:
Caudate function?
```
Functions primarily in emotional/cognitive
70
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Basal nucleus (ganglia) components:
Striatum (neostriatum)
```
caudate + putamen
71
What is the ventral striatum? What does it contain? What is its function?
- Area of striatum where caudate joins putamen
- Contains nucleus accumbens
- Function primarily limbic
72
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Basal nucleus (ganglia) components:
Globus pallidus (GP) (internus/externus)
```
```
Internus = medial GP
Externus = lateral GP
```
73
WHat two things make up the lentiform?
putamen + globus pallidus
74
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Basal nucleus (ganglia) components:
What do you find in the substantia nigra?
```
1. Compacta (dopamine)
| 2. Reticularis
75
What is the overall function of the basal ganglia?
| Describe behavior and motor aspects.
Psychomotor:
Behavior - goal directed behavior, social behavior, emotions
Motor - decision making (initiation), judgment (force), prioritizing (multi-join movement and sequencing), emotional response, learning, eye movements, spatial attention
76
T/F The BG acts by increasing excitatory input to the motor cortex
False, it acts by reducing excitatory input to the motor cortex (inhibitory)
77
T/F most afferent input to BG is excitatory
True
78
Where does the BG receive afferent input from (3 places)?
1. Cerebral cortex (glutamate - excitatory)
2. Pedunculopontine nucleus (PPN) (glutamate & AcH - excitatory)
3. Raphe nucleus (serotonin - inhibitory)
79
What NT sends efferent output from BG?
GABA - inhibitory
80
What three places do efferent output from BG go to?
1. Thalamus - VA and VL = motor & MD = limbic to decrease activity precentral gyrus
2. . Pedunculopontine nucleus (PPN; part of reticular formation) to increase activity of axial, postural muscles
3. Tectum to decrease activity of stepping pattern generators (walking); affect reflex eye movements
81
Non motor BG loops:
| Goal directed behavior loop (pathway and role)
1. Prefrontal cortex -> caudate -> GPi -> decrease activity VA thalamus
2. Decision making, goal directed behavior, planning, choose action, learning
82
Non motor BG loops:
| Social behavior loop (pathway and role)
1. Prefrontal cortex -> head/caudate nucleus + Substantia nigra reticularis -> Mediodorsal thalamus
2. Recognize social cues, regulate self control, evaluates what information is relevant and irrelevant
83
```
Non motor BG loops:
Emotion loop (pathway and role)
```
1. Prefrontal cortex -> striatum -> Mediodorsal thalamus
| 2. Link emotions to cognitive and motor systems, reward seeking, outcome predictions (emotions to facial expressions)
84
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Motor BG loops:
Oculomotor loop (pathway and role)
```
1. Frontal and supplementary eye fields -> caudate nucleus -> Substanta nigra reticularis -> decrease activity VA thalamus allow for reflexive prosaccades
2. Spatial attention, initiate fast eye movements toward an object = prosaccades
85
Motor loop Basal ganglia (pathway and role)
1. Motor and premotor cortex -> affect level of GAB inhibitory activity of GPi
2. Muscle contraction, muscle force, multi-joint movements, muscle sequencing
86
The motor loop of the BG sends output to what 3 locations?
1. motor cortex = voluntary movement
2. PPN = posture muscle control
3. Midbrain tectum (superior colliculus) = eye movements and step generator = walking
87
General role hyperdirect no go pathway of BG motor pathway:
Uses subthalamic nucleus which stimulates GPi
88
Describe the hyperdirect no go pathway from cortex (BG motor pathway)
Cortex -> subthalamic nucleus -> GPi activity increases -> resulting in:
1. inhibition of motor thalamus = precentral gyrus
2. inhibit PPN = increase activity reticulospinal tract/postural and girdle muscles (inhibit and inhibitor = disinhibition)
3. Inhibit midbrain locomotor/step pattern generator
89
General role of go pathway of BG motor pathway:
Direct pathway decreases activity of GPi
90
Describe the go pathway from cortex (BG motor pathway)
Cortex -> putamen -> decreases activity of GPi (stimulate an inhibition of GPi so activity GPi decreases) resulting in:
1. Disinhibition motor thalamus/cortex to increase precentral gyrus activity
2. Disinhibition PPN to inhibit reticulospona/postural and girdle muscle activity
3. Disinhibition midbrain locomotor/step pattern generator
91
Basic role of no go pathway in BG motor pathway
Indirect pathway works by inhibiting GPe which normally inhibits GPi = disinhibition to increase activity of GPi
92
Describe the no go pathway from cortex (BG motor pathway)
Cortex -> putamen -> decrease activity of GPe which was an inhibitor of GPi so GPi activity goes up & GPe disinhibits STN which will stimulate GPi (increase activity) resulting in:
1. Inhibit motor thalamus/cortex
2. Inhibit PPN = increase reticuluospinal/postural and girdle muscle activity
3. Inhibit midbrain locomotor/step pattern generator
93
Substantia nigra modulates neostriatum to modulate what structure?
GPi
94
Substantia nigra reticularis:
Input =
Output =
```
Input = GABA inhibitory from neostriatum
Output = GABA inhibitory to:
1. substantia nigra compacta
2. Midbrain tectum (superior colliculus)
3. Motor thalamus (VA, VL)
```
95
Substantia nigra compacta:
Input =
Output =
```
Input = GABA inhibitory from substantia nigra reticularis
Output = dopamine stimulation (D1 receptor) and inhibition (D2 receptor) of neostriatum
```
96
Substantia nigra reticularis pathway from cortex->
Cortex -> stimulate putamen -> inhbit SN reticularis resulting in:
1. Disinhibition thalamus -> increase motor cortex activity
2. Disinhibition tectum -> increase eye movement step generator
3. Disinhibition SN compacta
97
Substantia Nigra compacta putamen D1 receptor ->
Stimulates go pathway resulting in:
1. Disinhibition on thalamus -> increase motor cortex activity limbs
2. Disinhibition PPN -> decrease reticulo and vestibulospinal tract activity to decrease activity of postural muscles
98
Substantia Nigra compacta putamen D2 receptor ->
Inhibit no go pathway resulting in:
1. Disinhibition on thalamus -> increase motor cortex activity limbs
2. Disinhibition PPN -> decrease reticulo and vestibulospinal tract activity to decrease activity of postural muscles
99
When substantia nigra compacta putamen D1 and D2 receptors is results in =
Stimulates voluntary movement
| Inhibits postural muscles
100
Describe disease states:
| Parkinson's Disease (hypokinetic)
1. Due to loss of dopamine from sunstantia nigra pars compacta
2. Go pathway no longer stimulated = decrease thalamic motor activity
3. No go pathway no longer inhibited = decrease thalamic motor activity
101
Describe disease states:
| Huntington's Disease (hyperkinetic)
1. Due to loss of GABA from neostriatum
| 2. No go pathway no longer inhibits thalamus = increase thalamic motor activity
102
What are the functions of the cerebellum?
1. Modulation of somatomotor signaling
2. Balance
3. Tone
103
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Cerebellum anatomy:
Vermis -
Cortex -
White matter below cortex -
Nuclei -
```
Vermis - jois 2 hemis
Cortex - gray matter
White matter below cortex - afferent and efferent axons
Nuclei - gray mater located in white matter
104
Anterior lobe (paleocerebellum) receives what signals and what are its functions?
1. Receives spinal cord afferents (spinocerebellum)
| 2. Functions in controlling axial muscle tone and degree of flexion and extension
105
Posterior lobe (neocerebellum) receives what signals and what are its functions?
1. Is linked input and output to the cerebral cortex (cerebrocerebellum)
2. Functions in planning, organization, and coordination fo motor activity
106
Flocculonodular lobe receives what signals and what are its functions?
1. Receives input from the vestibular system (vestibulocerebellum)
2. Control of eyes and head position
107
Lateral anterior/posterior lobe signals?
Efferent fine motor to limbs
108
Vermal/paravermal (medial ant/post lobe) signals?
efferent axial muscles for head turning, posture, and tone
109
Fastigial nucleus -
relay efferent signals to vestibular nuc and reticular formation
110
Dentate nucleus -
relay efferent signals to cortex via superior colliculus
111
interposed nucleus:
globose nucleus -
emboliform nucleus -
globose nucleus - efferent to red nucleus
| emboliform nucleus - efferent to red nucleus
112
Inferior peduncles -
afferent from spinal cord/medulla (cuneocerebellar, rostrocerebellar, and posterior spinocerebellar)
113
Middle peduncle -
afferent from cerebral cortex to cerebellum via pontine nucleus
114
Superior peduncle -
efferent from cerebellar nuclei to brain stem and cortex (anterior spinocerebellar)
115
How does CSF enter subarachnoid space from Cerebellum?
2 lateral foramen of Lushka
| Median foramen of Magendie
116
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Afferent input to cerebellum:
Spinal cord (body) -
```
To vermis and perivermal cortex of anterior and adjacent posterior lobes
117
Dorsal spinocerebellar from body to cerebellum carries what?
proprioception of legs
118
Ventral spinocerebellar from body to cerebellum carries what?
monitor ventral horn activity of leg spinal cord segments
119
Cuneocerebellar from body to cerebellum carries what?
proprioception of arms
120
Rostrocerebellar from body to cerebellum carries what?
monitor ventral horn activity of arm spinal cord segments
121
Inferior olivary nucleus acts as relay receiving input from where and sends output to where?
Receives:
1. Spinal cord proprioception
2. Sensory motor cerebral cortex -> red nucleus -> inferior olivary nucleus
Output:
1. To ant and post lobes of cerebella hemis
122
The vestibular apparatus acts as direct connection between what nuclei and what lobe?
Vestibular nuclei and the flocculonodular lobe
123
Reticular formation carries afferent signals to what part of cerebellum?
Vermis and paravermis of ant and post lobes
124
The cerebral cortex sends afferent signals to cerebellum via these three tracts?
1. Red nucleus -> inferior olivary nucleus -> ant and post lobes of cerebellum hemi
2. Deep pontine nuclei -> ant and post lobes and cerebellar hemi
3. Reticular formation -> vermis and paravermis of ant and post lobes
125
The tectum sends signals to cerebellum -
superior/inferior colliculi to ant and post lobes of cerebellar hemi
126
The mesencephalic trigeminal nucleus sends signals where in cerebellum?
vermal and paravermal regions
127
Afferent neurons from input sources to cerebellum have what 2 fiber types?
1. Mossy
| 2. Climbing
128
What are mossy fibers?
| What 3 things do they synapse with?
- Glutamate excitatory fibers from all areas of afferent input except inferior olivary nucleus
- Synapse with:
1. Deep cerebella nuclei
2. Excitatory granule cells of cortex
3. Inhibitory golgi cells of cortex
129
What are climbing fibers?
| What 2 things do they synapse with?
- Glutamate excitatory fibers from inferior olivary nucleus that synapse with:
1. Deep cerebellar nuclei
2. Purkinje cells of cortex making the refractile to granule cell stimulation
130
The cerebellar cortex granule cell layer has what two cell types?
Innermost layer:
1. Granule cells
2. Golgi cells
131
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Granule cells
What NT? Excitatory/Inhibitory?
What type of neuron? What cells do they stimulate?
What will they influence?
What cell will they also stimulate?
```
Glutamate excitatory cells with diverging collaterals capable of exciting many purkinje cells by parallel fiber activation to influence broad regions of body musculature simultaneously (also stimulates basket cells)
132
Golgi cells
What NT? Excitatory/Inhibitory?
What two possible fibers stimulate golgi cells?
- GABA inhibitory interneurons that inhibit granule cells
- Stimulated by afferent fibers or granule cells themselves
- Limit granule cell excitation to a burst
133
Granule cells turn itself off by activating what type of cell?
Golgi
134
Purkinje cell layer (middle layer) has what cell types?
Purkinje cells
135
Purkinje cells
What NT? Excitatory/Inhibitory to what nuclei?
What are they stimulated by?
What are they inhibited by?
- GABA inhibitory cells which inhibit deep cerebellar nuclei
- Stimulated by granule cells via parallel fiber activation
- Inhibit by basket cells
136
Vermal perkinje cells project to -
fastigial nucleus
137
Anterior and posterior lobe purkinje cells project to -
dentate nucleus
138
Paravermal purkinje cells project to -
interposed nucleus
139
Some anterior lobe purkinje cells project to
vestibular nucleus
140
Purkinje cell interconnections can be changed to facilitate what?
Motor learning
141
The molecular layer (surface layer) contains basket cells.
| What are they stimulated by and why?
- Stimulated by granule cells to inhibit Purkinje cells adjacent to those stimulated by granule cells to focus granule cell stimulation
142
Mossy fiber and climbing fiber afferents initially excite deep cerebellar nuclei to stimulate what?
Excitatory cerebellar efferent signals
143
Mossy fiber and climbing fiber afferents also activate what type of cell in the cerebellar cortex?
Purkinje cells
144
Purkinje cells have what affect of deep cerebellar nuclei
inhibition
145
Deep cerebellar nuclei are disinhibited when what occurs to purkinje cells?
Purkinje cells are inhibited by golgi cell mediated granule cell inhibition to stop purkinje stimulation
146
Efferents from cerebellum are (inhibitory/excitatory) and come from the where?
Excitatory and come from deep cerebellar nuclei
147
Cerebellar pathways:
Mossy fiber afferent stimulation from
vestibular system ->
1. (+) -> fastigial nucleus -> vestibular nucleus -> head/eye = balance + vestibulospinal tract (axial posture and tone)
2. Cerebellar cortex (flocculonodular lobe + posterior vermis) -> purkinje cell inhibition -> (-) on fastigial nucleus
148
Cerebellar pathways:
| Mossy fiber afferent stimulation from pontine/medularry reticular nucleus ->
1. (+) fastigial nucleus -> reticular nucleus -> reticulospinal tract (axial posture + tone)
2. Cerebella cortex (vermal and paravermal) -> purkinje cell inhibition -> (-) fastigial nucleus
149
Cerebellar pathways:
| Mossy fiber afferent stimulation from the 4 spinocerebellar tracts ->
1. (+) fastigial nucleus -> reticulospinal, vestibulospinal tracts and MLF
2. Cerebellar cortex (vermal and paravermal) -> purkinje cell inhibition -> (-) fastigial nucleus
150
Cerebellar pathways:
| Cerebral cortex -> red nucleus
- > Red nucleus -> inferior olivary nucleus -> climbing fiber afferent stimulation from inferior olivary nucleus:
1. (+) Interposed nucleus -> red nucleus -> rubrospinal tract (hand extensors)
2. Cerebellar cortex (lateral anterior and posterior lobes) -> purkinje cell inhibition -> (-) interposed nucleus
151
Cerebellar pathways:
| Cerebral cortex -> deep pontine nucleus
- > mossy fiber afferent stimulation from deep pontine nucleus ->
1. (+) dentate nucleus -> Ventrolateral thalamus -> motor cortex -> fine movement
2. Cerebellar cortex (vermal and paravermal) -> purkinje cell inhibition -> (-) dentate nucleus
