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Year 2: NeuroBiology > Lecture 7: CNs and Special Sensation > Flashcards

Lecture 7: CNs and Special Sensation Flashcards

1
Q

Number/type of neurons involved with olfaction/CN I and how often they renew

A

approximately 3 million bipolar neurons

they renew every 30-60 days by stem cells

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2
Q

how do signals for the olfactory n travel

A

axons of olfactory receptor neurons in sphenoethmoid recess of nasal cavity

dendrites have multiple cilia at the ends of neurons

odorant receptor = defines chemical identity

odorant binding protein = facilitates odors to cross mucus surface

CN V fibers are spread throughout the sheath of the olfactory epithelia and can detect pungency too

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3
Q

What defines a smell’s chemical identity

A

Odor receptors

mainly GPCR

some ionotropic receptors but less

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4
Q

speed/myelination of olfactory n

A

nonmyelinated

thinnest axons (0.2 micro m)

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5
Q

what is an olfactory fila

A

20-30 axons bundled together

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6
Q

where does the olfactory n cross/synapse

A

cribiform plate

synapse with olfactory bulb in CNS

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7
Q

describe the olfactory bulb (where, what it does)

A

component of telencephalon

specific synapse with mitral cell dendrite (glomeruli are odorant specific functional unit)

sort signals

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8
Q

how does signal sorting work at the olfactory bulb

A

olfactory receptor protein defines odor specificity

axons of olfactory receptor neurons for the same odor run together

mitral cells of same odor synapse with pyramidal cells in neocortex (olfactory cortex)

glutamate and carnosine as excitatory neurotransmitters

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9
Q

what are centrifugal fibers important for

A

negative circuit regulating odorant detection

adapting to odors

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10
Q

where are the 1st-3rd order neurons of the olfactory path

A

1st = olfactory receptor neuron

2nd = mitral cell

3rd = only for sensation; doesn’t need thalamic relay for conscious perception

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11
Q

describe the path of olfactory projection

A
  1. anterior olfactory nucleus in olfactory tract
  2. cross at anterior commisure
  3. olfactory tubercle
  4. piriform cortex (uncus, limbic lobe)
  5. amygdala (emotional learning, aversion)
  6. periamygdaloid cortex
  7. anterior portion of parahippocampal gyrus (entorhinal cortex specifically: memory)
  8. primary olfactory cortex
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12
Q

indirect projections from the primary olfactory cortex (piriform cortex and periamygdaloid)

A

hypothalamus: drive

amygdala: emotional learning

hippocampus: memory

thalamus: relay station and coordination (goes to
olfactory association cortex in insula near the gustatory cortex; gives perception of flavor)

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13
Q

4th week landmark of eye development

A

protrusion of optic vesicle from diencephalon

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14
Q

5th week landmarks of eye development

A

optic vesicle folds in to form double layered optic cup

invasion of ectoderm forms lens vesicle

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15
Q

6th week landmarks of eye development

A

optic cup inner later: retina

optic cup external layer: retinal pigment epithelia

both layers: continue to grow anteriorly to form ciliary body and iris

lens vesicle: pinch off to form lens

leftover ectoderm: forms cornea

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16
Q

what are the 2 anatomic landmarks around the eye

A

ora serrata: anterior end of photosensitive retina

limbus: circular transition zone, junction of cornea and sclera

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17
Q

structures in internal and external layers of the eye

A

sclera and cornea (junction = limbus)

choroid capillaries: provides blood supply and obsorbs stray light

retina and cilliary body (end forms ora serrata)

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18
Q

special structures found in the eye

A

ciliary body = lens accomodation and aqueous humor secretion

iris = adjusts to allow light to pass through

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19
Q

what is the aqueous humor

A

anterior to the lens

secreted by epithelias in ciliary body

drains into scleral venous sinus and then to venois drainage of the eye

increases inner pressure to maintain eyeball shape along with vitreous humor

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20
Q

what is glaucoma

A

increased production or blocked circulation of aqueous humor

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21
Q

what is vitreous humor

A

glass like humor in eyeball

posterior to lens

increases inner pressure to maintain eyeball shape along with aqueous humor

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22
Q

how does the eye “focus” on something

A

refraction of light by the transparent cornea and lens

cornea = conves anteriorly; maintained through intraocular pressure; light passes through with most refraction - gross adjustment

lens = biconvex; but only anterior portion can be adjusted - fine adjustment

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23
Q

how does the lens adjust for near vs far sight

A

ciliary muscle contraction = zonular fibers loosen; for NEAR sight

ciliary muscle relaxation = zonular fibers tighten; for FAR sight

controlled by parasympathetic motor from CN III

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24
Q

what is a cataract

A

degeneration of lens that results in blindness

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25
what components are involved with adjustment of brightness and image quality of the eye
iris: pinhole effects- pupil dilation/constriction retina: major role in visual sensitivity adjustment; absorbs stray light by pigmented epithelia
26
describe how the "pinhole effect" works with pupil dilation/constriction
pupillary sphincter/constrictor pupillae (controlled by CN III) - m is circular, developed from edge of optic cup - decreases iris diameter to allow less light into eye pupillary dilatro/dilator pupillae (sympathetic motor) - radiating spokes - increases diameter of iris to allow more light into eye
27
how many layers in human retina
10 opposite to direction of light and information processing
28
describe the layers/cells of the retina from outer to inner side
outer synaptic layer = 5 cells - rods and cones: photoreceptors - bipolar neurons: converge info from photo receptors inner synaptic layer = 2 cells (interneuron and ganglion) - axonal bundles of ganglion cells form optic n coursing through optic canal
29
describe the blind spot of the retina
optic disk = no photoreceptors cant feel it but can be proved; lose huge visual field without being aware
30
describe the macula portion of the retina
circular portion lateral to optic disk 2mm diameter yellowish in color due to numerous blue light absorbing cells (macula lutea) fovea = center of macula; 0.35 mm diameter, concentrated cones, high visual acuity peripheral retina: more rods for black and white
31
what is macular degeneration
lost visual acuity legally blind
32
what is a bipolar cell and the different types
NOT a neuron; no initiation of AP "on" bipolar cell = active in light; inhibit glutamate production; metabotropic receptor "off" bipolar cell = inactive in light; activate glutamate production; ionotropic receptor 1st order neuron to converge signals from photon receptors
33
describe a ganglion/its role in the visual system
2nd order neuron over 20 types in humans further converge signals from bipolar cells
34
X/P/beta ganglion cell functions with vision
color and finer details convergence from cones
35
Y/M/alpha ganglion cell functions with vision
motion and course patterns convergence from rods
36
purpose of melanopsin containing ganglion cells
sensitive to light intrinsically; no convergence from bipolars W/K type for circadian rhythm pupillary light reflex still exists in blind people with injured photoreceptors
37
what cells modulate the transmission pathway of the visual system
horizontal and amacrine cells
38
describe the projection of the optic tract
ganglion axons project to lateral genticulate nuclei of thalamus (3rd order neuron) relayed info goes to V1 (primary visual cortex)
39
what information is received/interrpreted at the primary visual cortex
only directional bars detected macula projects to posterior/occipital part; takes over 60% of V1 Meyer's loop: inferior projection fibers course through the temporal lobe; superior quadrant of V1 contralateral visual field is detected by visual cortex, NOT visual field of each eye
40
where does the dorsal stream projections from the primary visual cortex project to? and what information does it carry?
via Y/M/alpha ganglia to parietal lobe: where (location/shape/motion/speed of objects); R side dominant to medial temporal lobe: navigation to frontal lobe: how
41
where does the ventral stream projections from the primary visual cortex project to? and what information does it carry?
X/P/beta ganglia to the inferior temporal lobe: what - retrieve memory about name of objects - continue to project to medial temporal lobe
42
what kind of info does V1 provide in visual perception
lines with different directions maintains retinotopy
43
what kind of info does V4 provide in visual perception
different colors retinotopy maintained
44
integration of the visual cortex and the dorsal/ventral streams allows us to maintain what
object shape/color perception - name/correlated info - spatial location - action
45
describe how a visual field works
both eyes have right and left visual field with central region overlapping
46
nasal vs temporal retina
nasal is side of retina toward nose temporal is side of retina towards temple
47
how does cross projection of the visual field to the retina work
L visual hemifield by right temporal and left nasal retina ("right side of each eye") R visual field by L temporal and R nasal retina ("left side of each eye")
48
what forms the optic chiasm
contralateral nasal retina axons cross to form optic chiasm
49
what forms optic tract
axons from temporal retina and contralateral nasal retina L optic tract for R visual field and R optic tract for L visual field
50
what pathology should be screened when a pt presents with tunnel vision
pituitary gland tumor impinging optic chiasm
51
what is L homonymous hemianopia
lost visual field of one side entirely
52
what is blindsight/Riddoch's phenomena
V1 lost function entirely still with vision of motion
53
what happens with parallel processing at tectopulvinar pathway
pretectal area and superior colliculus coordinate eye movement pupillary light reflex visual association area via dorsal stream
54
importance of projection of optic tract to hypothalamus
suprachiasmatic nuclei relay info for circadian rhythm
55
what are the locations that CNs III, IV, and VI cross the meninges and cranium
meninges = different cranium = superior orbital fissure - sphenoid bone has multiple CN crossing openings
56
what does levator palpebrae muscle control and what is its innervation
CN III common tendinous ring in the posterior orbital wall controls upper eyelid and opens the eye
57
extraocular muscles innervated by CN III
superior rectus medial rectus inferior rectus inferior oblique (maxilla)
58
extraocular muscles innervated by CN VI
lateral rectus
59
extra occular muscles innervated by CN IV
superior oblique
60
what is convergence
adduction of bilateral eyeballs at the same time focusing on same targe (near triads)
61
what is pathological strabismus
2 eyes not lined up properly to different directions
62
esotropia
adducted eyeball(s) convergence (functional) CN VI palsy
63
exotropia
abducted eyeball(s) divergence medial rectus strain CN III palsy
64
hypertropia
elevated eyeballs CN IV palsy (superior oblique)
65
hypotropia
depressed eyeballs inferior oblique muscle strain CN III palsy
66
describe the path for visceral motor function via CN III `
preganglionic axons from Edinger Westphal nuclei (EW) synapse with 2nd cell body in ciliary ganglion post ganglionic axons hike on short ciliary n
67
ciliary body function
regulate lens convexity
68
pupillary sphincter function
constrict iris
69
where does efferent and afferent info come from in relation to pupillary light reflex
afferent = optic n; ganglionic cells; no photoreceptor needed efferent = oculomotor n, Vm effects = constrict pupil
70
where are the nuclei for the trigeminal n
in whole brainstem and upper cervical spinal cord 3 ss nuclei 1 sm nucleus
71
where is CN V located
middle and lateral pons
72
CN V crosses the dura and then each branch crosses at different cranial foramina. what are the foramina for each branch
V1, opthalmic n, ss only: superior orbital fissure V2, maxillary, ss only: foramen rotundum V3, mandibular, ss and sm: foramen ovale
73
somatosensory functions of CN V
facial sensory stimuli chemical sensation of taste and smell
74
somatic motor functions of CN V
mastication (temporalis, masseter, medial and lateral pterygoids) tensor tympani: hearing tensor veli palatini: swallowing digastric anterior belly and mylohyoid: speaking/swallowing
75
how does CN V act as a shuttle for other CNs
CN III and sympathetic post ganglionic axon: short ciliary n CN VII - zygomatic n to lachrymal n: postganglionic axon to lacrimal glands - lingual n: chorda tympani for taste and parasympathetic components CN IX: auriculotemporal n for postganglionic axon to parotid gland
76

Year 2: NeuroBiology (10 decks)

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