Olfactory and Visual System

Question 1

what detects odorants vs. irritants?

Answer 1

CN V is irritants (like amonia) and CN I is olfaction

Question 2

what is olfactory epithelium?

Answer 2

• patch in the roof of the nasal cavity, bilateral, that is the peripheral origin of the olfactory system
• contains 3 million receptor cells, bowmans gland ducts and irritant sensory endings (CN V)

Question 3

explain the olfactory receptor

Answer 3

bipolar neuron thats dendrites end in cilia in the bowman’s glands. Cilia are stimulated by odorants. axons collect in a series of bundles and go through the cribiform plate of the ethmoid bone (end in olfactory bulb)

Question 4

what makes up cranial nerve I?

Answer 4

olfactory filia going through the cribiform plate (axons)

** olfac bulb and tract are CNS

Question 5

what makes up the olfactory bulb and tract?

Answer 5

tufted cells and mitral cells

Question 6

where does the tract lie on the brain?

Answer 6

in the gyrus rectus

Question 7

explain how the olfactory receptors sort themselves

Answer 7

they each send their axons to one glomerulus of a mitral cell that that receptor was sensitive for

Question 8

what is the anterior olfactory nucleus?

Answer 8

• a raised bulb in the olfactory tract thought to regulate sensitivity
• regulates the fibers of both bulbs by crossing to the other through the anterior commisure

Question 9

what is the anterior olfactory nucleus?

Answer 9

• a raised bulb in the olfactory tract thought to regulate sensitivity
• regulates the fibers of both bulbs by crossing to the other through the anterior commisure

Question 10

where do olfactory fibers project?

Answer 10

in the olfactory tubercle, but most go laterally to the medial temporal lobe

Question 11

what are the “two general areas” that the olfactory bulb projects

Answer 11

1. primary olfac cortex (piriform cortex, periamygdaloid cortex, and parahippocampal gyrus
2. amygdala

Question 12

the information from the olfactory cortex is sent to..

Answer 12

hypothalamus, thalamus, hippocampus, orbital cortex and olfac association cortex (frontal lobe and anterior insulae)
**thalamus relays to association cortex

Question 13

the information from the olfactory cortex is sent to..

Answer 13

hypothalamus, thalamus, hippocampus, orbital cortex and olfac association cortex (frontal lobe and anterior insulae)
**thalamus relays to association cortex

Question 14

what are the retina and sclera continuous with?

Answer 14

retina - diencephalon and sclera - brain dura

**CNS

Question 15

how do you focus light on the retina?

Answer 15

refraction of light

Question 16

what contributes to the eyes refractive property?

Answer 16

lens (30 %) and most refraction is at the corneal surface (air-water interface)

Question 17

what does the iris do?

Answer 17

affects the brightness and quality of the image focused on the retina

Question 18

pupillary sphincter

Answer 18

** parasym

smaller pupil improves performance with small aperature

Question 19

pupillary dilator

Answer 19

**symp

Question 20

explain retina structure

Answer 20

-light passes through all of the layers to hit the rods and cones layer and then goes through amacrine cells and horizontal cells that spread laterally to terminate on ganglion cells (where light first hit) to leave the retinal layer and go to processing

Question 21

where do thy synapses occur in the retinal layer?

Answer 21

in the interposed layers

Question 22

rods

Answer 22

contain the visual protein rhodopsin, low acuity, monochromatic vision in the dark

Question 23

cones

Answer 23

cone pigment, high-acuity, color vision, needs light

Question 24

visual pigment synthesize and transport

Answer 24

happens near the inner segment and travels up the stalk to the disk membrane where older disks are phagocytosed by pigment epithelium
**if no cell death then retinal degeneration and blindness

Question 25

what is the area of highest visual acuity?

Answer 25

the fovea | **where VOR centers on

Question 26

what is the area of highest visual acuity?

Answer 26

the fovea | **where VOR centers on

Question 27

explain the optic pathway

Answer 27

ganglion cell axons up the optic nerve to the chiasm to the tract to the lateral geniculate in thalamus (or superior colliculus of hypothalamus) -from LGN to the primary visual cortex (striate)

Question 28

how do we get depth perception?

Answer 28

BOTH RETINAS help to compare and get depth perception as well as the fact that our eyes are faced inwards

Question 29

structure of LGN

Answer 29

6-layers renotopically organized - each layer gets input from one eye, pattern in the same layer so any point in the visual field is represented 6 times - 1,4,6 ipsalteral eye and 2,3,5 contralateral

Question 30

what are the parvocellular layers?

Answer 30

3-6 in the LGN used for color and form

Question 31

what are the magnocellular layers?

Answer 31

1-2 in the LGN for movement and contrast

Question 32

where is the macula vs. the peripheral visual field located on the occipital lobe?

Answer 32

macula is posteriorly and periphery is more anterior towards parietal lobes **Dr. Tatsuji found this based on gun shots to the head and what vision was lost

Question 33

where is the macula vs. the peripheral visual field located on the occipital lobe?

Answer 33

macula is posteriorly and periphery is more anterior towards parietal lobes **Dr. Tatsuji found this based on gun shots to the head and what vision was lost

Question 34

explain occipital lobe in terms of vision

Answer 34

line of gennari is a strip on mylein in the primary visual cortex (also known as striate) that parallels the calcarine sulcus, surrounded by 18, which is surrounded by 19 which are both part of the extrastiate (or association visual cortex)

Question 35

how are visual defects named?

Answer 35

based on the visual field, not the retina

Question 36

anopia/anopsia

Answer 36

one or more quadrants lost in vision

Question 37

hemianopia

Answer 37

loss of half of the visual field

Question 38

quadrantanopia

Answer 38

loss of a quarter of the visual field

Question 39

homonymous

Answer 39

same visual field lost in each eye

Question 40

heteronymous

Answer 40

two eyes have non-overalpping visual field loss congrous: identical noncongruous: overlapping, but not the same

Question 41

deficit if damage anterior to the chiasm

Answer 41

ipsalateral eye blindness

Question 42

deficit if damage to the chiasm

Answer 42

bilateral heteronymous hemianopia

Question 43

deficit if ICA impinges?

Answer 43

nasal hemianopia

Question 44

deficit if temporal lobe lesion

Answer 44

-meyers loop affected, inferior retinal quadrants | contralateral homonymous superior quadrantanopia (macula sparing)

Question 45

deficit if posterior cerebral artery infarction

Answer 45

-sparing macula because normally MCA wraps around and gets brain portion of macula(based on person though) contralateral homonymous hemianopia

Question 46

what would happen if there was a lesion in the optic nerve, how would it afffect the pupillary reflex?

Answer 46

in affected eye, no constriction, but in unaffected eye both eyes constrict because the bilateral processing not affected

Question 47

how would either a lesion in optic radiations (LGN to primary visual cortex) or lesion in the visual cortex affect the pupillary reflex?

Answer 47

unaffected

Question 48

how would either a lesion in optic radiations (LGN to primary visual cortex) or lesion in the visual cortex affect the pupillary reflex?

Answer 48

unaffected | **even cortically blind people constrict eyes

Question 49

where in the hypothalamus does visual information project?

Answer 49

the suprachiasmatic nucleus to master circadian rhythm

Question 50

how does the cortex process vision?

Answer 50

parellel processing to striate and extrastriate

Question 51

cortical modules

Answer 51

striate is arranged in repeating modules that contain columns that contain discrete info from the visual field (to each column) -modules in fovea analyze smaller areas of the visual field, so more, smaller modules and in the periphery the modules are larger and fewer

Question 52

cortical modules

Answer 52

striate is arranged in repeating modules that contain columns that contain discrete info from the visual field (to each column) -modules in fovea analyze smaller areas of the visual field, so more, smaller modules (for resolution) and in the periphery the modules are larger and fewer