Lecture 78 Flashcards by Shelby Rainbolt

_______ is the visual field of a prey animal

320 degrees

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_______ is the visual field of a predator

250 degrees

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_______ is the depth perception?

binocular field

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_______ is the simple term for refraction

light bends

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each visual field represented in the _______ optic tract

contralateral

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The closer together the eyes the more input each eye gets from _______

BOTH visual fields

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If an animal has an increased medial eye placement (predators) they have an increased _______?

Binocular vision

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If an animal has an increased binocular vision they have a _______ percent of decussation at optic chiasm

decreased

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Predators have a _______ percent of cross over/decussation

less

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_______ are the three layers of the eye?

Fibours, Vascular (Uvea) and Nervous

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_______ is apart of the fibours portion of the eye?

cornea and sclera

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_______ is apart of the vascular (uvea) portion of eye

Choroid, ciliary body, iris

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_______ is apart of the nervous portion of the eye

retina

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Light is _______ as it passess through the the cornea and lens

refracted

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light passing through the center of the cornea is _______ bent

NOT

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Light is upside down and _______ on retina

reversed

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_______ reflects light more than lens does

Cornea

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lens _______s the image

Fine-tunes

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to accommodate light the _______ of the lens can be altered

shape

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to accommodate light _______ and _______ also help

suspensory ligaments and ciliary muscles

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Lens can change shape and become rounder to _______ refraction for near vision or _______ for distance vision

Increase, thinner

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_______ layer in choroid that increases light detection in dark conditions

Retroreflective

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_______ is the retroreflective layer

tapetum lucidum

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_______ layer is this: Absorbs light and prevents light scatter between photoreceptors; Convert trans-retinal to cis-retinal needed by photopreceptors

Pigment cell layer

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_______ layer is this: Outer portion of rods and cones that contain light sensitive pigments

Photoreceptor layer

_______ layer is this: Cell bodies and nuclei of rods and cones

Outer nuclear layer

_______ layer is this: Synapses of photoreceptor cell axon terminals with dendrites of retinal interneurons (bipolar and horizontal cells

Outer plexiform layer

_______ layer is this: Cell bodies of retinal interneurons; Bipolar cells (B), Horizontal cells (H), Amacrine cells (A)

Inner nuclear layer

_______ layer is this: Synapses of retinal interneuron axon terminals with dendrites of ganglion

cells

Inner plexiform layer

_______ layer is this: Cell bodies of ganglion cells (G); These are the 'output' cells of the retina

Ganglion cell layer

_______ layer is this: Axons of ganglion cells traversing, the inner retina on their way to, the optic disk to the optic nerve

Optic nerve layer

Reflective layer in choroid thatincreases light detection in darkconditions

Tapetum lucidum

Retinal pigment epithelium lacks _______ overlying tapetum

melanin

Tapetum lucidum: Allows light to pass through and reflect back to stimulate _______

photoreceptors

Outer segment: contains photopigments specialized toabsorb light

Rod cell

_______ is involved in the rod cells that help absorb light?

Rhodopsin

Low threshold; Contains Retinal (Vit A derivative) in combination with anopsin (G-protein coupled receptor)

Rhodopsin

(color, photopic, or day vision)

Cone cell

_______ are the outer segment tapers of the cone cells

Photopsins or Iodopsins- higher threshold

_______ is the pathway for conscious perception of vision?

Optic nerve, Optic chiasm, optic tract

the optic chiasm is the _______

Cross over (double decussation)

this nucleus is located in the Diencephalon in the thalamus and is the 3rd order neuron

lateral geniculate nucleus

The lateral geniculate nucleus (LGN) is needed for?

Vision

The dicephalon has the LGN and the

Subcortical

Axons of LGN neurons in optic radiation is in the

cerebral cortex

Axons of LGN in cerebral coretx: Visial cortex in _______

occipital lobe

Cerebral cortex: Axons of LGN neurons in optic radiation to visual cortex in occipital lobe to visual association areas of the _______ lobes

parietal and temporal

_______ work best in dim light/dark conditions

Rods

One photon of light can activate a rod, many needed to activate a cone due to ?

greater sensitivity and amount ofphotopigment in rods

Light causes rods and cons to become _______

Hyperpolarized

Many rods converge on one _______

bipolar cell

Bipolar cell more likely to be activated by low levels of light due to _______

convergence of rod

One cone or just a few cones converge onone bipolar cell, so there is _______ of cone pathway to light

less sensitivity

Optic tract contains a mixture of _______

'PLR' and 'vision' fibers

PLR' (Pulpillary light response) fibers (20%) go to midbrain pretectal nucleus and move to _______

rostral colliculus (bypass the LGN)

Vision fibers (80%) goes to the _______ in the thalamus

LGN

PLR is subcortical (midbrain) reflex inducing _______ pupil constriction

parasympathetic induced

Phototransduction: Conversion of cis to trans-retinal changes shape of _______

G-protein

Phototransduction: Conversion of cis to trans-retinal changes shape of G-protein. _______ happens next?

PDE degrades cGMP

Light stimulates _______ on R receptors to activate phototransduction

Rhodopsin

Phototransduction: Once PDE degrades cGMP _______ happens next?

cGMP gated Na+ channels close

Phototransduction: cGMP gated Na+ channels close. _______ happens next?

Hyperpolarize the cell and decrease glutamate release (NT)

Photon activates phosphodiesterase so Na cannot come in (no depolarizing) causes a _______ bc there is still active K+ channels

hyperpolarizing

Light activates _______ in photoreceptors

Pigment molecules

Phototransduction: Light converted to

electrical signal

In the dark, rhodopsin contains _______

cis-retinal

Light absorption causes transformation to _______, which dissociates from opsin(bleaching reaction

trans-retinal

Light absorption causes transformation to trans-retinal, which dissociates from _______

opsin (bleaching reaction)

_______ converts 11 cis-retinal to all trans retinal when light is seen

photoisomerization

11 cis-retinal is convert to all-trans retinal by photoisomerizes _______ is turned into all-trans retinal

Metarhodopsin II

When all-trans retinal is created GPCR tranducin is activated which activated ?

PDE (phosphodiesterase)

PDE once activated changes _______

cGMP

So when there is more light there is more PDE which means there is _______

LESS cGMP

Light indirectly decreases _______?

cGMP

When there is PDE _______

cGMP-gated channels close

When the cGMP-gated channels close there is a decrease in Na and a decrease in glutamate which causes?

Hyperpolarization

There is an increased _______ release at rest (no light) so there is more cGMP so the cells are depolarized

Glutamate

Steady _______ hyperpolarizes cell

K+

Photoreceptor membrane potential changes when there is a decrease in cGMP. The more light the _______

less cGMP

During a dark current (-40mv) there is a steady _______

inward Na+

The cells are _______ in the DARK

depolarized (bc Na is coming in)

In the dark there is an increase in _______ release

glutamate

When do rods work the best?

Dark/dim rooms

Why are bipolar cells more likely to be activated by low levels of light?

Due to convergence of rods (scotopic vision)

_______: Tranduction (one rhdopsin molecule can activate 100s of transuction molecules0 each of which stimulate PDE

Amplification

_______ protein blocks the ability of activated rhodopsin to activate transduction

Arrestin

cGMP is outer segments is modulated by

light and Ca2+

Ca2+ has _______ on guanylate cyclase

Inhibitory effects

During blinding bright light all cGMP channels are _______ and photoreceptors are _______

CLOSED, Saturated

The _______ tests the retina goes to optic nerve (II) then to optic chiasm then optictract then to visual cortex then to facial nerve(VII) nucleus in medulla

menace reflex

The menace response is a learned response and is a

cortical response

Initiates compensating eyemovement to keep vision fixedwhen head turns

Vestibulo-ocular reflex

Rostral colliculus in midbrain; Decussates; Descends cord in tectospinal tract; Contraction of neck muscles to turn towards stimulus

Visual startle reflex

Lecture 78 Flashcards

(94 cards)