Physiology of Vision

Question 1

What is the direct (vertical) pathway for signal transmission?

Answer 1

Photoreceptors -> bipolar cells -> ganglion cells

Question 2

What cells are involved in influencing signal processing?

Answer 2

Horizontal cells and Amacrine Cells

Question 3

Horizontal cells receive input from ____________ and project to other ____________ and _______ cells

Answer 3

Horizontal cells receive input from photoreceptors and project to other photoreceptors and bipolar cells

Question 4

Amacrine cells receive input from _______ cells and project to _____ cells, _____ cells and other _______ cells

Answer 4

Amacrine cells receive input from bipolar cells and project to ganglion cells, bipolar cells and other amacrine cells

Question 5

In the dark P_{__} = P_{_}; Vm therefore between E_{__} and E_{_}

_{P= permeability}

_{E= equilibrium potential}

Answer 5

In the dark P_Na = P_K; Vm therefore between E_Na and E_K

Question 6

In response to light;

P_{__} is reduced ; Vm –> E_{_}

_{Change is local and graded}

Answer 6

In response to light;

P_Na is reduced ; Vm –> E_K

_{Change is local and graded}

Question 7

Light converts __-___-______ to ___-_____-_______ (activated form)

Answer 7

Light converts 11-cis-retinal to all-trans-retinal (activated form)

Question 8

Vitamin A is sometimes known as;

Answer 8

All-trans-retinal

Question 9

Rods see in…. light

Cones are for seeing in … light

Answer 9

Rods see in dim light

Cones are for seeing in daylight

Question 10

Why do cones have a higher acuity?

Answer 10

Due to less convergence- high density of cone cells

Question 11

What is the basis for colour vision?

Answer 11

Different opsins for discrete wavelengths

Question 12

Short wave cones see which colour?

Answer 12

Blue

Question 13

Middle wave cones see which colour?

Answer 13

Green

Question 14

Long wave cones see which colour?

Answer 14

Red

Question 15

Rods;

Ach_____

________ retina

____ convergene

_____ light sensitivity

___ visual acuity

Answer 15

Rods;

Achromatic

Peripheral retina

High convergene

High light sensitivity

Low visual acuity

Question 16

Cones

____tic

_____ retina (_____)

___ convergence

___ light sensitivity

____ visual acuity

Answer 16

Cones

Chromatic

Central retina (fovea)

Low convergence

Low light sensitivity

High visual acuity

Question 17

How does lateral inhibition achieve localisation?

Answer 17

By exaggerating the difference in stimulus detected by adjacent neurones, aids with localisation

Question 18

Horizontal cells interconnect a group of ‘surround’ neurones. It samples the total amount of excitation in the surorund and responds by releasing ____. If low surround, ____ ____ is released.

Answer 18

Horizontal cells interconnect a group of ‘surround’ neurones. It samples the total amount of excitation in the surorund and responds by releasing GABA. If low surround, less GABA is released (less inhibitory neurone)

Question 19

Our visual system detects _____ _______ in light _____ not the absolute amount of light.

Answer 19

Our visual system detects local differences in light intensity not the absolute amount of light.

Question 20

Which retinal output signals are sent to the brain?

Answer 20

Simultaenous input from two eyes to cortex

Information about light and dark

Information about form and colour, movement

Question 21

What retinal ganglion cells are there?

Answer 21

M (movement)

P (form and colour)

nonM-nonP (colour)

Question 22

What is retinotopy?

Answer 22

The visual field representation on the retina

Question 23

The retina is divided in half relative to the fovea into a _____ and ______ hemiretina.

Nerve fibres from the ____ half of each retina cross over at the _____ _____.

The resulting two optic tracts allow left and right visual fields to reach separately the left and right hemispheres.

Answer 23

The retina is divided in half relative to the fovea into a nasal and temporal hemiretina.

Nerve fibres from the nasal half of each retina cross over at the optic chiasm.

The resulting two optic tracts allow left and right visual fields to reach separately the left and right hemispheres.

Question 24

About half of the visual cortex is dedicated to information from the relatively small _____.

Answer 24

About half of the visual cortex is dedicated to information from the relatively small fovea.

Question 25

Retinal output cells representing movement and form are _______ in the ________

Answer 25

Retinal output cells representing movement and form are segragated in the LGN

Question 26

A lesion in one of the optic nerves causes

Answer 26

Monocular blindness

Question 27

A lesion in the centre of the optic chiasm causes

Answer 27

Bitemporal hemianopia

Question 28

A lesion in the optic tract causes

Answer 28

Contralateral hemianopia

Question 29

A lesion of part of the fibres after the LGN causes

Answer 29

Quadrantic hemianopia

Question 30

A lesion in the striate cortex causes _____ sparing

Answer 30

A lesion in the striate cortex causes foveal sparing

Question 31

Retinal synapses in LGN are ____ _____ by deprivation bevause they are _______

In the cortex, monocular deprivation during a critical period in development results in active afferents from one eye and _____ _____ from the other eye

Answer 31

Retinal synapses in LGN are not affected by deprivation bevause they are monocular

In the cortex, monocular deprivation during a critical period in development results in active afferents from one eye and lower activity from the other eye

Question 32

Sensory deprivation in early life can alter the shape of the ______ _____.

Answer 32

Sensory deprivation in early life can alter the shape of the cerebral cortex.