Physiology of Vision Flashcards
What is the direct (vertical) pathway for signal transmission?
Photoreceptors -> bipolar cells -> ganglion cells
What cells are involved in influencing signal processing?
Horizontal cells and Amacrine Cells
Horizontal cells receive input from ____________ and project to other ____________ and _______ cells
Horizontal cells receive input from photoreceptors and project to other photoreceptors and bipolar cells
Amacrine cells receive input from _______ cells and project to _____ cells, _____ cells and other _______ cells
Amacrine cells receive input from bipolar cells and project to ganglion cells, bipolar cells and other amacrine cells
In the dark P__ = P_; Vm therefore between E__ and E_
P= permeability
E= equilibrium potential
In the dark PNa = PK; Vm therefore between ENa and EK
In response to light;
P__ is reduced ; Vm –> E_
Change is local and graded
In response to light;
PNa is reduced ; Vm –> EK
Change is local and graded
Light converts __-___-______ to ___-_____-_______ (activated form)
Light converts 11-cis-retinal to all-trans-retinal (activated form)
Vitamin A is sometimes known as;
All-trans-retinal
Rods see in…. light
Cones are for seeing in … light
Rods see in dim light
Cones are for seeing in daylight
Why do cones have a higher acuity?
Due to less convergence- high density of cone cells
What is the basis for colour vision?
Different opsins for discrete wavelengths
Short wave cones see which colour?
Blue
Middle wave cones see which colour?
Green
Long wave cones see which colour?
Red
Rods;
Ach_____
________ retina
____ convergene
_____ light sensitivity
___ visual acuity
Rods;
Achromatic
Peripheral retina
High convergene
High light sensitivity
Low visual acuity
Cones
____tic
_____ retina (_____)
___ convergence
___ light sensitivity
____ visual acuity
Cones
Chromatic
Central retina (fovea)
Low convergence
Low light sensitivity
High visual acuity
How does lateral inhibition achieve localisation?
By exaggerating the difference in stimulus detected by adjacent neurones, aids with localisation
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.
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)
Our visual system detects _____ _______ in light _____ not the absolute amount of light.
Our visual system detects local differences in light intensity not the absolute amount of light.
Which retinal output signals are sent to the brain?
Simultaenous input from two eyes to cortex
Information about light and dark
Information about form and colour, movement
What retinal ganglion cells are there?
M (movement)
P (form and colour)
nonM-nonP (colour)
What is retinotopy?
The visual field representation on the retina
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.
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.
About half of the visual cortex is dedicated to information from the relatively small _____.
About half of the visual cortex is dedicated to information from the relatively small fovea.
Retinal output cells representing movement and form are _______ in the ________
Retinal output cells representing movement and form are segragated in the LGN
A lesion in one of the optic nerves causes
Monocular blindness
A lesion in the centre of the optic chiasm causes
Bitemporal hemianopia
A lesion in the optic tract causes
Contralateral hemianopia
A lesion of part of the fibres after the LGN causes
Quadrantic hemianopia
A lesion in the striate cortex causes _____ sparing
A lesion in the striate cortex causes foveal sparing
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
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
Sensory deprivation in early life can alter the shape of the ______ _____.
Sensory deprivation in early life can alter the shape of the cerebral cortex.
