physiology of hearing, balance and vision

Question 1

what cells are involved in the direct (vertical) pathway for signal transmission

Answer 1

ganglion cells, bipolar cells and phtoreceptors

Question 2

what do lateral connections influence

Answer 2

signal processing

Question 3

what do horizontal cells receive input from

Answer 3

photoreceptros and project to other photoreceptors and bipolar cells

Question 4

what do photoreceptors do

Answer 4

convert electromagnetic radiation to neural signals-TRANSDUCTION

Question 5

what are the 4 main regions

Answer 5

outer segment
inner segment
cell body
synaptic terminal

Question 6

in what region of the photoreceptor is the photopigment found

Answer 6

in membranous discs in the outer segment

Question 7

what happens in the light to the Vm and why

Answer 7

with light exposure, Vm hyperpolarises
this positive Vm is because of the ‘dark current’. A cGMP hated Na+ channel that is open in the dark and closes in the light

Question 8

explain what happens in response to light

Answer 8

Pna is reduced (outer segment channels close)
Pk>PNa
therefore Vm-EK hyperpolarises
change is local and graded

Question 9

what does light do to 11-cis retinal

Answer 9

converts it to trans retinal

Question 10

which is the activated form cis or trans retinal

Answer 10

trans retinal is the activated form

Question 11

in the dark is there more or less glutamate

Answer 11

MORE GLUTAMATE IN THE DARK

Question 12

WHAT HAPPENS TO THE ROD IN DARKNESS

Answer 12

inactivate rhodopsin, cAMP levels high
membrane potential in dark -40mv
tonic release of neurotransmitter onto bipolar neurones

Question 13

rod in light

Answer 13

rhodopsin bleaching 
opsin (bleached pigment)
Na channel closes 
membrane hyperpolarises to -70mV
neurotransmitter release decrease in proportion to amount of light

Question 14

what allows for visual acuity

Answer 14

photoreceptor spacing

Question 15

what colour are the short wavelength cones

Answer 15

blue

Question 16

red represents what length of wavelength

Answer 16

long

Question 17

what colour are medium wavelength cones

Answer 17

green

Question 18

what colour are long wavelength ones

Answer 18

red

Question 19

what does lateral inhibition do

Answer 19

exaggerates the difference in stimulus intensity detected by adjacent neurons

Question 20

what does lateral inhibition aid with

Answer 20

LOCALIZATION

Question 21

what does on centre mean

Answer 21

off surround

Question 22

off centre

Answer 22

on surround

Question 23

what does centre surround organisation/lateral inhibition serve to do

Answer 23

emphasise areas of difference (contrast) ie it sharpens the boundary between objects of different luminance

Question 24

where are segregation of cells representing movement and form

Answer 24

LGN and VI

Question 25

what is about halg of the visual cortex dedicated to info from

Answer 25

the fovea

Question 26

what does magnocellular LGN project form which layer

Answer 26

IVCa

Question 27

what does parvocellular LGN neurons project to which layer

Answer 27

IVCb

Question 28

what does koniocellular LGN axons project to

Answer 28

by passes layer IV to make synapses in II and III

Question 29

what is the competition hypothesis

Answer 29

connections from the 2 eye compete with each other in cortex

retinal synapses in LGN are not affected by deprivation because they are monocularr

Question 30

in the cortex monocular deprivation during a critical period results in what

Answer 30

active afferents from one eye and lower activity from the other eye