1.8: Physiology 2 Flashcards Preview

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Flashcards in 1.8: Physiology 2 Deck (32):
1

Give a quick summary of how vision works?

1. The amount of light hitting the retina is regulated by the eye 2. Lights falls upon the rods and cones in the retina 3. Energy from waves of photons is changed into signals 4. Brain receives and interprets signals

2

Describe the order of the cells of the retina involved in signal transmission? (Front of the eye to the back)

- Optic Nerve Cells - Ganglion Axons - Ganglion Cells - Bipolar Cells - Photoreceptors

3

Describe the direct pathway for signal transmission?

- Photoreceptors - Bipolar Cells - Ganglion Cells - Ganglion Axons - Optic Nerve

4

Describe how the retina is considered 'back to front' when it comes to signal transmission?

The optic nerve cells and ganglion axons are furthest forward The Photoreceptors are furthest back However, light hits the photoreceptors first then travels forward

5

What are the two types of photoreceptors?

Rods Cones

6

Function of photoreceptors?

Convert light into neural signs

7

Describe rods and cones?

Rods are found on the periphery and work best in dark, low level light conditions (Eg: Night) Cones are central and work best in high level light conditions (Eg: Daytime) and colour

8

Describe the structure of a photoreceptor?

Synaptic Terminal Inner Segment Cell Body Outer Segment

A image thumb
9

What is in the outer segment of photoreceptors?

There is are membranous disks containing photopigment

10

Describe the physiology of phototransduction?

Photoreceptors have a depolarized resting membrane potential When light is shone, a cGMP-gated Na+ channel closes This causes hyperpolarization The change in Na+ is the signal that allows the brain to perceive objects in the visual field

11

What channel is involved in phototransduction? When is it open, when is it closed? What is this current called?

cGMP-gated Na+ channel Closed during light, open during dark This is the dark current

12

What is the dark current?

This is a cGMP-gated Na+ channel that is open during the dark and closed during the light

13

What is the photopigment in rods called?

Rhodopsin

14

What is retinal? Where is it found?

Retinal is the light-absorbing part of photopigment Opsin (the G-protein coupled receptor) makes a pocket where retinal is found

15

Rhodopsin = X + Y What does X mean? What does Y mean?

Rhodopsin = Opsin + Retinal Opsin is a G-protein coupled receptor Retinal is the light absorbing part

16

What confirmation of Retinal is used in phototransduction?

11-Cis-Retinal

17

What is retinal derived from?

Vitamin A

18

What happens when 11-cis-retinal absorbs a photon of light?

It becomes all-trans retinal This is the active form

19

What happens once 11-cis-retinal has been converted into all-trans-retinal?

This causes closure of cGMP Na+ Gate There is reduced Na+ entry This results in hyperpolarization

20

http://sites.sinauer.com/neuroscience5e/animations11.02.html Watch this animation

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21

What molecule regulates the dark current?

Rhodopsin

22

What facilitates visual acuity?

Photoreceptor spacing

23

Where is the highest number of cones?

Fovea

24

Where is the highest number of rods?

Periphery

25

What part of the electromagnetic spectrum can we detect?

Only visible light

26

What colour do the short wave cones detect?

Blue

27

What colour do the medium wave cones detect?

Green

28

What colour do the long wave cones detect?

Red

29

Compare visual acuity between rods and cones?

Rods = Low Visual Acuity Cones = High Visual Acuity

30

Compare convergence between rods and cones?

High Convergence = Rods Low convergence = Cones

31

Describe light sensitivity between rods and cones?

Rods = High sensitivity Cones = Low Light Sensitivity

32

Nerve fibres from the XXX half of each retina cross at the optic chiasm. XXX =?

Nerve fibres from the NASAL half of each retina cross at the optic chiasm