Nerve Impulse Transmission- Initiation Of A Nerve Impulse In Response To An Environmental Stimulus: The Vertebrate Eye Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is the retina?

A

It is an area within the eye that detects light and contains two types of photoreceptor cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two type of photoreceptor cells within the retina?

A

Rods and cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do rods function?

A

In dim light but do not allow colour perception

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are cones responsible for?

A

Cones are responsible for colour vision and only function in bright light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In animals the light-sensitive molecule what is retinal combined with to form the photoreceptors of the eye?

A

a membrane protein called opsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

In the rod cells what is the retinal-opsin complex called?

A

rhodopsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the retinal response to light?

A

Retinal absorbs a photon of light and rhodopsin changes conformation to photoexcited rhodopsin, which causes the following process involving a cascade of proteins to amplify the signal:
Photoexcited rhodopsin activates a G-protein called transducin. A single photoexcited rhodopsin activates hundreds of molecules of G-protein. Transducin activates the enzyme phosphodieesterase (PDE). Each activated G-protein activates one molecule of PDE. PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP). Each active PDE molecule breakes down thousands of cGMP molecules per second. The reduction in cGMP concentration as a result of its hydrolysis affects the function of ion channels in the membrane of rod cells. There is a closure of ion channels in the membrane of the rod cells causing the inward leakage of positive Na+ ions is halted (so the membrane potential increases) causing hyperpolarisation. Hyperpolarisation triggers nerve impulses in neurons in the retina.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the high degree of amplification of the retinal response to light result in?

A

The rod cells being able to respond to low intensities of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In cone cells what do the different forms of opsin combine with?

A

With retinal to give different photoreceptor proteins, each with a maximal sensitivity to specific wavelengths: red, green, blue or UV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly