Cone and Rod cells.

Question 1

What is a stimulus?

Answer 1

A change in an organisms internal or external environment.

Question 2

What is a transducer?

Answer 2

Converts mechanical energy into electrical energy on a nerve impulse (pacinian corpuscle)

Question 3

What is the generator potential?

Answer 3

The change in potential difference across a cell membrane due to the presence of a stimulus

Question 4

What is a stretch-mediated Na channel?

Answer 4

These channels open to let Na in when they are stretched.

Question 5

What is a rod cell?

Answer 5

A photoreceptor found in peripheral parts of the retina. Only give information in black and white (monochromatic)

Question 6

What is a cone cell?

Answer 6

A photoreceptor found in the fovea. Only gives information is colour (photochromatic). 3 types of cone cells: red-sensitive, green-sensitive and blue-sensitive.

Question 7

What is visual acuity?

Answer 7

The ability to tell apart points that are close together.

Question 8

Explain how a pacinian corpuscle produces a generator potential in response to a specific stimulus. (3 marks)

Answer 8

Pressure distorts the Na-channel shape, leading to an influx of Na ions. This changes the potential of the membrane by depolarising it. If the activator potential reaches the threshold, the adjacent sodium-channels become activated/open causing an action potential to eb generated.

Question 9

What is the fovea?

Answer 9

Contains most of the cone cells and is where the clearest image is formed.

Question 10

What pigment does the cone cell contain?

Answer 10

IODOPSIN - requires high light intensity to be broken down and carried in a membrane

Question 11

What pigment does the rod cell contain?

Answer 11

RHODOPSIN - requires low light intensity to be broken down and carried in vesicles.