The Role Of Receptors

Question 1

Why is the pacinian corpuscle specific?

Answer 1

It only responds to a single type of stimulus - mechanical pressure, not heat, light or sound

Question 2

How does the pacinian corpuscle produce a generator potential?

Answer 2

It acts as a transducer

Question 3

What is the role of the transducer?

Answer 3

It converts the information provided by the stimulus into a form that can be understood by the body, namely the nerve impulses

Question 4

What is the role of receptors?

Answer 4

They convert, or transduce, one form of energy to another

Question 5

What is the conversion of the energy of the stimulus into a nervous impulse known as?

Answer 5

A generator potential

Question 6

Where are the pacinian corpuscles located?

Answer 6

Deep in the skin and in joints, ligaments and tendons

Question 7

What does the sensory neurone ending at the centre of the pacinian corpuscle have in its plasma membrane, and what is this called?

Answer 7

A special type of sodium channel called a stretch-mediated sodium channel

Question 8

What happens when pressure is applied to the pacinian corpuscle?

Answer 8

It changes shape and the membrane around its neurone becomes stretched which widens the sodium channels in the membrane and sodium ions diffuse into the neurone, thereby producing a generator potential

Question 9

What does the generator potential produce?

Answer 9

An action potential that passes along the neurone and then, via other neurones, to the central nervous system

Question 10

Where are the light receptor cells of the mammalian eye found?

Answer 10

The retina

Question 11

What are the two types of light receptors?

Answer 11

Rods and cones

Question 12

What do rod and cone cells act as?

Answer 12

Transducers that convert light energy into the electrical energy of a nerve impulse

Question 13

What can rod cells not do, and what does this mean?

Answer 13

They cannot distinguish between different wavelengths of light so they can only produce black and white images

Question 14

Which light receptors are most abundant within the eyes?

Answer 14

Rod cells

Question 15

What does the pacinian corpuscle respond to?

Answer 15

Changes in mechanical pressure

Question 16

What do many rod cells share?

Answer 16

A single sensory neurone

Question 17

What does the fact that many rod cells share a single sensory neurone allow them to do?

Answer 17

Detect light of very low intensities

Question 18

How does the fact that rod cells share a single sensory neurone allow them to respond to light of very low intensities?

Answer 18

A certain threshold value must be exceeded before a generator potential is created in the bipolar cells that they are attached to but as a number of rod cells are are attached to a single bipolar cell, there is a much greater chance that the threshold value will be exceeded than if only a single rod cell were attached to each bipolar cell

Question 19

What must be done in order to create a generator potential?

Answer 19

The pigment - rhodopsin, in the rod cells, must be broken down

Question 20

How does the idea of breaking down rhodopsin allow rod cells to respond to low light intensities?

Answer 20

Low light intensity is sufficient to cause this breakdown

Question 21

What is low in rod cells?

Answer 21

Visual acuity

Question 22

What are the differences in the distribution of the rod and cone cells in the eye?

Answer 22

The rod cells are distributed at the periphery of the retina whereas cone cells are more concentrated at the fovea

Question 23

What pigment is found in cone cells?

Answer 23

Iodopsin

Question 24

Why are cone cells less responsive to low light intensities?

Answer 24

A higher light intensity is required for the break down of Iodopsin and only a higher light intensity is therefore able to Crete a generator potential

Question 25

What makes cone cells have high visual acuity?

Answer 25

Each cone cell has its own connection to a single bipolar cell which means the brain receives separate impulses that allow it to distinguish between two separate sources of light