Unit 2: Role of Receptors

Question 1

What are pacinian corpuscles?

Answer 1

mechanoreceptors found in skin or joints.

Question 2

What do pacinian corpuscles do?

Answer 2

they detect strong pressure and vibrations

Question 3

How is the pacinian corpuscle specific?

Answer 3

It only response to mechanical pressure and not to any other stimuli.

Question 4

How does the pacinian corpuscle act as a transducer?

Answer 4

it converts energy from the stimulus into a nervous impulse known as a generator potential. It transduces mechanical energy of the stimulus into a generator potential.

Question 5

How do receptor cells pass on the information to sensory neurones?

Answer 5

It can synapse with the sensory neurone or sometimes the receptor cell is a sensory neurone itself.

Question 6

Where are pacinian corpuscles found?

Answer 6

deep in the skin as well as in ligments and joints

Question 7

Describe the structure of a pacinian corpuscle

Answer 7

a single sensory neurone at the centre surrounded by layers of flattened schwann cells and fluid called lamellae

Question 8

What type of channel are present in the plasma membranes of pacinian corpuscles?

Answer 8

Stretch mediated sodium channels.

Question 9

When do stretch mediated sodium channels change shapes?

Answer 9

When the permeability of sodium in the membrane changes.

Question 10

What is the permeability of the stretch mediated sodium channels like at resting potential and why?

Answer 10

no permeable to sodium ions because the membrane around the neurone is too narrow for the ions to pass through

Question 11

What happens when pressure is applied to the stretch mediated sodium channels? What does this cause?

Answer 11

the membrane changes shape and becomes stretched. Strecthing causes the sodium channels to widen, allowing Na+ to diffuse in.

Question 12

When pressure is applied to pacinian corpuscle, the sodium channels stretch, allowing sodium ions to diffuse in. What does this cause?

Answer 12

A generator potential to be produced.

Question 13

How is an action potential triggered?

Answer 13

When the generator potential reaches threshold potential

Question 14

How is the eye a complex sense organ?

Answer 14

Because no only does it detect light, but it also regulates the intensity and focuses it to form sharp images.

Question 15

Which part of the eye detects light?

Answer 15

photoreceptors in the retina

Question 16

What are the two types of photoreceptors in the eye?

Answer 16

Rod cells and cone cells.

Question 17

What is the name of the interneurones that rod and cone cells synapse with?

Answer 17

Bipolar neurones.

Question 18

What cells do bipolar neurones synapse with?

Answer 18

ganglion cells and rod and cone cells.

Question 19

The axons of which cells cover the inner surface of the retina?

Answer 19

ganglion cells.

Question 20

What is the optic nerve made up of?

Answer 20

millions of ganglion axons.

Question 21

What does the optic retina do?

Answer 21

connects the retina to the brain.

Question 22

How many cone cells connect to one bipolar neurone?

Answer 22

one

Question 23

How many rod cells connect to one bipolar neruone?

Answer 23

groups of up to 100 rod cells.

Question 24

What is the linkage called between a bipolar cell and a photoreceptor (rod and cone cells)?

Answer 24

retinal convergence

Question 25

Which part of the eye is referred to as the blind spot?

Answer 25

the optic nerve.

Question 26

Why is it called the blind spot?

Answer 26

because it contains no photoreceptors.

Question 27

Which part of the eye does light pass through?

Answer 27

the pupil

Question 28

Which muscles control the amount of light entering the eye?

Answer 28

iris

Question 29

What do the lens in the eye do?

Answer 29

focus light onto the retina

Question 30

Which part of the eye contains lots of photoreceptors?

Answer 30

fovea

Question 31

How is the eye an example of a transducer?

Answer 31

it converts light energy into a nerve impulse

Question 32

What colour images do rod cells produce?

Answer 32

black and white

Question 33

Why are black and white images produced in rod cells?

Answer 33

because rod cells cannot distinguish between the different wavelengths of light

Question 34

Which part on the photoreceptor cells detcts light?

Answer 34

the membrane discs on the outer segment

Question 35

What is rhodopsin?

Answer 35

a photoreceptor protein, pigment in rod cells.

Question 36

In which photoreceptor cell is rhodopsin found?

Answer 36

rod cells

Question 37

What happens when rhodopsin becomes illuminated?

Answer 37

the rhodopsin molecule changes shape and so is able to bind with sodium channels in the receptor cell membranes

Question 38

What happens when rhodopsin binds to sodium channels?

Answer 38

allows sodium ions to diffuse in causing local depolarisation.

Question 39

When is threshold potential reached in a rod cell?

Answer 39

When sufficient number of sodium channels open.

Question 40

What happens when an action potential is triggered in a rod or cone cell?

Answer 40

the action potential is passed to the bipolar neurone and then to the ganglion cells in the retina.

Question 41

How come rod cells are able to responds to low intensity light?

Answer 41

because many rods connected one bipolar cell so greater chance of exceeding generator potential to reach threshold potential.

Question 42

Why do rod cells have a low visual acuity?

Answer 42

because many rod cells to one bipolar means the the light received by the rod cells will only generate one impulse. Unable to distinguish between separate light source.

Question 43

How many types of cone cells are there?

Answer 43

3 types

Question 44

Why are there three different types of cone cells?

Answer 44

because each one responds to a different wavelength of light

Question 45

Why do cone cells only respond to high intensity light?

Answer 45

because only one cone cell to one bipolar so cannot use retinal convergence to exceed threshold potential.

Question 46

What is the pigment in cone cells called?

Answer 46

iodopsin

Question 47

What happens when two adjacent cone cells are stimulated?

Answer 47

two separate impulses are generated

Question 48

Why do cone cells have high visual acuity?

Answer 48

because there is a high density of cone cells in the fovea and the 1:1 connections with the bipolar cells mean that it is able to tell the difference between separate impulses.