Receptors

Question 1

What are receptors?

Answer 1

specialised structures that detect stimuli

Question 2

What is the parcinian corpsucle?

Answer 2

a areceptor specialised to detect pressure changes

it can be found deep in the skin (of the fingers or soles of your feet)

Question 3

What happens when the parcinican corpsucle is stimulated?

Answer 3

it converts mechanical energy (pressure) into an electricle impulse called the generator potential

therefore they act as a trasducer

Question 4

Describe the structure of the pacinican copsucle?

Answer 4

• a sensory neurone surrounded by layers of lamellae
• each layer of lamellae is separated by a layer of gel

Question 5

Describe the cell membrane of the sensory neurone at resting potential.

Answer 5

• polarised
• the inner membrane is more negatively charged than the outer membrane
• this is because there is more sodium ions inner membrane
• has a millivoltage of 70

Question 6

Explain how is the generator potential established?

Answer 6

• change of pressure occurs
• this distorts the shape of the sensory neurone’s membrane by causing it to stretch
• this causes the stretch-mediated sodium channel proteins widen, causing sodium ions to diffuse into the sensory neurone
• this depolarises the membrane by making the inner membrane more positively charged

Question 7

How does an generator potential cause an action potential?

Answer 7

it causes a wave of depolarisation to be sent down the axon of the sensory neurone, which is an action potential

Question 8

What is a photoreceptor?

Answer 8

a specialised structure that detects light

Question 9

How does light reach the brain?

Answer 9

• light enters through the pupil
• the amount of light can enter is controlled by the iris
• the light is then focused by the retina
• photoreceptors cause light to be turned to an electricle impulse that is carried to the brain by the optic nerve

Question 10

Where are photoreceptors found?

Answer 10

in the retina

Question 11

What types of photoreceptors?

Answer 11

• cones
• rods

Question 12

Describe cones.

Answer 12

• involved in colour vision
• found mainly in fovea
• not sensitive to light
• has a high visual acuity
• there are three types that detect three colours of light (red, green, blue)
• contains the pigment iodopsin

Question 13

What is visual acuity?

Answer 13

clarity of vision

Question 14

Why do cones have a high visual acuity?

Answer 14

• because each cone is connected to it’s own bipolar neurone that connect to the optic neurone
• therefore it can send seperate sets of impulses to the brain

Question 15

How does the iris control how much light enters the eye?

Answer 15

• the iris is made up of circular and radial muscles
• the circular muscle contracts and the radial muscle relaxes which makes the pupil more narrow

Question 16

Describe rods.

Answer 16

• only detects light (not colours)
• found mainly outside the fovea
• sensitive to light
• low visual acuity
• contains the pigment rhodopsin

Question 17

Why do rods have a low visual acuity

Answer 17

multiple rods share a synapse with a neurone and therefore multiple rods are needed to create an action potentiaol/ send impulses to the brain