Receptors

Question 1

What does it mean for receptors to be specific?

Answer 1

They can only detect one particular stimulus, which means many different types of receptors each detect a different stimulus

Question 2

What can receptors be?

Answer 2

Cells
Proteins on cell surface membrane

Question 3

How do receptor cells work?

Answer 3

1. When a nervous system is in its resting state there is a difference in charge inside and outside the cell. This is generated by ion pumps/channels and means there’s a potential difference across the membrane
2. When a stimulus is detected the cell is excited becoming more permeable. This alters the potential difference. The change in potential difference is called the generator potential.
3. A bigger stimulus excites the membrane more causing a bigger movement of ions and a bigger change in potential difference so a bigger generator potential is produced.
4. If the generator potential is big enough it will trigger an action potential (an electrical impulse along a neurone). An action potential is only triggered if the action potential reaches the threshold level.
5. The strength of the stimulus is measure by frequency of action potentials. If the stimulus is too weak the generator potential won’t reach the threshold so there is no action potential

Question 4

What are Pacinian corpuscles?

Answer 4

Mechanoreceptors (detect mechanical stimuli) found in your skin

Question 5

What do Pacinian corpuscles contain?

Answer 5

The end of a sensory neurone called the sensory nerve ending

Question 6

What is the sensory nerve ending wrapped in?

Answer 6

Connective tissue called lamella

Question 7

How do Pacinian corpuscles work?

Answer 7

1. When a Pacinian corpuscles is stimulate the lamella are deformed and press on the sensory nerve endings
2. This causes the sensory neurone cell membrane to stretch , deforming the stretch mediated sodium ion channels. The channels open and sodium ions diffuse into the cell, creating a generator potential
3. If the generator potential reaches threshold it triggers an action potential

Question 8

How does light enter the eye?

Answer 8

Through the pupil

Question 9

What does the iris do?

Answer 9

Controls the amount of light that enters the eye

Question 10

What does the retina contain?

Answer 10

Photoreceptor cells

Question 11

What is the fovea?

Answer 11

An area of the retina where there are lots of photoreceptors

Question 12

How are nerve impulses from the photoreceptors carried from the retina to the brain?

Answer 12

By the optic nerve (a bundle of neurones)

Question 13

What is the blind spot?

Answer 13

Where the optic nerve leaves the eye
There are not any photoreceptor cells so it is not sensitive to light

Question 14

What light enters the eye what happens?

Answer 14

The light hits the photoreceptors and is absorbed by light sensitive optical pigments

Question 15

What does light do to the pigments?

Answer 15

Bleaches the pigments which causes a chemical change and alters the permeability to sodium ions

Question 16

What happens if the generator potential that is created reaches threshold?

Answer 16

A nerve impulse is sent along a bipolar neurone

Question 17

What does a bipolar neurone do?

Answer 17

Connect photoreceptors to the optic nerve which takes impulses to the brain

Question 18

Name the 2 photoreceptors in the eye

Answer 18

Rod
Cone

Question 19

Where are rods found?

Answer 19

In the peripheral parts of the retina

Question 20

What do the rods do?

Answer 20

Give information in black and white
(monochromatic vision)

Question 21

Where are cones found?

Answer 21

In the fovea

Question 22

What do the cones do?

Answer 22

Give information in colour
(trichromatic vision)

Question 23

Name the 3 different types of cones

Answer 23

Red sensitive
Green sensitive
Blue sensitive

Question 24

Why are rods sensitive to light?

Answer 24

Many rods join one neurone so many weak generator potentials combine to reach threshold and trigger an action potential

Question 25

What are cone less sensitive to light?

Answer 25

One cone joins to one neurone so it take more light to reach the threshold and trigger an action potential

Question 26

What is visual acuity?

Answer 26

The ability to tell apart points that are close

Question 27

Why do rods have low visual acuity?

Answer 27

Many rods join to the same neurone which means light from 2 points close together can’t be told apart

Question 28

Why do cones have high visual acuity?

Answer 28

Cones are close together and 1 cone joins one neurone. When light from 2 points hits two cones , 2 action potentials go to the brain so you can distinguish 2 points that are close together as two separate points