Receptors

Question 1

What are receptors?

Answer 1

a specific cell or protein on a cell-surface membrane, that detects a stimulus

Question 2

What do receptors in the nervous system do?

Answer 2

Convert the energy of the stimulus into the electrical energy used by neurones

Question 3

What are the three potentials of a cell membrane?

Answer 3

Resting
Generator
Action

Question 4

What is the resting potential of a membrane?

Answer 4

It is not being stimulated.
The inside of the membrane is relatively negative compared to the outside so there is a voltage across the membrane, also known as potential difference

Question 5

How is the resting potential maintained?

Answer 5

Through ion pumps and ion channels

Question 6

What is the resting membrane potential in mV?

Answer 6

about -70 mV

Question 7

What happens to the membrane when a stimulus is initially detected?

Answer 7

The cell membrane becomes excited and more permeable, allowing more ions to more in and out of the cell, altering the potential difference

Question 8

What is a generator potential?

Answer 8

A change in potential difference due to a stimulus

Question 9

What happens to the generator potential when the stimulus is bigger?

Answer 9

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

Question 10

What is an action potential?

Answer 10

An electrical impulse sent along a neurone

Question 11

How is an action potential triggered?

Answer 11

When the generator potential is enough to reach the threshold level

Question 12

How is the strength of the stimulus measured? Why?

Answer 12

The frequency of action potentials as all action potentials are the same size

Question 13

What happens when the stimulus is too weak?

Answer 13

The generator potential will not reach the threshold level and there won’t be an action potential

Question 14

What are pacinian corpuscles?

Answer 14

mechanoreceptors

Question 15

What do mechanoreceptors detect?

Answer 15

Mechanical stimulus such as pressure and vibrations

Question 16

Where are pacinian corpuscles found?

Answer 16

In the skin at the end of a sensory neurone

Question 17

What is the sensory nerve ending wrapped up in?

Answer 17

Layers of connective tissue called lamellae

Question 18

What happens when the pacinian corpuscles are stimulated?

Answer 18

The lamellae become deformed and press on the sensory nerve ending, deforming the stretch-mediated sodium ion channels

Question 19

What happens when the stretch-mediated sodium ion channels become deformed?

Answer 19

They open and sodium ions diffuse into the cell, creating a generator potential. If the generator potential reaches the threshold, it’ll trigger an action potential

Question 20

What are photoreceptors?

Answer 20

Receptors in the eye which detect light

Question 21

What does the retina contain?

Answer 21

Photoreceptor cells

Question 22

Where in the retina are there the most photoreceptors?

Answer 22

Fovea

Question 23

Where are nerve impulses carried from and to in the eye?

Answer 23

From the photoreceptor cells in the retina to the brain by the optic nerve

Question 24

What is the blindspot?

Answer 24

Where the optic nerve leaves the eye

Question 25

Why is the blindspot not sensitive to light?

Answer 25

There aren’t any photoreceptor cells

Question 26

How do photoreceptors work?

Answer 26

The light that hits the photoreceptors is absorbed by light-sensitive optical pigments. The light bleaches the pigments causing a chemical change and altering the membrane permeability to sodium ions. A generator potential is created and if it reaches the threshold, an action potential is triggered and the nerve impulse is sent along a bipolar neurone

Question 27

What do bipolar neurones connect?

Answer 27

photoreceptors to the optic nerve which takes it to the brain

Question 28

What are the two types photoreceptors?

Answer 28

Rods and cones

Question 29

Where are rods mainly found?

Answer 29

Mainly found in peripheral parts of the retina

Question 30

Where are cones mainly found?

Answer 30

Packed together in the fovea

Question 31

What type of vision do rods give you?

Answer 31

monochromatic - black and white

Question 32

What type of vision do cones give you?

Answer 32

trichromatic - colour vision

Question 33

What are the three different optical pigments in the 3 different cones?

Answer 33

red-sensitive, green sensitive and blue-sensitive

Question 34

Are rods sensitive to light? Why?

Answer 34

Yes
Many rods join one bipolar neurone, so many weak generator potentials can combine to reach the threshold and trigger an action potentials

Question 35

Are cones sensitive to light? Why?

Answer 35

No

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

Question 36

What is visual acuity?

Answer 36

The ability to tell apart points that are close together

Question 37

Do rods have a high or low visual acuity? Why?

Answer 37

Low

Many rods jin the same bipolar neurone which means light from two points close together can’t be told apart

Question 38

Do cones have a high or low visual acuity? Why?

Answer 38

High
Cones are close together and one cone joins one bipolar neurone. When light from two points hit two cones, two action potentials go to the brain so you can distinguish between two points