Stimuli and Responses- Receptors

Question 1

What does it mean that receptors are specific?

Answer 1

They only detect one particular stimulus

Question 2

What is a receptor like in resting state?

Answer 2

There’s a difference in charge between the inside and the outside of the cell

Question 3

What is potential difference?

Answer 3

Voltage- generated by ion pumps and ion channels

Question 4

What is resting potential?

Answer 4

Potential difference when a cell is at rest

Question 5

What happens when a stimulus is detected?

Answer 5

Cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell (altering potential difference)

Question 6

What is a generator potential?

Answer 6

Change in potential difference due to a stimulus

Question 7

Why is a bigger generator potential produced when there is a bigger stimulus?

Answer 7

A bigger stimulus excites the membrane more so causes a bigger movement of ions and a bigger change in potential difference

Question 8

When will an action potential be generated?

Answer 8

Only if the generator potential reaches the threshold level

Question 9

What are Pacinian corpuscles?

Answer 9

Mechanoreceptors (detect mechanical stimuli)

Question 10

Where are Pacinian corpuscles found?

Answer 10

In your skin

Question 11

What do Pacinian corpuscles contain?

Answer 11

The end of a sensory neurone (sensory nerve ending) wrapped in lots of layers of connective tissue called lamellae

Question 12

What happens when a Pacinian corpuscle is stimulated?

Answer 12

Lamellae are deformed and press on the sensory nerve ending causing the sensory neurone’s 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

Question 13

When is an action potential triggered?

Answer 13

If the generator potential reaches the threshold

Question 14

How does light enter the eye?

Answer 14

Through the pupil

Question 15

What controls the amount of light entering the eye?

Answer 15

Muscles of the iris

Question 16

How are light rays focused?

Answer 16

By the lens onto the retina which lines the inside of the eye

Question 17

What does the retina contain?

Answer 17

Photoreceptor cells that detect light

Question 18

What is the fovea?

Answer 18

An area of the retina where there are lots of photoreceptors

Question 19

How are nerve impulses from photoreceptor cells carried from the retina to the brain?

Answer 19

By the optic nerve which is a bundle of neurones

Question 20

Why is the area where the optic nerve leaves the eye called the blind spot?

Answer 20

There aren’t any photoreceptor cells so it isn’t sensitive to light

Question 21

What happens when light enters the eye?

Answer 21

It hits the photoreceptors and is absorbed by light-sensitive optical pigments

Question 22

What does light bleaching the pigments cause?

Answer 22

A chemical change and alters membrane permeability to sodium ions

Question 23

What happens if a generator potential and it reaches the threshold is created in the eye?

Answer 23

A nerve impulse is sent along a bipolar neurone

Question 24

What do bipolar neurones do?

Answer 24

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

Question 25

What are the two types of photoreceptors in the human eye?

Answer 25

Rods and cones

Question 26

Where are rods found?

Answer 26

In the peripheral parts of the retina

Question 27

Where are cones found?

Answer 27

Packed together in the fovea

Question 28

What makes rods and cones sensitive to different wavelengths of light?

Answer 28

They contain different optical pigments

Question 29

Which photoreceptors give monochromatic vision (black and white)?

Answer 29

Rods

Question 30

Which photoreceptors give trichromatic vision (colour)?

Answer 30

Cones

Question 31

What are the three different types of cones with different optical pigments?

Answer 31

Red-sensitive, green-sensitive, blue-sensitive

Question 32

What happens when different types of cones are stimulated in different proportions?

Answer 32

You see different colours

Question 33

Why are rods very sensitive to light?

Answer 33

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

Question 34

Why are cones less sensitive to light?

Answer 34

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

Question 35

What does visual acuity mean?

Answer 35

The ability to tell apart points that are close together

Question 36

Why do rods give lower visual acuity?

Answer 36

Because many rods join the same neurone which means light from two points close together can’t be told apart

Question 37

Why do cones give higher visual acuity?

Answer 37

Because cones are close together and one cone joins one neurone- when light from two points hits two cones, two action potentials go to the brain so you can distinguish two points that are close together as two separate points