ORTCITIAEE: Receptors

Question 1

The Pacinian corpuscle is a ____ found deep in the skin of animals.

Answer 1

receptor

Question 2

Describe the structure of a Pacinian corpuscle:

Answer 2

• Single sensory neurone at its centre.
• Centre neurone is surrounded by layers of tissue

Question 3

Receptors only respond to _____ stimuli.

Answer 3

Specific.

Question 4

What does the Pacinical corpuscle respond to?

Answer 4

Mechanical pressure

Question 5

Explain the response of a sensory neurone’s (SN) membrane inside of
a Pacinian corpuscle when stimulated by the environment:

Answer 5

• Stretch-mediated sodium channels stretch when put under mechanical pressure.
• This causes an influx of sodium ions from the outisde of the SN into the SN.
• This causes the inside of the SN to become depolarised- establishing a generator potential.

Question 6

What are stretch-mediated channels inside of a sensory neurone’s membrane?

Answer 6

Transport proteins that open when the membrane is stretched or put under mechanical pressure.

Question 7

What happens when multiple generator potentials build up?

Answer 7

The threshold value is reached and an action potential is triggered inside the SN’s axon- which is passed on to the CNS.

Question 8

What is the human retina?

Answer 8

A layer of tissue in the back of the human eye that detects light from the environment.

Question 9

At the centre of the retina is the _____, where most of the light falls.

Answer 9

Fovea

Question 10

In the retina, where about does most of the light fall?

Answer 10

In the fovea

Question 11

What are the two types of light receptors?

Answer 11

• Rods
• Cones

Question 12

How many cones connect to a sensory neurone?

Answer 12

1

Question 13

How many rods connect to a sensory neurone?

Answer 13

3

Question 14

The axons of sensory neurones within the retina bundled together forms the _____ ______.

Answer 14

Optic Nerve

Question 15

What does the optic nerve do?

Answer 15

Transfers impulses from the retina to the brain.

Question 16

What are the 3 main structures in BOTH rods and cones?

Answer 16

• Nucleus
• Mitochondrion
• Membrane fold

Question 17

The membrane folds in rods and cones are dotted with _____ ______.

Answer 17

Optical pigments

Question 18

What are optical pigments?

Answer 18

Chemicals that enable the eye to respond to different wavelengths of light (seeing different colours).

Question 19

In cone cells there are __ optical pigments available.

Answer 19

3

Question 20

In cone cells there are 3 optical pigments available. What wavelengths (colours) are they sensitive to?

Answer 20

• Red
• Blue
• Green

Question 21

Cones have ____ visual acuity.

Answer 21

High

Question 22

What is visual acuity?

Answer 22

The ability to tell apart two points that are close together.

Question 23

Why do cone cells have high visual acuity?

Answer 23

As they are only attached to one sensory neurone, they can distinguish individual stimuli.

Question 24

Cone cells are sensitive to _____ light intensities.

Answer 24

High

Question 25

When it is dark, why do we struggle to see different colours?

Answer 25

- Cones are responsible for distinguishing wavelengths of light, allowing us to see blue, red and green colour variations. - Cones are sensitive to only high light intensities, meaning they don't work as effectively in low light intensities.

Question 26

Rods have ___ optical pigment.

Answer 26

1

Question 27

Rods only have 1 optical pigment. What does that mean?

Answer 27

They allow us to interpret colours in only black and white variations.

Question 28

Rods have ____ visual acuity.

Answer 28

Low

Question 29

Rods are sensitive to ____ light intensities.

Answer 29

Low

Question 30

Why are rod cells useful for seeing in the dark?

Answer 30

They are sensitive for low light intensities, meaning they work more effectively to interpret black and white colours in the dark.

Question 31

Rods have a low visual acuity. Why and what does this mean?

Answer 31

- 3 rods are attached to 1 sensory neurone, meaning they cannot distinguish individual stimuli. - They can only distinguish rough shapes.

Question 32

In rods ______ action potentials are sent to the brain.

Answer 32

single

Question 33

In cones ______ action potentials are sent to the brain.

Answer 33

separate

Question 34

The optic nerve transfers impulses from sensory neurones in the retina to the ______.

Answer 34

brain

Question 35

Which light receptor cell in the human retina relies on many generator potentials to trigger a single action potential

Answer 35

rods