13.3 Sensory receptors

Question 1

What does the body use to detect changes in its environment?

Answer 1

Specialised group of cells - sensory receptors

Question 2

Where are sensory receptors often located?

Answer 2

Sense organs, e.g. ear and eye

Question 3

What do sensory receptors do with a stimulus?

Answer 3

Convert the stimulus into a nerve impulse

Question 4

What happens after the sensory receptor converts a stimulus into a nerve impulse?

Answer 4

The information is passed through the nervous system and into the CNS, usually the brain

Question 5

What does the brain do after the sensory receptor converts a stimulus into a nerve impulse?

Answer 5

The brain coordinates the respnse and sends an impulse to an effector (muscle/gland) to provide the desired response

Question 6

What are the 2 main features of a sensory receptor?

Answer 6

1. Specific to a single type of stimulus

2. Act as a transducer - converts a stimulus into a nerve impulse

Question 7

Name the 4 types of sensory receptors.

Answer 7

Mechanoreceptor
Chemoreceptor
Thermoreceptor
Photoreceptor

Question 8

What are the characteristics of the mechanoreceptor?

Answer 8

Stimulus: Pressure and movement
Example of receptor: Pacinian corpuscle (detects pressure)
Example of sense organ: Skin

Question 9

What are the characteristics of the chemoreceptor?

Answer 9

Stimulus: Chemicals
Example of receptor: Olfactory receptor (detects smell)
Example of sense organ: Nose

Question 10

What are the characteristics of the thermoreceptor?

Answer 10

Stimulus: Heat
Example of receptor: End-bulbs of Krause
Example of sense organ: Tongue

Question 11

What are the characteristics of the thermoreceptor?

Answer 11

Stimulus: Light
Example of receptor: Cone cell (Detects light wavelengths)
Example of sense organ: Eye

Question 12

What do sensory receptors detect?

Answer 12

A range of stimuli e.g. light, heat, sound or pressure

Question 13

What does the receptor convert the stimulus into?

Answer 13

A nervous impulse, called a generator potential

Question 14

Give an example of a receptor responding to stimuli?

Answer 14

A rod cell (in eye) responds to light and produces a generator potential

Question 15

What are pacinian corpuscles?

Answer 15

Sensory receptors that detect mechanical pressure

Question 16

Where are pacinian corpuscles located?

Answer 16

• Deep within skin, most abundant in fingers + soles of feet.
• Within joints, enabling you to know which joints are changing direction.

Question 17

What is in the centre of the corpuscle and what is it surrounded by?

Answer 17

The end of a sensory neurone, sourrounded by connective tissue.
Each tissue layer is separated by a gel layer.

Question 18

What can be found in the membrane of the sensory neruone?

Answer 18

Sodium ion channels

Question 19

What is the role of the sodium ion channels in the membrane of the neurone?

Answer 19

To transport sodium ions across the membrane

Question 20

What’s special about the neurone ending in a Pacinian corpuscle?

Answer 20

It has a sodium channel called a ‘stretch-mediated sodium channel’

Question 21

What happens to stretch-mediated sodium channels when they stretch?

Answer 21

Their permeability to sodium changes

Question 22

Describe the 5 step process of how a Pacinian corpuscle converts mechanical pressure into a nerve impulse?

Answer 22

1. In its resting state, the stretch-mediated sodium ion channels, in the sensory neuron membrane, are too narrow to allow sodium ions to pass through them.
   The neurone of the Pacinian corpuscle has a resting potential.
2. When pressure is applied to the Pacinian corpuscle, the corpuscle changes shape.
   This causes the membrane surrounding the neurone to stretch.
3. When the membrane stretches, the sodium ion channels widen.
   Sodium ions can now diffuse into the neurone.
4. The influx of positive sodium ions changes the potential of the membrane - the membrane becomes depolarised.
   This results in a generator potential.
5. The generator potential creates an action potential (nerve impulse) that passes along the sensory neurone.

The action potential will then be transmitted along neurones to the CNS.