13.3 Sensory Receptors

Question 1

What is the role of sensory receptors?

Answer 1

Convert the stimulus they detect into a nerve impulse

Question 2

What is a transducer?

Answer 2

Something which converts one form of energy into another

Question 3

How do sensory receptors act as a transducer?

Answer 3

They convert the energy of a stimulus into a nervous impulse ( electrical energy)

Question 4

What are the main features of sensory receptors?

Answer 4

-Specific to a singe type of stimulus
-Act as a transducer, to convert a stimulus into a nerve impulse

Question 5

What is the stimulus detected and an example of a receptor and sense organ for mechanoreceptors?

Answer 5

Stimulus - Pressure and movement
Receptor example - Pacinian corpuscle
Sense organ example - Skin

Question 6

What is the stimulus detected and an example of a receptor and sense organ for chemoreceptors?

Answer 6

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

Question 7

What is the stimulus detected and an example of a receptor and sense organ for thermoreceptors?

Answer 7

Stimulus - Heat
Receptor example - End bulbs of Krause
Sense organ example - Tongue

Question 8

What is the stimulus detected and an example of a receptor and sense organ for photoreceptors?

Answer 8

Stimulus - Light
Receptor example - Cone cell
Sense organ example - Eye

Question 9

What is a generator potential?

Answer 9

When a receptor converts a stimulus into a nervous impulse

Question 10

Where are pacinian corpuscles located?

Answer 10

Found deep within the skin, most abundant in the fingers and soles of the feet, and also found within joints

Question 11

What is the structure of a pacinian corpuscle at rest?

Answer 11

-Contain the end of a sensory neurone called a sensory nerve ending, wrapped in lots of layers of connective tissue called lamellae
-Each layer of connective tissue is separated by a layer of viscous gel
-Neurone ending contains a stretch-mediated sodium channel

Question 12

What is the structure of a pacinian corpuscle at rest?

Answer 12

-Contain the end of a sensory neurone called a sensory nerve ending, wrapped in lots of layers of connective tissue called lamellae
-Each layer of connective tissue is separated by a layer of viscous gel
-Neurone ending contains a stretch-mediated sodium channel

Question 13

Explain how a Pacinian corpuscle converts mechanical pressure into a nervous impulse?

Answer 13

1. In its resting state the stretch-mediated sodium ion channels in the sensory neurones membrane are too narrow to allow sodium ions to pass through. The neurone of the Pacinian corpuscle has a resting potential
2. When pressure is applied to the Pacinian corpuscle, the corpuscle changes shape, lamellae stretch and deform
3. When the membrane stretches, the sodium ions channels present widen, sodium ions can now diffuse into the neurone
4. The influx of positive sodium ions changes the potential of the membrane, causing it to become depolarised, resulting in a generator potential
5. In turn, if the the generator potential is big enough it creates an action potential which passes along the sensory neurone

Question 14

What is a generator potential?

Answer 14

The change in potential difference due to a stimulus

Question 15

If the stimulus is bigger what occurs at the pacinian corpuscle ?

Answer 15

A greater pressure, greater stretch of the membrane, more sodium ions enter and a bigger generator potential is produced.