6.1.2 Receptors

Question 1

What are all receptors?

Answer 1

All receptors are specific to one type of stimulus

Question 2

What do receptors act as?

Answer 2

Transducer - they convert the stimulus into a nervous impulse (which travels to the CNS via a sensory neurone)

Question 3

Give two examples of receptors, and the stimuli they detect

Answer 3

Stimulus (heat, light, sound or mechanical energy) –> Nervous impulse (action potential)

Question 4

What are Parcinian corpuscles?

Answer 4

Pressure receptors found in the skin

Question 5

What are Parcinian corpuscles?

Answer 5

Pressure receptors found in the skin

Question 6

How does the Pacinian corpuscle generate a generator potential?

Answer 6

• Mechanical stimulus eg/ pressure deforms lamellae and stretch-mediated sodium ion channel
• Sodium ion channels open and sodium ions diffuse into sensory neurone
• Greater pressure causes more channels to open and more sodium ions to enter
• Causes depolarisation, leading to a generator potential
• If generator potential reaches threshold it triggers an action potential

Question 7

What does the Pacinian corpuscle illustrate?

Answer 7

• Receptors respond only to specific stimuli - only responds to mechanical pressure
• Stimulation of a receptor leads to the establishment of a generator potential. When threshold is reached, action potential sent, all-or-nothing principle

Question 8

What colours do you see for a rod?

Answer 8

Black and white

Question 9

What colours do you see for a cone?

Answer 9

Colour vision - bright light

Question 10

What happens when light hits a rod?

Answer 10

The pigment - Rhodopsin - broken down by the light
If there is enough light to reach the threshold potential then a generator potential is stimulated in the bipolar neurone
If this reaches a minimum level then an action potential will be stimulated in the sensory neurone
Several rods are connected to one sensory neurone - this is called retinal convergence

Question 11

How does this (rods) increase sensitivity, but reduce visual acuity?

Answer 11

• Sensitivity - low level stimulation in several different rods can combine to reach threshold in their shared neurone
• Lower acuity - brain cannot distinguish between rods that share a neurone

Question 12

What happens when light hits a cone?

Answer 12

• The pigment - Iodopsin - broken down by the light
• If there is enough light to reach the threshold potential then a generator potential is stimulated in the bipolar neurone
• If this reaches a minimum level then an action potential will be stimulated in the sensory neurone

Question 13

How does this (cones) decrease sensitivity, but increase visual acuity?

Answer 13

High visual acuity - The brain can distinguish between individual cones because each has its own sensory neurone

Low sensitivity - each individual cone must be stimulated enough to reach threshold