6.1.2 Receptors

Question 1

Basic structure of pacinian corpuscle

Answer 1

-lamellae (layers of protective tissues)
-gel
-sensory neurone ending
-sensory neuron axon
-myelin sheath (Schwann cells)
-stretch mediated sodium ion channel (closed)

Question 2

How is a generator potential is established within an pacinian corpuscle

Answer 2

Mechanical stimulus (pressure) deforms lamellae and stretched mediated sodium ion channels

So Na+ channels in membrane open and Na+ diffuses in.

This causes depolarisation leading to a generator potential.
If this reaches threshold it will trigger an action potential

Question 3

What does the pacinian corpuscle illustrate

Answer 3

Receptors respond only to specific stimuli -mechanical pressure

Stimulation of a receptor can establish and generator potential, which is reached threshold will cause an action potential

Question 4

Differences in sensitivity to light for rod and cones (in retina)

Answer 4

Rods are more sensitive:
-several rods connect to a single neurone
-spatial summation to overcome threshold to general action potential

Cones are less sensitive:
-each cone is connected to 1 neurone
-no spatial summation

Question 5

Diffrence visual in rods and cones

Answer 5

Rods give lower visual activity:
-several rods connect to 1 neurone
-so several rods send a set of impulses to Brian (can’t distinguish between sources of light)

Comes give higher visual activity:
-each cone to 1 neurone
-sends separate impulses to brain (can distinguish diffrent sources of light)

Question 6

Why is there is diffrence in sensitivity from rods vs cones

Answer 6

Rods allow monochromatic vision:
-1 type of pigment/ 1 rod

Cones allow colour vision:
-3 types, red, green and blue
-diffrent optical pigments to absorb different wavelengths
-stimulating diffrent combinations of cones to give a range in colour