receptors

Question 1

most receptors are cells and are …

Answer 1

most receptors are cells and are specific - they only detect one particular stimulus.

Question 2

what are pacinian corpuscles?

Answer 2

these receptors respond to changes in mechanical pressure. receptors act as transducers i.e. convert one form of energy e.g. light, heat, sound etc. into another i.e. a nerve impulse. this receptor detects pressure and converts it into a generator potential which creates a nerve impulse.

Question 3

draw a pacinian corpuscle

Answer 3

see diagram

Question 4

how do pacinian corpuscles work?

Answer 4

in its resting state, stretch-mediated sodium ion channels in the membrane of these receptors are closed and do not allow sodium ions to pass into the receptor. the receptor has a resting potential.

when pressure (stimulus) is applied the receptor changes shape and the membrane of the receptor becomes stretched.

this stretching causes opening of the sodium ion channels and Na+ diffuse in (i.e. depolarisation) which produces a generator potential.

if the generator potential is above threshold level an action potential is produced and nerve impulses are transmitted along the neurone.