Cutaneous receptors (365/351)

Question 1

define mechanotransduction

Answer 1

process where mechanical energy is converted into a voltage change in sensory afferent neurons

Question 2

what is a receptive field

Answer 2

region of the skin that is capable of evoking APs in a given cutaneous afferent

Question 3

which type of receptor has one large receptive field

Answer 3

type 2 deep receptors (one cell to one neuron)

Question 4

what type of receptor has multiple hotspots in its receptive field

Answer 4

type 1 superficial receptors (multiple cells attached to one neuron)

Question 5

which two cells are type 1 superficial receptors

Answer 5

SA1 - merkel cell
FA 1 - meissners corpuscle

Question 6

which two cells are type 2 deep receptors

Answer 6

SA2 - ruffini endings
FA2 - pacinian corpuscles

Question 7

which two cells are fast adapting

Answer 7

FA1 - meissners corpuscle
FA2 - pacinian corpuscle

Question 8

which two cells are slow adapting

Answer 8

SA1 - merkel cells
SA2 - ruffini endings

Question 9

which receptor is not present in non human primates (and allows us to walk on 2 feet instead of 4)

Answer 9

SA2 - ruffini endings

Question 10

what is the merkel cell - neurite complex

Answer 10

merkel cell and the sensory neuron it synapses with

Question 11

which two receptors are highly concentrated in the fingertips

Answer 11

SA1 - merkel cells
FA1 - meissners corpuscle

Question 12

which two receptors have equally distributed innervation density

Answer 12

SA2 - ruffini endings
FA2 - pacinian corpuscle

Question 13

which receptor responds to edges and curvature

Answer 13

SA1 - merkel cells

Question 14

which receptor responds to slippage and motion across skin

Answer 14

FA2 - meissner corpuscles

Question 15

which receptor is most sensitive to skin stretch

Answer 15

SA2 - ruffini endings

Question 16

which receptor is most sensitive to change in indentation rate (acceleration) and high frequency vibration

Answer 16

FA2 - pacinian corpuscles

Question 17

rank the 4 receptors on mean mechanical threshold from high to low

Answer 17

high (300um) - SA2 ruffini endings
moderate (30um) - SA1 merkel cells
low (6um) - FA1 meissner corpuscle
extreme low (0.08um) - FA2 pacinian corpuscle

Question 18

what happens with FA1 and FA2 as vibration frequency increases from 30-200 Hz)

Answer 18

meissner (FA1) firing rate increases until 50Hz and then firing rate remains the same at any frequency past 50Hz

• pacinian (FA2) firing rate increases continuously until 200 Hz (is capable of recognising frequencies up to 500 Hz)

Question 19

what does FA2s extremely low MM threshold mean

Answer 19

requires very little indentation to fire (lower than both superficial cells)

Question 20

do ruffini endings work the same in all directions of stretch

Answer 20

no - best firing rate when they are stretched end to end (highly tuned to direction of stretch)

Question 21

what allows pacinian corpuscles to be sensitive to vibration

Answer 21

concentric fluid filled laminae aorund a sensory nerve terminal that transmits vibration very well

• they are sensitve to alternating inputs (mechanical vibration - which is just repeated indentation)

Question 22

how can the CNS determine the location of stimuli

Answer 22

based on which afferents specifically are active and the neuron’s receptive field

Question 23

which receptor codes for spatial details (size and shape)

Answer 23

SA1 - merkel cells

Question 24

how does a small vs large probe impact discharge rate

Answer 24

small probe = high discharge in a few afferents (higher pressure with same force due to smaller SA)
large probe = lower discharge rate in more afferents (larger SA)

Question 25

would rough or slippery objects evoke a greater response in FA1 afferents

Answer 25

slippery = high afferent response because more grip force is required
rough = low afferent response because less grip force is needed