Unit 7 - Sensory Modalities

Question 1

overview of modalities

Answer 1

Question 2

mechanoreceptors

Answer 2

tactile info - skin and also visceral system

mostly associated with large diameter (Aβ) myelinated axons

Question 3

Merkel Cell complexes

proportion of mechanoreceptors composed of Merkel cell complexes

Answer 3

25% of mechanoreceptors - particularly dense in fingertips

Question 4

where can merkel cells be found

Answer 4

lie in primary epidermal ridges - fingerprints

Question 5

channels associated with merkel cells

Answer 5

VG Ca2+ channels

Question 6

resolution of merkel cell complexes

Answer 6

high spatial resolution - small receptive fields

Question 7

high spatial resolution ⇒

Answer 7

small receptive fields

Question 8

freq of stimulation merkel cells respond to

Answer 8

low freq stimulation - slight skin deformation

Question 9

Merkel cells are sensitive to

rate of adaptation

Answer 9

sensitive to points, edges, curvatures - form and texture

slowly adapting

Question 10

firing of merkel cells

Answer 10

As objects pass over your fingers they will cause deformations

Causing lamina surrounding nerve endings to change - open Ca2+ channels to depolarise neuron - reach threshold, travels towards Aβ fibre to CNS

Question 11

meissner corpusles - proportion of mechanoreceptors

Answer 11

40% of mechanoreceptors

Question 12

where are meissner corpusles found

Answer 12

tips of dermal papillae adjacent to primary ridges

Question 13

describe structure of meissner corpusles

Answer 13

elongated receptors - lamelle of Schwann cells

Question 14

what are meissner corpusles sensitive to

Answer 14

skin deformation

particularly low freq vibrations - objects moving over skin

objects slipping from hand - control of grip

Question 15

receptive fields of meissner corpusles

rate of adaptation

Answer 15

small receptive fields

rapidly adapting

Question 16

pacinian corpusles - proportion of mechanoreceptors

Answer 16

10-15% of mechanoreceptors

Question 17

where are pacinian corpusles located

Answer 17

deep in dermis

Question 18

freq of stimulation - pacinian corpusles

Answer 18

filters out low freq stimulation

responds to high freq (250-350 Hz)

Question 19

receptive fields of pacinian corpusles

Answer 19

large receptive fields

Question 20

type of stimulation associated with pacinian corpusles

Answer 20

pressure, vibration

important for skilled use of tools

Question 21

rate of adaptation of pacinian corpusles

Answer 21

rapidly adapting and low response to threshold

highly sensitive

Question 22

ruffini endings - proportion of mechanoreceptors

Answer 22

20% of mechanoreceptors

Question 23

shape and location of ruffini endings

Answer 23

elongated, spindle shaped, capsular

orientated parallel to stretch line in skin

Question 24

where are ruffini endings located

Answer 24

dermis, ligaments and tendons

Question 25

what do ruffini endings respond to

Answer 25

stretch and movement info on finger position and hand conformation as they stretch, open ion channels, allow Ca2+ and Na+ into neuron, activating AP

Question 26

rate of adaptation of ruffini endings

Answer 26

slowly adapting

Question 27

mechanoreceptors overview

Answer 27

Question 28

receptive field architecture

Answer 28

Question 29

comparing merkel, meissner, pacinian and ruffini afferents

Answer 29

Question 30

how do mechanoreceptors respond to braille

Answer 30

Merkle and Meissner recognise details of pattern Pacinian and Ruffini track movement and position of fingers

Question 31

Answer 31

Question 32

what is proprioception

Answer 32

perception of joint position, joint movements, velocity of joint movements and unconscious sensations

Question 33

mechanoreceptors involved in proprioception

Answer 33

low threshold mechanoreceptors golgi tendon organ muscle spindles joint receptors Not always conscious - constantly firing

Question 34

joint receptors role

Answer 34

resemble mechanoreceptors only minor role in proprioception important for judging finger position - Work with ruffini endings in order to allow us to know position of fingers in relation to each other - stretch skin protective role in signalling limits of joint range of motion

Question 35

GTO and muscle spindle

Answer 35

Question 36

rate of adaptation and fibre structure - thermoreceptors and nociceptors

Answer 36

free nerve ending associated with small diameter myelinated (Aδ) or unmyelinated (C) fibres slowly adaptation - continuous firing different ion channels - thermoreceptors and nociceptors

Question 37

thermoreceptors

Answer 37

cold (Aδ - more numerous) warm (c fibres) - unmyelinated

Question 38

nociceptors

Answer 38

Aδ - fast, ouch C - dull throbbing pain