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CNS > Unit 7 - Sensory Modalities > Flashcards

Unit 7 - Sensory Modalities Flashcards

1
Q

overview of modalities

A
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2
Q

mechanoreceptors

A

tactile info - skin and also visceral system

mostly associated with large diameter (Aβ) myelinated axons

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3
Q

Merkel Cell complexes

proportion of mechanoreceptors composed of Merkel cell complexes

A

25% of mechanoreceptors - particularly dense in fingertips

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4
Q

where can merkel cells be found

A

lie in primary epidermal ridges - fingerprints

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5
Q

channels associated with merkel cells

A

VG Ca2+ channels

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6
Q

resolution of merkel cell complexes

A

high spatial resolution - small receptive fields

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7
Q

high spatial resolution ⇒

A

small receptive fields

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8
Q

freq of stimulation merkel cells respond to

A

low freq stimulation - slight skin deformation

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9
Q

Merkel cells are sensitive to

rate of adaptation

A

sensitive to points, edges, curvatures - form and texture

slowly adapting

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10
Q

firing of merkel cells

A

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

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11
Q

meissner corpusles - proportion of mechanoreceptors

A

40% of mechanoreceptors

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12
Q

where are meissner corpusles found

A

tips of dermal papillae adjacent to primary ridges

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13
Q

describe structure of meissner corpusles

A

elongated receptors - lamelle of Schwann cells

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14
Q

what are meissner corpusles sensitive to

A

skin deformation

particularly low freq vibrations - objects moving over skin

objects slipping from hand - control of grip

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15
Q

receptive fields of meissner corpusles

rate of adaptation

A

small receptive fields

rapidly adapting

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16
Q

pacinian corpusles - proportion of mechanoreceptors

A

10-15% of mechanoreceptors

17
Q

where are pacinian corpusles located

A

deep in dermis

18
Q

freq of stimulation - pacinian corpusles

A

filters out low freq stimulation

responds to high freq (250-350 Hz)

19
Q

receptive fields of pacinian corpusles

A

large receptive fields

20
Q

type of stimulation associated with pacinian corpusles

A

pressure, vibration

important for skilled use of tools

21
Q

rate of adaptation of pacinian corpusles

A

rapidly adapting and low response to threshold

highly sensitive

22
Q

ruffini endings - proportion of mechanoreceptors

A

20% of mechanoreceptors

23
Q

shape and location of ruffini endings

A

elongated, spindle shaped, capsular

orientated parallel to stretch line in skin

24
Q

where are ruffini endings located

A

dermis, ligaments and tendons

25
Q

what do ruffini endings respond to

A

stretch and movement

info on finger position and hand conformation

as they stretch, open ion channels, allow Ca2+ and Na+ into neuron, activating AP

26
Q

rate of adaptation of ruffini endings

A

slowly adapting

27
Q

mechanoreceptors overview

A
28
Q

receptive field architecture

A
29
Q

comparing merkel, meissner, pacinian and ruffini afferents

A
30
Q

how do mechanoreceptors respond to braille

A

Merkle and Meissner recognise details of pattern

Pacinian and Ruffini track movement and position of fingers

31
Q
A
32
Q

what is proprioception

A

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

33
Q

mechanoreceptors involved in proprioception

A

low threshold mechanoreceptors

golgi tendon organ

muscle spindles

joint receptors

Not always conscious - constantly firing

34
Q

joint receptors role

A

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

35
Q

GTO and muscle spindle

A
36
Q

rate of adaptation and fibre structure - thermoreceptors and nociceptors

A

free nerve ending associated with small diameter myelinated (Aδ) or unmyelinated (C) fibres

slowly adaptation - continuous firing

different ion channels - thermoreceptors and nociceptors

37
Q

thermoreceptors

A

cold (Aδ - more numerous)

warm (c fibres) - unmyelinated

38
Q

nociceptors

A

Aδ - fast, ouch

C - dull throbbing pain

CNS (36 decks)

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