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Y2 LCRS - Neuro (additional) > Somatosensory system > Flashcards

Somatosensory system Flashcards

1
Q

What are the three main types of sensory receptor and what is each responsible for?

A

Mechanoreceptors –> touch, pressure, vibration, proprioception, muscle length, muscle tension
Thermoceptors –> temperature
Nociceptors –> pain

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2
Q

What are the three main types of sensory fibre?

A

A-beta –> large, myelinated, fast
A-delta –> myelinated, less fast than A-beta
C –> unmyelinated, slow, free nerve endings

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3
Q

What are the three types involved in?

A

AB –> skin mechanoreceptors
Ad –> pain, temp
C –> pain, temp, itch

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4
Q

What are sensory receptors?

A

transducers that convert energy from environment into neuronal APs

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5
Q

What is the absolute threshold?

A

level of stimulus that produces a positive response of detection 50% of the time

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6
Q

What are TPR channels?

A

transient receptor ion channels

family of heat channels activated by different temperatures

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7
Q

What are the types of TPR channel?

A

4x heat activated –> TRPV1-4

2x cold activated –> TRPM8, TRPA1

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8
Q

What are the features of tonic receptors?

A

= slow adapting receptors
continually transmit impulses
eg. Merkel cells

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9
Q

What are the features of phasic receptors?

A

= fast adapting receptors
only transmit impulse at start + end of stimulus
eg. Pacinian corpuscle

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10
Q

What is two point discrimination?

A

min distance at which two points are perceived as seperate

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11
Q

What type of pain do the following fibres mediate?

a) A-d
b) C

A

A-d –> sharp, intense, first pain

C –> dull, persistent, second pain

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12
Q

What is special about C fibres?

A

polymodal –> respond to all modalities (only one type)

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13
Q

What is the role of lateral inhibition?

A

prevents overlap of receptive fields

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14
Q

What fibres are involved in the dorsal column?

A

A-beta fibres

*see notes on pathways

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15
Q

Which part of the spinothalamic tract do the following ascend in:

a) pain
b) temp
c) crude touch

A

pain + temp = lateral

crude touch = anterior

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16
Q

Where do the first order neurons of the following terminate?

a) dorsal column
b) spinothalamic tract

A

a) medulla

b) dorsal horn

17
Q

What is the spinoreticular tract?

A

emotional component

18
Q

What does a blocked anterior spinal artery cause?

A

ischaemic damage to anterior part of SC

19
Q

What does spinothalamic tract damage cause?

A

pain + temp loss BELOW level of lesion

retained light touch + vibration sensation due to intact DC

20
Q

What can be used to establish the level of a lesion?

A

EPT (=electric perceptual thresholds)

21
Q

What is pain?

A

an unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage

22
Q

What are the types of pain?

A

Acute eg. skin cut
Muscle eg. lactic acidosis, fibromyalgia
Somatic –> well localised eg. inflammation, infection
Visceral –> deep, poorly localised eg. stomach, colon, IBS
Referred –> from internal organ/structure eg. angina
Neuropathic –> dysfunction of NS

23
Q

What is allodynia?

A

pain due to a stimulus that does not normally provoke pain

24
Q

What is hyperalgesia?

A

increased pain from a stimulus that normally provokes pain

25
Q

How can synaptic plasticity lead to chronic pain?

A

synaptic plasticity –> decreased inhibitory influences on DH –> chronic pain

26
Q

What happens in normal pain sensation?

A

chemical/heat stimulus –> nociceptor nerve ends –> DH –> pain –> inhibitory input

27
Q

What are the two pathways involved in descending pain modulation + what are their neurotransmitters?

A

Monoamines released from brain stem –> inhibit SC excitability
two types:
1) PAG-RVM axis –> seretonin
2) locus cereleus –> NA

28
Q

How do endogenous opioids affect descending inhibition of pain?

A

increase inhibition

29
Q

What is the underlying mechanism of hyperalgesia?

A

loss of inhibitory input of pain

30
Q

What is the underlying mechanism of allodynia?

A

rewiring in the DH

Y2 LCRS - Neuro (additional) (1 decks)

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