9: Physiology - Pain and thermosensation Flashcards

1
Q

What is pain?

A

Unpleasant sensory / emotional experience

Associated with tissue damage or described in terms of it

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2
Q

Does pain mean that tissue damage is occurring?

A

Not neccessarily

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3
Q

Which type of pain is a short-term response to prevent tissue damage?

A

Nociceptive pain

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4
Q

What is the purpose of inflammatory pain?

A

Stops you from touching a damaged area until healing has occurred

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5
Q

How long does inflammatory pain persist for?

A

Days - Weeks

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6
Q

What are some adjuvant drugs which can be used to control pain?

A

Antidepressants

Anticonvulsants

Local anaesthetics

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7
Q

Describe pain originating from the skin.

A

WELL LOCALISED

stabbing, pricking, burning

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8
Q

Pain originating from the muscle and viscera tend to be ___ localised.

A

poorly localised

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9
Q

Visceral pain tends to be ___.

Muscle pain tends to be ___.

A

dull

achey

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10
Q

Pain can be ___ to distant areas.

A

referred

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11
Q

Which receptors detect intense stimuli to cause the sensation of pain?

A

Nociceptors

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12
Q

What sort of stimulus triggers a nociceptor?

A

High intensity stimuli

of a THERMAL, MECHANICAL or CHEMICAL nature

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13
Q

Nociceptors are which order neurons?

A

FIrst order neurons

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14
Q

What are the factors influencing the conduction velocity of a neuron?

A

1. Myelination

2. Diameter of axon

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15
Q

Which type of sensory fibre transmits fast pain?

A

A-delta

look back at the table of conduction velocities

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16
Q

Which type of sensory fibre transmits slow pain?

A

C fibres

look back at table of conduction velocities

17
Q

What does

a) fast pain
b) slow pain

feel like?

A

a) Stabbing, pricking, burning

b) Aching, throbbing

18
Q

Which ions enter a neuron to cause a depolarisation?

A

Na+

Ca2+

19
Q

Why does injured tissue feel hot?

A

One of the TRP channels responsible for noxious heat is activated

20
Q

What does polymodal mean in terms of nociceptors?

A

Respond to more than one noxious stimulus

21
Q

At which specific temperature does warmth become unpleasant heat?

A

43 degrees Celsius

22
Q

Which two types of nerve fibre make up most nociceptors?

A

A-delta (‘fast’ pain fibre)

C (‘slow’ pain fibre)

23
Q

Which neurotransmitters are involved in the transmission of pain signals?

A

Glutamate

(excitatory)

24
Q

The more a synapse is activated, the more ___ it becomes.

A

efficient

25
Q

What is released at the peripheral terminal of a nociceptor when it is activated?

A

Inflammatory mediators

26
Q

What causes sterile neurogenic inflammation?

A

Release of inflammatory mediators from the PERIPHERAL terminal of activated nociceptors

27
Q

Which neurotransmitter is released into the synaptic cleft when a pre-synaptic sensory fibre is activated?

Which change in membrane potential does it cause?

A

Glutamate

Depolarisation (excitatory post-synaptic potential)

28
Q

Two ligands, AMPA and NMDA, bind to receptors to change the type of excitatory post-synaptic potential that is produced.

What does each cause?

A

AMPA - fast

NMDA - slow

29
Q

The excitatory post-synaptic potential causes a depolarisation which overcomes threshold potential.

What happens next?

A

Action potential

30
Q

What does repeated stimulation of a synapse cause in the long term?

A

Increased efficiency

giving rise to hyperalgesia and allodynia

31
Q

Which intensity of stimulus is picked up by wide dynamic range cells in the lamina V?

A

All intensities

32
Q

What does visceral pain feel like?

A

Dull, aching, poorly localised

33
Q

What stimulus activates visceral nociceptors?

A

Stretching, twisting, inflammation, ischaemia

34
Q

Visceral afferents from internal organs “plug in” to the spinal cord at the same spinal levels as somatic sensory fibres.

What does this lead to?

A

Referred pain

35
Q

What are autonomic symptoms?

A

Symptoms caused by sympathetic activation

e.g N&V, sweating, pallor

36
Q

What are the characteristics of somatic pain?

A

Sharp, stabbing, well-localised pain

37
Q

What causes viscerosomatic pain?

A

Inflammation from an organ making contact with the body wall

e.g enlarged, inflamed appendix in appendicitis

38
Q

What disease classically causes visceral pain followed by viscerosomatic pain?

A

Appendicitis

39
Q

What is the jist of the Gate Control Theory?

A

If you can activate other sensory fibres e.g A-alpha, A-beta, you can override or ‘close the gate’ to nociceptive signals from A-delta and C

i.e distracting the brain with other stimuli can lessen the experience of pain