9: Physiology - Pain and thermosensation

Question 1

What is pain?

Answer 1

Unpleasant sensory / emotional experience

Associated with tissue damage or described in terms of it

Question 2

Does pain mean that tissue damage is occurring?

Answer 2

Not neccessarily

Question 3

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

Answer 3

Nociceptive pain

Question 4

What is the purpose of inflammatory pain?

Answer 4

Stops you from touching a damaged area until healing has occurred

Question 5

How long does inflammatory pain persist for?

Answer 5

Days - Weeks

Question 6

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

Answer 6

Antidepressants

Anticonvulsants

Local anaesthetics

Question 7

Describe pain originating from the skin.

Answer 7

WELL LOCALISED

stabbing, pricking, burning

Question 8

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

Answer 8

poorly localised

Question 9

Visceral pain tends to be ___.

Muscle pain tends to be ___.

Answer 9

dull

achey

Question 10

Pain can be ___ to distant areas.

Answer 10

referred

Question 11

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

Answer 11

Nociceptors

Question 12

What sort of stimulus triggers a nociceptor?

Answer 12

High intensity stimuli

of a THERMAL, MECHANICAL or CHEMICAL nature

Question 13

Nociceptors are which order neurons?

Answer 13

FIrst order neurons

Question 14

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

Answer 14

1. Myelination

2. Diameter of axon

Question 15

Which type of sensory fibre transmits fast pain?

Answer 15

A-delta

look back at the table of conduction velocities

Question 16

Which type of sensory fibre transmits slow pain?

Answer 16

C fibres

look back at table of conduction velocities

Question 17

What does

a) fast pain
b) slow pain

feel like?

Answer 17

a) Stabbing, pricking, burning

b) Aching, throbbing

Question 18

Which ions enter a neuron to cause a depolarisation?

Answer 18

Na+

Ca2+

Question 19

Why does injured tissue feel hot?

Answer 19

One of the TRP channels responsible for noxious heat is activated

Question 20

What does polymodal mean in terms of nociceptors?

Answer 20

Respond to more than one noxious stimulus

Question 21

At which specific temperature does warmth become unpleasant heat?

Answer 21

43 degrees Celsius

Question 22

Which two types of nerve fibre make up most nociceptors?

Answer 22

A-delta (‘fast’ pain fibre)

C (‘slow’ pain fibre)

Question 23

Which neurotransmitters are involved in the transmission of pain signals?

Answer 23

Glutamate

(excitatory)

Question 24

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

Answer 24

efficient

Question 25

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

Answer 25

**Inflammatory mediators**

Question 26

What causes **sterile neurogenic inflammation**?

Answer 26

**Release of inflammatory mediators from the PERIPHERAL terminal of activated nociceptors**

Question 27

Which **neurotransmitter** is released into the synaptic cleft when a pre-synaptic sensory fibre is activated? Which **change in membrane potential** does it cause?

Answer 27

**Glutamate** **Depolarisation** (excitatory post-synaptic potential)

Question 28

Two ligands, **AMPA** and **NMDA**, bind to receptors to change the type of **excitatory post-synaptic potential** that is produced. What does each cause?

Answer 28

**AMPA** - fast **NMDA** - slow

Question 29

The **excitatory post-synaptic potential** causes a depolarisation which overcomes threshold potential. What happens next?

Answer 29

**Action potential**

Question 30

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

Answer 30

**Increased efficiency** giving rise to hyperalgesia and allodynia

Question 31

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

Answer 31

**All intensities**

Question 32

What does **visceral pain** feel like?

Answer 32

**Dull, aching, poorly localised**

Question 33

What stimulus activates **visceral nociceptors**?

Answer 33

**Stretching, twisting, inflammation, ischaemia**

Question 34

**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?

Answer 34

**Referred pain**

Question 35

What are **autonomic symptoms**?

Answer 35

**Symptoms caused by sympathetic activation** e.g N&V, sweating, pallor

Question 36

What are the **characteristics** of **s****omatic pain?**

Answer 36

**Sharp, stabbing, well-localised pain**

Question 37

What causes **viscerosomatic pain**?

Answer 37

**Inflammation from an organ making contact with the body wall** e.g enlarged, inflamed appendix in appendicitis

Question 38

What disease **classically** causes **visceral pain** followed by **viscerosomatic pain**?

Answer 38

**Appendicitis**

Question 39

What is the jist of the **Gate Control Theory**?

Answer 39

**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