Pain

Question 1

Acute pain

Answer 1

Less than 12 weeks

Question 2

Chronic pain

Answer 2

More than 12 weeks

Question 3

Nociceptive pain

Answer 3

Pain that arises from actual or threatened damage to non-neuronal tissue and is due to the activation of nociceptors

Question 4

Neuropathic pain

Answer 4

Pain that is initiated or caused by a primary lesion or dysfunction of the nervous system e.g. due to spinal nerve root compression

Question 5

1st, 2nd and 3rd order neurons between the sensory receptor located in the periphery and the perception of sensation at the level of the cerebral cortex:

Answer 5

1. First order (primary afferent) neurone enters the spinal cord through a spinal nerve, or the brainstem through the trigeminal nerve, on the same side of the body (ipsilaterally) as the peripheral receptor is located
2. The primary afferent neurone remains ipsilateral and synapses with a second order neurone within the CNS
3. The cell body of the second order neurone is located within the spinal cord or brainstem. Its axons decussate to the other side of the CNS and ascend to the thalamus where it terminates
4. The cell body of the third order neurone is located within the thalamus and its axons projects to the somatosensory cortex - located in the post-central gyrus of the parietal lobe of the cerebral hemisphere.

Question 6

What are nociceptors

Answer 6

Sensory neurones that are found in any area of the body that can sense pain either externally or internally

Question 7

External nociceptors

Answer 7

Skin
cornea
mucosa

Question 8

Internal nociceptors

Answer 8

Viscera
Joints
Muscles
Connective tissue

Question 9

Where do cell bodies of nociceptors resie

Answer 9

Either in dorsal root ganglion (body) or in trigeminal ganglion (face, head, neck)

Question 10

Hyperalgesia

Answer 10

When there is tissue damage, BRADYKININ and PROSTAGLANDIN E2 both reduce the nociceptive action potential threshold thereby increasing their sensitivity to stimuli

Question 11

Afferent fibres

Answer 11

Alpha delta fibres

C fibres

Question 12

Alpha delta fibres

Answer 12

• Thinly myelinated, small diameter (1-5 micrometres), medium conduction speed (5-40m/s)
• Carries TOUCH, PRESSURE, TEMPERATURE and FAST pain information

Question 13

C fibres

Answer 13

Unmyelinated, smallest diameter

SLOWEST conduction speed

Carries SLOW pain, temperature, touch, pressure, itch and postganglionic autonomic fibre information

Question 14

Where do nociceptors synapse with secondary afferent neurones

Answer 14

Alpha delta and C fibres synapse with secondary afferent neurones in the GREY MATTER of the DORSAL column of the spinal cord (divided up by Rexed laminae)

Question 15

Which neurotransmitters to afferent fibres release?

Answer 15

AD - Glutamate (Fast)

C - Glutamate and substance P (slow acting - involved in the mediation of dull aching pain)

Question 16

Second order neurones transmit pain impulse up the …

Answer 16

spinothalamic tract

Trigemino-thalamic tract

Question 17

Spinothalamic tract

Answer 17

Carries pain, temperature and crude touch sensation from the body and enters the spinal cord at Lissaeur’s fasciculus.

Question 18

Trigemino-thalamic tract

Answer 18

Carries pain, temperature and crude touch sensation from the FACE, HEAD and NECK. First order neurons enter at the pons and then descend to the medulla, forming the spinal trigeminal tract.
Receives contributions from the trigeminal, facial, vagus and glossopharyngeal nerves.

Question 19

Both tracts terminate at the

Answer 19

ventral posterior lateral nucleus at the thalamus

Question 20

What is analgesia?

Answer 20

selective suppression of pain without effects on consciousness or other sensations

Question 21

What is anaesthesia?

Answer 21

the uniform suppression of pain (no pain is felt at all) and sometimes consciousness is lost (under general anaesthesia)

Question 22

Melzack-Wall pain gate?

Answer 22

states that non-painful input closes the “gate” to painful input, thereby preventing pain sensation from travelling to the somatosensory cortex to be perceived and thus felt

Question 23

Substance P

Answer 23

• Peptide neurotransmitter involved in pain transmission
• Also a vasodilator
• Remains bound to receptors for longer time thereby transmitting long-lasting pain