Lecture 14

Question 1

Where can nociceptors CANNOT be found?

Answer 1

The brain

Question 2

Why is pain useful?

Answer 2

To avoid injury, alert a local infection, aid recovery, or indicate third pain.

Question 3

What are the two types of nerve fibres which carry nociception?

Answer 3

1. C fibers

2. A-alpha fibers

Question 4

What are the characteristics of C fibres?

Answer 4

• long-lasting, sustained contraction
• smallest diameter, unmyelinated axons
• slow conduction velocity
• signal ongoing damage

Question 5

What are the characteristics of A-alpha fibres?

Answer 5

• small diameter myelinated fiber
• immediate pain alert
• faster conduction velocity
• signal acute onset of painful stimulus

Question 6

When do pain pathways become more sensitive?

Answer 6

Following an injury, or inflammation disease. injury site and the area around it become tender. this is due to sensation of sensory endings by locally released factors, and changes at CNS synapses

Question 7

Why and how do damage area have local inflammatory changes?

Answer 7

To increase brain sensation. This happens due to mast cells in the area releasing histamine, which recruits and activates surrounding pain fibres to generate pain signals.

Question 8

What is the role of natural aspirin?

Answer 8

An anti-clotting agent.

Question 9

How can pain pathways be inhibited?

Answer 9

By ‘gating’ of pain impulses by non-painful stimuli of nearby nerves. this inhibits responses of ascending pain fibres.

Question 10

What sensory pathway delivers pain nerve signals?

Answer 10

The anterolateral pathway

Question 11

what is descending control?

Answer 11

Control which descends from the brain. pathways to the spinal cord from brain and brainstem regulate pain transmission.

Question 12

What are endogenous opiates?

Answer 12

They are chemicals released at synapses on pain-pathways neurons. They decrease synaptic excitability, so less pain is sensed. They are released in response to acute pain or stress.

Question 13

What are endocannabinoids?

Answer 13

They are chemical synthesised and released by neurons, but are not stored in vesicles (fat soluble). They decrease long-term sensitivity to pain and act on receptors as well as centrally. They are very slow. They are released by the postsynaptic neuron, to mediate the amount of neurotransmitter released by the presynaptic neurone.

Question 14

What modulates pain transmission?

Answer 14

• peripheral neural pathways
• descending pathways from several brain region
• various chemical transmitters

Question 15

What are some symptoms of diabetes neuropathy?

Answer 15

• tingling or burning in toes, feet, legs, fingers, hands, or arms
• a ‘pins and needles’ feeling
• pain or cramping
• numbness or loss of sensation
• insensitivity to heat or cold
• extreme sensitivity to even the lightest touch
• muscle weekness in hands or feet
• loss of coordination or balance that makes in harder to walk

Question 16

Does muscle pain always come directly from the muscle?

Answer 16

No. It could be in any of the surrounding tissues, or in the muscles nerves. lack of circulation can also cause pain.

Question 17

What is referred pain?

Answer 17

it is when feelings from the viscera are referred to the body surface. it is presumed to be due to ‘cross-talk’ of visceral and somatic sensory pathways.

Question 18

What is neurogenic pain?

Answer 18

It is pain due to damage to a nerve. nerve compression can cause pain to be felt in the region of nerve termination.

Question 19

What is phantom limb pain?

Answer 19

It is pain felt in a region that no longer exists (lost limbs)

Question 20

What are the two causes of phantom limb pain?

Answer 20

1. Ongoing activity in nerves that used to come from that part
2. invasion of cortical representation for that part by intact body regions, so input is misinterpreted