Anaesthesia and analgesia

Question 1

4 phases of nociceptive pain:

Answer 1

Tenderness Tells Possible Misery
Transduction
Transmission
Perception
Modulation

Question 2

What is transmission?

Answer 2

The action potential travels through a first order neuron to the spinal cord:
A-beta (fast, myelinated, large) - touch
A-delta (fast, myelinated, small) - mechanical, thermal
C (slow, unmyelinated) - mechanical, chemical, thermal
They go to the dorsal horn and the rexed laminae (greymatter) of spinal cord -> decussation (contralateral ventral horn) -> up 5 ascending tracts (spinothalamic tract to the thalamus and spinomesencephalic tract to periacqueductal grey to medulla)

Question 3

What is transduction?

Answer 3

Turns signal of noxious stimuli (chemical/thermal/mechanical) into an electrical stimulus (action potential).

Question 4

what is perception?

Answer 4

3rd order neuron sends information to the appropriate somatosensory cortex. The limbic system is contacted.

Question 5

what is modulation?

Answer 5

Descending neurons from the brain release substances that inhibit transmission of painful impulses and produce motor resoibse ti aviud oaub

Question 6

what are the 3 main endogenous mechanisms for pain modulation?

Answer 6

1. descending inhibitory nerve system (serotonin, norepinephrine), synapse dorsal horn of spinal cord
2. endogenous opioid system (inhibitory neuron): enkephalins, endorphins, dynorphins. Gate control: interneuron release these substances in response to stimulus of A-beta fibre that block pain signaling
3. peripheral modulation on terminal nociceptors: decrease Ca2+ entry and inhibit neurotransmitter release

Question 7

Opioid receptors are located in:

Answer 7

Brain: thalamus, limbic system
Spinal cord: substantia gelatinosa

Question 8

Explain ion trapping in COX-2 selective NSAIDs

Answer 8

• NSAIDs are weak acids that become lipid soluble in the highly acidic environment of the stomach
• Penetrate easily into gastric cells -> readily trapped in the more alkaline environment
• High local concentration of NSAID in the GI mucosa

Question 9

what is serotonin syndrome?

Answer 9

Overactivation of peripheral and central postsynaptic 5-HT1A and 5-HT2A receptors