topic 5 - pain and pain suppression

Question 1

types of nociceptors

Answer 1

Highly myelinated axons (Aδ fibres) convey mechanical pain very quickly and precisely: early pain. This is informative about location.

Unmyelinated axons (C fibres) convey different kinds of pain more slowly and less precisely: late pain. This is vague about location.

• C fibres can be sensitive to pungent irritants (mustard oil) and capsaicin

Question 2

prostaglandis

Answer 2

• molecules that help with inflamation and fight off invaders
• senstise the free nerve endings therefore pain perceived in that area is stronger

Question 3

Somatosensory pathways

Answer 3

• incoming nociceptor has a cell body in the dorsal root ganglion and they make a synapse in the dorsal horn of the spinal cord. Glutamate is the main neurotransmitter used in that synapse and substance P as a co-neurotransmitter (substance p used as an amplifier)
• that first CNS sensory neuron’s axon runs across other side of spinal cord, through medulla and through the mid brian and makes a synapse in the thalamus (ventral posterior nucleus)
• neurons from the thalamus make synapses onto the neurons in the primary somatosensory cortex which tells us where the pain is
• pathway that it comes through tells us there is pain - if it doesn’t make it to the brain it is not pain.

Question 4

phantom limb

Answer 4

feeling of pain in a lost limb due to it still being represented in the brain

Question 5

Dual brain mechanisms

Answer 5

Pain sensation (physical) - coded in the primary somatosensory cortex.
Unpleasantness perception (emotional) - anterior cingulate cortex.

Question 6

how to treat phantom limb pain

Answer 6

mirror with good limb seeing it being treated

Question 7

hypnosis induced analgesia

Answer 7

pain with sticking ur hand in rly hot water
hypnosis reduced pain of uncomfortablness by reducing activity in the anterior cingulate cortex

Question 8

pain suppression - non-drug approach

Answer 8

• direct stimulation of the PAG
• stressful situations (soldiers etc)
• placebo effect
• acupuncture (tested using naloxone)

Question 9

what blocks opiate receptors

Answer 9

naloxone, also used for heroin overdoses

Question 10

Capsaicin

Answer 10

• used topically on skin for muscle relief (deep heat)
• hot sensation depletes substance p

Question 11

NSAID

Answer 11

anti-inflamatory drugs
inhibit the enzymes that make prostaglandins - reduction in prostaglandins production

Question 12

NSAID side effects

Answer 12

COX1 - involved in blood clotting: aspirin prevents blood clotting. involved in protection of stomach lining from acid: NSAID bad for stomach

Question 13

paracetamol

Answer 13

works through CB-1 receptors (cannabis)

Question 14

morphine usage and half life

Answer 14

half life - 3/4 hours only 20% crosses blood-brain barrier

Question 15

heroin usage and half life

Answer 15

0.1-0.25 hours half life, lipid soluble so easily crosses blood-brain barrier

Question 16

morphine usage and half life

Answer 16

3-4 hours half life, 20% crosses barrier

Question 17

oxycodon half life

Answer 17

4.5 hours half life

Question 18

Fentanyl half life

Answer 18

3-7 hours

Question 19

opiates short term effects

Answer 19

• relieve pain
• relieve cough
• relieve diorhea
• induce hypothermia
• induce sleep
• stimulate pleasure

Question 20

opiates physiological action (how do they work)

Answer 20

• mimic the action of endogenous opioids: endorphins

Question 21

opioid receptors

Answer 21

3 major subtypes:
- delta
- kappa
- mu
maybe learn where they are and what for

Question 22

opioids on the periaqueductal gray matter in mid brain ( in the descending analgesia circuit DAC)

Answer 22

the inhibit activity of inhibitory neurons

Question 23

opioids on the spinal cord in the DAC

Answer 23

block the incoming pain signals

Question 24

opiates long term effect

Answer 24

mild as long as taken.
you will be:
- constipated
- reduced libido
- pupil constriction
- menstrual irregularity
But you will have withdrawals
You get all the pleasure you need so might not take care of yourself etc

Question 25

Heroin withdrawal effects

Answer 25

begin 6-12 hours after last dose, stop after around 7 days Includes: - restlessness - runny nose - sweating - muscle spasms - tremor - vomitting - sweating

Question 26

how to deal with heroin withdrawals

Answer 26

- avoid drug-related context - take more drugs - methadone - acupuncture

Question 27

opiate addictiveness

Answer 27

in Ventral tegmental area (VTA): - opiates inhibit GABA-ergic interneurons - this releases inhibition from neurons which project to nucleus accumbens - more dopamine release In nucleus Accumbens: -effects independent from but similar to dopamine from VTA

Question 28

cannabis usage

Answer 28

- 20-50% taken up from smoke, less from ingested (6%) - very lipid soluble and easily crosses the blood-brain barrier - easily stored in fat tissue, half life of 7 days

Question 29

cannabis short term effects

Answer 29

Recreational use: - reduction in anxiety - dissociation in ideas - heightened sensations - distorted sense of time (goes slower) - intense emotional experiences - hallucinations (infrequent) Medical use: - reduces nausea - increase in appetite - dilation of bronchioles - blocks seizures - decreases severity of glaucoma pain relief: - as effective as opiates for acute pain - greater potency and efficiency than opiates for chronic pain (but side effects) - sites of action include: peripheral nerves direct spinal chord activity descending analgesia circuit anterior cingulate cortex

Question 30

cannabinoid receptors

Answer 30

highest concentration exist in the hippocampus

Question 31

function of endocannabinoids

Answer 31

- released from the POST synaptic side of synapse and bind with pre synaptic side - work in close vicinity of other synapses - suppresses the pre-synaptic release of neurotransmitters - in the hippocampus, this affects GABA, hence suppressing inhibition: depolarisation-induced suppression of inhibition (DSI)

Question 32

DSI

Answer 32

-endogenous cannabinoids released from post-synaptic terminal when depolarised - cannabinoids sit on pre-synaptic terminals of other synapses ( i dont rly get this)

Question 33

person who doesnt feel pain

Answer 33

- burns herself on stove without realising - defect in the FAAH enzyme (breaks down anandamine (linked with cannabinoids))

Question 34

cannabis long-term effects

Answer 34

- problems associated with smoking - impairments in memory recall - impairments in attention - slower decision making - if taking skunk - increased odds of psychosis by up to 5x - decline in IQ with persistent use (age 13-39) - especially vulnerable if starting in adolescence

Question 35

physical dependance on cannabis

Answer 35

- tolerance develops during extended use but withdrawls are rare - long-term users may experience sensitization of the desired effect

Question 36

what drugs work on the CNS

Answer 36

cannabis and opiates

Question 37

cocaine usage and half-life

Answer 37

- reaches peak in blood in blood at 30-60 mins - half life of 30-90 mins - easily penetrates blood-brain barrier

Question 38

what does cocaine increase

Answer 38

- euphoria - energy - confidence - talkative - active - attention - alertness

Question 39

mono-amines

Answer 39

- seratonin - dopamine - noradrenaline - adrenalin cocaine acts at the mono-aminergic synapse