Pain Signalling

Question 1

Define pain

Answer 1

An unpleasant sensory + emotional experience associated with or resembling actual or potential tissue damage

Question 2

What are the types of pain receptors?

Answer 2

A delta
C

Question 3

Compare A delta + C pain receptors

Answer 3

• A delta: fast, sharp pain | myelinated
• C: slow, burning pain | unmyelinated

Question 4

Describe A delta pain recpetors

Answer 4

• fast pain |myelinated
• Sharp pain

Question 5

Describe C pain receptors

Answer 5

• slow pain | unmyelinated
• burning pain

Question 6

What pathway is pain a part of?

Answer 6

Spinothalamic pathway

Question 7

Location of 1st, 2nd + 3rd order neurone cell body in spinothalamic pathway

Answer 7

• 1st: dorsal root ganglion
• 2nd: dorsal horn
• 3rd thalamus

Question 8

Outline the sensory dimension of the pain pathway

Answer 8

• part of the spinothalamic pathway
• stimulus detected by either A delta or C pain receptors
• axon synapses on 2nd order neurones in dorsal horn (in pain gate)
• axon deccusates + ascend up to 3rd order neurones in thalamus

Question 9

What are the dimensions of pain?

Answer 9

Sensory (feeling of chemical or physical pain)
Affective (related to how you feel from limbic system)

Question 10

Outline the pain gate + its different synapses + neurotransmitters

Answer 10

• A delta + C 1st order neurones synapses on 2nd order neurone in dorsal horn (excitatory)
• neurones from mechanoreceptors synapse onto inhibitory neurones which project to pain gate using GABA + encephalins onto mu receptors > inhibit pain e.g. rubbing area to feel better
• descending pathways from cortex to spinal cord inhibit 2nd order sensory neurones using NA + serotonin

Question 11

Outline the effect of mechanoreceptors on the pain gate including neurotransmitters involved

Answer 11

Neurones from mechanoreceptors synapse onto inhibitory neurones which project to pain gate using GABA + encephalins onto mu receptors > inhibit pain
e.g. rubbing area to feel better

Question 12

Outline the general effect of descending pathways on the pain gate including neurotransmitters involved

Answer 12

• Descending pathways from cortex to spinal cord inhibit 2nd order sensory neurones using NA + serotonin
• can include stress, menstrual cycle + chocolate

Question 13

What structure in the midbrain is involved in pain transmission?

Answer 13

Peri-aqueductal grey
(Mickey mouse’s mouth)

Question 14

What structure in the medulla is involved in pain transmission?

Answer 14

Reticular formation

Question 15

Physiological affect on stress on pain

Answer 15

• involves amygdala
• sends axons onto peri-aqueductal grey in midbrain
• which sends axons to reticular formation in medulla
• descending pathway to spinal cord + pain gate
• inhibtis pain gate using NA + serotonin

Question 16

Physiological affect of menstrual cycle on pain transmission

Answer 16

• involves hypothalamus
• sends axons onto peri-aqueductal grey in midbrain
• which sends axons to reticular formation in medulla
• descending pathway to spinal cord

Question 17

Physiological affect chocolate of on pain transmission

Answer 17

• involves taste cortex in insula cortex
• sends axons onto peri-aqueductal grey in midbrain
• which sends axons to reticular formation in medulla
• descending pathway to spinal cord + modulates pain thresholds

Question 18

What receptors are involved in the pain pathway

Answer 18

Mu receptors

Question 19

Why can opioid drugs be addictive?

Answer 19

• Act a mu recpetors to reduce pain
• Mu recpetors can release dopamine which acts onto cortical structures > producing a high + euphoric feeling