Pain and analgesics second half of 2

Question 1

Where does the nucleus reticularis paragigantocellularis project to?

Answer 1

Raphe nuclei

Question 2

Where does the locus coeruleus project to?

Answer 2

Spinal cord

Question 3

Where does the hypothalamic paraventricular nuclei project to?

Answer 3

Periaqueductal grey

Question 4

Can the environment you are in affect the amount of pain you are in?

Answer 4

YEs

Question 5

Why may your environment having an effect on how much pain you are in be beneficial?

Answer 5

Get injured while running away from predator–> still need to run away so pain is reduced

Question 6

What effect does opioids have on nociceptive neurons?

Answer 6

Inhibit the free nerve endings, hyperpolarizing them and making them less likely to fire APs up pain pathway

Question 7

How does the PAG act as an inhibitor of pain?

Answer 7

Sends input to the raphe which causes the raphe to fire inhibitory APs down the spinal cord

Question 8

Which NT is used by the raphe to send inhibitory APs down the spinal cord?

Answer 8

Via release of 5HT

Question 9

How does the locus coeruleus inhibit pain pathways in the spinal cord?

Answer 9

Via the release of noradrenaline

Question 10

Effect of opioids on PAG?

Answer 10

Excitatory effect so more APs from PAG

Question 11

Effect of opioids on nucleus reticularis paragigantocellularis?

Answer 11

Excitatory so more APs from the NRP onto the raphe nuclei

Question 12

How do opioids inhibit pain?

Answer 12

Inhibit nociceptive neurons and the neurons in the spinal cord, and have an excitatory effect on PAG and NRP

Question 13

Three different types of opioid receptor?

Answer 13

Mew delta and kappa

Question 14

What are all of the endogenous agonists of opioid receptor?

Answer 14

Peptides

Question 15

What is similar between the four endogenous agonists of opioid receptors?

Answer 15

Their first 4 AAs are the same

Question 16

What are the four peptide opioid endogenous agonists?

Answer 16

Beta-endorphin, met-enkephalin, leu-enkephalin, dynorphin

Question 17

Which endogenous opioid agonist binds well at all receptors?

Answer 17

beta-endorphin

Question 18

Which opioid receptors are found in the brain (PAG)?

Answer 18

Mu

Question 19

Which opioid receptors are found in the spine?

Answer 19

Mainly mew and delta, also kappa

Question 20

Which opioid receptors are found in the nociceptive neurons?

Answer 20

Mu and kappa

Question 21

What type of receptor are all of the opioid receptors?

Answer 21

GPCRs

Question 22

What are the opioid receptors second messengers?

Answer 22

Gi/o

Question 23

What does the Gi/o unit of the opioid receptor inhibit once an agonist had bound?

Answer 23

The conservation of adenyl cyclase to cyclic AMP

Question 24

What is the effect of inhibiting the formation of cyclic AMP?

Answer 24

Less protein kinase A is formed

Question 25

Other than AMP, what does Gi/o of opioid receptors inhibit?

Answer 25

Calcium channels, meaning less calcium can enter the neuron so less NTs will be released

Question 26

What can the Gi/o of opioid receptors open?

Answer 26

Potassium channels, so more K+ leaves so neuron is hyperpolarized

Question 27

How does opioid receptors cause more APs to be fired down the PAG to the raphe nucleus and thus to the spinal cord?

Answer 27

They inhibit the release of GABA meaning less inhibition from GABA goes to the synapse between the PAG and raphe nuclei

Question 28

What is disinhibition?

Answer 28

Inhibiting something that is inhibitory

Question 29

Net effect of disinhibition?

Answer 29

Excitation

Question 30

What do the two branches of input from the raphe to the dorsal horn carry?

Answer 30

5HT to directly inhibit the synapse. The second one activates opioid interneurons neurons with enkephalins which also inhibit the synapse in the dorsal root

Question 31

What is the effect of enkephalin on an action potential?

Answer 31

Shortens them and leads to a lower frequency due to opening K+ channels (neuron hyperpolarises more quickly