pain 😢

Question 1

what is the definition of pain

Answer 1

an unpleasant sensory or emotional experience associated with potential tissue damage
-conscious
-arises in multiple sensory and emotional centres in the brain

Question 2

what is the definition of nociception

Answer 2

the narrow process of encoding noxious stimuli

Question 3

what is a noxious stimulus?

Answer 3

a stimulus strong enough to threaten the body’s integrity

Question 4

what does nociception involve (v briefly) - like where does it go to and from

Answer 4

physiological process involves transduction, transmission and modulation of neural signals from periphery to CNS

Question 5

is nociception conscious or unconscious

Answer 5

can be both

Question 6

is pain conscious or unconscious

Answer 6

conscious

Question 7

is nociception physiological or pathological

Answer 7

physiological

Question 8

is pain physiological or pathological

Answer 8

pathological
not all pain is associated with a disease state

Question 9

is acute pain physiological or pathological

Answer 9

physiological

Question 10

is pain preventative or a learning experience

Answer 10

pain is a learning experience
- eg happens after reflex withdrawal from stimulus

Question 11

is nociception preventative or a learning experience

Answer 11

preventative
enables healing and recovery

Question 12

what is chronic pain then

Answer 12

persists beyond healing
disproportionate to injury
- eg
– disproportionate to nociceptive input
– pain in absence of nociceptive input

Question 13

what type of nerves are sensory nerves

Answer 13

pseudounipolar nerves

Question 14

what is the structure of a nociceptor

Answer 14

unmyelinated, small diameter nerve endings in skin sense actual or potential tissue damage

Question 15

what are the 4 steps from initial physical stimulus to membrane depolarisation

Answer 15

1. physical force - touch, muscular tension/stress
2. changes membrane tension
3. piezo activation - causes cation influx Na+ and Ca2+
4. Na+ = membrane depolarisation - electrical signal
   Ca2+ = initiates calcium dependent signalling pathways

Question 16

when are nociceptors stimulated

Answer 16

if surrounding tissues are inflamed
if tissue isnt damaged its hard to stimulate

Question 17

which compounds make a high threshold nociceptor into a low threshold nociceptor

Answer 17

bradykinin
PGE2
NGF

Question 18

which cation is a trigger for secondary messengers in the nervous system

Answer 18

Ca2+

Question 19

what changes does ‘central sensitisation in dorsal horn’ make relating to nociception

Answer 19

• increases efficiency of nociceptive transmission
• amplifies nociceptive input after injury

Question 20

how is the excitatory input modulated + where

Answer 20

in dorsal horn
by inhibitory nerves

Question 21

how is the ascending output from spinal cord balanced

Answer 21

ascending output from spinal cord is balanced by descending modulation from the brain

Question 22

what are the 4 types of nerve fibres

Answer 22

Aα - (fast, large diameter, myelinated) - relating to motor
Aß - (fast, large diameter, myelinated) carry APs from mechanoreceptors. they modulate C and A∂ activity within the dorsal horn

A∂ fibres - (slow, thin, myelinated) associated with sharp localised pain

C - (slow, thin, unmyelinated) associated with a dull aching, throbbing diffuse pain

Question 23

where do sensory nerves have their cell bodies

Answer 23

dorsal root ganglion

Question 24

what are the 5 steps in the nociceptive pain pathway

Answer 24

1) Transduction,
2) Conduction,
3) Transmission,
4) Modulation,
5) Perception,

Question 25

describe the transduction step in nociceptive pain pathway

Answer 25

• peripheral terminals of nociceptive C fibers or A-delta (Aδ) fibers are depolarized by noxious mechanical, thermal, or chemical energy (which lowers activation threshold)
• energy converted to action potential

Question 26

describe the conduction step in nociceptive pain pathway

Answer 26

• the AP generated in the nociceptor terminal is conducted across the peripheral process to the central process
• interneurons can facilitate or inhibit transmission to second order neurons
• Ca2+ and second messengers induce central sensitisation in dorsal horn
• the excitatory input is modulated by inhibitory nerves in dorsal horn

Question 27

describe the transmission step in nociceptive pain pathway

Answer 27

• a nociceptive AP reaches the presynaptic terminal in the dorsal horn
• the AP causes the presynaptic terminals of A∂ and C fibres to release a variety of pro-nociceptive substances into the synaptic cleft
• this activates CGRP receptors
• this causes an influx of ions that depolarize second order neurons and interneurons

Question 28

what does the modulation step of the nociceptive pain pathway involve

Answer 28

excitatory and inhibitory mechanisms

Question 29

describe the perception step in nociceptive pain pathway

Answer 29

• dependant upon neural processing in the spinal cord and several brain regions
• Action potentials ascending the spinothalamic tract are decoded by the thalamus
• integration of sensations, emotions and cognition that result in our perception of pain

Question 30

what does the descending pain pathway do?

Answer 30

reduce the pain signal

Question 31

what is enkephalin

Answer 31

enkephalin is like a natural opioid - related to the endorphins. opioids activate the descending pain pathway

Question 32

what is gate control theory

Answer 32

rubbing the site of a painful stimulus helps alleviate pain
occurs at spinal cord level
concurrent activity in large-diameter AB primary afferents reducing the transmission of pain signals in small diameter C afferents