Pain pathways and central processing of pain

Question 1

where does somatosensory system receive info from

Answer 1

SKin
Muscle
Tendons 
Ligaments 
Connective tissu

Question 2

What does the somatosensory system detect

Answer 2

Touch 
Brush
Pressure
tickle 
Temperature 
Pain

Question 3

What is nociception

Answer 3

Neural process in which fibres (C-fibres) which detect stimuli are activated

Question 4

What is pain

Answer 4

feeling/perception pain includes psychological component

Question 5

What receptors exhibit selectivity

Answer 5

sensory receptors

Question 6

What do mechanoreceptors detect

Answer 6

Touch, pressure, vibration

Question 7

What do proprioreceptors detect

Answer 7

Position of body

Question 8

What do thermoreceptors detect

Answer 8

Warm, cool, hot

Question 9

What do nociceptors detect

Answer 9

Mechanical, thermal, chemical

Question 10

What is the sensory system

Answer 10

Sensory receptors and neurones have peripheral receptive fields. are area over which you can activate the neurone

Question 11

What is convergence

Answer 11

A single sensory neurone in the CnS can receive input from many sensory receptors

Question 12

Process of transduction

Answer 12

Deformation of membrane
Opening of Na+ and K+ channels
Receptor potential. Local depolarisation of receptive membrane
Action potential propagated to CNS

Question 13

What are receptive potentials like with stronger stimuli

What is the frequency like

Answer 13

Larger receptive potentials

Higher frequency

Question 14

What is the intensity of the stimulus encoded by

Answer 14

Size of the responding receptor population and the numbers of fibres activated

Question 15

What is recruitment

Answer 15

Increased number of responsive receptors and fibres

Question 16

Which sensory fibres are a lot bigger in diameter and what does this mean

Answer 16

Aalpha and Abeta.

can transfer signals much quicker

Question 17

How do Aalpha and Abeta fibres relay information by

Answer 17

Aalpha- proprioception

Abeta- mechanism

Question 18

Which primary afferent fibres relay information from pain and temperature sensory receptors

Answer 18

Agamma

C fibres

Question 19

Which primary afferent fibres have a smaller diameter and what does this mean. What other differences do they have

Answer 19

Much smaller diameter than Aalpha and Abeta and so transduction speed much slower.

They’re also unmyelinated which makes it slower too

Question 20

What is the Tactile (touch) pathways

Answer 20

Central branches of touch afferent fibres ascend in the dorsal columns

synapse in the dorsal column nuclei

Cross the midline in the medulla

Ascend through the brainstem as the medial lemnisus

Thalamus: synapse on cells

Send projections to the primary somatosensory cortex, post central gyrus of parietal lobe

Question 21

Where do pain tracts cross

Answer 21

In the spinal cord

Question 22

Where do tactile tracts cross

Answer 22

In the medulla

Question 23

Where do Abeta fibres terminate

Answer 23

Intermediate lamina (3-5) of dorsal horn

Question 24

What do Abeta fibres release

Answer 24

Glutamate

Question 25

Where do C fibres terminate

Answer 25

Superficial lamina (1-2) of the dorsal hormones

Question 26

What do C fibres release

Answer 26

Glutamate and other peptides and transmitters

Question 27

Where does spinal processing occur

Answer 27

Dorsal horn of spinal cord receives Ab fibres and C fibres messagees

Then processed

then out through the ventral horn

Question 28

What is the spinothalamic pathway

Answer 28

Projection neurones project to the brain and help discriminate where the pain is

Question 29

Why is it that if you’re already injured, and you accidentally hurt the injured part of your body, that it hurts more than if it was not injured

Answer 29

Neural responses to repeated stimulation of C fibres are not fixed and are not always proportional to the intensity of the stimulus applied

Enhanced responses for a given noxious stimulus are associated with repeated higher stimulation

(nerves are sensitised and so are easier to activate them)

Question 30

What is allodynia

Answer 30

Condition where pain is caused by a stimulus that does not normally elicit pain (e.g. sunburn. Sunburnt skin hurts when hot/cold or when touched etc)

The graph is shifted to the left

Question 31

what is hyperalgesia

Answer 31

abnormally increased sensitivity to pain which may be caused by damage to nociceptors or peripheral nerves and can cause hypersensitvivity to stimulus

Question 32

Role of brainstem in pain processing

Answer 32

Through the spinoreticular tract and branches of the STT, nociceptive signals activate brainstem systems giving rise to changes in BP, respiration and orientation toward stimulus

Question 33

Role of thalamus in pain processing

Answer 33

VPL is main somatosensory area of thalamus, but other components may be involved. Acts as the final relay before sensory signals reach the cortex

Question 34

Role of cortex in pain processing

Answer 34

Consciousness of pain, plus limbic system for emotional response

Question 35

Role of hypothalamus in pain processing

Answer 35

Response is mediated through hypothalamus. Neuroendocrine changes and some behaviours

Question 36

What is the descending inhibitory control of pain pathway

Answer 36

1) Painful input from spinal cord goes to thalamus and other brainstem regions
2) from the thalamus, this goes to PAG (periaqueductal grey matter)
3) cortex and hypothalamus also feed into the PAG
4) PAG feeds into Nucleus Raphe Magus (NRM) and so does the LC (locus ceruleus) and the NRPG (nucleus reticular paragigantocellaris)
5) NRM sends messages to spinal cord (inhibitory transmitters) which inhibit excitability in spinal cord

Question 37

What does the sensory system allow

Answer 37

Converts a natural stimulus (energy) to action potentials

Intensity and duration of the stimulus is conveyed