Pain ( Garner) Flashcards
What is nociception?
Nociception is the sensory process that provides the signals that trigger pain.
where are nocicpetors found?
Nociceptors are found in the periphery as simple free nerve endings
What substances does tissue damage and inflammation trigger the release of?
*these substances sensitise peripheral nociceptors and induce hyperalgesia.
1) prostaglandins
2) Bradykinin
3) Histamine
These substances sensitize peripheral nociceptors and induce hyperalgesia
What type of free nerve endings allows the transduction of nociceptive stimuli?
Unmyelinated “C” fibres (polymodal nociceptors)
and
Thinly Myelinated “Ad” Fibres (thermal and mechanical nociceptors)
TRUE or FALSE :
Conduction velocity is possitively correlated with axon diameter
TRUE:
as the axon diameter increases the conduction speed increases.
TRUE or FALSE :
Thermal and mechanical nociceptors have A-delta fibres which are thin and have a conduction speed of 5-30?
TRUE :
The thermal and mechanical nociceptors have A-Delta fibres.
**the polymodal nociceptors have C fibres
TRUE or FALSE:
Polymodal nocicptors have myelinated C fibres
FALSE:
Polymodal nociceptors have UNMYELINATED C fibres.
These have a slow conduction velocity and transmit dull ache / burning pain.
What types of fibres transmit 1st pain (sharp / easily localised /short duration ) Vs. 2nd pain (dull ache / poorly localised / persistent)
1st pain:
-fast A-Delta fibres
2nd pain
-Slow C-unmyelinated fibres
Once the afferent nociceptive fibres enter the dorsal horn they travel up and down a short distance within the ……
Zone of Lissauer
What accounts for referred pain?
The nociceptive afferents from the interal organs and skin enter the spinal cord through common routes and target overlapping populations of spinal neurons.
This cross talk accounts for referred pain whereby the visceral pain is percieved as having a cutaneous source by the sufferer.
Where is reffered pain of the oseophagus?
Chest wall
Where is referred pain of the heart?
Chest and arms
Where is referred pain of the bladder?
Perineum
Where is referred pain of the ureter?
lowe abdomen and back
Where is referred pain of the prostate?
Lower trunk and legs
Where is the pain from appendicitis usually felt in the early stages?
Pain is referred to the abdominal wall around the navel
Where is the pain from angina usually felt?
upper chest wall and left arm
What excitatory neurotransmitter is released by the pain afferents?
Glutamate
What is the outcome of a unilateral spinal cord injury?
What is this called?
- loss of touch, pressure, vibration and proprioception (dorsal column~) on same side as lesion.
- loss of pain / temp of opposited side of lesion.
This is called DISSOCIATED SENSORY LOSS.
What causes DISSOCIATED SENSORY LOSS?
Unilateral spinal cord injury
(loss of dorsal column on same side (below) lesion and loss of spinothalamic on opposite side (below) lesion.
What is Brown- Sequard syndrome?
Dissociated sensory loss caused by a unilateral lesion of the spinal cord.
(ie loss of dorsal column on same side of lesion and loss of spinothalamic on opposite side of lesion.)
Describe the pathway of pain and temperature sensationr from the face and head?
1) Cell body lies in the trigeminal ganglion.
2) fibres descends in the spinal tract.
3) Then enters the caudal part of the spinal nucleus.
4) Synapse with 2’ fibre.
5) crosses midline
6) Ascends to VPM of thalamus via the trigeminothalamic tract.
Who came up with the gate theory of pain.
Melzack and Wall (1965)
