PHANTOM PAIN :::
There is an illusive type of pain which occurs when the thing does not exist at that time A patient whose leg is amputed and still experiences pain in toes is an example of phantom pain
The receptors for pain called nociceptors are found through out the body They are probably the free nerve endings These nerve endings may be either small myelinated (A) fibres or unmyelinated (C- Fibres) The nerve endings with A fibres respond to mechanical stimuli whereas C-fibres respond to mechanical thermal or noxious chemical stimuli Nociceptors are found in larger number in the skin whereas in viscera there are few receptors Thus for the visceral pain to be felt a large area of the organ must be involved as compared to the cutaneous pain where a small painful area is enough for appreciation or pain sensation when one pain is overlapped by the other the deeper pain may appear to be lesser than the superficial one
Referred pain ::
Damage or difficulty to an internal organ is commonly associated with pain or tenderness not in the organ but in some skin region sharing the same segmental innervation This is known as referred pain A classical example of this type of pain is anginal pain in substernal region and the medial part of left shoulder and the left hand indicating the pain of heart attack The most likely explanation for referred pain is that some central cells receive both cutaneous and visceral inputs The pathway of such impulses is common in spinal cord and higher up areas
For pain to be perceived the brain must be functioning normally the pathway to the brain must be intact and the pain receptor must respond to the stimulus Each of these three factors is important in different types of anaesthesia In general anaesthesia the brain cannot perceive the pain when a nerve is blocked the pathway to the brain is interrupted A local injection of procaine renders the pain receptors insensitive to the pain stimulus
Pain receptors relay their impulses through dorsal root of spinal ganglia to the substantia gelationsa of the spinal cord From here impulses reach to thalamus through spinothalamic tracts passing via medulla oblongata from the thalamus they finally reach the cerebral cortex for appreciation of epieritic pain
Pain can by relieved by lulling the protopathic sensations at the thalamic level (analgesic drugs ) or by calming down the brain cortex (sedatives ) Antispasmodics relieve the pain by decreasing the visceral spasm
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