All of the following are thermal modalities except:
Correct Answer: All
Description: A i.e. Cold receptor B i.e. Warm receptor C i.e. Pain receptorCold receptors are inactive at 40deg but then steadily increase their firing rate as skin temperature falls to about 24degC. As skin (subepithelial) temperature fuher decreases upto 10degC the firing rate of cold receptor decreases. Below 10degC the receptor are inactive and cold becomes an effective local anesthetic (i.e. respond to 10degC - 38degC).- Histologically definitive cold receptors are nerve endings of AS myelinated nerves, that branches a number of times, the tip of which protrude into the bottom surfaces of basal epidermis. So. it is the temperature of subepithelial subcutaneous tissue that determine the responses.Cold signals are transmitted mainly by AS nerve fibres. Some cold sensation may also travel in type C fibres as well.There are 4-10 times as many cold sensitive as hot sensitive spots and the number in different areas of body varies from 15-20 cold spots/cm2 in lips to 3-5 colds spots/cm2 in fingers to < 1 cold spot/cm2 in trunk.The receptors for moderate cold is the cold and menthol sensitive receptor 1 (CMRI)Threshold for activation is 30degC & they increase their firing rate upto 46degC (i.e. respond to 30-46deg)- Warmth receptor, not being identified histologically are presumed to be free nerve endings because heat signals are transmitted mainly by type C nerve fibres.* In addition to ending in post central gyrus, fibers from thalamus end in I/L insular coex (true primary thermal receiving area)Q
Category:
Physiology
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