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26 Cards in this Set
- Front
- Back
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A-alpha
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Motor: large a-motoneurons
Sensory: Ia = Primary afferents of muscle spindle Sensory: Ib = Golgi tendon organ |
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A-beta
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Sensory: II = secondary afferents of m. spindles, touch, pressure, and pacinian corpuscles
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A-gamma
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Motor: Innervate intrafusal fibers
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A-delta
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Sensory: III = Touch, pressure, pain, temp
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B
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Motor: Preganglionic autonomic
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C
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Motor: Unmyelinated, postganglionic autonomic
Sensory: Unmyelinated pain and temp fibers Type IV |
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Group I
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A-alpha fiber
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Group II
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A-beta fiber
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Group III
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A-delta fiber
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Group IV
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C fibers
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A group
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large
myelinated alpha, beta, gamma, delta From fast to slow |
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B group
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small
lightly myelinated |
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C group
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smallest
unmyelinated |
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Two types of Adaptation
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Tonic - slow adapting - receptor response is maintained throughout the stimulus
Phasic - rapid adapting - detects the rate of change but stops firing when the stimulus is constant. |
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Adaptation occurs for two reasons
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Structural changes in the receptor itself - i.e. pacinian corpuscle.
accommodation in the sensory endings |
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Hair follicle receptors
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** Mechanoreceptor**
Nonencapsulated hairy skin light touch slow/fast adapting |
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Meissner's corpuscle
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** Mechanoreceptor**
encapsulated superficial layers of glabrous skin rapid adapting low freq (20-50 HZ) vibration small receptive field Fine tactile discrimination |
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Merkel receptor
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**Sensory receptor**
superficial layers of hairy and glabrous skin Slow adapt small receptive field Sense of pressure, aids in fine tactile discrimination |
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Ruffini ending
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**Sensory receptor**
encapsulated deep dermal layer slow adapting large receptive field Unknown function |
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Pacinian corpuscle
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**Sensory receptor**
encapsulated Subcutaneous over entire body rapid adapting large receptive field vibrations of 200 - 300 Hz |
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Free nerve endings
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**Sensory receptor**
Nonencapsulated All over body both rapid and slow adapt Crude touch |
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Nocicepter
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Free nerve ending
Cell bodies in dorsal roots and trigeminal ganglia Least differentiated sensory receptor of the skin |
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Where nociceptors are not found
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Not found in parenchyma of internal organs (including brain)
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Classes of Nociceptors:
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1) Thermal or mechanical
A-delta fibers = fast, first, early pain, sharp. Temp of >45 C or <5 C 2) Polymodal Variety of high intense mechanical, temp stimuli, chemical - C fibers = dull, aching, diffuse pain, slow, second, late pain. |
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Hyperglasia
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Increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves.
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Primary hyperglasia
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Peripheral sensitization
At the side of tissue damage Nociceptors become more sensitive to pain because their endings interact with chemical medicators released by tissue damage: K+, 5HT, Serotonin, histamine, bradykinin, and prostaglandins. Neurogenic inflammation - substance P, CGRP are released from nociceptive endings that cause histamine release from mast cells. ... they also cause vasodilation and edema. |
