|
Fiber Types |
Conduction velocity |
Myelination |
Diameter |
Serves which receptors |
Sensation carried/ projection to cord |
|
Mixed nerve--Motor and sensory |
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|
Type Ia |
Rapid |
Heavily |
Largest |
Afferent fibers |
|
|
Type Ib |
Rapid |
Heavily |
Largest |
Golgi tendon organs |
|
|
Type II |
Fast |
Lots |
Medium |
Afferent fibers |
|
|
Type III |
Slower |
Less |
Small |
Temp, crude touch, pricking pain |
|
|
Type IV |
Slow |
none |
smallest |
Pain, itch, temp, crude touch |
|
|
Cutaneous Nerve--Sensory only |
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|
A-alpha |
Rapid |
Heavily. Similar to type Ia |
Largest |
Golgi tendon organ, skeletal motor neuron |
Stretch reflex |
|
A-beta |
Fast |
Heavily. Similar to type II |
medium |
Meissner’s, Merkel’s, Ruffini, Pacinian, Hair follicle receptors |
High discriminative touch, projects to lamina IV |
|
A-gamma |
Medium |
Medium similar to II |
Medium |
Muscle spindle |
Deep pressure, touch |
|
A-delta |
Slower |
Lightly. Similar to type III |
Small |
Free nerve endings |
Fast pain to lamina I & V, Flexor reflex |
|
B |
Slow |
Autonomic |
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|
C |
Slowest |
None. Similar to type IV |
Smallest |
Free nerve endings |
Slow pain, dull, burning or diffuse pain; are polymodal nociceptors, project to lamina II, flexor reflex |
Last Updated 04/10/00 12:27:16 PM
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