Sunday, 7 June 2015

Nerve fibres

NERVE FIBRES

✔ Nerve fibers within peripheral nerves are divided into 3
types A, B and C according to their diameters,
conduction velocities, and physiologic characteristics.

✔A fibers are large, myelinated, conduct rapidly, and carry
various motor or sensory impulses.

✔B fibers are smaller myelinated axons that conduct less
rapidly than A fibers. These fibers serve autonomic
functions.

✔C fibers are the smallest and are non myelinated. They
conduct impulses the slowest and serve pain conduction
and autonomic functions.

✔A delta fibers carries pain and temperature.

✔A alpha fibers are related to motor function and reflex
activity.

✔A beta fibers innervate muscle and transmit touch and
pressure sensations.

✔A gamma fibers control muscle spindle tone.

✔B fibers are thinly myelinated preganglionic autonomic
axons that ultimately control vascular smooth muscle.

✔ A alpha and A beta fibers have maximum conduction
velocity of 30-70m/s.

✔ Conduction velocity of A gamma
fiber is 15 -30m/s and that of A delta fiber is 12-30m/s.

✔Type C fiber has a velocity of 0.5-2 m/s.

✔Type A fiber have the largest diameter, type B fibers
are smaller and type C is the smallest.

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