Muscle Spindles Flashcards
how many spindles per muscle?
40-60 spindles/muscle
what is the length of a muscle spindle?
4-10 mm
what are the 2 types of intrafusal fibers?
1: nuclear bag (DB1, SB2)
(2x the length & diameter of chain (8mm)
2: nuclear chain (long & short)
(1/2 the length (4mm)
how many nerve fibers go to the spindle?
more than 1/2
the muscle spindle lie_____ to the extrafusal fibers?
in parallel
gross movement muscles have _______ spindles than a muscle with finer movements?
less spindles
what are muscle spindles?
a length detector
what is a muscle spindles novel stimulus?
stretch
gets stretched bc its fibers lay parallel to the extrafusal fibers of the muscle
what are the 2 parts of the muscle spindle inside the capsule?
1: receptor (afferent)
2: associated striated muscle fibers (efferent)
what are extrafusal muscle fibers?
regular muscle fibers
controls where the limb is in space
what are intrafusal muscle fibers?
associated with spindle
skeletal muscle
has efferent motor component as well as afferent sensory component that controls contraction of intrafusal ms fiibers
controls the length of the spindle
what is the equatorial portion?
the nuclear bag?
what are the 2 types of intrafusal fibers?
1: nuclear bag
2: nuclear chain
nuclear chain fibers are more responsive to ___?
more responsive to slower changes in length
nuclear chain fibers line up in series; static; slow adapting
nuclear bag fibers are more responsive to ___?
more responsive to rapid changes in velocity
bulbous area where fibers stay in center; little longer; more type 1a
nuclear bag 1 responds to ___?
rapid changes in muscle length