When the muscle is stretched, it stretches the intrafusal fibers within the
muscle spindle
a.
When the intrafusal fibers are stretched, the firing rate in the
afferent sensory nerve fibers is increased
2.
The afferent sensory neuron synapses with alpha motor neurons, causing
a contraction of the muscle
3.
This reflex serves as a negative feedback mechanism to sense and resist
changes in muscle length when an additional load is applied
4.
Examples of stretch reflexes
a.
Patellar tendon (knee jerk) reflex: the patellar tendon connects the
quadriceps femoris to the tibia
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1.Gamma motor neurons will stimulate the contraction of intrafusal fibers at the same time that alpha motor neurons stimulate the contraction of extrafusual fibers
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