Download Stretch reflex

 The stretch (myotatic) reflex is exemplified by the knee jerk
reflex
 used routinely in clinical neurophysiology as a tool for
diagnosis of certain neurological condition
 The stretch reflex has only one synapse betweenThe
sensory afferent nerves (group Ia afferents)and the motor
efferent nerves (α moroneurons).
 When the muscle is stretched, group Ia afferent fibers
in the muscle spindle are activated and their firing rate
increase
 The group Ia afferents enter the spinal cord and
synapse directly on and activate α motoneurons.
 When these α motoneurons are activated, they cause
contraction of the muscle that was originally stretched
 When the muscle contracts, it shortens, thereby
decreasing stretch on the muscle spindle.
 The muscle spindle returns to its original length, and
the firing rate of the group Ia afferents returns to
baseline
 Simultaneously, information is sent from the spinal
cord to cause contraction of synergistic muscles and
relaxation of antagonistic muscles.