on 05-Jan-2016 (Tue)

Two features of the connections between sensory and motor neurons deserve special mention: (1) a particular sensory fiber makes contact with more than one quadriceps motor neuron; this is called divergence and implies that a single sensory fiber can influence a number of motor neurons.

2) a particular motor neuron receives contacts from a number of sensory fibers; this is called convergence and implies that a single motor neuron is influenced by a number of sensory fibers.

The reflex operates as follows: the tap on the tendon stretches the muscle and generates signals in the sensory fiber. These signals are relayed at the synapse to the motor neuron. The motor neuron, having gotten the news of the stretch, sends signals back to the muscle. After these signals are received by the muscle fibers, the muscle contracts, taking the stretch off the muscle spindles. When the spindles are put at rest, the original disturbance is canceled and the contraction is terminated. Thus the reflex is a control mechanism which keeps the quadriceps at constant length