Muscle06/muscle spindle introduction

When the muscle is stretched by external force, the muscle spindles are also stretched as they are in parallel position with the extrafusal muscle fibers, the main muscle fibers providing the contraction force. Afferent fiber from the muscle spindle form an excitatory synapse with motor neuron that innervate that muscle, in the spinal cord. So, when a muscle is stretched, reflex contraction of the muscle is induced, and the muscle shortens.

In patella tendon reflex, the muscle spindles are the receptors.

Challenge Quiz

1.

The muscle spindles are stimulated and generate action potentials when the extrafusal muscles are stretched contracting too strongly  正解!.

2.

The afferent activity from the muscle spindles elicits a spinal reflex that enhances inhibits  正解! that muscle activity.

3.

The receptor in the patella tendon reflex is the muscle spindles in the femoral quadriceps tendon spindles in the quadriceps tendon  正解!.