Final answer:
A stretch reflex is a type of reflex that occurs when a skeletal muscle is stretched. It involves a muscle spindle receptor that is activated when the muscle is stretched, causing the muscle to contract.
Step-by-step explanation:
A stretch reflex is a type of reflex that occurs when a skeletal muscle is stretched. It involves a muscle spindle receptor that is activated when the muscle is stretched, causing the muscle to contract. The reflex helps to maintain muscles at a constant length and is important for stability.
In the reflex arc of the stretch reflex, the muscle spindle receptor sends a signal to the spinal cord through the dorsal root. The signal then synapses directly on the ventral horn motor neuron that activates the muscle, resulting in muscle contraction.