Final answer:
C, A, D, B - The stretch reflex initiates with a Hammer tap (C), followed by sensory signals to the cerebrum (A), excitation of flexor muscles (D), and cerebrum-mediated relaxation of flexors (B), outlining the sequential events in muscle stretching response.
Step-by-step explanation:
The stretch reflex is a precisely orchestrated sequence of events that occurs in response to the stretching of muscles, aimed at maintaining balance and stability. Initiating with a Hammer tap (C), this physical stimulus stretches sensory receptors in leg extensor muscles, triggering a series of events. Information travels to the dorsal root, where an interneuron synapse occurs, leading to knee extension. This initial stretch sets the reflex in motion.
Subsequently, sensory receptors in the extensor muscles send signals up a sensory afferent axon to the cerebrum (A). This step involves the transmission of information from the periphery to the central nervous system, providing the brain with crucial data about the muscle's length and initiating a response. Following this, the excitation of flexor muscles (D) takes place, involving an interneuron synapse that further contributes to knee extension. Finally, efferent currents carry information to the spine, and the cerebrum instructs the flexors to relax (B), completing the reflex loop.
Understanding the chronological order of these events sheds light on the intricate mechanisms underlying the stretch reflex, illustrating how the nervous system rapidly processes and responds to changes in muscle length to maintain optimal motor function.