Question

put the steps into the correct order to trace a reflex arc.
1 afferent sensory fiber transmits the signal to the spinal cord
2 the spinal cord returns the signal back to the muscle via the efferent motor nerve. at the same time, the signal is transmitted up the spinal cord to the brain
3 the muscle receives the signal from the efferent nerve and contracts, before the brain realizes it
4 a stimulus is received (such as the sudden stretch of a tendon when hit with a reflex hammer)

Explanation:

A reflex arc starts with a stimulus being detected. Next, the sensory signal travels to the spinal cord via afferent fibers. The spinal cord then sends a motor response signal back through efferent nerves (while also sending the signal to the brain). Finally, the muscle contracts in response to the efferent signal before the brain processes the event.

Answer:

1. 4. A stimulus is received (such as the sudden stretch of a tendon when hit with a reflex hammer)
2. 1. Afferent sensory fiber transmits the signal to the spinal cord
3. 2. The spinal cord returns the signal back to the muscle via the efferent motor nerve. At the same time, the signal is transmitted up the spinal cord to the brain
4. 3. The muscle receives the signal from the efferent nerve and contracts, before the brain realizes it