Which term describes the simple, quick, automatic responses to certain stimuli?

Which term describes the simple, quick, automatic responses to certain stimuli?

• A. Reflex arc
• B. Spinal cord
• C. Hormone
• D. Negative-feedback mechanism

Answer: (A)

Automatic, quick responses to a stimulus are produced by a reflex arc. This neural circuit runs from a sensory receptor through a sensory neuron to the spinal cord (often via an interneuron) and then out via a motor neuron to the effector, typically a muscle. That short, direct pathway lets the body respond rapidly without conscious thought. The spinal cord is central to many reflex arcs, providing the quick integration that enables these fast actions. In contrast, hormones are slow chemical signals circulating in the body, and negative-feedback mechanisms regulate internal states rather than producing immediate external responses.

Automatic, quick responses to a stimulus are produced by a reflex arc. This neural circuit runs from a sensory receptor through a sensory neuron to the spinal cord (often via an interneuron) and then out via a motor neuron to the effector, typically a muscle. That short, direct pathway lets the body respond rapidly without conscious thought. The spinal cord is central to many reflex arcs, providing the quick integration that enables these fast actions. In contrast, hormones are slow chemical signals circulating in the body, and negative-feedback mechanisms regulate internal states rather than producing immediate external responses.