What secretes epinephrine and norepinephrine in response to sympathetic nervous system signals?

The adrenal medulla is the correct answer because it is the inner portion of the adrenal glands, which sit atop the kidneys. This structure is responsible for producing and releasing the catecholamines, epinephrine and norepinephrine, particularly in response to sympathetic nervous system activation during stress or danger, commonly referred to as the "fight or flight" response.

When the sympathetic nervous system is activated, signals stimulate the adrenal medulla to release these hormones directly into the bloodstream. Epinephrine is mainly associated with increasing heart rate, muscle strength, and energy availability, while norepinephrine primarily helps maintain blood pressure and redirect blood flow to critical areas.

The adrenal cortex, which is the outer part of the adrenal glands, produces different hormones, including cortisol and aldosterone, but is not involved in the immediate response to sympathetic stimulation. The hypothalamus plays a role in regulating the autonomic nervous system and hormone release but does not secrete epinephrine or norepinephrine directly. The thymus gland is involved in immune system function and does not produce these hormones. Thus, the adrenal medulla is uniquely positioned and specialized for the production of epinephrine and norepinephrine in response to sympathetic nervous activation.