Question

the adrenal medulla secretes epinephrine during sympathetic stimulation. which of the following statements describes why epinephrine would increase the sympathetic response?
epinephrine has no effect on sympathetic targets.
epinephrine binds to a separate receptor than norepinephrine, which increases the sympathetic response.
epinephrine increases the action of pre- and postganglionic axons.
the same receptors that respond to norepinephrine also respond to epinephrine, increasing the action of both.

Explanation:

To solve this, we analyze each option:

• Option 1: Epinephrine does affect sympathetic responses (e.g., fight - or - flight), so this is wrong.
• Option 2: Epinephrine and norepinephrine can bind to the same adrenergic receptors (like alpha and beta receptors), not a separate receptor for epinephrine to increase the response this way, so this is wrong.
• Option 3: Epinephrine is a hormone from the adrenal medulla and doesn't directly act on pre - or postganglionic axons to increase their action in the context of sympathetic response enhancement, so this is wrong.
• Option 4: Sympathetic postganglionic neurons release norepinephrine, and epinephrine (from adrenal medulla) can bind to the same adrenergic receptors as norepinephrine. This means that when epinephrine is present, it can activate those receptors too, thereby increasing the overall sympathetic response. This matches the physiological mechanism.

Answer:

The same receptors that respond to norepinephrine also respond to epinephrine, increasing the action of both.