More than one choice may apply.
ANP, the hormone secreted by the heart, has exactly the opposite function to this hormone secreted by the outermost zone of the adrenal cortex.
a. Epinephrine
b. Cortisol
c. Aldosterone
d. Testosterone

Verified step by step guidance

1. Step 1: Begin by identifying the hormone mentioned in the question, ANP (Atrial Natriuretic Peptide). ANP is secreted by the heart and plays a role in reducing blood pressure and blood volume by promoting sodium excretion and inhibiting water reabsorption in the kidneys.
2. Step 2: Understand the function of ANP. It works to counteract the effects of hormones that increase blood pressure and blood volume, such as those that promote sodium retention and water reabsorption.
3. Step 3: Review the hormones listed in the options and their functions. For example: - Epinephrine: A stress hormone that increases heart rate and blood pressure. - Cortisol: A stress hormone involved in glucose metabolism and immune response. - Aldosterone: A hormone from the adrenal cortex that promotes sodium retention and water reabsorption, increasing blood pressure. - Testosterone: A sex hormone involved in male reproductive functions.
4. Step 4: Compare the function of ANP with the listed hormones. Identify which hormone has a function opposite to ANP. Specifically, focus on aldosterone, as it promotes sodium retention and water reabsorption, which increases blood pressure—directly opposing ANP's effects.
5. Step 5: Conclude that the correct answer involves identifying aldosterone as the hormone with a function opposite to ANP. Other hormones listed do not directly oppose ANP's role in regulating blood pressure and volume.

Key Concepts

Atrial Natriuretic Peptide (ANP)

ANP is a hormone produced by the heart's atria that helps regulate blood pressure and fluid balance. It promotes natriuresis, the excretion of sodium through urine, and inhibits the renin-angiotensin-aldosterone system, leading to decreased blood volume and lower blood pressure.

Adrenal Cortex Hormones

The adrenal cortex produces several hormones, including cortisol and aldosterone. Cortisol is involved in stress response and metabolism regulation, while aldosterone primarily regulates sodium and potassium levels, influencing blood pressure. Understanding these hormones is crucial for identifying their opposing functions to ANP.

Opposing Hormonal Functions

In physiology, many hormones have opposing effects to maintain homeostasis. For instance, while ANP decreases blood volume and pressure, hormones like aldosterone increase sodium retention and blood volume. Recognizing these interactions is essential for understanding the body's regulatory mechanisms.