Question

Which of these is not a pair of antagonistic hormones? a. insulin- glucagon b. calcitonin- parathyroid hormone c. cortisol- epinephrine d. aldosterone- atrial natriuretic hormone (ANH)

Short answer

The pair of hormones that are not antagonistic is c. cortisol and epinephrine.

Step-by-step solution

Define antagonistic hormones

Antagonistic hormones are hormones that have opposite or opposing actions in the body. They help to maintain homeostasis by regulating various physiological processes through their opposing actions.

Evaluate each pair of hormones

a. Insulin and glucagon are antagonistic hormones. Insulin lowers blood glucose levels, while glucagon raises them. b. Calcitonin and parathyroid hormone are also antagonistic hormones. Calcitonin lowers blood calcium levels, while parathyroid hormone raises them. d. Aldosterone and atrial natriuretic hormone (ANH) are antagonistic as well. Aldosterone promotes the reabsorption of sodium and water, leading to increased blood volume and blood pressure. ANH acts in the opposite way by promoting the excretion of sodium and water, thus decreasing blood volume and blood pressure.

Identify the non-antagonistic pair

c. Cortisol and epinephrine are not antagonistic hormones. Both cortisol and epinephrine play a role in the body's response to stress. Cortisol helps to mobilize energy sources and suppress the immune system in response to stress, while epinephrine (also known as adrenaline) activates the "fight or flight" response, increasing heart rate, blood pressure, and metabolism. Though they have different specific actions, they do not exhibit opposite or opposing effects on the body and thus are not antagonistic hormones.

Provide the final answer

The pair of hormones that are not antagonistic is c. cortisol and epinephrine.

Key concepts

Understanding Homeostasis

Homeostasis is the term used to describe the dynamic equilibrium your body maintains to keep your internal environment stable, despite changes in the external environment. It involves various physiological processes that balance your bodily functions. Imagine homeostasis as a smart thermostat for your body, constantly adjusting the 'settings' to ensure that everything runs smoothly.

For example, if you're exercising and your body temperature rises, homeostatic mechanisms kick in to cool you down. Similarly, if you haven't eaten for a while and your blood sugar levels drop, your body has mechanisms to raise those levels. Hormones play a crucial role in this regulatory process, often operating in pairs known as antagonistic hormones, which have opposing effects to fine-tune body functions.

Insulin and Glucagon: Balancing Blood Sugar

Insulin and glucagon are perfect examples of how antagonistic hormones work together to manage homeostasis, specifically in regulating blood sugar levels. When you eat a meal, your blood sugar (glucose) levels rise. In response, the pancreas secretes insulin. This hormone acts like a key, allowing glucose to enter your body's cells and be used for energy, thus lowering blood sugar levels.

Glucagon's Role

On the flip side, when your blood sugar levels fall, say between meals, glucagon comes into play. Glucagon signals the liver to release stored glucose, elevating your blood sugar levels. These two hormones are in a continuous dance, making sure your blood sugar levels remain stable.

Calcitonin and Parathyroid Hormone: A Duel for Calcium

Calcitonin and parathyroid hormone (PTH) have a unique interplay that is critical for regulating calcium levels in the blood. Calcium is vital not just for bone health but also for muscle function, nerve signaling, and blood clotting.

How Calcitonin Works

When calcium levels are high, the thyroid gland releases calcitonin which encourages the deposition of calcium into the bones and reduces calcium absorption in the intestines and kidneys. It acts as a 'save' button for calcium in your body.

Parathyroid Hormone in Action

In contrast, when calcium levels drop, the parathyroid glands produce PTH, which does the opposite, releasing calcium from bones, increasing absorption in the gut, and reducing the amount lost in urine.

Aldosterone and ANH: Volume and Pressure Regulators

Aldosterone and atrial natriuretic hormone (ANH) might not be as well-known as insulin and glucagon, but they're just as crucial for maintaining homeostasis, especially in relation to blood volume and pressure.

Meet Aldosterone

Aldosterone, part of the renin-angiotensin-aldosterone system, helps to increase blood volume and pressure by promoting the reabsorption of sodium (and consequently water) in the kidneys.

ANH's Counter-Move

ANH, produced by the heart when the blood volume gets too high, has the opposite effect. It triggers the excretion of sodium and water into the urine, which can help to decrease blood volume and pressure. This balancing act is vital for preventing conditions like hypertension or edema.