Question

Antidiuretic hormone (ADH) a. increases water reabsorption in the kidneys. b. regulates blood pressure by constricting arterioles. c. decreases the volume of urine produced by the kidneys. d. probably arose from the same ancestral gene as that of oxytocin. e. does all of the above.

Short answer

The correct answer to the question is option e - ADH does all of the above.

Step-by-step solution

Option a

Antidiuretic hormone (ADH) indeed increases water reabsorption in the kidneys. So, option a is correct.

Option b

ADH also plays a role in regulating blood pressure. When ADH levels rise, the blood vessels constrict, which helps to increase blood pressure. Hence, option b is also correct.

Option c

ADH acts to regulate the body's retention of water; it decreases the volume of urine produced by the kidneys, therefore, option c is correct.

Option d

Various research studies suggest that ADH and oxytocin arose from the same ancestral gene, hence option d is also valid.

Option e: Analysis

Considering all options a–d are correct, the option that says 'does all of the above' becomes the right choice. All the listed attributes of ADH are correct, so the best answer is to choose option e.

Key concepts

Water Reabsorption in Kidneys

The antidiuretic hormone (ADH) plays a crucial role in the body's water balance by increasing water reabsorption in the kidneys. When ADH is released into the bloodstream, it directs the kidney tubules to reabsorb more water back into the blood. This process reduces the amount of water lost through urine, concentrating the urine as the volume decreases. The ability of the kidney to reclaim water effectively is essential for maintaining the body's fluid balance and ensuring that cells receive an adequate supply of water to function properly.

ADH achieves this by making the walls of the kidney's collecting ducts more permeable to water, allowing water to pass from the filtrate back into the bloodstream. This is a finely tuned mechanism that responds to the body's hydration status, ensuring efficient water conservation when needed.

Blood Pressure Regulation

In addition to its vital role in water balance, ADH assists in the regulation of blood pressure. The hormone has vasopressor properties, meaning it can induce the constriction of blood vessels, specifically small arteries known as arterioles. This vasoconstriction leads to an increase in blood pressure, an important effect when the body experiences low blood volume or low blood pressure.

For instance, when a person is dehydrated or loses blood, the body's blood pressure can drop. ADH is one of the hormones the body releases in response to restore blood pressure to normal levels. By constricting arterioles, ADH helps increase the force of blood flow, counteracting the hypotensive state and bringing blood pressure back within a normal range, ensuring a consistent blood flow to organs and tissues.

Volume of Urine Production

The release of ADH has a direct impact on the volume of urine produced by the kidneys. When the body needs to conserve water, ADH production increases, leading to reduced urine output. Conversely, when the body has excess water, ADH levels decrease, which results in an increased volume of urine with a more diluted concentration. This regulation helps maintain homeostasis by precisely adjusting urine volume to match the body's hydration status.

Factors Influencing Urine Volume

Several factors can influence urine volume, including fluid intake, external temperature, and physiological states like sweating or illness. With the precise control orchestrated by ADH, the kidneys can ensure that the right volume of urine is produced to keep the body's fluid levels in balance.

ADH and Oxytocin Gene Ancestry

Research has uncovered a fascinating genetic story behind ADH and another significant hormone, oxytocin. These two hormones are thought to have evolved from the same ancestral gene. Both hormones are similar in structure and are part of the neurohypophysial family of hormones, which are produced in the hypothalamus and released by the posterior pituitary gland.

Despite their common genetic origin, ADH and oxytocin serve distinct physiological roles. Oxytocin is primarily known for its involvement in childbirth and lactation, as well as its role in social bonding and behaviors. The insight into their shared gene ancestry aids in understanding the evolutionary pathway that led to the functional diversification of these hormones, illustrating how gene duplication and mutation can result in new hormones with unique functions.