1.
Thyroid-stimulating hormone (TSH) is
Correct Answer
A. Produced in the pituitary gland.
Explanation
Thyroid-stimulating hormone (TSH) is produced in the pituitary gland. This hormone is responsible for regulating the production and release of thyroid hormones from the thyroid gland. The pituitary gland, located at the base of the brain, produces and releases TSH in response to signals from the hypothalamus. TSH then travels through the blood to the thyroid gland, where it stimulates the production of thyroid hormones. Therefore, the correct answer is that TSH is produced in the pituitary gland.
2.
An injection of TSH to an otherwise normal animal will cause which of the following?
Correct Answer
B. Goiter development
Explanation
An injection of TSH to an otherwise normal animal will cause goiter development. TSH, or thyroid-stimulating hormone, is released by the pituitary gland and stimulates the thyroid gland to produce thyroid hormones, including T4. When TSH is injected into an animal, it can cause the thyroid gland to become overactive and produce excessive amounts of thyroid hormones. This can lead to the enlargement of the thyroid gland, known as a goiter. Therefore, the correct answer is goiter development.
3.
Thyroxine is
Correct Answer
D. The most important hormone for maintaining the metabolic rate and body temperature.
Explanation
Thyroxine is the most important hormone for maintaining the metabolic rate and body temperature. It plays a crucial role in regulating the body's energy production, metabolism, and heat generation. It helps to control the rate at which cells convert nutrients into energy, thus affecting overall metabolic activity. Additionally, thyroxine helps to regulate body temperature by influencing the body's heat production and dissipation mechanisms.
4.
Thyrotropin-releasing hormone (TRH) is
Correct Answer
D. Secreted by the hypothalamus.
Explanation
Thyrotropin-releasing hormone (TRH) is a hormone that is secreted by the hypothalamus. It acts as a stimulator for the production of T4 (thyroxine) in the pituitary gland. TRH is not produced in the pituitary gland itself, nor is it held at a low plasma concentration by low levels of TSH (thyroid-stimulating hormone). Therefore, the correct answer is that TRH is secreted by the hypothalamus.
5.
Which of the following statements is true?
Correct Answer
A. The hypothalamus primarily secrets tropic hormones that stimulate the secretion of other hormones.
Explanation
The correct answer is that the hypothalamus primarily secretes tropic hormones that stimulate the secretion of other hormones. This means that the hypothalamus produces hormones that act on the pituitary gland, which then releases hormones that act on other endocrine glands in the body. This is an important regulatory mechanism in the endocrine system, as it allows for the control and coordination of hormone secretion throughout the body.
6.
Which of the following statements about metabolism is false?
Correct Answer
C. All of the energy from metabolism is ultimately stored in the chemical bonds of ATP.
Explanation
The correct answer is "All of the energy from metabolism is ultimately stored in the chemical bonds of ATP." This statement is false because not all of the energy from metabolism is stored in ATP. Some energy is released as heat during metabolic reactions.
7.
How would you treat a thyroidectomized animal so that it functions like a "normal" animal?
Correct Answer
A. Provide the animal T4 supplements.
Explanation
When an animal undergoes a thyroidectomy, its thyroid gland is removed, resulting in a lack of thyroid hormones such as T4. To treat this condition and help the animal function normally, T4 supplements need to be provided. T4 is the main hormone produced by the thyroid gland, and supplementing it can help restore normal thyroid function in the animal.
8.
As a result of the missing hormone(s) in the hypophysectimized rat, what would be some expected symptoms?
Correct Answer
B. Decreased basal metabolic rate
Explanation
The hypophysectomized rat is missing hormones that are normally produced by the pituitary gland. One of these hormones is thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to produce thyroid hormones. Without TSH, the thyroid gland is not properly stimulated and therefore the basal metabolic rate (BMR) decreases. This decrease in BMR can lead to symptoms such as unexplained weight loss, as the body is not able to efficiently burn calories. The other symptoms listed, such as high body temperature and hyperactivity, are not directly related to the missing hormones in the hypophysectomized rat.
9.
An injection of thyroxine to an otherwise normal rat will cause which of the following?
Correct Answer
A. Hyperthyroidism
Explanation
An injection of thyroxine to an otherwise normal rat will cause hyperthyroidism. Thyroxine is a hormone produced by the thyroid gland that regulates metabolism. When injected into a rat, it will increase the levels of thyroxine in the body, leading to an overactive thyroid gland and excessive production of thyroid hormones. This condition is known as hyperthyroidism, which can result in symptoms such as weight loss, increased appetite, rapid heartbeat, and nervousness.
10.
Why didn't any of the rats develop a goiter after thyroxine injection?
Correct Answer
B. In all cases, TSH levels were not elevated by the thyroxine injection.
Explanation
The rats did not develop a goiter because their TSH levels were not elevated by the thyroxine injection. TSH, or thyroid-stimulating hormone, is responsible for stimulating the thyroid gland to produce and release thyroid hormones. In this case, since the TSH levels were not elevated, it suggests that the rats' thyroid glands were not being stimulated to produce excessive amounts of thyroid hormones, which can lead to the development of a goiter.
11.
Why did the normal rat develop a palpable goiter with the TSH injection?
Correct Answer
A. The TSH receptors on the thyroid gland were excessively stimulated.
Explanation
The correct answer is that the TSH receptors on the thyroid gland were excessively stimulated. This is because TSH (thyroid-stimulating hormone) is responsible for stimulating the thyroid gland to produce and release thyroid hormones, including T4. When TSH is injected, it can cause an excessive stimulation of the TSH receptors on the thyroid gland, leading to increased production and secretion of thyroid hormones. This can result in the development of a palpable goiter, which is an enlargement of the thyroid gland.
12.
An injection of propylthiouracil to an otherwise normal animal will cause which of the following?
Correct Answer
D. Goiter development
Explanation
An injection of propylthiouracil can cause goiter development. Propylthiouracil is a medication used to treat hyperthyroidism by inhibiting the production of thyroid hormones. However, in some cases, it can cause an increase in the size of the thyroid gland, leading to the development of a goiter. This is because propylthiouracil can disrupt the balance of thyroid hormones in the body, leading to an overstimulation of the thyroid gland and subsequent enlargement.
13.
Why did the normal rat develop a palpable goiter with the propylthiouracil injection?
Correct Answer
A. The injection decreased the negative feedback mechanism on TSH.
Explanation
The normal rat developed a palpable goiter with the propylthiouracil injection because the injection decreased the negative feedback mechanism on TSH. This means that the normal inhibitory signals that regulate the secretion of TSH were reduced, leading to an overproduction of TSH. As a result, the thyroid gland was stimulated to produce excessive amounts of T4, causing the development of a goiter.