Chapter 14: Endocrine System

T3, T4, and calcitonin are hormones that are secreted by the thyroid gland. These hormones play important roles in regulating metabolism, growth, and development in the body. T3 and T4 are thyroid hormones that help control the body's metabolism, while calcitonin helps regulate calcium levels in the blood. The thyroid gland is responsible for producing and releasing these hormones into the bloodstream to maintain overall balance and function in the body.

Insulin and glucagon are both hormones that are secreted by the pancreas and play a crucial role in the regulation of blood glucose levels. Insulin is released when blood glucose levels are high and helps to lower them by promoting the uptake of glucose into cells and the storage of excess glucose as glycogen. On the other hand, glucagon is released when blood glucose levels are low and stimulates the liver to convert stored glycogen into glucose, which then raises blood glucose levels. Therefore, both insulin and glucagon work together to maintain the balance of blood glucose levels in the body.

The adrenal medulla is part of the "fight or flight" response. This means that it is involved in the body's response to stress or danger. During a stressful situation, the adrenal medulla releases hormones called adrenaline and noradrenaline, which increase heart rate, blood pressure, and energy levels. These hormones help prepare the body to either confront the threat or flee from it. Therefore, the adrenal medulla plays a crucial role in the body's response to stress and is an important component of the "fight or flight" response.

The islets of Langerhans are clusters of cells found in the pancreas, not the adenohypophysis. These cells are responsible for secreting hormones such as insulin and glucagon, which play a crucial role in regulating blood sugar levels. Insulin helps lower blood sugar levels by allowing cells to take in glucose, while glucagon helps raise blood sugar levels by stimulating the liver to release stored glucose. Therefore, the correct answer is that the islets of Langerhans secrete insulin and glucagon.

Steroids include the glucocorticoids, mineralocorticoids, and androgens. These are hormones that are secreted by various glands in the body, such as the adrenal medulla. They have different functions and play important roles in regulating various processes in the body. Glucocorticoids, for example, are involved in regulating metabolism and immune response, while mineralocorticoids help regulate electrolyte balance and blood pressure. Androgens are primarily known for their role in male sexual development, but they also have other functions in both males and females. Overall, steroids are a diverse group of hormones with important physiological functions.

The hypothalamus is a small region in the brain that plays a crucial role in regulating various bodily functions. It secretes releasing hormones that control the secretion of hormones from the anterior pituitary gland. It also synthesizes and releases oxytocin and antidiuretic hormone (ADH) which are involved in reproductive and water balance functions respectively. However, the hypothalamus itself does not directly secrete adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), and gonadotropins. These hormones are actually secreted by the anterior pituitary gland, which is under the control of the hypothalamus.

Iodine-containing hormones regulate metabolic rate. These hormones are secreted by the hypothalamus as releasing hormones. They are not steroids, but they play a crucial role in controlling the body's metabolism. These hormones, such as thyroid-stimulating hormone (TSH), help in regulating the rate at which the body converts food into energy. By controlling the metabolic rate, these hormones influence various bodily functions, including growth, development, and energy production.