Chapter 18 - The Endocrine System

Oxytocin enhances uterine contractions during labor and stimulates milk ejection. It is released by the posterior pituitary gland and plays a crucial role in childbirth and breastfeeding. Oxytocin helps to stimulate the muscles of the uterus to contract, which aids in the progression of labor. It also triggers the release of milk from the mammary glands during breastfeeding, allowing for the proper feeding of the newborn.

ADH, also known as antidiuretic hormone, is released by the posterior pituitary gland and plays a role in regulating water balance in the body. One of its main functions is to inhibit water loss through the kidneys by increasing the reabsorption of water in the renal tubules. This helps to concentrate urine and conserve water in the body. Therefore, the statement "Inhibits water loss through the kidneys" accurately describes the function of ADH.

Glucagon is the hormone that increases blood glucose levels. It is released by the pancreas when blood sugar levels are low. Glucagon stimulates the liver to convert stored glycogen into glucose, which is then released into the bloodstream. This helps to raise blood sugar levels and provide energy to the body.

FSH (follicle-stimulating hormone) stimulates egg and sperm formation.

The correct answer is 16. Thyroid stimulating hormone (TSH) stimulates the synthesis and release of T4 (thyroxine) and T3 (triiodothyronine) from the thyroid gland. TSH is produced and released by the pituitary gland in response to thyrotropin-releasing hormone (TRH) from the hypothalamus. T4 and T3 are important hormones for regulating metabolism, growth, and development in the body.

Prolactin is the hormone that initiates and maintains milk secretion by the mammary glands.

Epinephrine and norepinephrine, also known as adrenaline and noradrenaline, are hormones that are released during the fight-or-flight response. These hormones increase heart rate, blood pressure, and blood sugar levels, preparing the body to respond to a perceived threat or danger. Therefore, the correct answer, 18, aligns with the given statement that epinephrine and norepinephrine augment fight-or-flight responses.

Calcitonin is the hormone that decreases blood Ca2+ level.

Insulin is the hormone that decreases blood glucose levels. It is produced by the pancreas and helps to regulate the amount of glucose in the bloodstream. Insulin allows cells to take in glucose from the blood and use it for energy or store it for later use. When blood glucose levels are high, insulin is released to lower them back to normal levels. This is important for maintaining stable blood sugar levels and preventing complications associated with high blood sugar, such as diabetes.

Melatonin is a hormone that is produced by the pineal gland in the brain and is responsible for regulating the body's biological clock. It helps to control the sleep-wake cycle and is released in response to darkness, signaling to the body that it is time to sleep. Therefore, option 20, melatonin, is the correct answer as it directly relates to the regulation of the body's biological clock.

Melanocyte-stimulating hormone (MSH) is responsible for increasing skin pigmentation when present in excess.

Luteinizing hormone (LH) stimulates sex hormone production and triggers ovulation. LH is produced by the pituitary gland and plays a crucial role in the reproductive system. It stimulates the production of estrogen and progesterone in females, which are necessary for the menstrual cycle and ovulation. In males, LH stimulates the production of testosterone, which is responsible for the development and maintenance of male reproductive organs and secondary sexual characteristics. Therefore, the correct answer is 5.

The correct answer is 14. Hypothalamic regulating hormones stimulate and inhibit the secretion of anterior pituitary hormones. These hormones are released by the hypothalamus and act on the anterior pituitary gland to control the release of other hormones such as thyroid stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and growth hormone (GH). Therefore, the hypothalamic regulating hormones play a crucial role in regulating the secretion of anterior pituitary hormones.

Androgens are responsible for stimulating the growth of axillary and pubic hair. These hormones are produced primarily in the testes in males and in the adrenal glands in both males and females. Androgens play a crucial role in the development of secondary sexual characteristics, including the growth of hair in specific areas of the body.

Inhibin is a hormone that is released by the gonads (testes in males and ovaries in females). It functions to inhibit the release of follicle-stimulating hormone (FSH) from the anterior pituitary gland. FSH is responsible for stimulating the growth and development of ovarian follicles in females and the production of sperm in males. Therefore, the release of inhibin suppresses the release of FSH, regulating the reproductive system.

Thymosin is the hormone that promotes T cell maturation.

Thyroxine (T4) and triiodothyronine (T3) are hormones produced by the thyroid gland. They play a crucial role in regulating oxygen use, basal metabolic rate, cellular metabolism, growth, and development. These hormones are responsible for controlling the rate at which cells utilize energy and affect various bodily functions. Therefore, option 6, which is thyroxine (T4) and triiodothyronine (T3), is the correct answer.

Cortisol is the correct answer because it is a hormone that regulates metabolism and helps the body respond to stress. It is produced by the adrenal glands and plays a role in controlling blood sugar levels, reducing inflammation, and regulating the immune system.

Parathormone (PTH) is the hormone that increases blood Ca2+ levels.

Prostaglandins are local hormones involved in inflammation, smooth muscle contraction, and blood flow. They are produced by cells in response to various stimuli, such as injury or infection, and play a role in the inflammatory response. Prostaglandins can cause blood vessels to dilate, increase blood flow to the affected area, and promote the migration of immune cells to the site of inflammation. They can also cause smooth muscle contraction, which can contribute to pain and discomfort. Therefore, prostaglandins are directly related to the processes mentioned in the question.

Human growth hormone (hGH) stimulates protein synthesis, inhibits protein breakdown, stimulates lipolysis (the breakdown of fats), and retards the use of glucose for ATP production.

Aldosterone is the correct answer because it is a hormone that helps control water and electrolyte homeostasis. It is produced by the adrenal glands and acts on the kidneys to increase the reabsorption of sodium and water while promoting the excretion of potassium. This helps regulate blood pressure and maintain the balance of electrolytes in the body.

In the direct gene activation method of hormone action, the hormone enters the target cell and binds to an intracellular receptor. This activated receptor-hormone complex then interacts with specific DNA sequences, leading to changes in gene expression. These changes result in the production of proteins that are responsible for the physiological responses associated with the hormone. Therefore, the statement is true.

The hypothalamus is the major integrating link between the nervous and endocrine systems because it controls the release of hormones from the pituitary gland, which in turn regulates many other endocrine glands in the body. It also acts as an endocrine gland itself by producing and releasing hormones. Additionally, the hypothalamus plays a crucial role in controlling the stress response by activating the release of stress hormones like cortisol.

Down-regulation refers to the decrease in the number or sensitivity of hormone receptors on the target cell. This decrease makes the target cell less sensitive to the hormone. On the other hand, up-regulation refers to the increase in the number or sensitivity of hormone receptors on the target cell, making it more sensitive to the hormone. Therefore, down-regulation makes a target cell less sensitive to a hormone, while up-regulation makes a target cell more sensitive to a hormone.

Steroids are not a category of water-soluble hormones. Water-soluble hormones, such as peptides, amines, eicosanoids, and proteins, are able to dissolve in water and travel freely in the bloodstream. Steroids, on the other hand, are lipid-soluble hormones and require carrier proteins to be transported in the bloodstream. This is because steroids are derived from cholesterol and have a structure that is not easily dissolved in water. Therefore, steroids are not considered water-soluble hormones.

The statement is false because if the effect of two or more hormones acting together is greater than the sum of each acting alone, then the two hormones are said to have a synergistic effect, not a permissive effect. A permissive effect occurs when one hormone enhances the response of another hormone, but the combined effect is not necessarily greater than the sum of each acting alone.

Glucocorticoids are a class of adrenal gland hormones that play a key role in providing resistance to stress, producing anti-inflammatory effects, and promoting normal metabolism to ensure adequate quantities of ATP. These hormones are involved in regulating various physiological processes and help the body cope with stressors. They are also involved in suppressing the immune response and reducing inflammation. Overall, glucocorticoids play a crucial role in maintaining homeostasis and ensuring the body's proper functioning during times of stress.

The correct answer is 3, 5, 7. The stress response or general adaptation syndrome occurs in three stages. The first stage is the fight-or-flight response, which is the initial physiological reaction to stress. The second stage is the resistance reaction, where the body tries to adapt and cope with the ongoing stressor. The third and final stage is exhaustion, which occurs when the body's resources are depleted and it can no longer sustain the stress response.

Graves disease is an autoimmune disease that causes hyperthyroidism. It is characterized by the overproduction of thyroid hormones, leading to symptoms such as weight loss, rapid heartbeat, and bulging eyes. This condition occurs when the immune system mistakenly attacks the thyroid gland, causing it to produce excessive amounts of hormones. Unlike the other conditions listed, Graves disease specifically involves an autoimmune response targeting the thyroid gland, resulting in hyperthyroidism.

Insulin and thyroxine arrive at the organ at the same time, but only thyroxine causes an effect on the organ. This is because the organ's cells have receptors for thyroxine but not for insulin. Receptors are proteins on the surface of cells that bind to specific hormones or molecules, triggering a response inside the cell. In this case, the organ's cells have receptors that specifically recognize and bind to thyroxine, allowing it to exert its effect on the organ. On the other hand, insulin does not have receptors on the organ's cells, so it is unable to cause any effect on the organ.

The correct order of actions for a water-soluble hormone on its target cell is as follows: (3) The hormone binds to a membrane receptor, (5) The hormone-receptor complex activates G proteins, (1) Adenylate cyclase is activated, catalyzing the conversion of ATP to cAMP, (6) Cyclic AMP activates protein kinases, (4) Activated protein kinases phosphorylate cellular proteins, and (2) Enzymes catalyze reactions that produce a physiological response attributed to the hormone. This sequence of events allows the hormone to signal and elicit a response in the target cell.

Hormones generally utilize negative feedback mechanisms to regulate their secretion, which is explained in statement (1). Statement (4) states that hormones may be released in low concentrations but can produce large effects in the target cells because of amplification. This means that even a small amount of hormone can have a significant impact on the target cells. Statement (5) states that hormones can regulate the responsiveness of the target tissue by controlling the number of receptor sites for the hormone. This means that the hormone can adjust the sensitivity of the target tissue to its effects by increasing or decreasing the number of receptor sites available. Therefore, the correct answer is 1, 4, 5.

The pituitary gland is connected to the hypothalamus by the infundibulum (2) and has a posterior portion that contains axon terminals from hypothalamic neurosecretory cells (3). It also has a vascular connection with the hypothalamus known as the hypophyseal portal system (5). Therefore, the correct answer is 2, 3, 5.

The correct answer is 1, 2, 3, 4. This is because all the statements are true. Statement 1 states that nerve impulses produce their effects quickly, while hormonal responses are generally slower. Statement 2 states that nervous system effects are brief, while endocrine system effects are longer lasting. Statement 3 states that the nervous system controls homeostasis through neurotransmitters, while the endocrine system works through hormones. Statement 4 states that the nervous system can stimulate or inhibit the release of hormones, and some hormones are released by neurons as neurotransmitters.