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Test yourself 11-1 ​ How do endocrine glands differ from exocrine gland?​ Endocrine glands secrete tiny amounts of hormones directly into the bloodstream and not through ducts. This feature differentiates them from exocrine glands, which secrete their products onto epithel...

Test yourself 11-1 ​ How do endocrine glands differ from exocrine gland?​ Endocrine glands secrete tiny amounts of hormones directly into the bloodstream and not through ducts. This feature differentiates them from exocrine glands, which secrete their products onto epithelial surfaces through tiny tubes called ducts​ ​ In what ways are the functions and characteristics of the endocrine system similar to those of the nervous system? In what ways are they different?​ Both systems regulate body functions to maintain homeostasis. The endocrine system’s rection to stimuli is slow, whereas the reaction of the nervous system to stimuli is fast. The endocrine system’s duration of effects is long, whereas the duration of effects of the nervous system is short. The target tissues for the endocrine system are virtually all body cells and tissues, whereas the target tissue for the nervous system are muscle and glandular tissue. The chemical messengers of the endocrine system are hormones, whereas the chemical messengers of the nervous system are neurotransmitters. The messenger-producing cells of the endocrine gland are cells or modified neurons, whereas the messenger-producing cells of the nervous system are neurons. The distance from chemical message production to the target for the endocrine system is long (via the blood stream), whereas this distance for the nervous system is short (across the synaptic space)​ Test yourself 11-2 ​ What is a hormone?​ Hormones are chemical messengers produced by endocrine glands and are secreted directly into blood vessels.​ ​ What is a hormone target?​ A cell that has receptors for a particular hormone is referred to as a target of that hormone​ ​ What are the three main chemical groumps of hormones?​ Peptide hormones, steroid hormones, and monoamine hormones​ ​ Which chemical hormone group(s) bind to receptors on the target cell membrane? In the cytoplasm of nucleus?​  Peptide hormones and monoamine catecholamine hormones bind to receptors on the target cell membrane. Steroid hormones and monoamine thyrois hormones bind to receptors in the cytoplams or nucleus.​ ​ How does the negative feedback system control the secretion of many hormones?​ Hormone secretion is controlled by a feedback system. The level of hormone directly or indirectly feeds back to the gland that produced and affects its activity. Negative feedback decreases hormone production from a certain gland because there is too much or just the right amount of that hormone in the bloodstream.​ Test yourself 11-3 ​ Through what mechanisms does the hypothalmus control the production or release of hoemones from the pituitary gland? How do its effect on the anterior and posterior portions of the pituitary differ?​ A system of tiny blood vessels called a portal system links the hypothalamus with the anterior portion of the pituitary gland. Modified neurons in the hypothalamus secrete hormones into these portal blood vessels. The hormones travel the short distance down to the anterior pituitary and regulate much of its function. These hypothalamic hormones, called releasing and inhibiting factors, are each specific for a particular anterior pituitary hormone. As their names imply, a releasing factor causes the anterior pituitary to produce and release a particular hormone, and an inhibiting factor has the opposite effect of inhibiting the production and release of a hormone. Because some anterior pituitary hormones influence all the body’s cells, the hypothalamus indirectly affects the whole body by regulating anterior pituitary gland functions. The effect of the hypothalamus on the posterior part of the pituitary gland is more direct. Modified neurons in the hypothalamus produce two hormones, antidiuretic hormone and oxytocin, that are transported down nerve fibers to the posterior pituitary gland, where they are stored. They are then released into the bloodstream by nerve impulses from the hypothalamus.​ ​ Why is the pituitary gland referred to as the master endocine gland?​ the pituitary gland is often called the master endocrine gland because many of its hormones direct the activity of other endocrine glands.​ ​ Other than promoting growth in young animals, what are some of other effects of GH?​ Growth hormone (GH) helps regulate the metabolism of proteins, carbohydrates, and lipids in all the body’s cells. The effect of GH on protein metabolism is to encourage the anabolism, or synthesis, of proteins by body cells. The effects of GH on carbohydrate and lipid metabolism are linked. GH causes the mobilization (release) of lipids from storage in adipose (fat) tissue and their catabolism (breakdown) in body cells for energy  production. At the same time, it discourages the cells from using carbohydrates, principally glucose, as energy sources. Because glucose is such an important energy source for the body’s cells, a balance between GH and insulin is important to maintain homeostasis of glucose levels in the blood.​ ​ What stimulates the continued release of prolactin during lactation?​ Once lactation begins, prolactin production and release by the anterior pituitary gland continues if the teat or nipple continues to be stimulated by nursing or milking.​ ​ Do FSH and LH play important roles in male animals? If so, what are they?​ Yes. In the male, FSH has an effect similar to one of its effects in the female. It stimulates spermatogenesis, the development of male reproductive cells (the spermatozoa) in the seminiferous tubules of the testes. In the male, LH stimulates cells in the testes called interstitial cells, develop and produce the male sex hormone testosterone. Therefore, LH is sometimes called interstitial cell-stimulating hormone (ICSH) in the male.​ ​ Does ADH help promote the loss or large amount of water in the urine? What effect would the inhibition of ADH release have on the body?​ ADH helps prevent the loss of large quantities of water in the urine. Inhibition of ADH would cause more water to flow out of the body in the urine.​ ​ When milking a cow by hand, why does it take a minute or two to teat stimulation before milking starts flow freely?​ When milking a cow it takes a minute or two of teat stimulation for the sensory stimulation to reach the brain and signal the hypothalamus to release oxytocin from the posterior pituitary and for the oxytocin to reach the mammary gland via blood circulation.​ Test yourself 11-4 ​ what hormone plays an important role in helping an animal maintain its body temperature under cold envirinmental conditions?​ The thyroid hormones uses the calorigenic effect to regulate the body’s temperature. The production of thyroid hormone increases with exposure to cold temperatures. This response increases the body’s metabolic rate, which generates more heat. It also causes nutrients to be burned at a faster rate thus preventing significant loss of body weight. Therefore, animals housed outdoors in cold temperatures need to be fed more calories than those kept in warmer temperatures.​ How do the clinical signs of hypothyroidism and hyperthyroidism relate to the normal functions of thyroid hormone?​ The thyroid hormone plays a part in the metabolism of proteins, carbohydrates, and lipids. It also helps to regulate the body’s temperature.​ Hypothyroidism occurs when there is a deficiency of the thyroid hormone in the bloodstream. Clinical signs can be weight gain without increased caloric intake, loss of hair, lethargy, reluctance to exercise, and dry skin. These symptoms relate to the body’s metabolism decreasing. Hyperthyroidism occurs because the body is flooded with too much thyroid hormone. It is most commonly seen in cats, although it is seen occasionally in dogs. Excessive amounts of thyroid hormone speed up cellular metabolism all over the body. This results in symptoms such as nervousness, excitability, weight loss, increased appetite, tachycardia (abnormally fast heart rate), vomiting, diarrhea, polyuria (excessive urine production), and polydipsia (excessive thirst). ​ ​ What two hormones play important roles in maintaining homeostasis of blood calcium levels in the body? Which one prevents hypercalcemia? Which prevents hypocalcemia?​ Parathyroid hormone (PTH), also called parathormone, and calcitonin. PTH helps prevent hypocalcemia, and calcitonin helps prevent hypercalcemia.​ Test yourself 11-5 ​ What three groups of hormones are produced in the adrenal cortex? What are their effects?’​ Glucocorticoid hormones, mineralocorticoid hormones, and sex hormones*. Glucocorticoids* have a general hyperglycemic effect: that is, they cause the blood glucose level to rise. Mineralocorticoid hormones regulate the levels of some important electrolytes (mineral salts) in the body. The principal mineralocorticoid hormone aldosterone affects the levels of sodium, potassium, and hydrogen ions in the body. Aldosterone’s target is the kidney, where it causes sodium ions to be reabsorbed from the urine back into the bloodstream in exchange for potassium and hydrogen ions. Aldosterone also affects water levels in the body, in that water accompanies sodium back into the bloodstream when sodium ions are reabsorbed. The amounts of sex hormones are very small, and their effects are usually minimal.​ ​ How are the hormones of the adrenal medulla involved in the fight-or-flight response?​ The adrenal medullary hormones circulate around the body, helping to produce the  whole-body fight-or-flight response. These effects of the fight-or-flight response are produced partly by direct sympathetic nerve stimulation of target tissues and partly by the epinephrine and norepinephrine released into the bloodstream by the adrenal medulla. After the threat has passed, it takes the body a while to come down from its excited state. This delay results from the epinephrine and norepinephrine circulating in the bloodstream. It takes some time for them to be metabolized and removed from circulation​ Test yourself 11-6 ​ which hormones have hyperglycemic effects in the body? What is the only hormone that acts to lower the blood glucose level?​ Growth hormone, thyroid hormone, glucocorticoid hormones, and glucagon all serve to increase the level of glucose in the blood. Insulin acts to lower the blood glucose level.​ ​ Which hormone are anabolic steroid drugs related to?​ Testosterone​ ​ How do the basic actions and purpose of estrogens and progetins differ?​ Estrogen is responsible for the physical and behavioral changes that prepare the female for breeding and pregnancy and signal the male that the time for breeding is approaching. Progesterone, the primary progestin, helps prepare the uterus to receive the fertilized ovum and is necessary for pregnancy to be maintained once the fertilized ovum implants in the uterus.​ ​ How does relaxin help prepare a pregnant animal for parturition?​ Relaxin causes ligaments between the bones surrounding the birth canal to soften and relax, facilitating the passage of the newborn during parturition.​ Test yourself 11-7 ​ Why are patients with kidney failure often anemic?​ Kidney failure patients are often anemic because of their deficiency of erythropoietin produced by the failing kidney. Erythropoietin stimulates red bone marrow to increase production of oxygen-carrying red blood cells.​ ​ How do the actions of gastrin on the stomach differ from those of secretin and cholecystokinin?​  When released by stomach cells, gastrin stimulates gastric (stomach) glands to secrete hydrochloric acid and digestive enzymes, and it encourages muscular contractions of the stomach wall. Secretin and cholecystokinin are produced in the small intestine. Secretin stimulates the pancreas to secrete fluid rich in sodium bicarbonate into the duodenum to neutralize the acidic chyme from the stomach. Cholecystokinin stimulates the release of digestive enzymes from the pancreas into the duodenum. Both secretin and cholecystokinin also act on the stomach to inhibit gastric gland secretions and stomach motility. This slows the movement of chyme into the small intestine. They also stimulate the gallbladder of the liver to contract, sending bile down into the small intestine to aid the digestion and absorption of fats and fat-soluble vitamins.​ ​ Why are prostaglandins referred to as tissue hormones?​ Prostaglandins are sometimes called tissue hormones because they travel only a short distance from where they are produced as opposed to hormones, whose effects occur at a longer distance from where they are produced. They regulate the activity of neighboring cells.​ ​ Why do hormonelike drugs generally have a high potentail for undesirable side effects?​ Hormonelike drugs have a high potential for undesirable side effects because the production and effects of natural hormones are intertwined with each other. Adjusting the amount of 1 hormone can unbalance others producing some potent and widespread problems. The amounts of hormones used therapeutically are usually very large compared with the normal physiologic hormone levels in the body; therefore, the potential for undesired side effects increases accordingly. If these drugs are not discontinued gradually, serious side effects can occur.​