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The Endocrine System By: Karl, Manny, Alondra, and Joseph.

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1 The Endocrine System By: Karl, Manny, Alondra, and Joseph

2 The Endocrine System The endocrine system includes all of the glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands. By regulating the functions of organs in the body, these glands help to maintain the body’s homeostasis. Cellular metabolism, reproduction, sexual development, sugar and mineral homeostasis, heart rate, and digestion are among the many processes regulated by the actions of hormones.


4 Hypothalamus and Pituitary Gland  The hypothalamus regulates the internal environment.  Example: through the autonomic system it helps control heartbeat, body temperature, and water balance.  Control the glandular secretions of the pituitary gland (hypophysis).  A small pituitary glad is about 1cm in diameter and is connected to the hypothalamus by a stalk like structure.  The pituitary consist of the: posterior pituitary portion (neurohypophysis) and the anterior pituitary portion (adrenohypophysis)

5 Posterior Pituitary  Neurosecretory cells (neurons in hypothalamus) produce the antidiuretic hormone (ADH) and oxytocin.  These hormones pass through the axons into the posterior pituitary where they are stored in axon endings.  The hypothalamic hormone, antidiuretic hormone, and oxytocin are produced in the hypothalamus but are released into the bloodstream from the posterior pituitary.

6 Antidiuretic hormone and Oxytocin  ADH (antidiuretic hormone also known called vasopressin) also called vasopressin is released from the posterior pituitary  Upon reaching the kidneys, ADH causes more water to be reabsorbed into kidney capillaries.  as the blood become dilute once again ADH is no longer released  an additional effect of ADH is to raise blood pressure by vasoconstruction of blood vessels through out the body  inability to produce ADH causes diadetes insipidus (watery urine) in which a person produces copious amounts of urine with a resultant loss of ions from the blood  oxytocin which is the other hormone made in the hypothalamus cause uterine contraction during childbirth and milk letdown when a baby is nursing

7 Anterior Pituitary  T he portal system of two capillary networks or beds connected by a vein lies between the hypothalamus and the anterior pituitary  T he hypothalamus controls the anterior pituitary by providing hypothalamic-releasing hormones and hypothalamic-inhibiting hormones

8 Hormones that affect other glands  Three hormones produced by the anterior pituitary have an effect on other glands  Thyroid-stimulating hormone (TSH) stimulates the thyroid to produce the thyroid horomones  Adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce its hormones  Gonadotropic Hormones stimulates the gonads, the testes in the males, and the ovaries in females to produce gametes and sex hormones  The hypothalamus the anterior pituitary and other glands controlled by anterior pituitary are all involved in self-regulating negative feedback mechnism that maintain stable condition

9 Effects of other hormones  Other hormones produced by the anterior Pituitary do not affect other endocrine glands  Prolactin (PRL) is produced at the beginning of the 5 th month of a pregnancy  It causes the mammary glands in the breast to develop milk  Growth Hormones (GH) – somatotropic hormone stimulates protein synthesis with in cartilage bone and muscle

10 Effects of growth hormones  If to little GH is produced during childhood they have pituitary dwarfism which are characterized by perfect proportions but small stature  If to much GH is secreted then the person ca become a giant, which usually have poor health become secondary effect on blood sugar level

11 Thyroid and parathyroid glands  Thyroid Gland is a large gland located in the where it is attached trachea just below the larynx  Is Composed f a large number of follicles each a small spherical structure made of thyroid cells filed with triiodothyronine which contains three iodine atom  Thyroxine which four iodine atoms

12 Effects of thyroid hormones  The thyroid gland actively acquires iodine to produce triiodothyronine and thyroxine.  If iodine is lacking in a diet the Thyroid glands are unable to produce thyroid hormones  Constant stimulation by the anterior pituitary results in the thyroid enlarging, resulting in a simple, or endemic, goiter.  Thyroid hormones do not have single target organs; instead they stimulate all cells of the body to metabolize at a faster rate  Congenital hypothyroidism : undesecretion of thyroid hormone  Hypothyroidism stocky and short in extreme cases since infancy or childhood.  For adults with this condition its called mixedema, which is characterized by lethargy, weight gain, loss of hair, slower pulse rate, lowered body temperature, and thickness and puffiness of the skin.  Hyperthyroidism: oversecretion of thyroid hormone  The thyroid gland is overactive and a exophthalimic goiter forms.  Hyperthyroidism can also be caused by a thyroid tumor which is determined as a lump.  Treatment is surgery with administration of radioactive iodine.

13 Calcitonin  Calcitonin: a hormone secreted by the thyroid gland when the blood calcium level rises  Primary effect is to bring the deposit of calcium in the bones (osteoclasts)  Low calcium level stimulates the release of parathyroid hormones by the parathyroid glands  Calcitonin can be used therapeutically in adults to reduce the effects of osteoporosis.

14 Parathyroid glands  Parathyroid Glands: causes the blood phosphate level to derease and the ionic blood calcium level to increase  The antagonistic actions of calcitonin from the thyroid gland and parathyroid glands maintain the blood calcium level within normal limits  When insufficient parathyroid hormone production leads to a dramatic drop in blood calcium level, hypocalcmic tenani makes the body shake from continuous muscle contraction.  The effect is brought by increased excitability of the nerves, which initiates nerve impulses spontaneously and without rest (severe cases can be fatal)

15 Adrenal Glands The adrenal glands are a pair of roughly triangular glands found immediately superior to the kidneys. The adrenal glands are each made of 2 distinct layers, each with their own unique functions: the outer adrenal cortex and inner adrenal medulla. adrenal glandsadrenal glands Adrenal cortex: The adrenal cortex produces many cortical hormones in 3 classes: glucocorticoids, mineralocorticoids, and androgens.Adrenal cortex: The adrenal cortex produces many cortical hormones in 3 classes: glucocorticoids, mineralocorticoids, and androgens. 1.Glucocorticoids have many diverse functions, including the breakdown of proteins and lipids to produce glucose. Glucocorticoids also function to reduce inflammation and immune response. 2.Mineralocorticoids, as their name suggests, are a group of hormones that help to regulate the concentration of mineral ions in the body. 3.Androgens, such as testosterone, are produced at low levels in the adrenal cortex to regulate the growth and activity of cells that are receptive to male hormones. In adult males, the amount of androgens produced by the testes is many times greater than the amount produced by the adrenal cortex, leading to the appearance of male secondary sex characteristics.

16 Adrenal Medulla The adrenal medulla produces the hormones epinephrine and norepinephrine under stimulation by the sympathetic division of the autonomic nervous system. Both of these hormones help to increase the flow of blood to the brain and muscles to improve the “fight-or-flight” response to stress. These hormones also work to increase heart rate, breathing rate, and blood pressure while decreasing the flow of blood to and function of organs that are not involved in responding to emergencies.


18 Pancreas The pancreas is a large gland located in the abdominal cavity just inferior and posterior to the stomach. The pancreas is considered to be a heterocrine gland as it contains both endocrine and exocrine tissue. The endocrine cells of the pancreas make up just about 1% of the total mass of the pancreas and are found in small groups throughout the pancreas called islets of Langerhans. Within these islets are 2 types of cells—alpha and beta cells. The alpha cells produce the hormone glucagon, which is responsible for raising blood glucose levels. Glucagon triggers muscle and liver cells to break down the polysaccharide glycogen to release glucose into the bloodstream. The beta cells produce the hormone insulin, which is responsible for lowering blood glucose levels after a meal. Insulin triggers the absorption of glucose from the blood into cells, where it is added to glycogen molecules for storage. pancreasstomachpancreasstomach

19 Adipose Tissue Adipose tissue produces the hormone leptin that is involved in the management of appetite and energy usage by the body. Leptin is produced at levels relative to the amount of adipose tissue in the body, allowing the brain to monitor the body’s energy storage condition. When the body contains a sufficient level of adipose for energy storage, the level of leptin in the blood tells the brain that the body is not starving and may work normally. If the level of adipose or leptin decreases below a certain threshold, the body enters starvation mode and attempts to conserve energy through increased hunger and food intake and decreased energy usage. Adipose tissue also produces very low levels of estrogens in both men and women. In obese people the large volume of adipose tissue may lead to abnormal estrogen levels.

20 Other thyroid glands The body has many other endocrine glands, such as the testes in males and ovaries in females. The thymus and pineal glands produce hormones. Some tissues within organs produce hormones and/ or growth factors. Individual body cells produce local messenger chemicals called prostaglandin. Testes and Ovaries The testes are located in the scrotum, and the ovaries are located in the pelvic cavity. The testes produce androgens (i.e. testosterone), which are the male sex hormones. The ovaries produce estrogens and progesterone, the female sex hormones. The hypothalamus and pituitary gland control the hormonal secretions of these organs. (See page 208)


22 Cont. Androgens Puberty is the moment in life when sexual maturation occurs. The greatly increased testosterone secretion during this time stimulates the growth of the penis and the testes. Testosterone also brings about and maintains the male secondary sex characteristics that develop during puberty, including the growth of a beard, axillary hair, and pubic hair. It prompts the larynx and vocal cords to enlarge, causing the voice to change. It’s partially responsible for the muscular strength of males. This is why some athletes take large amounts of anabolic steroids. (See page 220). Testosterone also stimulates oil and sweat glands in the skin; therefore it’s largely responsible for acne and body odor. Another side effect of testosterone is baldness. Genes for baldness are probably inherited by both sexes, but baldness is seen more in males due to the presence of testosterone. Estrogen and Progesterone The female sex hormones have many effects on the body. In particular, estrogens secreted during puberty stimulate the growth of the uterus and the vagina. Estrogen is necessary for ovum maturation and it’s largely responsible for the secondary sex characteristics in females, including female body hair and fat distribution. The pelvic girdle is wider in females than it is in males, resulting in a larger pelvic cavity. Both estrogen and progesterone are needed for breast development and for regulation of the uterine cycle, which includes monthly

23 Thymus Gland The lobular thymus gland, which lies just beneath the sternum, reaches its largest size and is most active during childhood. (See figure 10.1). When lymphocytes pass complete development in the thymus, they’re transformed into thymus-derived lymphocytes, or T-lymphocytes. The lobules of the thymus gland are lined by epithelial cells that secrete hormones called thymosins. This hormone aids in the differentiation of lymphocytes packed inside the lobules.

24 Pineal gland The pineal gland, which is located in the brain, produces the hormone melatonin, primarily at night. (See figure 10.1). Melatonin is involved in our daily sleep-wake cycle; normally we grow sleepy at night when melatonin levels increase and awake once daylight returns and melatonin levels decrease. (See figure 10.15). Daily 24- hour cycles such are this are called circadian rhythms. Circadian rhythms are controlled by an internal timing mechanism called a biological clock. Based on animal research, it appears that melatonin also regulates sexual development. It’s also been noted that children whose pineal gland has been destroyed due to a brain tumor experience early puberty. The pineal gland, which is located in the brain, produces the hormone melatonin, primarily at night. (See figure 10.1). Melatonin is involved in our daily sleep-wake cycle; normally we grow sleepy at night when melatonin levels increase and awake once daylight returns and melatonin levels decrease. (See figure 10.15). Daily 24- hour cycles such are this are called circadian rhythms. Circadian rhythms are controlled by an internal timing mechanism called a biological clock. Based on animal research, it appears that melatonin also regulates sexual development. It’s also been noted that children whose pineal gland has been destroyed due to a brain tumor experience early puberty. Hormones from Other Tissues We previously mentioned that the heart produces atrial natriuretic hormone (see page 214). The kidney also influences the cardiovascular system function by producing the hormone erythropoietin (EPO), which stimulates red blood cell reproduction by the bone marrow.

25 Leptin Leptin is a protein hormone produced by adipose tissue. Leptin acts on the hypothalamus, where its signals satiety- that the individual has had enough to eat. Oddly, the blood of obese individuals may be rich in leptin. It may be possible that the leptin that they produce is ineffective because of a genetic mutation, or else their hypothalamic cells lack a suitable number of receptors for leptin.

26 Growth factors Many different types of organs and cells produce peptide growth factors, which stimulate cell division and mitosis. Some, like lymphokines are released into the blood; others diffuse into nearby cells. These growth factors include:  Granulate and macrophage colony-stimulating factor (GM-CSF) is secreted by many different tissues. GM-CSF causes bone marrow stem cells to form either granulocyte or macrophage cells (both are forms of white blood cells), depending on whether the concentration is high.  Platelet –derived growth factor is released from platelets and from many other cell types. It helps in wound healing and causes an increase in the number of fibroblasts, smooth muscle cells, and certain cells of the nervous system.  Epidermal growth factor and nerve growth factor stimulate the cells indicated by their names, as well as many others. These growth factors are also important in wound healing.  Tumor angiogenesis factor stimulates the formation of capillary networks and is released by tumor cells. One treatment for cancer is to halt the activity of this growth factor.

27 Prostaglandins Prostaglandins are potent chemical signals produced within cells by arachidonate, a fatty acid. Prostaglandins aren’t distributed in the blood. Instead, they work close to where they’re produced. In the uterus, prostaglandins cause muscles to contract and are involved with the pain and discomfort of menstruation. They also mediate the effects of pyrogens, chemicals that are believed to reset the temperature regulatory center in the brain. For example, aspirin reduces body temperature and controls pain because of its effect on prostaglandins. Some prostaglandins can reduce gastric and have been used to treat ulcers. Others lower blood pressure and have been used to treat hypertension. And others still inhibit platelet aggregation and have been used to prevent thrombosis (the formation of stationary clots in blood vessels). However, different prostaglandins have contrary effects, and it’s very difficult to standardize their use.

28 Effects of Aging T hyroid disorders and diabetes are the most significant endocrine problems affecting health and function as we age. Both hypo- and hyperthyroidism are seen in the elderly. Graves’ disease is an autoimmune disease that targets the thyroid, resulting in symptoms of cardiovascular disease, increased body temperature and fatigue. A person may also experience weight loss of as much a 20 pounds, depression and mental confusion. Hypothyroidism (myxedema) may fail to be diagnosed because they symptoms may simply be attributed to the process of aging (hair loss, mental deterioration, and skin changes). The true incidence of IDDM (insulin-dependent, commonly referred to as Type-1 diabetes) diabetes among the elderly is unknown. Its symptoms can be confused with those of other medical conditions that are present.. As in all adults, NIDDM (non-insulin-dependent, mellitus type-2 diabetes) diabetes is associated with being overweight and often can be controlled by proper diet.

29 Medical focus Side Effects of Anabolic Steroids The story amazed major league baseball across the world; baseball sluggers - homerun hitters who had set new records for baseball – were implicated in a scandal involving abuse of anabolic steroids. In testimony before the U.S. House of Representatives in March 2005, Mark McGwire of the St. Louis Cardinals, denied using steroids during his baseball career, and stood by his hitting records. However, other players, most notably, Jose Canseco and Jason Giambi, admitted using PED’s (performance-enhancing drugs). During the hearings, Congressional officials announced a ten-game suspension for players who texted positive for steroids. Many legislators questioned whether the records created by those who tested positive should be allowed to stand. The most tremendous concern to the general public, is the increased use of steroids by teens wanting to bulk up quickly, probably wanting to be just like the athletes they admire. Anabolic steroids are synthetic forms of testosterone. Taking doses 10 to 100 times the amount prescribed by doctors for illnesses promotes larger muscles when the person also exercises. Trainers were probably the first to acquire steroids for weight lifters, body builders, and other athletes, like professional baseball players. However, being on steroids can have adverse effects. Men experience decreased sperm counts and decreased sexual desire due to reduction of the size of the testis. Some develop an enlarged prostate, or grow breasts. On the other hand, women can develop male sexual characteristics, such as hair on their chests and faces, balding, and most experience and abnormal enlargement of the clitoris. Some stop ovulation and/or menstruating, sometimes permanently. Researchers predict that two or three months of high-dosage use of steroids as a teen can cause death by 30 or 40. Steroids have been linked to heart disease in both sexes and implicated in the deaths of young athletes from liver cancer and kidney problems. Steroids cause the body to retain fluid, which results in increased blood pressure. Users normally try to get rid of “steroid bloat” by taking large doses of diuretics (A diuretic is any substance that promotes the production of urine. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way). A young California weight lifter had a fatal heart attack after using steroids, and the post-mortem report showed a lack of electrolytes, salts that help regulate the heart. And lastly, steroid abuse has psychological effects, like depression, hostility, aggression, and eating disorders. Unfortunately, these drugs cause the user to feel invincible. One particular abuser had his friend record him as he drove his car at 40 miles an hour into a tree. (Look at fig 10B). The FDA (Federal Food and Drug Administration now bans most steroids, and steroid use has been banned by the National Collegiate Athletic Association (NCAA), the National Football League (NFL), and the International Olympic Committee (IOC).

30 Homeostasis The endocrine system works alongside of the nervous system to form the control systems of the body. The nervous system provides a very fast and narrowly targeted system to turn on specific glands and muscles throughout the body. The endocrine system, on the other hand, is much slower acting, but has very widespread, long lasting, and powerful effects. Hormones are distributed by glands through the bloodstream to the entire body, affecting any cell with a receptor for a particular hormone. Most hormones affect cells in several organs or throughout the entire body, leading to many diverse and powerful responses.

31 Hormonal regulation The levels of hormones in the body can be regulated by several factors. The nervous system can control hormone levels through the action of the hypothalamus and its releasing and inhibiting hormones. For example, TRH produced by the hypothalamus stimulates the anterior pituitary to produce TSH. Tropic hormones provide another level of control for the release of hormones. For example, TSH is a tropic hormone that stimulates the thyroid gland to produce T3 and T4. Nutrition can also control the levels of hormones in the body. For example, the thyroid hormones T3 and T4 require 3 or 4 iodine atoms, respectively, to be produced. In people lacking iodine in their diet, they will fail to produce sufficient levels of thyroid hormones to maintain a healthy metabolic rate. Finally, the number of receptors present in cells can be varied by cells in response to hormones. Cells that are exposed to high levels of hormones for extended periods of time can begin to reduce the number of receptors that they produce, leading to reduced hormonal control of the cell.


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