Chapter 17 - Lecture notes 17 PDF

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Chapter 17 of EHS 115 chapter notes...

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Chapter 17

● Functions Of The Endocrine Syste ○ Primary function: to produce hormones that work together to maintain homeostasis. ○ Hormones = chemical messengers that are secreted by endocrine glands directly into the bloodstream; each hormone has specialized functions in regulating the activities of specific cells, organs, or both. ● Structures Of The Endocrine System ○ Endocrine glands = produce hormones; do not have ducts; there are 13 major glands that make up the endocrine system. ■ One pituitary gland (divided into two lobes) ■ One pineal gland ■ One thyroid gland ■ Four parathyroid glands ■ One thymus ■ One pancreas (pancreatic islets) ■ Two adrenal glands ■ Two gonads (either a pair of ovaries in females or a pair of testicles in males) ● The Pituitary Gland ○ Pituitary gland (hypophysis) = pea-sized gland that is divided into two parts, the anterior and the posterior lobes. ○ Functions of the Pituitary Gland ■ Secretes hormones that control the activity of other endocrine glands. ■ Pituitary gland acts in response to stimuli from neurohormones secreted by the hypothalamus; this creates a system of checks and balances to maintain an appropriate blood level of each hormone. ○ Secretions of the Pituitary Gland: Anterior Lobe ■ Adrenocorticotropic hormone = stimulates the growth and secretions of the adrenal cortex. ■ Follicle-stimulating hormone = stimulates the secretion of estrogen and the growth of ova (eggs) in the ovaries of the female; in males, it stimulates the production of sperm in the testicles (testes).

■ Growth hormone (somatotropic hormone) = regulates the growth of bone, muscle, and other body tissues (somat/o → body; trop → change) ■ Lactogenic hormone (prolactin) = stimulates and maintains the secretion of breast milk in the mother after childbirth (lact/o → milk; gen → producing) ■ Luteinizing hormone = stimulates ovulation in the female; in males, the hormone stimulates the secretion of testosterone. ■ Melanocyte-stimulating hormone = increases the production of melanin in melanocytes, thereby causing darkening of skin pigmentation; this hormone production usually increases during pregnancy. ■ Thyroid-stimulating hormone = stimulates the secretion of hormones by the thyroid gland. ○ Secretions of the Pituitary Gland: Posterior Lobe ■ Antidiuretic hormone = secreted by the hypothalamus and stored in the pituitary gland; helps control blood pressure by reducing the amount of water that is excreted through the kidneys. ■ Oxytocin = stimulates uterine contractions during childbirth; after childbirth, oxytocin controls postnatal hemorrhage and stimulates the flow of milk from the mammary glands. ● Pitocin → synthetic form of oxytocin that is administered to induce or speed up labor. ● The Pineal Gland ○ Pineal gland (pineal body) = very small endocrine gland; located in the central portion of the brain and takes its name from the Latin word for pinecone, referring to the shape of the gland. ○ Functions and Secretions of the Pineal Gland ■ Secretions of the pineal gland influence the sleep-wakefulness cycle ■ Melatonin = a type of secretion that influences the sleep-wakefulness portions of the circadian cycle.

● Circadian cycle → biological functions that occur within a 24-hour period. ● The Thyroid Gland ○ Thyroid gland = butterfly-shaped; lies on either side of the larynx, just below the thyroid cartilage. ○ Functions and Secretions of the Thyroid Gland ■ One primary function is to regulate the body’s metabolism ■ Metabolism → all of the processes involved in the body's use of nutrients, including the rate at which they are used. ■ Thyroxine and Triiodothyronine = the two primary thyroid hormones which regulate the rate of metabolism and affect the growth and rate of function of many other body systems. ● Rate of secretion of these two hormones is controlled by the thyroid-stimulating hormone produced by the anterior lobe of the pituitary gland. ■ Calcitonin = a hormone that works with the parathyroid hormone to decrease calcium levels in the blood and tissues by moving calcium into storage in the bones and teeth. ● The Parathyroid Gland ○ Parathyroid glands = four parathyroid glands each the size of a grain of rice; are embedded in the posterior surface of the thyroid gland ○ Functions and Secretions of the Parathyroid Gland ■ Regulates calcium levels throughout the body ■ Parathyroid hormone = works with the hormone calcitonin that is secreted by the thyroid gland to regulate the calcium levels in the blood and tissues. ● The Thymus ○ Thymus = located near the midline in the anterior portion of the thoracic cavity; is posterior to (behind) the sternum and slightly superior to (above) the heart. ○ Functions and Secretions of the Thymus

■ Secretes a hormone that functions as part of the immune system, helping develop the body's immune system before birth and in childhood; its function is greatly reduced after puberty, and it slowly turns into fatty tissue. ■ Thymosin = plays an important part in the immune system by stimulating the maturation of lymphocytes into T cells. ● The Pancreas (Pancreatic Islets) ○ Pancreas = feather-shaped organ located posterior to the stomach that functions as part of both the digestive and the endocrine systems. ○ Pancreatic islets = parts of the pancreas that have endocrine functions ■ Islet → a small isolated mass, or island, of one type of tissue within a larger mass of a different type. ○ Functions and Secretions of the Pancreatic Islets ■ Control the blood glucose levels and glucose metabolism throughout the body. ■ Glucose = basic form of energy used by the body ● Blood sugar → glucose in the bloodstream ■ Glucagon = the hormone secreted by the alpha cells of the pancreatic islets in response to low levels of glucose in the bloodstream; glucagon increases the glucose level by stimulating the liver to convert glycogen into glucose for release into the bloodstream. ■ Insulin = the hormone secreted by the beta cells of the pancreatic islets in response to high levels of glucose in the bloodstream; insulin functions in two ways: 1. When energy is needed, insulin allows glucose to enter the cells to be used as this energy. 2. When additional glucose is not needed, insulin stimulates the liver to convert glucose into glycogen for storage. ● The Adrenal Glands

○ Adrenal glands (suprarenals) = located on top of each kidney; each of these glands consists of an outer portion, known as the adrenal cortex, and the middle portion, which is the adrenal medulla. ○ Functions of the Adrenal Glands ■ Control electrolyte levels within the body, help regulate metabolism, and interacts with the sympathetic nervous system in response to stress. ■ Electrolytes = mineral substance (calcium, chloride, magnesium, phosphorus, sodium, and potassium) that are normally found in the blood and other bodily fluids. ○ Secretions of the Adrenal Cortex ■ Androgens = sex hormones secreted by the gonads, the adrenal cortex, and fat cells. ■ Corticosteroids = the steroid hormones produced by the adrenal cortex ● Aldosterone = a corticosteroid that regulates the sodium and water levels in the body by increasing sodium reabsorption and potassium excretion by the kidneys. ○ Reabsorption → returning a substance to the bloodstream ● Cortisol (hydrocortisone) = a corticosteroid that has an antiinflammatory action; also helps regulate the metabolism of carbohydrates, fats, and proteins in the body. ○ Secretions of the Adrenal Medulla ■ Epinephrine (adrenaline) = stimulates the sympathetic nervous system in response to physical injury or to mental stress such as fear; makes the heart beat faster and can raise blood pressure; also helps the liver release glucose and limits the release of insulin. ■ Norepinephrine = is both a hormone and a neurohormone; released as a hormone by the adrenal medulla and as a neurohormone by the sympathetic nervous system; plays an important role in the “fight-or-flight response” by raising blood pressure, strengthening the heartbeat, and stimulating muscle contractions. ● The Gonads ○ Gonads = gamete-producing glands; ovaries in females and testicles in males

○ Functions of the Gonads ■ Secrete the hormones that are responsible for the development and maintenance of the secondary sex characteristics that develop during puberty. ● Secondary sex characteristics → features that distinguish the two sexes but are not directly related to reproduction. ■ Puberty = process of physical changes by which a child's body becomes an adult body that is capable of reproducing; marked by maturing of the genital organs, the development of secondary sex characteristics, and the first occurrence of menstruation in the female; in the U.S., the average age is 12 for girls and 11 for boys. ● Precocious puberty → the early onset of the changes of puberty, usually before age 8 in girls and age 9 in boys. ○ Secretions of the Gonads ■ Estrogen = a hormone secreted by the ovaries that is important in the development and maintenance of the female secondary sex characteristics and in regulation of the menstrual cycle. ■ Progesterone = the hormone released during the second half of the menstrual cycle by the corpus luteum in the ovary; function is to complete the preparation of the uterus for possible pregnancy. ■ Gamete = reproductive cell; sperm in the male and ova (eggs) in the female. ■ Gonadotropin = any hormone that stimulates the gonads (-tropin → to stimulate) ■ Androgens = sex hormones, primarily testosterone, secreted by the gonads, the adrenal cortex, and fat cells; they promote the development and maintenance of the male sex characteristics. ■ Testosterone = steroid hormone secreted by the testicles and the adrenal cortex to stimulate the development of male secondary sex characteristics.

■ Estrogen and testosterone are present in both males and females but in dramatically different amounts depending on gender. ○ Specialized Types of Hormones ■ Steroids = large family of hormone-like substances that share the same fat-soluble chemical structure; secreted by endocrine glands or artificially produced as medications to relieve swelling and inflammation in conditions such as asthma. ● Anabolic steroids = man-made substances that are chemically related to male sex hormones; used in the treatment of hormone problems in men and to help the body replace muscle mass lost due to disease; athletes sometime use anabolic steroids illegally to build muscle mass, a dangerous practice that can lead to lasting damage to the body. ■ Leptin = protein hormone secreted by fat cells that is involved in the regulation of appetite; leptin leaves the fat cells and travels in the bloodstream to the brain, where it acts on the hypothalamus to suppress appetite and burn fat stored in adipose tissue. ■ Ghrelin = a hormone produced in the gastrointestinal tract; sometimes referred to as the hunger hormone. ■ Neurohormones = produced and released by neurons in the brain, rather than by the endocrine glands, and delivered to organs and tissues through the bloodstream. ● Medical Specialties Related To The Endocrine System ○ Endocrinologist = physician who specializes in diagnosing and treating diseases and malfunctions of the endocrine glands. ○ Certified diabetes educator = a health care professional qualified to teach people with diabetes how to manage their disease. ● Pathology Of The Endocrine System ○ The Pituitary Gland ■ Acromegaly = rare chronic disease characterized by abnormal enlargement of the extremities (hands and feet) caused by the excessive secretion of growth hormone after puberty (acr/o → extremities; -megaly → enlargement)

■ Gigantism = abnormal growth of the entire body that is caused by excessive secretion of growth hormone before puberty. ■ Hyperpituitarism = the excess secretion of growth hormone that causes acromegaly and gigantism. ■ Short stature (dwarfism) = sometimes caused by deficient secretion of growth hormone. ■ Pituitary adenoma (pituitary tumor) = slow-growing benign tumors of the pituitary gland; there are two types: ● Functioning pituitary tumors often produce hormones in large and unregulated amounts. ● Nonfunctioning pituitary tumors do not produce excessive amounts of hormones. ■ Galactorrhea = condition in which an excess of prolactin causes the breasts to produce milk spontaneously, not due to childbirth. ■ Prolactinoma = a benign tumor of the pituitary gland; causes the pituitary gland to produce too much of the lactogenic hormone known as prolactin, which can cause infertility in women and erectile dysfunction in men and can impair vision. ■ Diabetes insipidus = uncommon disorder caused by an insufficient production of the antidiuretic hormone ADH or by the inability of the kidneys to respond appropriately to this hormone. ■ Syndrome of inappropriate antidiuretic hormone = caused by the overproduction of the anti-diuretic hormone ADH; often as a result of cancer or its treatment. ○ Pathology of the Pineal Gland ■ Pinealoma = tumor of the pineal gland that can disrupt the production of melatonin; can also cause insomnia by disrupting the circadian cycle. ○ The Thyroid Gland ■ Thyroid carcinoma = most common cancer of the endocrine system and the most rapidly increasing cancer in the U.S.; has a high survival rate;

affects significantly more women than men and is commonly diagnosed between ages 20 and 55. ■ Hashimoto’s disease (chronic lymphocytic thyroiditis) = an autoimmune disease in which the body's own antibodies attack and destroy the cells of the thyroid gland; this inflammation often leads to hypothyroidism. ■ Hypothyroidism (underactive thyroid) = caused by a deficiency of thyroid secretion; symptoms include fatigue, depression, sensitivity to cold, and a decreased metabolic rate. ■ Cretinism = congenital form of hypothyroidism; if treatment is not started soon after birth, cretinism causes arrested physical and mental development. ■ Myxedema (adult hypothyroidism) = caused by an extreme deficiency of thyroid secretion; symptoms include swelling (particularly around the eyes and cheeks), fatigue, and a subnormal temperature. ■ Thyroid nodules → lumps in the thyroid that can grow large enough to cause a goiter; most nodules are benign; however, some are malignant or produce too much thyroxine. ■ Thyroid storm (thyrotoxic crisis) = relatively rare, life-threatening condition caused by exaggerated hyperthyroidism; symptoms: fever, chest pain, palpitations, shortness of breath, tremors, increased sweating, disorientation, and fatigue. ■ Hyperthyroidism (thyrotoxicosis) = overproduction of thyroid hormones, which causes an imbalance of metabolism; symptoms: increased metabolic rate, sweating, nervousness, and weight loss; most common cause of hyperthyroidism is Graves' disease. ■ Graves’ disease = disorder of unknown cause in which the immune system attacks the thyroid gland and stimulates it to make excessive amounts of thyroid hormone; results in hyperthyroidism and can also cause goiter, exophthalmos, or both. ● Goiter (thyromegaly) = an abnormal, benign enlargement of the thyroid gland; this enlargement produces a swelling in the front of the neck; usually occurs when the thyroid gland is not able to

produce enough thyroid hormone to meet the body's needs, either due to Graves' disease, other medical conditions, or an iodine deficiency. ● Exophthalmos = abnormal protrusion of the eyeball out of the orbit. ○ The Parathyroid Glands ■ Hyperparathyroidism = the overproduction of the parathyroid hormone; causes hypercalcemia; can result from a disorder of the parathyroid gland or from a disorder elsewhere in the body, such as kidney failure. ■ Hypoparathyroidism = caused by an insufficient or absent secretion of the parathyroid hormone; causes hypocalcemia, and in severe cases, it leads to tetany. ● Tetany → condition of periodic, painful muscle spasms and tremors. ■ Hypercalcemia = characterized by abnormally high concentrations of calcium circulating in the blood instead of being stored in the bones and teeth; can lead to weakened bones and the formation of kidney stones. ■ Hypocalcemia = characterized by abnormally low levels of calcium in the blood. ○ The Thymus ■ Thymitis = an inflammation of the thymus gland ○ The Pancreas ■ Insulinoma = a benign tumor of the pancreas that causes hypoglycemia by secreting additional insulin. ■ Pancreatitis = inflammation of the pancr ■ Hyperglycemia = an abnormally high concentration of glucose in the blood; seen primarily in patients with diabetes mellitus; symptoms include polydipsia, polyphagia, and polyuria. ■ Polydipsia = excessive thirst (-dipsia → thirst) ■ Polyphagia = excessive hunger (-phagia → eating)

■ Polyuria = excessive urination (-uria → urination) ■ Hyperinsulinism = condition of excessive secretion of insulin in the bloodstream; can cause hypoglycemia. ■ Hypoglycemia = an abnormally low concentration of glucose (sugar) in the blood; symptoms include nervousness and shakiness, confusion, perspiration, or feeling anxious or weak. ○ Diabetes Mellitus ■ Diabetes mellitus = a group of metabolic disorders characterized by hyperglycemia resulting from defects in the body's production of insulin (type 1) or its ability to use it properly (type 2); most common endocrine system disease. ■ Type 1 diabetes = an autoimmune insulin deficiency disorder caused by the destruction of pancreatic islet beta cells. ● Insulin deficiency → the pancreatic beta cells do not secrete enough insulin. ● Symptoms of type 1 diabetes: polydipsia, polyphagia, polyuria, weight loss, blurred vision, extreme fatigue, and slow healing. ● The onset of type 1 diabetes is often triggered by a viral infection. ● Treatment for type 1 diabetes involves a combination of diet, exercise and carefully regulated insulin replacement therapy administered by injection or insulin pump ■ Type 2 diabetes = an insulin resistance disorder; increasingly common in children and young adults; obese adults are also at high risk. ● Insulin resistance → insulin is being produced, but the body does not use it effectively. ● Prediabetes = condition in which the blood glucose level is higher than normal, but not high enough to be classified as type 2 diabetes; however, this condition indicates an increased risk of developing type 2 diabetes, heart disease, and stroke.

■ Latent autoimmune diabetes in adults (type 1.5 diabetes) = a condition in which type 1 diabetes develops in adults; usually occurs in adults with a normal weight and family history of type 1 diabetes; treated with diet, exercise, oral medications, and insulin. ● Latent → present but not visible ■ Gestational diabetes mellitus = form of diabetes mellitus that occurs during some pregnancies; usually disappears after delivery; however, many of these women have an increased risk of developing type 2 diabetes in later life. ■ Diabetic coma (diabetic ketoacidosis) = caused by very high blood glucose (hyperglycemia); treated by the prompt administration of insulin. ■ Insulin shock = caused by very low blood glucose (hypoglycemia) ● Oral glucose → a sugary substance that can quickly be absorbed into the bloodstream; consumed to rapidly raise the blood sugar level. ■ Diabetic retinopathy = occurs when diabetes damages the tiny blood vessels in the retina; this causes blood to leak into the posterior segment of the eyeball and produce the damage that causes the loss of vision. ■ Ketosis = normal metabolic process that helps the body utilize stored fat when other sources of energy are lacking; excessively high level of ketosis may indicate that the body is not producing enough insulin to convert glucose into energy. ○ The Adrenal Glands ■ Addison’s disease = occurs when the adrenal glands do not produce enough of the hormones cortisol or aldosterone; characterized by chronic, worsening fatigue and muscle weakness, loss of appetite, low blood pressure, and weight loss; many patients also develop patches of dark skin. ■ Adrenalitis = inflammation of the adrenal glands ■ Aldosteronism = an abnormality of the electrolyte balance that is caused by the excessive secretion of aldosterone.

■ Conn’s syndrome = disorder of the adrenal glands that is caused by the excessive production of aldosterone; can cause weakness, cramps, and con...