Chapt.14 Endocrine System

Parathyroid Hormone elevates plasma calcium in three ways:

1.PTH increase the release of calcium from bone tissue,called resorption.It does so by stimulating osteoclastic activity.In response,calcium moves from the bone to the blood. 2.PTH stimulates the kidneys to reabsorb calcium from the urine.PTH causes the kidneys to excrete phosphate. 3.PTH increases the absorption of dietary calcium by the digestive tract(intestine).A vitamin D deficiency can decrease the dietary absorption of calcium.

Glucagon,Infection, and Diabetes

A patient with diabetes is prone to infection. Infection increases glucagon secretion as well as the secretion of all stress hormones,including epinephrine,cortisol,and growth hormone. All these hormones elevate blood glucose levels,causing hyperglycemia.

Positive Feedback Loop

A positive feedback loop causes an enhanced response,a self-amplification cycle in which a change is the stimulus for an even greater change in the same direction-the "give me more". Positive feedback loops are often designed to produce a rapid response.

Glucocorticoids

Affect carbohydrates. Convert amino acids into glucose(gluconeogenesis) and hep maintain blood glucose levels between meals. Glucocorticoids also effect protein and fat metabolism,burning both substances as fuel to increase energy production.The chief glucocorticoid is cortisol.

Blood Calcium

Blood calcium concentration is also regulated by calcitonin.The thyroid gland secretes calcitonin in response to elevated blood levels of calcium.Calcitonin decreases blood calcium primarily by stimulating osteoblastic(bone-making)activity in the bones,thereby moving calcium from the blood into the bone. In general,calcitonin acts as an antagonist to PTH.

Biorhythms

Blood levels of most hormones are also controlled by biorhythms. A biorhythm is a rhythmic alteration in a hormone's rate of secretion.

Insulin Receptors and The Diabetic State

Diabetes mellitus can be caused by a lack of insulin. Some diabetics(who have adult-onset,or type 2 diabetes mellitus),however,have excess insulin and are still hyperglycemic. 1.The insulin receptors are damaged. 2.There is a diminished number of receptors 3. Excess fat(adipose)tissue secretes hormones that oppose the effects of insulin.

Adipose Tissue Hormones

Excess adipose tissue acts as a gland-a very nasty gland-that secretes hormones called cytokines. There's the bad fat that collects around the thighs,giving the person a pear-shaped appearance. There's also a worse fat that collects around the abdominal area(Ab Flab),creating an apple shape. The apple shape is also associated with excess visceral fat(surrounding the organs).

Gigantism

Excess secretion of growth hormone in a child,usually caused by a pituitary tumor. A deficiency of growth hormone in a child causes pituitary dwarfism.

Parathyroid Glands

Four tiny parathyroid glands lie along the posterior surface of the thyroid gland.The parathyroid glands secrete parathyroid hormone(PTH).PTH is to increase plasma calcium levels.

Glucosuria/Glycosuria

Glucose in the urine. The hyperglycemia causes more glucose to be eliminated in the urine.

Cretinism

If an infant is born with no thyroid gland,this condition develops.An infant with cretinism fails to develop both physically and mentally.The child will be short and stocky,with abnormal skeletal development and severe mental retardation.

Acromegaly

If hypersecretion of GH occurs in an adult after the epiphyseal discs of the long bones have sealed,only the bones of the jaw,eyebrow ridges,nose,hands,and feet enlarge.

Iodine Deficiency

In an iodine-deficient state,the amount of T3 and T4 production decreases because iodine is necessary for the synthesis of the thyroid hormones. Persistent stimulation of the thyroid gland by TSh causes the thyroid gland to enlarge;an enlarged thyroid gland is called a goiter.

Insulin and Blood Glucose

Insulin decreases blood glucose levels for two reasons. First, insulin increase the transport of glucose from the blood into the cells. Second,insulin stimulates the cells to burn glucose as fuel. Insulin is the only hormone that lowers blood glucose levels.

Diabetes Mellitus

Metabolism of all types of foods(carbohydrates, proteins, and fats),a deficiency of insulin causes severe metabolic disturbances.Insulin deficiency or insulin ineffectiveness.

Milk Let-down reflex

Oxytocin also plays a role in breast-feeding.When the baby suckles at the breast,oxytocin is released and stimulates contraction of the smooth muscles around the mammary ducts within the breasts,thereby releasing breast milk.The release of milk in response to suckling is called the milk let-down reflex.

Glucagon

Pancreatic hormone, is secreted by the alpha cells of the islets of Langerhans. Its primary action is to increase blood glucose levels.Glucagon raises the blood glucose level in two ways,by stimulating the conversion of glycogen to glucose in the liver and by stimulating the conversion of proteins into glucose(gluconeogenesis).

Polyphagia

Polyphagia refers to excessive eating.Despite plenty of glucose in the blood,the cells cannot use it;instead,the diabetic eats excessive amounts of food to fuel the cells. Despite the polyphagia,the diabetic person continues to lose weight.

Synthesis of Thyroid Hormone

THe synthesis of T3 and T4 requires iodine.The iodine in the body comes from dietary sources. Tetraiodothyronine, or thyroxine,contains four iodine atoms and therefore is called T4. Triiodothyronine contains three iodine atoms and is called T3.

Control by the Central Nervous System

The CNS helps control the secretion of hormones in two ways,activation of the hypothalamus and stimulation of the sympathetic nervous system.

Joint Disease

The added body weight puts additional stress on joints such as the knees. The joints simply cannot support the extra weight.

Negative Feedback Loop

The adrenal cortex,like many other endocrine glands,is subject to negative feedback control.With negative feedback control,information about the hormone or the effects of that hormone is fed back to the gland that "gets it all going". The pattern of ACTH and cortisol secretion is one example of negative feedback loop.ACTH,secreted by the anterior pituitary gland,stimulates its target organ to secrete cortisol in the blood chemically "tells" the anterior pituitary glad to slow further secretion of ACTH.The diminished ACTH,in turn,decreases the secretion of cortisol by the adrenal cortex.

Adenohypophysis

The anterior pituitary gland is composed of glandular epithelial tissue and is also called adenohypophysis.The anterior gland secretes six major hormones.These hormones control other glands and affect many organ systems.

Mineralocorticoids

The chief mineralocorticoids is aldosterone. Especially sodium and potassium. Aldosterone is often called the salt-retaining hormone. The primary target organ of aldosterone is the kidney. Aldosterone reabsorbs sodium and water and eliminates potassium in the urine.

Psychoneuroendocrinology

The functions of the nervous system and the endocrine system are so closely related that the word Psychoneuroendocrinology.

Islets of Langerhans

The hormone-secreting cells of the pancreas.

Anterior Pituitary Gland

The hormones of the anterior pituitary include thyroid-stimulating hormone(TSH),adrenocorticotropic hormone(ACTH),growth hormone(GH),the gonadotropins; and prolactin(PRL).

Regulation of Secretion

The hypothalamus secretes a releasing hormone,which stimulates the anterior pituitary to secrete TSH. TSH stimulates the thyroid gland to secrete T3 and T4. When the plasma levels of the thyroid hormones increase sufficiently,negative feedback inhibition prevents further secretion of TSH.

Specificity

The lock and key theory guarantees that a particular hormone affects only certain cells. The hormone-receptor relationship ensures specificity,meaning that there is a specific hormone for each receptors. 1.Protein hormones-are generally combined with the receptor sites located on the cell membrane. 2.The second type of receptor is located intracellularly.

Adrenal Cortex

The outer region of the adrenal gland,secretes hormones called steroids.Steroids are lipid-soluble hormones made from cholesterol.The adrenal cortex secretes three steroids:1.glucocorticoids(sugar) 2.mineralocorticoids(salt) 3.Sex hormones(sex). Adrenal cortical hormones are essential for life.

Hypersecretion

This condition may be caused by a hypersecretion of either ACTH by the anterior pituitary gland or cortisol by the adrenal cortex. Elevated levels of cortisol are caused by the administration of steroids as drugs such as prednisone.Elevated blood levels of steroids cause a condition called Cushings' Syndrome. Characterized by truncal obesity,a rounded facial appearance(moon face),excess fat deposition between the shoulders(buffalo hump),masculinizing effects(virilization),facial hair(hirsutism),thin skin that bruises easily,bone loss,and muscle weakness.

What Thyroid Hormones do?

Thyroid hormones regulate all phases of metabolism and are necessary for the proper functioning of all other hormones.Thyroid hormones are necessary for the normal maturation of the nervous system and for normal growth and development.

Growth Hormone(GH)

is also called somatotropin or somatotropic hormone.Its primary effects are on the growth of skeletal muscles and the long bones of the body,thereby determining a person's size and height. It also stimulates the conversion of protein to glucose(gluconeogenesis),especially during periods of fasting between meals.GH thus causes blood glucose levels to rise.GH exerts a profound effect on growth.

Fruity odor to the breath

the rapid,incomplete breakdown of fatty acids causes the formation of acetone,a ketone body.

Prolactin

Also called lactogenic hormone. PRL promotes milk production in women.PRL stimulates the growth in mammary glands and stimulates the mammary glands to produce milk after childbirth.

Goiter

An enlargement of the thyroid gland. A toxic goiter is an enlargement that secretes excess thyroid hormones and produces symptoms of hyperthyroidism. A nontoxic goiter or iodine deficiency goiter does not produce excess thyroid hormones and therefore is not accompanied by symptoms of hyperthyroidism.

Acidosis

An excess of hydrogen in the blood causes acidosis. The cells cannot burn glucose as fuel,they burn fatty acids instead. The rapid,incomplete breakdown of fatty acids produces strong acids called ketoacids.

Hyperthyroidism

An excess of thyroid hormones produces hyperthyroidism,a speeded up metabolic state.A common type of hyperthyroidism is Graves' disease.It is characterized by an increase in heart rate,increase in peristalsis resulting in diarrhea,elevation in body temperature(heat intolerance),hyperactivity,weight loss,and wide emotional swings.

Vasopressin

Antidiuretic hormone also causes the blood vessels to constrict,thereby elevating blood pressure.Because of this blood pressure-elevating effect,ADH is also called vasopressin.(A vassopressor agent is one that elevates blood pressure)

Tropic Hormones

Are aimed at and control other glands. The remaining hormones of the anterior pituitary gland.

Prostaglandins

Are hormones derived from a fatty acid called arachidonic. The prostaglandins play an important role in the regulation of smooth muscle contraction and the inflammatory response. Drugs such as aspirin and ibuprofen block the synthesis of prostaglandins and are therefore useful in relieving pain and inflammation.

Catecholamines

Epinephrine and norepinephrine are classified as catecholamines,are secreted in emergency or stress situations.Help the body respond to stress by causing the following effects: 1.elevatin blood pressure2.Increasing heart rate3.converting glycogen to glucose in the liver,thereby making more glucose available to the cells.4.Increasing metabolic rate of most cells,thereby providing more energy.5.Causing bronchodilation to increase the flow of air into the lungs.6.Changing blood flow patterns,causing dilation of the blood vessels to the heart and muscles and constriction of the blood vessels to the digestive tract.

Hyperglycemia

Excess glucose in the blood. The excess glucose cannot be used by the cells and therefore accumulates in the blood. In essence,the diabetic body converts its protein to glucose that it cannot burn as fuel and then eliminates it in the urine.

Polydipsia

Excessive thirst is called polydipsia. Polyuria causes an excessive loss of body water,thereby stimulating the thirst mechanism in an attempt to replace the water lost in the urine.

Polyuria

Excretion of a large volume of urine is called polyuria.Whenever the kidneys excrete a lot of glucose,they must also excrete a lot of water. Glucosuria therefore causes polyuria.

Pituitary Dwarfism

GH deficiency in childhood causes the opposite effect. With this condition,body proportions are normal,but the person's height is very short.

Diabetes Insipidus

In the absence of ADH,a profound diuresis occurs,and the person may excrete up to 25L/day of dilute urine. Should not be confused with the more common diabetes mellitus,which is an insulin deficiency.

Hypocalcemia

In the absence of sufficient calcium,the nerve and muscle membranes become unstable and continuously fire electrical signals,causing the muscles to remain contracted.Sustained skeletal muscle contraction is referred to as tetany.Hypocalcemic tetany not only contorts the wrist;more seriously, it causes sustained contractions of the muscles of the larynx(laryngospasm)and the breathing muscles.

Insulin secretion and effects

Insulin is released in response to increased blood levels of glucose,such as what occurs after a meal. Has many target tissues and therefore exerts widespread effects: 1.Insulin helps transport glucose into most cells. 2.Insulin helps control carbohydrate,protein,and fat metabolism in the cell.Insulin stimulates the breakdown of glucose(glycolysis) for energy and stimulates the liver and skeletal muscles to store excess glucose as glycogen(glycogensis).

Circadian Rhythm

Is a 24 hour rhythm. Its pattern repeats every 24 hours.Because of circadian rhythm,cortisol secretion is highest in the morning hours(peak at 8am) and lowest in the evening hours(lowest at midnight). They are secreted in a monthly pattern-hence,the monthly menstrual cycle.

Hormone

Is a chemical messenger that influences or controls the activities of other tissues or organs. Hormones also play an important role in growth and reproduction and help regulate water and electrolyte balance.

Pineal Gland

Is a cone-shaped gland located close to the thalamus in the brain.It has been called the body's "biological clock",controlling many of the biorhythms. The pineal gland secretes a hormone called melatonin. Melatonin affects the reproductive cycle by influencing the secretion of hypothalamic-releasing hormones. The amount of melatonin secreted is related to the amount of daylight.Melatonin secretion is lowest during daylight hours and highest at night.

Pancreas

Is a long slender organ that lies transversely across the upper abdomen,extending from the curve of the duodenum to the spleen. Functions both as an exocrine gland and an endocrine gland.

Myxedema

Is a slowed down metabolic state characterized by a slow heart rate,sluggish peristalsis resulting in constipation,a low body temperature,low energy,loss of hair,and weight gain. The skin becomes thick and puffy.

Cortisol

Is a stress hormone in that it is secreted in greater amounts during times of stress. Cortisol also has an anti-inflammatory effect.

Pituitary Gland

Is also called the hypophysis,is a pea-sized gland located in a depression of the sphenoid bone.The pituitary contains two main parts,the anterior pituitary gland and posterior pituitary gland.The secretion of the anterior pituitary gland is controlled by the hypothalamus.These hormones are called releasing hormones and release-inhibiting hormones.

Graves' Disease

Is also characterized by bulging eyes,a condition known as exophthalmia. In exophthalmia,the eyes are thought to bulge because the fat pads behind the eyeballs enlarge,pushing the eyeballs forward in the eye socket.

Posterior Pituitary Gland

Is an extension of the hypothalamus.Is composed of nervous tissue and is therefore called the neurohypophysis.The two hormones of the posterior pituitary gland are produced in the hypothalamus and transported to the gland,where they are stored until needed.The two hormones are antidiuretic hormone and oxytocin.

Thyroid Gland

Is located in the anterior neck;it is situated on the front and sides of the trachea and is easily palpated. The thyroid gland is butterfly-shaped and has two lobes connected by a band of tissue called the isthmus.The thyroid gland contains two types of cells;the follicular cells,located within the thyroid follicle,and the parafollicular cells,located between the follicles.

Antidiuretic hormone(ADH)

Is released from the posterior pituitary gland in attempt to conserve water.The primary target organ for ADH is the kidney.ADH causes the kidney to reabsorb water from the urine and return it to the blood.By doing so,the amount of urine that the kidney excretes decreases.

Adrenal Medulla

Is the inner region of the adrenal gland and is considered an extension of the sympathetic nervous system.Remember that they sympathetic nervous system is called the "fight or flight" system. Secretes two hormones,epinephrine(adrenaline)and norepinephrine.

Endocrinology

Is the study of the endocrine system.

Hyposecretion

The adrenal gland fails to secrete adequate amounts of adrenal cortical hormones.This condition is called chronic adrenal coritcal insufficiency,or Addison's Disease. It is characterized by generalized weakness,muscle atrophy,a bronzing of the skin,hyperkalemia,and severe loss of fluids and electrolytes,especially NA+. Adrenal insufficiency is life-threatening and must be treated with steroids and replacement of fluids and electrolytes.

Hypercalcemia

The patient develops hyperparathyroidism in response to a tumor in the parathyroid gland.The PTH stimulates osteoclastic activity in the bones,thereby moving calcium from the bones to the blood and causing hypercalcemia. Hypercalcemia causes excess calcium to be filtered into the urine,causing hypercalciuria;the excess calcium in the urine precipitates out as kidney stones.Hypercalcemia also depresses the nervous,cardiac,and gastrointestinal systems causing a variety of symptoms,including depression(moans),fatigue,bradycardia, anorexia,and constipation.

Control of Cortisol Secretion

The secretion of cortisol involves that hypothalamus,anterior pituitary gland,and adrenal gland.The hypothalamus secretes a releasing hormone,which then stimulates the anterior pituitary gland to secrete ACTH. Through negative feedback control,the cortisol inhibits the further secretion of ACTH.

Sex hormones

The sex hormones,secreted in small amounts,include the female hormones,primarily estrogens,and male hormones,called androgens(primarily testosterone)

Adrenocorticotropic Hormone(ACTH)

The target gland is the adrenal cortex.ACTH stimulates the adrenal cortex to secrete steroids.

Thyroid-stimulating hormone(TSH)

The target gland is the thyroid gland.TSH stimulates the thyroid gland to secrete two thyroid hormones.

Gonadotropic Hormones

The target glands are the gonads,or sex glands(ovaries and testes).The two gonadotropins are follicle-stimulating hormone(FSH) and luteinizing hormone(LH).FSH stimulates the development of ova(eggs)in the female and sperm in the male.LH causes ovulation in the female and causes the secretion of sex hormones in both the male and the female.

Oxytocin

The target organs in the female are the uterus and the mammary glands.Oxytocin stimulates the muscles of the uterus to contract and plays a role in labor and delivery of a baby.

Follicles

The thyroid gland is composed of many secretory units that are follicles.Follicular cells secrete two thyroid hormones,triidothyronine(T3)and tetraiodothyronine(T4 or thyroxine).

Adrenal Glands

The two small glands located above the kidneys are called adrenal glands. An adrenal gland consists of two regions,an inner medulla and an outer cortex.Secrete different hormones.

Hormone Receptors

The two types of receptors are those located on the outer surface of the cell membrane(membrane receptors) and those located within the cell(intracellular receptors).