Anatomy: Ch. 17 Endocrine System

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Endocrine system

Concerned mainly with hormones and to some extent, paracrine secretions. The glands, tissues, and cells that secrete hormones constitute the WHAT?

endocrinology

The study and medical treatment of the Endocrine system

endocrine vs exocrine

The classical distinction between exocrine and endocrine glands has been the presence or absence of ducts. Most exocrine glands secrete their products by way of a duct onto an epithelial surface such as the skin or the mucosa of the digestive tract. Endocrine glands, by contrast, are ductless and release their secretions into the bloodstream. Exocrine secretions have extracellular affects such as the digestion of food, whereas endocrine secretions have intracellular effects- they alter the metabolism of their target cells.

means of communication

Nervous system: electrochemical (nerve signals and neurotransmitters) Endocrine: Chemical (hormones)

reaction time

Nervous: Quick but short-lived responses. Endocrine: Slower but longer-lasting responses

Effect

Nervous: Usually local and specific. Endocrine: Often more widespread and general

cessation of reaction

Nervous: Stops quickly when stimulus stops. Endocrine: Reaction may last longer after stimulus stops

Adaption to continual stimulation

Nervous: Adapts quickly, stops responding. Endocrine: May continue responding for days, weeks.

pituitary gland

suspended from the floor of the hypothalamus by a stalk and housed in a depression of the sphenoid bone, the sella turcica.

adenohypophysis and neurohypophysis

Pituitary gland is composed of two structures: WHAT and WHAT with independent origins and separate functions.

anterior lobe

The adenohypophysis constitutes the anterior three-quarters of the pituitary. It has two parts: a large WHAT, also called the pars distalis because it is most distal to the pituitary stalk, and a less important pars tuberalis, a small mass of cells that wraps around the stalk.

hypophyseal portal system

The anterior pituitary has no nervous connection to the hypothalamus but is linked to it by a complex of blood vessels called the WHAT? This system consists of a network of primary capillaries in the hypothalamus, a group of small veins called portal venules that travel down the stalk, and a complex of secondary capillaries in the anterior pituitary by secreting hormones that enter the primary capillaries, travel down the portal venules, and diffuse out of the secondary capillaries into the pituitary tissue.

posterior lobe

The neurohypophysis constitutes the posterior one-quarter of the pituitary. The largest part, the WHAT. The neurohypophysis is actually nervous tissue, not a true gland. The nerve fibers arise from certain cell bodies in the hypothalamus, pass down the stalk as a bundle called the hypothalamohypophyseal tract, and end in the posterior lobe. The hypothalamic nervous synthesize hormones and transport them down the axons to the posterior pituitary. Here they are stored until a nerve signal coming down those same axons triggers their release into the blood.

anterior pituitary hormones

WHAT employs the hypophyseal portal system?

follicle-stimulating hormone

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) FSH is secreted by pituitary cells called gonadotropes. In the ovaries, it stimulates the secretion of ovarian sex hormones. In the testes, it stimulates sperm production.

luteinizing hormone

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) (LH) LH is also secreted by the gonadotropes. In females, it stimulates ovulation, the release of an egg. It is named for the fact that after ovluation, the follicle becomes a yellowish body called the corpus luteum. In males, LH stimulates the testes to secrete testosterone.

thyroid-stimulating hormone

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) (TSH) secreted by pituitary cells called thyrotropes. It stimulates growth of the thyroid gland and the secretion of thyroid hormone, which has widespread effects on metabolic rate, body temperature, and other functions.

adrenocorticotropic hormone

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) (ACTH) secreted by cells called corticotropes. ACTH stimulate sthe cortex to secrete hormones called glucocorticoids which regulate glucose, protein, and fat metabolism and are important in the body's response to stress.

prolactin

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) (PRL) secreted by pituitary cells called lactotropes. During pregnancy, the lactotropes increase greatly in size and number, and PRL secretion rises proportionately, but it has no effect until after a woman gives birth. Then, it stimulates the mammary glands to synthesize milk. In males, PRL has a gonadotropic effect that makes the testes more sensitive to LH. Thus, it indirectly enhances the secretion of testosterone.

growth hormone somatotropin

(anterior lobe of the pituitary synthesizes and secretes 6 principal hormones) (GH) secreted by somatotropes, the most numerous cells of the anterior pituitary. Produces a thousand times as much GH as any other hormone. The general effect of GH is to stimulate mitosis and cellular differentiation and thus to promote tissue growth throughout the body.

endocrine axis

The relationship between the hypothalamus, pituitary gland, and another endocrine gland, mediated by tropic hormones.

hypothalamo-pituitary-thyroid

TRH->TSH->thyroid hormone

hypothalamo-pituitary-gonadal

GnRH->FSH, LH-> estrogen, progesterone

hypothalamo-pituitary-adrenal

CRH->ACTH->cortisol

ADH and OT

Two posterior lobe hormones are WHAT and WHAT?They are synthesized in the hypothalamus, then transported to the posterior pituitary and stored until their release on command.

supraoptic nucleus

WHAT produces ADH?

antiduiretic hormone

(ADH) increases water retention by the kidneys, reduces urine volume, and helps prevent dehydration. It is also called vasopressin because it can cause vasoconstriction. This requires concentrations so unnaturally high for the human body.

oxytocin

(OT) has a variety of reproductive functions n situations ranging from intercourse to breast-feeding. It surges in both sexes during sexual arousal and orgasm. In feelings of sexual satisfaction and emotional bondings between partners. In childbirth, it stimulates labor contractions, and in lactating mothers, it stimulates the flow of milk from the mammary gland acini deep in the breast to the nipple. It also promotes emotional bonding between mother and infant.

paraventricular nucleus

WHAT produces oxytoxin?

neuroendocrine reflexes

The posterior pituitary is controlled by WHAT- the release of hormones in response to signals from the nervous system. Ex.) the suckling of an infant stimulates nerve endings in the nipple. This causes the release of oxytocin, which results in milk ejection

neuroendocrine reflex

Antidiuretic hormone is also controlled by WHAT? Dehydration raises the osmolarity of the blood, which is detected by hypothalamic neurons called osmoreceptors. They trigger ADH release, and ADH promotes water conservation. Excessive blood pressure, by contrast, stimulates stretch receptors in the heart and certain arteries. By another neuroenocrine reflex, this inhibits ADH release, increases urine output, and brings blood volume and pressure back to normal.

negative feedback inhibition

The pituitary stimulates another endocrine gland to secrete its hormone, and that hormone feeds back to the pituitary or hypothalamus and inhibits further secretion of the pituitary hormone. Ex.) the Thyroid hormone inhibits TRH and TSH secretion

negative feedback inhibition

1. The hypothalamus secretes thyrotropin-releasing hormone (TRH) 2. TRH stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH) 3. TSH stimulates the thyroid gland to secrete thyroid hormone (TH) 4. TH stimulates the metabolism of most cells throughout the body 5. TH also inhibits the release of TSH by the pituitary 6. To a lesser extent, TH also inhibits the release of TRH by the hypothalamus.

positive feedback

Hormone from target organ stimulates secretion of tropic hormone ex.) estrogen from ovaries stimulates LH secretion

pineal gland

WHAT is attached to the roof of the third ventricle of the brain, beneath the posterior end of the corpus callosum. The philosopher Rene Descartes thought it was the seat of the human soul.

melatonin

During the night, the pineal gland synthesizes melatonin, a monoamine, from serotonin. Its secretion fluctuates seasonally with changes in day length, and in animals with seasonal breeding, it regulates the gonads and the annual breeding cycle. Removal of the pineal from animals causes premature sexual maturation. May regulate the timing of puberty in humans. Implicated in mood disorders such as seasonal affective disorder (SAD) and premenstrual syndrome (PMS)

thymus

WHAT plays a role in three stages: endocrine, lymphatic, and immune. It is a bilobed gland in the mediastinum superior to the heart, behind the sternal manubrium. Curls after puberty

thymopoietin, thymosin, and thymulin

The thymus is a site of maturation for certain white blood cells called T cells that are critically important for immune defense. It secretes several hormones WHAT, WHAT, and WHAT that stimulate the development of other lymphatic organs and regulate the development and activity of T cells.

thyroid gland

WHAT is the largest endocrine gland in adults. It is composed of two lobes that lie adjacent to the trachea immediately below the larynx.

follicular cells

The thyroid is composed mostly of sacs called thyroid follicles. Each is filled with a protein-rich colloid and lined by a simple cubodial epithelium of WHAT?

thyroxine

Follicular cells secrete mainly the hormone WHAT? Also known as T4 or tetraiodothyroine because of its four iodine atoms.

thyroid hormone

The expression WHAT (TH) refers to T4 and T3 collectively

calorigenic effect

The primary effect of TH is to increase the body's metabolic rate. AS a result, it raises oxygen consumption and has a WHAT- it increases heat production. TH secretion rises in cold weather and thus helps to compensate for increased heat loss

C cells

The thyroid gland also contains nests of WHAT between follicles. They respond to rising levels of blood calcium by secreting the hormone calcitonin. Calcitonin antagonizes the action of parathyroid hormone and stimulates osteoblast activity, thus promoting calcium deposition and bone formation.

parathyroid glands

WHAT are ovoid glands. Usually here are four of them, partially embedded in the posterior surface of the thyroid.

parathyroid hormone

The parathyroid glands secrete WHAT (PTH) in response to hypocalcemia. PTH raises blood calcium levels

adrenal glands

WHAT sits like a cap on the superior to the superomedial surface of each kidney. They are retroperioneal. Its inner core, the adrenal medulla, is 10-20% of the gland. Surrounding it is a much thicker adrenal cortex, constituting 80-90% of the gland

adrenal medulla

WHAT has a dual nature, acting as both an endocrine gland and a ganglion of the sympathetic nervous system. It lies on superior pole of each kidney (but no direct relation to kidney function)

epinephrine and norepinephrine

Upon stimulation by the nerve fibers- the chromaffin cells in the medulla release a mixture of catecholamines: about 85% WHAT and 15% WHAT? They increase alertness and prepare the body in several ways for physical activity. They mobilize high-energy fuels such as lactase, fatty acids, and glucose.

zona glomerulosa

(layer of adrenal gland) WHAT is a thin layer, located just beneath the capsule at the gland surface. It secretes mainly aldosterone, a mineralocorticoid that stimulates the kidneys to retain sodium in the body fluids and excrete potassium in the urine. Aldosterone helps to maintain blood volume and pressure.

zona fasciculata

(layer of adrenal gland) WHAT is a thick middle layer constituting about 3/4 of the adrenal cortex. It secretes glucocorticoids in response to ACTH from the pituitary. The most potent of these is cortisol. They stimulate fat and protein catabolism, glyconeogenesis, and the release of fatty acids and glucose into the blood. This helps the body adapt to stress and repair damaged tissues. Glucocorticoids also have an anti-inflammatory effect.

zona reticularis

(layer of adrenal gland) WHAT is the narrow, innermost layer, adjacent to the adrenal medulla. They secrete sex steroids such as adrogens and some estrogen. The adrogens are dehydroepiandrosterone (DHEA). DHEA plays an important role in the adolescent development and induce the growth of pubic and axillary hair and stimulates the libido and bone deposition.

pancreas

WHAT is an elongated, spongy gland located below and behind the stomach. Scattered throughout the exocrine tissue are 1 to 2 million endocrine cell clusters called pancreatic islets. The islets secrete hormones of vital importance, especially in the regulation of glycemia, the blood glucose concentration. These are about 20% of alpha cells, 70% beta cells, and 5% delta cells.

alpha cells

WHAT secrete glucagon between meals when the blood glucose concentration is falling. Raises the blood glucose level.

beta cells

WHAT secrete insulin during and immediately following a meal, when glucose and amino acid levels are rising. Insulin stimulates cells to absorb these nutrients and store or metabolize them, therefore it lowers the blood glucose level.

ovaries

The WHAT secrete estradiol, progesterone, and inhibin.

granulosa cells

Each egg develops in its own follicle, which is lined by a wall of WHAT which secrete ovarian hormones.

estradiol and progesterone

WHAT and WHAT are in the second half of menstral cycle. They contribute to the development of the reproductive system and feminine physique, promote adolescent bone growth, regulate the menstrual cycle, sustain pregnancy, and prepare the mammary glands for lactation.

estrogen

WHAT is the first half of menstral cycle?

testosterone

The testis consists mainly of microscopic seminiferous tubules that produce sperm. It endocrine secretions are WHAT, lesser amounts of weaker androgens and estrogens, and inhibin. The WHAT stimulates development of the male reproductive system in the fetus and adolescent, the development of the masculine physique in adolescence, and the sex drive.

skin

(other endocrine tissue and organs) Keratinocytes of the epidermis convert a cholesterol-like steroid into cholecalciferol using UV radiation from the sun. The liver and kidneys further convert cholecalciferol to a calcium-regulating hormone, calcitriol.

liver

(other endocrine tissue and organs) Involved int he production of 5 hormones: 1. calcidiol (converts the cholecalciferol from the skin) 2. angiotensinogen (the kidneys, lungs, and other organs convert to a hormone called angiotensin II) 3. secretes the body's erythropoietin (EPO) (a hormone that stimulates the red bone marrow to produced red blood cells) 4. secretes hepcidin (body's principal hormone mechanism of iron homeostasis) 5. secretes insulin-like growth factor I (a hormone that mediates the action of growth hormone)

kidneys

(other endocrine tissue and organs) production of 3 hormones: calcitriol, angiotensin II, and erythropoietin. 1. Kidneys convert calcidiol into calcitriol (vitain D3) thus completing the three-step process begun by the skin and liver. Calcitriol raises the blood concentration of calcium. 2. secretes renin which secretes angiotensin II. This is a potent hormone that constricts blood vessels throughout the body and thereby raises blood pressure 3. Kidneys secrete about 85% of body's erythropoietin

heart

(other endocrine tissue and organs) Raising blood pressure stretches the heart wall and stimulates cardiac muscle int he atria to secrete atrial natriuretic peptide (ANP). Both of these increase sodium excretion and urine output and oppose the action of angiotensin II. Together these effects lower the blood pressure

stomach and small intestine

(other endocrine tissue and organs) have enteroendocrine cells which secrete enteric hormones. One role of these hormones is to coordinate different regions and glands of the digestive system with each other.

adipose tissue

(other endocrine tissue and organs) Fat cells secrete the hormone leptin. A low level of leptin, signifying a low level of body fat, increases appetite and food intake, whereas a high level of leptin tends to blunt the appetite. Leptin also serves as a signal for the onset of puberty.

placenta

(other endocrine tissue and organs) Secretes estrogen, progesterone, and other hormones that regulate pregnancy and stimulate development of the fetus and the mother's mammary glands.

steroid hormones

Derived from cholesterol. They include sex steroids produced by the testes and ovaries (such as estrogens, progesterone, and testosterone) and corticosteroids produced by the adrenal gland (such as cortisol, corticosterone, aldosterone, and DHEA)

peptide hormones

WHAT are chairs of 3 to 200 or more amino acids. Most hormones of the anterior pituitary are polypeptides or glycoproteins- polypeptides conjugated with short carbohydrate chains.

monoamines

Include dopamine, epinephrine, norepinephrine, melatonin, and thyroid hormone. They are made from amino acids and retain an amino group.

hormone synthesis and secretion

how the hormone is produced by the endocrine cells

steroids

WHAT are synthesized from cholesterol and differ mainly in the functional groups attached to the four-ringed steroid backbone.

insulin

WHAT begins as preproinsulin (synthesized by ribosomes on the rough ER of the pancreatic beta cell). It is now called proinsulin. Enzymes remove a large middle segment called the connecting (C) peptide. The remainder is now insulin, composed of two polypeptide chains connected to each other by two of the three disulfide bridges.

monoamines

Melatonin is synthesized from the amino acid truptophan and the other monoamines from the amino acid tyrosine.

transport

How the hormone is carried in the bloodstream to its target organ

action

How the hormone bonds to the target cells and alters their physiology

testosterone

(steroid synthesis) estradiol from WHAT?

progesterone

testosterone, cortisol, and aldosterone from WHAT?

cholestrol

Progesterone from WHAT?

thyroid hormone synthesis

1. Iodine absorption and oxidation 2. Thyroglobulin synthesis and secretion into follicle 3. Iodine added to thyroglobulin 4. Thyroglobulin uptake and hydrolysis 5. Release of T4 and a small amount of T3 into the blood

preproinsulin

(insulin synthesis) WHAT is synthesized by ribosomes on the rough ER of the pancreatic beta cells

Proinsulin

(insulin synthesis) An enzyme in the ER cisterna cleaves off part of the chain (signal peptide), leaving WHAT?

C peptide

(insulin synthesis) In the golgi complex, another enzyme removes a large middle segment called WHAT?

insulin

(insulin synthesis) This leaves the WHAT molecule, composed of two peptide chains, connected by -S-S- bonds. This is the final product secreted by the beta cell.

monoiodotyrosine

If one iodine is added to tyrosine ring, it becomes WHAT? (MIT)

diiodotyrosine

If the tyrosine ring binds a second iodine atom, it becomes WHAT (DIT)

T3

DIT+MIT-> WHAT? (triiodothyronine)

T4

DIT+MT-> WHAT? (tetraiodothyronine, or thyrozine). Has a fourth iodine.

thyroxine

WHAT is released from the rest of the thyroglobulin and then secreted into the bloodstream.

hydrophilic

To get from an endocrine cell to a target cell, a hormone must travel in the blood, which is mostly water. Most of the monoamines and peptides are WHAT, so mixing with the blood plasma presents no problem for them. (surface receptors and second messengers)

transport proteins

Steroids and thyroid hormones are hydrophobic and must bind to hydrophilic WHAT to get to their destination.

bound hormone

A hormone attached to a transport protein is called WHAT? And one that is not attached is an unbound hormone. Only the unbound hormone can leave a blood capillary and get to a target cell.

half-lives

Transport proteins are not only enable hydrophobic hormones to travel in the blood, but also prolong their WHAT. They protect circulating hormones from being broken down by enzymes in the blood plasma and liver and from being filtered out of the blood by the kidneys. Free hormone may be broken down or removed from the blood in a few minutes, where are bound hormones may circulate for hours to weeks

hydrophobic hormones

WHAT diffuse easily through the phospholipid-cholesterol regions of the plasma membrane. Most of them pass directly into the nucleus and bind to a receptor there. The receptor associates with the target gene in the nucleus, controlling its transcription. Ex.) Steroid hormones (nuclear receptors)

the action of thyroid hormone on a target

the action of thyroid hormone on a target: T3 and T4 dissociate from thyroxine-binding globulin (TBG), leave the bloodstream, and enter the target cell cytoplasm. Here, T4 is converted to T3 by the removal of one iodine atom. T3 enters the nucleus and activates genetic transcription. (nuclear receptor/hydrophobic hormone)

hydrophilic

Peptides and catecholamines are WHAT and cannot penetrate into a target cell, so they must stimulate its physiology indirectly. They bind to CELL-SURFACE RECEPTORS, which are linked to second-messenger systems on the other side of the plasma membrane. Ex.) cAMP. Leads ultimately to the activation of enzymes that hydrolyze glycogen stored in the cell. Second messengers do not longer in the cell for long. cAMP is broken down very quickly by an enzyme called phosphodiesterase, and the hormonal effect is short-lived. Other second messengers include diacyglycerol and inositol triphosphate

where DAG comes from and how it affects target cell metabolism

where DAG comes from and how it affects target cell metabolism: A hormone binds to its receptor and activates a G protein. The G protein migrates to a phospholipase molecule and activates it. Phospholipase removes the head of a membrane phospholipid, leaving DAG. DAG activates protein kinase (PK), an enzyme that phosphorylates other enzymes. By doing so, PK can turn metabolic pathways on or off.

where inositol triphosphate comes from and how it affects target cell metabolism

where inositol triphosphate comes from and how it affects target cell metabolism: The phosphate-containing group removed is IP3. IP3 raises calcium concentration int he cytosol. Calcium has 3 affects: Ca2+ may bind to other gated membrane channels and alter the membrane potential of the cell or its permeability to various solutes. Ca2+ may activate cytoplasmic enzymes that alter cell metabolism. Ca2+ may bind to the cytoplasmic receptor protein calmodulin, which in turn activates a protein kinase (PK)

enzyme amplification

One hormone molecule can trigger the synthesis of not just one enzyme molecule but enormous number. A single hormone molecule can trigger the production of many cAMP molecules and activation activation of many molecules of protein kinase. Every protein kinase molecule can phosphorylate and activate many other enzymes. Each of those enzyme molecules can produce many molecules of a metabolic product. Amplification of the process at each step allows for a very small hormonal stimulus to cause a very large metabolic effect. (small stimulus->cAMP and protein kinase->activated enzymes->metabolic product->great effect)

up-regulation

Target cells can adjust their sensitivity to a hormone by changing the number of receptors for it. In WHAT a cell increases the number of hormone receptors and becomes more sensitive to the hormone. Ex.) In late pregnancy, the uterus produces oxytocin receptors, pregnancy itself for the surge of oxytocin that will occur during childbirth.

down-regulation

WHAT is the process in which a cell reduces its receptor population and thus becomes less sensitive to a hormone. This sometimes happens in response to long-term exposure to a high hormone concentration. Ex.) Adipocytes down-regulate when exposed to high concentrations of insulin, and cells of the testis down-regulate in response to high concentrations of luteinizing hormone.

synergist effects

(synergist=helping eachother) WHAT in which two or more hormones act together to produce an effect that is greater than the sum of their separate effect. Ex.) Neither FSH nor testosterone alone can stimulate significant sperm production. When they act together, the testes produce some 300,000 sperm per minute. (effect of 2 hormones working together is greater than the sum of their separate effects)

permissive effects

WHAT in which one hormone enhances the target organ's response to a second hormone that is secreted later. Ex.) Estrogen stimulates the up-regulation of progesterone receptors in the uterus. The uterus would respond poorly to progesterone, had it not been primed by the first hormone. Estrogen thus has a permissive effect on progesterone action. (one hormone preconditions an organ to respond to another hormone that comes later)

antagonistic effects

WHAT in which one hormone opposes the action of another. Ex.) Insulin lowers blood glucose level and glucagon raises it.

stress

WHAT is defined as any situation that upsets homeostasis and threatens one's physical or emotional well-being

physical

WHAT causes of stress include injury, surgery, hemorrhage, infection, intense exercise, temperature extremes, pain, and malnutrition

emotional

WHAT causes include anger, grief, depression, anxiety, and guilt.

alarm reaction, stage of resistance, stage of exhaustion

A pioneering researcher on stress physiology, Canadian biochemist Hans Selve showed in 1936 that the GAS (general adaptation syndrome) typically occurs in three stages, which he called the WHAT, WHAT, and WHAT?

alarm reaction

The initial response to stress is an WHAT mediated mainly by norepinephrine from the sympathetic nervous system and epinephrine from the adrenal medulla. These catecholamines prepare the body to take action such as fighting or escaping danger. Ex.) Angiotensin helps to raise the blood pressure, and aldosterone promotes sodium and water conservation. Epinephrine and norepinephrine raises BP

alarm reaction

Epinephrine (adrenal medulla) & norepinephrine (SNS). Raises BP and heart rate. Raises circulation to skeletal muscles. Decreases circulation to kidneys, skin, GI tract. Raises glycogenolysis, gluconeogenesis-> blood glucose. Decrease insulin-> blood glucose reserved for bran. Aldosterone (adrenal cortex) increase sodium and water retention; supports blood volume. Angiotensin (skin, liver, kidneys) increases blood pressure and circulation

stage of resistance

If a stressful situation is not resolved before the glycogen is gone, the body enters the WHAT in which the first priority is to provide alternative fuels for metabolism.

cortisol

The stage of resistance is dominated by WHAT? The hypothalamus secretes corticotropin-releasing hormone (CRH); the pituitary responds by secreting adrenocorticotropic hormone (ACTH); and this, in turn, stimulates the adrenal cortex to secrete cortisol and other glucocorticoids. Cortisol promotes the breakdown of fat and protein into glycerol, fatty acids, and amino acids. Cortisol inhibits glucose uptake by most organs and thus has a glucose-sparing effect. It also inhibits protein synthesis.

stage of resistance

Supplying glucose after glycogen reserved are depleted. Cortisol (hypothalamo->pituitary->adrenal axis, CRH->ACTH->cortisol). Increase fat and protein catabolism, releasing glycerol, fatty acids, amino acids. Increase gluconeogenesis: liver converts these fuels to glucose. Decrease glucose uptake by organs other than brain. Decrease protein synthesis; spares AAs for gluconeogenesis but inhibits immune system. Decrease levels of antibodies and WBCs; atrophy of lymphoid tissues. More susceptibility to infection and cancer; slower wound healing. Decrease sex hormone secretion; disrupted fertility and sexual function. Increase gastric secretion and susceptibility to ulcers.

stage of exhaustion

WHAT if marked by rapid decline and death. When its fat stores gone, the body now relies primarily on protein breakdown to meet its energy needs. Thus, there is a progressive wasting away of the muscles and weakening of the body. The adrenal cortex may stop producing glucocorticoids, making it difficult to maintain glucose homeostasis. Water retention that it creates a state of hypotension, and while it conserved sodium, it hastens the elimination of potassium and hydrogen ions. This creates a state of hypokalemia (potassium deficiency in the blood) and alkalosis (excessively high blood pH), resulting in nervous and muscular system dysfunctions. Death frequently results from heart failure, kidney failure, or overwhelming infection.

stage of exhaustion

Fat reserves can carry one through months of stress. When fat is depleted, body relies on protein breakdown to meet energy needs. Wasting of muscles, progressive weakness. Adrenal cortex stops producing cortisol, making it difficult to maintain glucose balance. Aldosterone hypersecretion causes Na+ and water retention, leading to hypertension. Aldosterone promotes K+ and H+ excretion, leading to hypokalemia and alkalosis; these lead in turn to neuromuscular dysfunction. Chronic stress overwhelms body's homeostasis. Death commonly from heart failure, kidney failure, or overwhelming infection.

paracrine

WHAT messengers. These are chemical signals released by cells into the tissue fluid; they do not travel to their target cells by way of the blood, but diffuse from their source to nearby cells in the same tissue. Ex.) Histamine, is released by mast cells that lie alongside the blood vessels in a connective tissue. It diffuses to the smooth muscle of the blood vessel. It diffuses to the smooth muscle of the blood vessel, relaxing it and allowing vasodilation.

lipoxygenase

WHAT helps to convert arachidonic acid to leukotrienes, eicosandoids that mediate allergic and inflammatory reactions.

cyclooxygenase

WHAT converts arachidonic acid to three other types of eicosanoids: prostacyclin, thromboxanes, prostaglandins (PGs)

prostacyclin

WHAT is produced by the walls of the blood vessels, where it inhibits blood clotting and vasoconstriction

thromboxanes

WHAT are produced by blood platelets. In the event of injury, the override prostacyclin and stimulate vasoconstriction and clotting.

prostaglandins

(PGs) The most diverse eicosandoids. They are named PG for WHAT, plus a third letter that indicates the type of ring structure (PGE, PGF). They are produced in most organs of the body. The PGEs are usually antagonized by PGFs. For ex.) the PGE family relaxes smooth muscle in the bladder, intestines, bronchioles, and uterus and stimulates contraction of the smooth muscle of blood vessels. PGF has precisely the opposite effects. (See table 17.7

hyposecretion

Inadequate hormone release is called WHAT. It can result from tumors or leisons that destroy an endocrine gland or interfere with its ability to receive signals from another gland. Ex.) a fractured sphenoid bone can sever the hypothalamo-hypophyseal tract and thus prevent the transport of oxytocin and antidiuretic hormone (ADH) to posterior pituitary. ADH hyposecretion leads to diabetes insipidus (lack of glucose in urine and increase uria) and chronic polyuria.

hypersecretion

Excessive hormone release, called WHAT. Some tumors result in the overgrowth of functional endocrine tissue. A pheochromocytoma is a tumor of the adrenal medulla that secretes excessive amounts of epinephrine and norepinephrine. Some tumors in nonendocrine organs produce hormones. Ex.) Some lung tumors secrete ACTH and thus overstimulate cortisol secretion by the adrenal gland. Ex. 2) toxic goiter in which antoantibodies mimic the effect of TSH in the thyroid, causing thyroid hypersecretion.

acromegaly

The hypersecretion of growth hormone (GH) in adults causes WHAT-thickening of the bones and soft tissues with especially noticeable effects on the hands, feet, and face.

pituitary gigantism

When hypersecretion of GH begins in childhood it causes WHAT?

pituitary dwarfism

Hyposecretion of GH causes WHAT?

congenital hypothyroidism

WHAT is thyroid hyposecretion present from birth. Severe or prolonge adult hypothyroidism can cause myxedema. (A syndrome occurring insevere or prolonged adult hypothyroidism, characterized by low metabolic rate, sluggishness and sleepiness, weight gain, constipation, dry skin and hair, abnormal sensitivity to cold)

crushing syndrome

WHAT is excess cortisol secretion owing to any of several causes: ACTH hypersecretion by the pituitary, ACTH-secreting tumors, or hyperactivity of the adrenal cortex independently of ACTH. WHAT disrupts carbohydrate and protein metabolism, leading to hyperglycemia, hypertension, muscular weakness, and edema. Muscle and bone mass are lost rapidly as protein is catabolized. Some patients exhibit fat deposition in the face.

diabetes mellitus

(DM) WHAT can be defined as a disruption of carbohydrate, fat, and protein metabolism resulting from the hyposecretion or inaction of insulin. Classic signs and symptoms are "the three polys": polyuria (excessive urine output), polydipsia (intense thirst), and polyphagia (ravenous hunger). Three further clinical signs are revealed by blood and urine tests: hyperglycemia (elevated blood glucose), glycosuria (glucose in the urine), and ketonuria (ketones in the urine).

transport maximum

The maximum rate of reabsorption is called the WHAT? (Tm). In diabetes mellitus, the glucose enters the tubules so rapidly that it exceeds the Tm and the tubules cannot reabsorb it fast enough. The excess passes through into the urine.

osmotic diuresis

Glucose and ketones in the tubules also raise the osmolarity of the tubular fluid and cause WHAT- water remains in the tubules with these solutes, so large amounts of water are passed in the urine. 10 to 15 L of urine per day, compared with 1 or 2 L in a healthy person.

Type 1 diabetes mellitus

(IDDM) accouts for 5% to 10% of cases. What causes it? It begins with heredity. Several genes have been identified that predispose a person to type 1 DM. Then, when a genetically susceptible individual is infected by certain viruses, the body produced autoantibodies that destroy pancreatic beta cells. When 80-90% of beta cells are gone, insulin falls to such a critically low level that it can no longer regulate glycemia, the blood glucose level. (insulin hyposecretion). Diagnosed before the age of 30. Treatments: Meal planning, exercise, and self-monitoring of blood glucose levels

Type 2 diabetes mellitus

90-95% of cases. Here, the chief problem is not lack of insulin, but INSULIN RESISTANCE-inresponsiveness of the target cells to the hormone. Again, heredity is on eof the causes. High among people of Native American, Hispanic and Asian descent. Other important risk facts are age, obesity, and a sedentary lifestyle. It develops slowly and is usually diagnosed after age 40. Treatments: A weight-loss program of diet and exercise, supplemented if necessary with oral glycemia-lowering medications.

Pathogenesis

When cells cannot absorb glucose, tey must get their energy someplace else; they metabolize fat and protein. In time, this leads to muscular atrophy, emaciation, and weakness.

ketoacidosis

Ketonuria promotes osmotic diuresis, flushing Na+ and K+ from the body and creating electrolute deficiencies that can lead to abdominal pain, vomiting, irregular heartbeat, and neurological dysfunction. As acids, ketones lower the pH of the blood and produce a condition called WHAT? This causes a deep, gasping breathing called Kussmaul respiration, typical of terminal diabetes. It also depresses the nervous system and produced diabetic coma.

blindness and renal failure

DM also leads to long-term degenerative cardiovascular and neurological diseases. Two of the common complications of long-term DM are WHAT and WHAT, brought on by arterial degeneration in the retinas and kidneys. Death from kidney failure is much more common in type 1 DM than in type 2.

diabetic neuropathy

In type 2, the most common cause of death is heart failure stemming from coronary artery disease. WAHT- nerve damage resulting from impoverished blood flow. This can lead to erectile dysfunction, incontinence, and loss of sensation from affected areas of the body.

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