Slide 1 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 10 The Endocrine System

Slide 1Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

Chapter 10Chapter 10The Endocrine SystemThe Endocrine System


MECHANISMS OF HORMONE MECHANISMS OF HORMONE ACTIONACTION

Endocrine glands secrete chemicals (hormones) Endocrine glands secrete chemicals (hormones) into the blood (Figure 10-1)into the blood (Figure 10-1)

Hormones perform general functions of Hormones perform general functions of communication and control but a slower, communication and control but a slower, longer-lasting type of control than that provided longer-lasting type of control than that provided by nerve impulsesby nerve impulses

Cells acted on by hormones are called Cells acted on by hormones are called target target cells; cells; organs containing target cells are organs containing target cells are target target organsorgans



MECHANISMS OF HORMONE MECHANISMS OF HORMONE ACTION (cont.)ACTION (cont.)

Nonsteroid hormones (first messengers) bind to Nonsteroid hormones (first messengers) bind to receptors on the target cell membrane, triggering receptors on the target cell membrane, triggering second messengers to affect the cell’s activities second messengers to affect the cell’s activities (Figure 10-2)(Figure 10-2)

Steroid hormonesSteroid hormones Primary effects produced by binding to receptors Primary effects produced by binding to receptors

within the target cell nucleus and influence cell activity within the target cell nucleus and influence cell activity by acting on DNA—a slower process than nonsteroid by acting on DNA—a slower process than nonsteroid action (Figure 10-3)action (Figure 10-3)

Secondary effects may occur when steroid hormones Secondary effects may occur when steroid hormones bind to membrane receptors to rapidly trigger bind to membrane receptors to rapidly trigger functional changes in the target cellfunctional changes in the target cell




REGULATION OF HORMONE REGULATION OF HORMONE SECRETIONSECRETION

Hormone secretion is controlled by homeostatic Hormone secretion is controlled by homeostatic feedbackfeedback

Negative feedback—mechanisms that reverse the Negative feedback—mechanisms that reverse the direction of a change in a physiological system direction of a change in a physiological system (Figure 10-4)(Figure 10-4)

Positive feedback—(uncommon) mechanisms that Positive feedback—(uncommon) mechanisms that amplify physiological changesamplify physiological changes



PROSTAGLANDINSPROSTAGLANDINS

Prostaglandins (PGs) are powerful substances Prostaglandins (PGs) are powerful substances found in a wide variety of body tissuesfound in a wide variety of body tissues

PGs are often produced in a tissue and diffuse only PGs are often produced in a tissue and diffuse only a short distance to act on cells in that tissuea short distance to act on cells in that tissue

Several classes of PGs include prostaglandin A Several classes of PGs include prostaglandin A (PGA), prostaglandin E (PGE), and prostaglandin F (PGA), prostaglandin E (PGE), and prostaglandin F (PGF)(PGF)

PGs influence many body functions, including PGs influence many body functions, including respiration, blood pressure, gastrointestinal respiration, blood pressure, gastrointestinal secretions, and reproductionsecretions, and reproduction


PITUITARY GLAND PITUITARY GLAND (Figure 10-5)(Figure 10-5)

Anterior pituitary gland (adenohypophysis)Anterior pituitary gland (adenohypophysis) Names of major hormonesNames of major hormones

• Thyroid-stimulating hormone (TSH)Thyroid-stimulating hormone (TSH)

• Adrenocorticotropic hormone (ACTH)Adrenocorticotropic hormone (ACTH)

• Follicle-stimulating hormone (FSH)Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)Luteinizing hormone (LH)

• Growth hormone (GH)Growth hormone (GH)

• Prolactin (PRL) (lactogenic hormone)Prolactin (PRL) (lactogenic hormone)



PITUITARY GLAND (cont.)PITUITARY GLAND (cont.) Anterior pituitary gland (cont.)Anterior pituitary gland (cont.)

Functions of major hormonesFunctions of major hormones• TSH—stimulates growth of the thyroid gland; also stimulates it to secrete TSH—stimulates growth of the thyroid gland; also stimulates it to secrete

thyroid hormonethyroid hormone• ACTH—stimulates growth of the adrenal cortex and stimulates it to secrete ACTH—stimulates growth of the adrenal cortex and stimulates it to secrete

glucocorticoids (mainly cortisol)glucocorticoids (mainly cortisol)• FSH—initiates growth of ovarian follicles each month in the ovary and FSH—initiates growth of ovarian follicles each month in the ovary and

stimulates one or more follicles to develop to the stage of maturity and stimulates one or more follicles to develop to the stage of maturity and ovulation; FSH also stimulates estrogen secretion by developing follicles; ovulation; FSH also stimulates estrogen secretion by developing follicles; stimulates sperm production in the malestimulates sperm production in the male

• LH—acts with FSH to stimulate estrogen secretion and follicle growth to LH—acts with FSH to stimulate estrogen secretion and follicle growth to maturity; causes ovulation; causes luteinization of the ruptured follicle and maturity; causes ovulation; causes luteinization of the ruptured follicle and stimulates progesterone secretion by corpus luteum; causes interstitial cells stimulates progesterone secretion by corpus luteum; causes interstitial cells in the testes to secrete testosterone in the malein the testes to secrete testosterone in the male

• GH—stimulates growth by accelerating protein anabolism; also accelerates GH—stimulates growth by accelerating protein anabolism; also accelerates fat catabolism and slows glucose catabolism; by slowing glucose catabolism, fat catabolism and slows glucose catabolism; by slowing glucose catabolism, tends to increase blood glucose to higher than normal level (hyperglycemia)tends to increase blood glucose to higher than normal level (hyperglycemia)

• PRL, or lactogenic hormone—stimulates breast development during PRL, or lactogenic hormone—stimulates breast development during pregnancy and secretion of milk after the delivery of the babypregnancy and secretion of milk after the delivery of the baby


PITUITARY GLAND (cont.)PITUITARY GLAND (cont.)

Posterior pituitary gland (neurohypophysis)Posterior pituitary gland (neurohypophysis) Names of hormonesNames of hormones

• Antidiuretic hormone (ADH)Antidiuretic hormone (ADH)

• OxytocinOxytocin Functions of hormonesFunctions of hormones

• ADH—accelerates water reabsorption from urine in ADH—accelerates water reabsorption from urine in the kidney tubules into the blood, thereby decreasing the kidney tubules into the blood, thereby decreasing urine secretionurine secretion

• Oxytocin (OT)—stimulates the pregnant uterus to Oxytocin (OT)—stimulates the pregnant uterus to contract; may initiate labor; causes glandular cells of contract; may initiate labor; causes glandular cells of the breast to release milk into ducts; enhances social the breast to release milk into ducts; enhances social bondingbonding


HYPOTHALAMUSHYPOTHALAMUS Actual production of ADH and oxytocin occurs in Actual production of ADH and oxytocin occurs in

the hypothalamusthe hypothalamus After production in the hypothalamus, hormones After production in the hypothalamus, hormones

pass along axons into the pituitary glandpass along axons into the pituitary gland The secretion and release of posterior pituitary The secretion and release of posterior pituitary

hormones is controlled by nervous stimulationhormones is controlled by nervous stimulation The hypothalamus controls many body functions The hypothalamus controls many body functions

related to homeostasis (temperature, appetite, related to homeostasis (temperature, appetite, and thirst)and thirst)


THYROID GLAND THYROID GLAND (Figure 10-6)(Figure 10-6)

Names of hormonesNames of hormones Thyroid hormones—thyroxine (TThyroid hormones—thyroxine (T44) and ) and

triiodothyronine (Ttriiodothyronine (T33))

Calcitonin (CT)Calcitonin (CT) Functions of hormonesFunctions of hormones

Thyroid hormones—accelerate catabolism Thyroid hormones—accelerate catabolism (increase the body’s metabolic rate)(increase the body’s metabolic rate)

CT—decreases the blood calcium concentration by CT—decreases the blood calcium concentration by inhibiting breakdown of bone, which would release inhibiting breakdown of bone, which would release calcium into the bloodcalcium into the blood



PARATHYROID GLANDS PARATHYROID GLANDS (Figure 10-8)(Figure 10-8)

Name of hormone—parathyroid hormone (PTH)Name of hormone—parathyroid hormone (PTH) Function of hormone—increases blood calcium Function of hormone—increases blood calcium

concentration by increasing the breakdown of concentration by increasing the breakdown of bone with the release of calcium into the bloodbone with the release of calcium into the blood



ADRENAL GLANDS ADRENAL GLANDS (Figure 10-9)(Figure 10-9)

Adrenal cortexAdrenal cortex Names of hormones (corticoids)Names of hormones (corticoids)

• Glucocorticoids (GCs)—chiefly cortisol Glucocorticoids (GCs)—chiefly cortisol (hydrocortisone)(hydrocortisone)

• Mineralocorticoids (MCs)—chiefly aldosteroneMineralocorticoids (MCs)—chiefly aldosterone• Sex hormones—small amounts of male hormones Sex hormones—small amounts of male hormones

(androgens) secreted by adrenal cortex of both (androgens) secreted by adrenal cortex of both sexessexes

Three cell layers (zones)Three cell layers (zones)• Outer layer, secretes mineralocorticoidsOuter layer, secretes mineralocorticoids• Middle layer, secretes glucocorticoidsMiddle layer, secretes glucocorticoids• Inner layer, secretes sex hormonesInner layer, secretes sex hormones

Mineralocorticoids—increase blood sodium and Mineralocorticoids—increase blood sodium and decrease body potassium concentrations by decrease body potassium concentrations by accelerating kidney tubule reabsorption accelerating kidney tubule reabsorption of sodium and excretion of potassiumof sodium and excretion of potassium



ADRENAL GLANDS (cont.)ADRENAL GLANDS (cont.) Adrenal cortex (cont.)Adrenal cortex (cont.)

Functions of glucocorticoidsFunctions of glucocorticoids• Help maintain normal blood glucose concentration by increasing Help maintain normal blood glucose concentration by increasing

gluconeogenesis—the formation of “new” glucose from amino acids gluconeogenesis—the formation of “new” glucose from amino acids produced by the breakdown of proteins, mainly those in muscle tissue produced by the breakdown of proteins, mainly those in muscle tissue cells; also the conversion to glucose of fatty acids produced by the cells; also the conversion to glucose of fatty acids produced by the breakdown of fats stored in adipose tissue cellsbreakdown of fats stored in adipose tissue cells

• Play an essential part in maintaining normal blood pressure—make Play an essential part in maintaining normal blood pressure—make it possible for epinephrine and norepinephrine to maintain a normal it possible for epinephrine and norepinephrine to maintain a normal degree of vasoconstriction, a condition necessary for maintaining normal degree of vasoconstriction, a condition necessary for maintaining normal blood pressureblood pressure

• Act with epinephrine and norepinephrine to produce an antiinflammatory Act with epinephrine and norepinephrine to produce an antiinflammatory effect, to bring about normal recovery from inflammations of various effect, to bring about normal recovery from inflammations of various kindskinds

• Produce anti-immunity, antiallergy effect; bring about a decrease in the Produce anti-immunity, antiallergy effect; bring about a decrease in the number of lymphocytes and plasma cells and therefore a decrease number of lymphocytes and plasma cells and therefore a decrease in the amount of antibodies formedin the amount of antibodies formed

• Secretion of glucocorticoid quickly increases when the body is thrown Secretion of glucocorticoid quickly increases when the body is thrown into a condition of stress; high blood concentration of glucocorticoids, into a condition of stress; high blood concentration of glucocorticoids, in turn, brings about many other stress responses (Figure 10-10)in turn, brings about many other stress responses (Figure 10-10)



ADRENAL GLANDS (cont.)ADRENAL GLANDS (cont.)

Adrenal medullaAdrenal medulla Names of hormones—epinephrine (Epi), Names of hormones—epinephrine (Epi),

or adrenaline, and norepinephrine (NR)or adrenaline, and norepinephrine (NR) Functions of hormones—help the body resist stress Functions of hormones—help the body resist stress

by intensifying and prolonging the effects of by intensifying and prolonging the effects of sympathetic stimulation; increased epinephrine sympathetic stimulation; increased epinephrine secretion is the first endocrine response to stresssecretion is the first endocrine response to stress


PANCREATIC ISLETS PANCREATIC ISLETS (Figure 10-11)(Figure 10-11)

Names of hormonesNames of hormones Glucagon—secreted by alpha cellsGlucagon—secreted by alpha cells Insulin—secreted by beta cellsInsulin—secreted by beta cells

Functions of hormonesFunctions of hormones Glucagon increases the blood glucose level by Glucagon increases the blood glucose level by

accelerating liver glycogenolysis (conversion accelerating liver glycogenolysis (conversion of glycogen to glucose)of glycogen to glucose)

Insulin decreases the blood glucose by Insulin decreases the blood glucose by accelerating the movement of glucose out accelerating the movement of glucose out of the blood into cells, which increases glucose of the blood into cells, which increases glucose metabolism by cellsmetabolism by cells



FEMALE SEX GLANDSFEMALE SEX GLANDS

The ovaries contain two structures that secrete The ovaries contain two structures that secrete hormones—the ovarian follicles and the corpus hormones—the ovarian follicles and the corpus luteum; see Chapter 20luteum; see Chapter 20

Effects of estrogen (feminizing hormone)Effects of estrogen (feminizing hormone) Development and maturation of breasts Development and maturation of breasts

and external genitalsand external genitals Development of adult female body contoursDevelopment of adult female body contours Initiation of menstrual cycleInitiation of menstrual cycle


MALE SEX GLANDSMALE SEX GLANDS

The interstitial cells of testes secrete the male The interstitial cells of testes secrete the male hormone testosterone; see Chapter 20hormone testosterone; see Chapter 20

Effects of testosterone (masculinizing hormone)Effects of testosterone (masculinizing hormone) Maturation of external genitalsMaturation of external genitals Beard growthBeard growth Voice changes at pubertyVoice changes at puberty Development of musculature and body contours Development of musculature and body contours

typical of the maletypical of the male


THYMUSTHYMUS

Name of hormone—thymosinName of hormone—thymosin Function of hormone—plays an important role in Function of hormone—plays an important role in

the development and function of the body’s the development and function of the body’s immune systemimmune system


PLACENTAPLACENTA

Name of hormones—chorionic gonadotropins, Name of hormones—chorionic gonadotropins, estrogens, and progesteroneestrogens, and progesterone

Functions of hormones—maintain the corpus Functions of hormones—maintain the corpus luteum during pregnancyluteum during pregnancy


PINEAL GLANDPINEAL GLAND

A small gland near the roof of the third ventricle of A small gland near the roof of the third ventricle of the brainthe brain Glandular tissue predominates in children and Glandular tissue predominates in children and

young adultsyoung adults Becomes fibrous and calcified with ageBecomes fibrous and calcified with age

Called Called third eyethird eye because its influence on because its influence on secretory activity is related to the amount of light secretory activity is related to the amount of light entering the eyesentering the eyes

Secretes melatonin, which:Secretes melatonin, which: Inhibits ovarian activityInhibits ovarian activity Regulates the body’s internal clockRegulates the body’s internal clock


OTHER ENDOCRINE STRUCTURESOTHER ENDOCRINE STRUCTURES

Many organs (e.g., the stomach, intestines, and Many organs (e.g., the stomach, intestines, and kidney) produce endocrine hormoneskidney) produce endocrine hormones Stomach lining produces ghrelin, which affects Stomach lining produces ghrelin, which affects

appetite and metabolismappetite and metabolism The atrial wall of the heart secretes atrial The atrial wall of the heart secretes atrial

natriuretic hormone (ANH), which stimulates natriuretic hormone (ANH), which stimulates sodium loss from the kidneyssodium loss from the kidneys

Fat-storing cells secrete leptin, which controls how Fat-storing cells secrete leptin, which controls how full or hungry one feelsfull or hungry one feels

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Slide 1 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 10 The Endocrine System