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I. Overview of the Endocrine Functions1. Metabolism 2. Control of food intake and digestion3. Tissue maturation4. Ion regulation5. Water balance6. Heart rate and blood pressure regulation7. Control of blood glucose and other nutrients8. Control of reproductive functions9. Uterine contractions and milk release10. Immune system regulation

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II. Special relationship of the Pituitary Gland and Hypothalamus

• A. Where nervous and endocrine systems interact

• B. Nervous system regulates homeostasis on a short term basis

• C. Endocrine system regulates homeostasis on a longer time frame

• D. But the two do interact• E. Hypothalamus regulates

secretions of anterior pituitary• F. Posterior pituitary is an

extension of the hypothalamus• H. Anterior pituitary produces

nine major hormones that– Regulate body functions– Regulate the secretions of

other endocrine glands

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I. Structure of the Pituitary Gland• 1. Posterior pituitary (neurohypophysis):

• a. extension of the nervous system via the infundibulum

• b. Secretes and stores neuropeptides like oxcytocin

• 2. Anterior pituitary (adenohypophysis)

• a. Connected to hypothalamus by portal vein running through the infundibulum

• b. Hypothalamus controls the adenohypophysis by release of releasing hormone or inhibiting hormone

• c. Example would be GHRH or GHIH (somatostatin)

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Hypothalamus, Anterior Pituitary, and Target Tissues

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J. Hypothalamic Releasing and Inhibiting Hormones

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Hypothalamus, Posterior Pituitary, and Target Tissues

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III. Hormones of Posterior Pituitary A. ADH• 1. Also called vasopressin.

• 2. Osmoreceptors (specialized neurons of hypothalamus monitor changes in intercellular osmolality (relative concentrations of electrolytes and water).

• 3. If the concentration of electrolytes increases or if the concentration of water decreases, then ADH secretion is stimulated.

• 4. Baroreceptors (specialized neurons found in walls of atria of heart, large veins, carotid arteries, aortic arch) sense changes in blood pressure (BP). If BP decreases, then ADH secretion is stimulated.

• 5. ADH works on the collecting ducts of the kidneys to produce a more concentrated urine as water is reabsorbed into the body

B. Oxcytocin

• 1. produced in the hypothalamus and stored in the posterior or neurohypophysis

• 2. target tissues include myometrium and muscle cells around milk ducts of mammary glands

• 3. stimuli bringing about release of oxcytocin stretching of the uterus, cervix, sexual intercourse, and stimulation of nipple during nursing

• 4. functions:

• a. Onset of delivery

• b. Expulsion of uterine lining during menses

• c. Sperm transport during intercourse

• d. Milk letdown

• 5. special cases

• a. Nursing mothers and uterine shape

• b. Neural input to oxcytocin release

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Control of ADH Secretion

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Control of Oxytocin Secretion

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III. Anterior Pituitary Hormones A. Summary list

• 1. Growth hormone (GH) or somatotropin• 2. Thyroid-stimulating hormone (TSH)• 3. Adrenocorticotropic hormone (ACTH)• 4. Melanocyte-stimulating hormone (MSH)• 5. Beta endorphins• 6. Lipotropins• 7. Luteinizing hormone (LH)• 8. Follicle-stimulating hormone (FSH)• 9. Prolactin

B. Generalized traits

• 1. controlled by releasing and inhibiting hormones from the hypothalamus

• 2. the hormones are proteins, glycoproteins, or polypeptides-generally too large to pass through the membrane

• 3. bind to receptors on the target cell membrane

• 4. short half life and generally quick acting

• 5. many of the hormones are tropic hormones-stimulate other endocrine glands to produce hormones

• 6. therefore sometimes called the master gland

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C. Specific Anterior Pituitary Hormones

1.Growth Hormone (GH or somatotropin)

• a. Stimulates uptake of amino acids; protein synthesis• b. Stimulates breakdown of fats (lipolysis) to be used as an

energy source but stimulates synthesis of glycogen (glycogenesis)

• c. glucose sparing• d. Promotes bone, muscle and cartilage growth by bringing

about the release of somatomedins (insulin-like growth factors)• e. Regulates blood levels of nutrients after a meal and during

periods of fasting• f. Produced by biotech• g. Potentials for abuse-acromegaly

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Regulation of Growth Hormone Secretion

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2. TSH (tropic hormone) and Thyroid Hormones• a. TRH from hypothalamus causes the release of TSH

from anterior pituitary which causes secretion and storage of hormones T3 and T4 within the thyroid gland

• b. T3 and T4 inhibit TRH and TSH secretion in a negative

feedback pattern.

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3. Adrenocorticotrophic Hormone (ACTH)• a. CRH (corticotropin releasing hormone) from

hypothalamus causes release of ACTH from anterior pituitary

• b. ACTH causes cortisol secretion from the adrenal cortex (a glucocorticoid from the zona fasciculata)

• c. Causes aldosterone secretion from the adrenal cortex (a mineralocorticoid from the zona glomerulosa)

• d. If adrenal cortex is diseased and malfunctional, ACTH levels rise and

• e. Binds directly to melanocytes of the skin; causes increase in production of melanin.

• f. ACTH, lipotropins, B endorphins and MSH are manufactured from the same precursor

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4. Melanocyte Stimulating Hormone, Endorphins, and Lipotropins

• a. ACTH, MSH, endorphins and lipotropins all derived from the same large precursor molecule when stimulated by CRH

• b. MSH causes melanocytes to produce more melanin

• -plays a role in appetite

• -sexual behavior??

• c. Endorphins act as an analgesic; produced during times of stress.

• d. Lipotropins cause adipose cells to catabolize fat, lipolysis

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5. LH, FSH, Prolactin

• a. Gonadotropins: glycoprotein hormones that promote growth and function of the gonads

• b. LH and FSH– Both hormones regulate production of gametes and

reproductive hormones• Testosterone in males• Estrogen and progesterone in females

• c. GnRH from hypothalamus stimulates LH and FSH secretion• d. Prolactin: role in milk production

– Regulation of secretion: prolactin-releasing hormone (PRH) and prolactin-inhibiting hormones (PIH)

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IV. Thyroid Gland

• A. One of largest endocrine glands;

• 1. Highly vascular.• 2. appears dark red• 3. Iodine enters follicular

cells by active transport.• 4. low levels of iodine

thryroid hypertrophies called goiter

• B. Composed of follicles: • 1. follicular cells surrounding

thyroglobulin/thyroid hormone• 2. Parafollicular cells:

between follicles secrete calcitonin

• 3. calcitonin reduces blood calcium levels by stimulating activity of osteoblasts in bone

C. Thyroid hormones• 1. two major iodine based hormones produced- triodothyronine (T3) and

thyroxine (T4)

• 2. more thyroxine is produced than the T3 which is physiologically more active

• 3. these hormones are carried in the blood connected to globulin molecules which protects them from breakdown-gives them a very long half life

• 4. a lot of these hormones are stored in the thyroid gland which also helps to maintain very stable levels of these two hormones in the blood

• 5. when thyroid function is being measured by blood work, it is the TSH which is measured

• 6. it is a more direct barometer of thyroid activity

• 7. these two hormones elevate metabolic rate

• 8. Increase rate of glucose, fat, protein metabolism in many tissues thus increasing body temperature

• 9. Normal growth of many tissues dependent on presence of thyroid hormones

• 10. hypothyroidism vs. hyperthyroidism 18-21

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D. Regulation of Calcitonin Secretion• 1. Produced by parafollicular

cells• 2. Secretion triggered by high

Ca2+ concentration in blood; acts to decrease Ca2+ concentration

• 3. Primary target tissue: bone. Decreases osteoclast activity, lengthens life span of osteoblasts.

• 4. calcitonin concentrations decrease with age more in females than males

• 5. postmenopausal women and calcitonin nasal sprays

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V. Parathyroid Glands• 1. Embedded in thyroid• 2. Historical surgery story• 3. Two glands on each side • 4. Secrete PTH: target tissues are bone,

kidneys and intestines.– Increases blood calcium and phosphate

levels– Stimulates osteoclasts– Promotes calcium reabsorption by

kidneys and PO4 excretion because rise of both causes bone deposition in wrong amounts

– Increases synthesis of vitamin D which, in turn, increases absorption of Ca and PO4 by intestines. Net loss of PO4 under influence of PTH.

• 5. Regulation depends on calcium levels.• 6. inactive parathormone-hypocalcemia-

open voltage-gated sodium ion channels

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VI. Adrenal Glands A. Anatomy

• 1. Near superior poles of kidneys; retroperitoneal

• 2. Inner medulla; outer cortex

• 3. Medulla: formed from neural crest; sympathetic. Secretes epinephrine and norepinephrine

• 4. Cortex: three zones from superficial to deep– Zona glomerulosa– Zona fasciculata– Zona reticularis

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B. Hormones of the Adrenal Medulla• 1. Secretory products are neuropeptides: epinephrine and

norepinephrine• 2. Combine with adrenergic membrane-bound receptors• 3. Secretion of hormones prepares body for physical activity• 4. Effects are short-lived; hormones rapidly metabolized; half-life is

minutes • 5. Epinephrine

– Increases blood levels of glucose via glycogenolysis– Increases fat breakdown in adipose tissue– Causes dilation of blood vessels in skeletal muscles and cardiac

muscles.• 6. Epinephrine and norepinephrine increase heart rate and force of

contraction; cause blood vessels to constrict in skin, kidneys, gastrointestinal tract, and other viscera

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C. Hormones of Adrenal Cortex• 1. Mineralocorticoids: Zona glomerulosa

– Aldosterone produced in greatest amounts. Increases rate of sodium reabsorption by kidneys increasing sodium blood levels

– Stimulus for production is low blood pressure

– Increases water reabsorption and therefore blood volume

• 2. Glucocorticoids: Zona fasciculata– Cortisol is major hormone. Increases fat

and protein breakdown, increases glucose synthesis(gluconeogenesis), promotes the increased use of fats and proteins by muscles, decreases inflammatory response

• 3. Androgens: Zona reticularis– Weak androgens secreted then

converted to testosterone by peripheral tissues. Stimulate pubic and axillary hair growth and sexual drive in females

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VII. Pancreas

• A. Located along small intestine and stomach; retroperitoneal

• B. Exocrine gland– Produces pancreatic digestive juices

• C. Endocrine gland– Consists of pancreatic islets– Composed of

• Alpha cells; secrete glucagon• Beta cells; secrete insulin• Delta cells; secrete somatostatin

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D. Histology of the Pancreatic Islets

E. Effects of insulin

• 1. direct effect is to reduce blood glucose

• 2. acts on a number of different target tissues

• 3. muscle-causes uptake of glucose to promote glycogenesis

• 4. adipose tissue-lipogenesis

• 5. liver-glycogenesis and increased use of glucose to drive ATP production

• 6. also acts to increase uptake of amino acids and stimulates protein synthesis

• 7. insulin is a protein hormone-therefore binds to a membrane receptor

• 8. increases the number of glucose carrier molecules

• 9. low levels of insulin lead to a very rapid increase of blood glucose

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G. Effects of glucagon• 1. Affects of glucagon are antagonistic to insulin

• 2. acts to increase blood glucose levels

• 3. secreted from pancreas alpha cells and enters hepatic portal circulation

• 4. travels directly to liver where it stimulates the liver to break down glycogen stores-glycogenolysis

• 5. also stimulates glucose sparing and encourages the use of alternate fuels for energy source

• 6. important to maintain adequate glucose levels as the nervous system is an obligate consumer of glucose

• 7. promotes gluconeogenesis in liver from amino acids

• 8. glucagon does not affect many other target tissues as the liver breaks down glucagon before it can pass on to other organs

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H. Diabetes mellitus• 1. normal range fasting blood sugar is 70-100 mg./deciliter

• 2. low insulin activity raises this level drastically-diabetes usually confirmed with reading of 200mg/deciliter

• 3. two types of diabetes

• a. Type I

• -individuals don’t produce sufficient insulin

• -usually children

• - approximately 10% of diabetic population

• -insulin dependent

• b. Type II

• -individuals don’t respond to insulin normally produced

• -faulty receptors or enzymes produced after insulin combines

• -majority

• -adult onset

• -meds taken to increase insulin production

• -exercise 18-34

4. Symptoms of diabetes type I

• a. Frequent urination –due to high osmotic pressures of glucose in urine

• b. Unusual thirst –replacing fluid loss in the high urine production

• c. Extreme hunger-satiety center in hypothalamus insulin dependent

• d. Unusual weight loss- low fuel source availability

• e. Extreme fatigue and irritability

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Insulin and Glucagon

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18.7 Hormonal Regulation of Nutrient Utilization

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18.7 Hormonal Regulation of Nutrient Utilization

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Regulation of Blood Nutrient Levels During Exercise

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VIII. Hormones of the Reproductive System Previously Discussed

IX. Hormones of the Pineal GlandA. Main hormone is melatonin

B. Melatonin inhibits GnRH and therefore inhibits reproductive function

C. Also may help sleep cycles by stimulating sleep

D. Some animals pineal regulates breeding cycles

1. light inhibits pineal secretion of melatonin

2. dark stimulates pineal’s secretion of melatonin

3. animals that breed in spring experience increased day length and decreased melatonin secretion-reproductive structures hypertrophy

4. repurcussion-

-use as a sleep aid

-earlier onset of puberty

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X. Thymus gland

• A. Location-superior mediastinum

• B. Produces hormone thymosin

• C. Activity-maturation and development of the immune system

• D. Culinary-sweet breads