The Endocrine System. I. Overview of the Endocrine System. II. Three Families of Hormones. III. Hormone Receptors. IV. Classes of Hormone Receptor

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1 The Endocrine System I. Overview of the Endocrine System A. Regulates long term metabolic processes B. Releases hormones from endocrine cells 1. Hormones are chemicals 2. Alter metabolism of cells 3. Release regulated by negative feedback 4. Act on target cells II. Three Families of Hormones A. Amino acid derivatives (epinephrine, thyroid hormones) B. Peptides and proteins 1. Chains of amino acids 2. Insulin, ADH C. Lipid derivatives 1. Steroids (testosterone) 2. Eicosanoids (prostaglandins) III. Hormone Receptors A. Receptors are hormone binding proteins B. Triggers action on a target cell IV. Classes of Hormone Receptor A. Extracellular Receptors 1. Located in cell 2. Targeted by a) Amino acid derivatives b) Peptides c) Eicosanoids 3. Operates through a second messenger such as cyclic-amp Membrane G protein (inactive) 1

2 Membrane Hormone complex First messengers (E, NE, peptide hormones, and eicosanoids) Membrane Hormone complex First messengers (E, NE, peptide hormones, and eicosanoids) G protein (inactive) G protein G protein (inactive) (activated) Activates adenylate cyclase Membrane Hormone complex First messengers (E, NE, peptide hormones, and eicosanoids) Membrane Hormone complex First messengers (E, NE, peptide hormones, and eicosanoids) G protein G protein (inactive) (activated) G protein G protein (inactive) (activated) ATP Activates adenylate cyclase Acts as camp second messenger ATP Activates adenylate cyclase Acts as camp second messenger Activates kinase Activates kinase Alterations in enzyme activity; opens ion channels Membrane Hormone complex G protein G protein (inactive) (activated) First messengers (E, NE, peptide hormones, and eicosanoids) Activates adenylate cyclase ATP Acts as camp second messenger Activates kinase Alterations in enzyme activity; opens ion channels IV. Classes of Hormone Receptor B. Intracellular Receptors 1. Located in cytoplasm or nucleus 2. Targeted by steroid and thyroid hormones 3. Operates through changes in gene expression 4. Thyroid hormones also act on mitochondria TARGET CELL RESPONSE 2

3 V. Hormone Secretion and Distribution VI. Control of Endocrine Secretion A. Hormones directly enter capillaries 1. Most hormones travel free in solution 2. Steroid, thyroid hormones bind to blood proteins for transport B. Hormones are inactivated by 1. Binding to cell s 2. Removal by liver, kidney cells 3. Breakdown by extracellular enzymes A. Humoral Stimuli: Ca 2+ controls parathyroid hormone and calcitonin release B. Hormonal Stimuli: thyroid stimulating hormone triggers thyroid hormone release C. Neural Stimuli: epinephrine release from adrenals VII. The Hypothalamus and Endocrine Control A. Secretes hormones directly B. Secretes regulatory hormones to control pituitary gland C. Autonomic centers exert direct control of adrenal medullae VIII. The Pituitary Gland A. Also called the hypophysis B. Releases nine important hormones C. Two lobes VIII. The Pituitary Gland 1. Anterior Pituitary a) Thyroid-Stimulating Hormone (TSH) Triggers thyroid hormone release b) Adrenocorticotropic Hormone (ACTH) Stimulates glucocorticoid release from adrenal gland VIII. The Pituitary Gland c) Follicle-Stimulating Hormone (FSH) Stimulates estrogen secretion, egg production (females), sperm production (males) d) Luteinizing Hormone (LH) Triggers ovulation, progestin production (females), androgen production (males) e) Prolactin (PRL) Stimulates mammary gland development and milk secretion f) Growth hormone (hgh) Stimulates cell growth g) Melanocyte Stimulating Hormone (MSH) 3

4 VIII. The Pituitary Gland 2. Posterior Pituitary Hormones a) Antidiuretic Hormone (ADH) 1) Reduces water loss in the urine 2) Increases thirst b) Oxytocin 1) Stimulates uterine contraction, milk delivery 2) Stimulates prostate gland smooth muscle VIII. The Pituitary Gland Pituitary Hormones and Their Targets IX. The Thyroid Gland A. Lies near thyroid cartilage of larynx B. Has a rich blood supply C. Consists of two lobes connected by the isthmus IX. The Thyroid Gland D. Thyroid Follicles 1. Produce and store colloid (needs iodine) 2. Two forms, thyroxine (T 4 ) and triiodothyronine (T 3 ) a) Increases metabolism and heat production (calorigenic effect) in most cells b) Required for normal development IX. The Thyroid Gland E. C s 1. Scattered outside of follicle epithelium 2. Also called parafollicular cells 3. Secrete calcitonin a) Lowers blood Ca 2+ b) Inhibits osteoclasts of bone c) Increases urinary calcium loss 4. Triggered by high blood Ca 2+ level X. The Parathyroid Glands A. Four glands on thyroid posterior B. Chief cells produce parathyroid hormone C. Low blood Ca 2+ triggers secretion D. PTH raises blood Ca PTH speeds bone breakdown by osteoclasts 2. Increases dietary absorption 3. Slows loss in kidney 4

5 Thyroid gland produces calcitonin Rising calcium in blood Rising calcium in blood Thyroid gland produces calcitonin Increased excretion of calcium in kidneys Thyroid gland produces calcitonin Increased excretion of calcium in kidneys Calcium deposition in bone (inhibition of osteoclasts) Blood calcium decline Rising calcium in blood Rising calcium in blood Thyroid gland produces calcitonin Increased excretion of calcium in kidneys Calcium deposition in bone (inhibition of osteoclasts) Blood calcium decline in blood Rising calcium in blood RESTORED 5

6 in blood in blood Release of stored calcium from bone (stimulation of osteoclasts, inhibition of osteoblasts) Parathyroid glands parathyroid hormone (PTH) Parathyroid glands parathyroid hormone (PTH) in blood Release of stored calcium from bone (stimulation of osteoclasts, inhibition of osteoblasts) in blood Release of stored calcium from bone (stimulation of osteoclasts, inhibition of osteoblasts) Parathyroid glands parathyroid hormone (PTH) Enhanced reabsorption of calcium in kidneys Parathyroid glands parathyroid hormone (PTH) Enhanced reabsorption of calcium in kidneys Blood calcium increase Stimulation of calcitriol production at kidneys; enhanced Ca 2+, PO 4 3- absorption by digestive tract in blood Release of stored calcium from bone (stimulation of osteoclasts, inhibition of osteoblasts) RESTORED XI. The Adrenal Glands A. Lie along superior border of each kidney B. Surrounded by fibrous capsule C. Made of two parts Parathyroid glands parathyroid hormone (PTH) Enhanced reabsorption of calcium in kidneys Blood calcium increase Stimulation of calcitriol production at kidneys; enhanced Ca 2+, PO 4 3- absorption by digestive tract 6

7 XI. The Adrenal Glands 1. Adrenal Cortex (corticosteroids) a) Glucocorticoids (cortisol) 1) Stimulated by ACTH 2) Affect glucose metabolism b) Mineralocorticoids (aldosterone) 1) Stimulated by angiotensin II 2) Restricts loss of water, Na + in urine, sweat, digestive tract, saliva c) Androgens (male hormone) XI. The Adrenal Glands 2. Adrenal Medulla a) Nerves stimulate hormone secretion b) Produces two related hormones 1) Epinephrine (adrenaline) 2) Norepinephrine (noradrenaline) c) Increases heart rate and force, releases glucose, fatty acids into blood, opens airways XII. The Pineal Gland A. Located deep within the brain B. Synthesizes melatonin 1. Establishes daily wake-sleep cycle 2. Inhibits reproductive function 3. Protects neural tissue from free radicals XIII. The Pancreas A. Exocrine and endocrine cells B. Endocrine cells organized into islets of Langerhans C. Islet cells and glucagon 1. Insulin produced by beta cells 2. Glucagon produced by alpha cells D. Exocrine cells enzyme-rich digestive fluid XIII. The Pancreas E. Actions of Insulin and Glucagon 1. Insulin a) Lowers blood glucose b) Increases glucose uptake, storage, and use by target cells c) Targets liver, muscle, fat cells 2. Glucagon a) Raises blood glucose concentration b) Increases glycogen breakdown and glucose synthesis c) Targets liver cells glucose 7

8 glucose glucose glucose utilization and ATP generation glucose utilization and ATP generation Increased conversion of glucose to glycogen glucose glucose glucose utilization and ATP generation glucose utilization and ATP generation Increased conversion of glucose to glycogen Increased conversion of glucose to glycogen Blood glucose concentration declines Increased amino acid absorption and protein synthesis Increased amino acid absorption and protein synthesis Increased fat synthesis (adipose tissue) glucose glucose 8

9 glucose utilization and ATP generation Increased conversion of glucose to glycogen Blood glucose concentration declines glucose Increased amino acid absorption and protein synthesis Increased fat synthesis (adipose tissue) glucose RESTORED glucose glucose of glycogen to glucose Alpha cells glucagon Alpha cells glucagon glucose glucose of glycogen to glucose of glycogen to glucose Alpha cells glucagon of fats to fatty acids (adipose tissue) Alpha cells glucagon of fats to fatty acids (adipose tissue) Blood glucose concentration rises Increased synthesis and release of glucose (liver) 9

10 glucose of glycogen to glucose RESTORED XIV. Endocrine Functions of Other Organs A. Intestines- Secretes hormones to control digestion B. Kidneys (3 hormones) 1. Calcitriol Stimulates calcium and phosphate absorption in intestine 2. Erythropoietin (EPO) Stimulates red blood cell production by bone marrow 3. Renin Enzyme that leads to angiotensin II that triggers aldosterone from adrenal cortex Alpha cells glucagon of fats to fatty acids (adipose tissue) Blood glucose concentration rises Increased synthesis and release of glucose (liver) XIV. Endocrine Functions of Other Organs C. Heart- Secretes atrial natriuretic peptide (ANP) to lower blood volume or blood pressure D. Thymus- Secretes thymosins that control immune system defenses E. Adipose tissue (fat cells) 1. Secretes leptin to control appetite 2. Secretes resistin to reduce response XIV. Endocrine Functions of Other Organs F. Testis (male gonad) 1. Interstitial cells androgens (testosterone) 2. Sustentacular cells inhibin (anterior pituitary) G. Ovary (female gonad) 1. Follicle cells estrogens and inhibin 2. Corpus luteum cells estrogens and progesterone H. Placenta- Secretes several hormones in pregnancy XV. Hormones and Behavior A. Sex hormones 1. Testosterone fosters aggressiveness 2. Estrogen fosters sexual receptivity B. Thyroid hormones 1. Excess leads to nervousness, restlessness 2. Deficiency leads to sluggishness C. Antidiuretic hormone: Leads to feeling of thirst, water intake 10