Chapter 13 The Endocrine System Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. General Function Integrate body systems (maintain homeostasis) Glands = effectors stimulated by the motor impulses from the autonomic nervous system Copyright 2010, John Wiley & Sons, Inc.

Comparison: Nervous v. Endocrine Nervous system Neurons  neurotransmitters, neuromuscular or neuroglandular Effectors = neurons, muscles, glands Rapid responses Endocrine system Releases hormones interstitial fluid or blood  general circulation Effectors: any type of body cell - widespread effects on metabolism Slower, longer-lasting response Copyright 2010, John Wiley & Sons, Inc.

Comparison of Nervous and Endocrine Systems Copyright 2010, John Wiley & Sons, Inc. 13-4

Comparison: Endocrine v. Exocrine Endocrine glands Secretions interstitial fluid then  bloodstream Stay in the body: endo- Examples: all hormones (growth hormone, insulin, adrenalin, estrogen, testosterone) Exocrine glands Secrete substances - ducts Ultimately exit the body (exo-) Examples: mucus, saliva and other digestive secretions, sweat, tears Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc.

Endocrine Cells that Make Hormones Cells In Endocrine glands Pituitary, thyroid, parathyroid, adrenal, pineal Cells within organs - produce hormones but also have other functions Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, adipose tissue, and placenta Copyright 2010, John Wiley & Sons, Inc. Copyright 2009, John Wiley & Sons, Inc.

Location of Endocrine Glands Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormone Action Hormones are carried in blood stream Target cells can be affected by hormones 1000’s of receptors specific for a particular hormone. Response determined by responding cell: Cell may have > 1 type of receptor, can respond to more than one hormone Copyright 2010, John Wiley & Sons, Inc.

General Hormone Characteristics Needed in very small amounts (potent) Regulated by negative-feedback mechanisms Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hormone Chemistry Lipid-soluble (Steroid) testosterone, estrogens Passes easily through target membrane Water-soluble (Non-steroid) Amino acid derivatives (epinephrine, norepinephrine) Peptides: antidiuretic hormone (ADH), oxytocin Proteins: insulin and growth hormone Requires a receptor on the target membrane Copyright 2010, John Wiley & Sons, Inc.

Structural Formula of Hormones Copyright 2010, John Wiley & Sons, Inc. 13-6

Lipid-Soluble (Steroid) Action Hormone/blood stream  Diffuses through interstitial fluid  through cell membrane Binds to receptor inside cell and activate it Alters gene expression New mRNA  protein synthesis New proteins alter cell activity Copyright 2010, John Wiley & Sons, Inc.

Actions of Steroid Hormones Copyright 2010, John Wiley & Sons, Inc. 13-8

Water-Soluble (Non-Steroid) Action Hormone (first messenger) diffuses from blood and binds to receptor in plasma membrane Either increasing or decreasing a second messenger Cyclic AMP is a common one Second messenger  activation of several proteins (enzymes) Activated proteins produce physiological responses Copyright 2010, John Wiley & Sons, Inc.

Actions of Non-Steroid Hormones Copyright 2010, John Wiley & Sons, Inc. 13-9

Control of Hormonal Secretions Release occurs in short bursts Generally one or any combination of 3 types of control Hormonal control Example: ACTH from pituitary stimulates release of cortisol from adrenal cortex Nervous control Example: adrenal medulla release of epinephrine Hormonal control by chemical changes in blood levels Example: blood Ca2+ affects parathyroid hormone Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Endocrine Glands Paracrine secretions act locally do not travel through blood Autocrine secretions affect only the secreting cell Copyright 2010, John Wiley & Sons, Inc. 13-3

Major Endocrine Glands Copyright 2010, John Wiley & Sons, Inc. 13-13

Hypothalamus and Pituitary Serve as major link between nervous and endocrine systems Hypothalamic cells make Many releasing and inhibiting hormones Two hormones (oxytocin and ADH) that are stored and released from the posterior pituitary Anterior pituitary makes 7 hormones Regulate growth, development, metabolism and homeostasis Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pituitary Located in depression in sphenoid bone just inferior to the brain Pituitary is attached to hypothalamus by stalk (infundibulum) Pituitary has 2 lobes: Anterior (Adenohypophysis) Posterior (neurohypophysis) Copyright 2010, John Wiley & Sons, Inc.

Pituitary Gland Control Copyright 2010, John Wiley & Sons, Inc. 13-15

Seven Anterior Pituitary Hormones Human growth hormone (hGH) Thyroid-stimulating hormone (TSH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin Adrenocorticotropic hormone (ACTH) Melanocyte-stimulating hormone (MSH) Copyright 2010, John Wiley & Sons, Inc.

1. Human Growth Hormone (hGH) hGH promotes synthesis of insulinlike growth factors (IGFs) = somatomedins Secreted by liver, muscle, cartilage, bone cells Regulation By hypothalamic hormones Growth hormone-releasing hormone (GHRH) Growth hormone-inhibiting Hormone (GHIH ) By blood glucose levels Low blood glucose levels  release of GHRH Copyright 2010, John Wiley & Sons, Inc.

1. Human Growth Hormone (hGH) Actions of hGH Stimulates protein synthesis Maintains muscle and bone mass Promotes healing of injuries, tissue repair Makes “fuel” (ATP) available for growth Causes fat breakdown and release of fatty acids into blood Breaks down liver glycogen  releases glucose into blood Copyright 2010, John Wiley & Sons, Inc.

Growth Hormone Imbalances Pituitary Dwarfism – hyposecretion of GH during growth years Slow bone growth Treatment = oral GH therapy Gigantism – hypersecretion of GH during growth years Abnormal increase in the length of long bones Acromegaly = hypersecretion of GH during adulthood Bones of hands, feet, cheeks, and jaw thicken Soft tissues also grow Copyright 2010, John Wiley & Sons, Inc.

2. Thyroid-Stimulating Hormone (TSH) Stimulates the formation and secretion of thyroid hormones (T3, T4) by thyroid gland Regulation (negative feedback) Low blood levels of T3, T4  Hypothalamus  Thyrotropin-releasing hormone (TRH)  TRH stimulates release of TSH TSH stimulates thyroid production of T3, T4 Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3, 4. Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) In females FSH starts follicle development  Starts egg production Starts estrogen production from follicle cells LH stimulates formation of corpus luteum Completion of egg and its ovulation Secretion of progesterone + estrogen In males FSH  sperm production in testes LH  release of testosterone from testes Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 3, 4. Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) Regulation (negative feedback) Gonadotrophin-releasing hormone (GnRH) from hypothalamus  release of FSH or LH from anterior pituitary High levels of Estrogen, Progesterone, and Testosterone suppress production of GnRH Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. 5. Prolactin (PRL) Initiates and maintains milk production Ejection of milk depends on oxytocin Regulation Prolactin inhibiting hormone (PIH) suppresses prolactin release High levels of estrogens  Prolactin Releasing Hormone (PRH)  prolactin release Unknown function in males Hypersecretion  erectile dysfunction Copyright 2010, John Wiley & Sons, Inc.

6. Adrenocorticotropic Hormone (ACTH) Controls production and secretion of glucocorticoids from adrenal cortex Regulation (negative feedback) Corticotrophin releasing hormone (CRH) from hypothalamus stimulates secretion of ACTH Stress-related stimuli can also stimulate ACTH release Glucocorticoids inhibit CRH and ACTH release Copyright 2010, John Wiley & Sons, Inc.

7. Melanocyte Stimulating Hormone (MSH) Small amounts in bloodstream Excess amounts causes skin darkening Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Hypothalmic Hormones Copyright 2010, John Wiley & Sons, Inc. 13-16

Copyright 2010, John Wiley & Sons, Inc. Posterior Pituitary Hormones from hypothalamus Create nerve impulses  release of hormones from posterior pituitary Two hormones released Oxytocin causes “letdown” of milk from glands to ducts Smooth muscle contraction of uterus Some sexual pleasure during sexual activity Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Posterior Pituitary Antidiuretic Hormone (ADH) = vasopressin Causes kidneys to retain more water Causes vasoconstriction  increases blood pressure Dehydration, pain, stress  increase ADH secretion Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Posterior Pituitary Copyright 2010, John Wiley & Sons, Inc.

Pituitary Gland Blood Supply Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Thyroid Gland Location: inferior to larynx: two lobes Structure and function Follicular cells produce hormones and store them in follicles Thyroxin (T4) Triiodothyronine (T3) Parafollicular cells (C-cells) produce Calcitonin (CT) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Thyroid Gland Copyright 2010, John Wiley & Sons, Inc. 13-21

Copyright 2010, John Wiley & Sons, Inc. Thyroid Gland Copyright 2010, John Wiley & Sons, Inc.

Thyroid Hormones: Actions T4 and T3 increase basal metabolic rate, protein synthesis, and growth Blood level controlled by TRH and TSH Increase in the body’s demand for ATP can also raise blood levels Calcitonin inhibits osteoclasts Effects: Strengthens bones Decreases blood Ca2+ Control based on Ca2+ blood levels Copyright 2010, John Wiley & Sons, Inc.

Thyroid Gland Disorders General Hyperthyroidism high metabolic rate hyperactivity weight loss protruding eyes Cretinism hypothyroidism in infants leads to small stature and mental retardation Prevention with new born testing Treatment – oral thyroid therapy Copyright 2010, John Wiley & Sons, Inc. 13-23

Thyroid Gland Disorders Myxedema Adult hypothyroidism Low metabolic rate Sluggishness Weight gain, muscle weakness Oral thyroid hormones reduce symptoms Simple Goiter Deficiency of iodine Leads to deficiency of thyroid hormones Gland enlarges but still functions normally Grave’s disease - autoimmune Overstimulation of gland by antibodies Hyperthyroidism Enlarged thyroid Bulging of the eyes Copyright 2010, John Wiley & Sons, Inc. 13-24

Copyright 2010, John Wiley & Sons, Inc. Parathyroid Glands Small round masses posterior of thyroid Parathyroid hormone (PTH) Increases blood Ca2+ in 3 ways Increases number and activity of osteoclasts Slows loss of Ca2+ and Mg2+ in urine Promotes production of calcitriol (vitamin D)  increases rate of Ca2+, Mg2+ and HPO42- absorption in GI tract  increase blood Ca2+ Decreases blood HPO42- by increasing loss of HPO42- in urine Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Parathyroid Glands Copyright 2010, John Wiley & Sons, Inc. 13-27

Copyright 2010, John Wiley & Sons, Inc. Parathyroid Glands Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Calcium Regulation 1 High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. Low level of Ca2+ in blood stimulates parathyroid gland chief cells to release more PTH. CALCITONIN inhibits osteoclasts, thus decreasing blood Ca2+ level. PARATHYROID HORMONE (PTH) promotes release of Ca2+ from bone extracellular matrix into blood and slows loss of Ca2+ in urine, thus increasing blood Ca2+ level. 3 4 2 1 High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. Low level of Ca2+ in blood stimulates parathyroid gland chief cells to release more PTH. CALCITONIN inhibits osteoclasts, thus decreasing blood Ca2+ level. 3 2 1 High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. 1 CALCITRIOL stimulates increased absorption of Ca2+ from foods, which increases blood Ca2+ level. PTH also stimulates the kidneys to release CALCITRIOL. High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. Low level of Ca2+ in blood stimulates parathyroid gland chief cells to release more PTH. CALCITONIN inhibits osteoclasts, thus decreasing blood Ca2+ level. PARATHYROID HORMONE (PTH) promotes release of Ca2+ from bone extracellular matrix into blood and slows loss of Ca2+ in urine, thus increasing blood Ca2+ level. 3 4 2 5 6 1 PTH also stimulates the kidneys to release CALCITRIOL. High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. Low level of Ca2+ in blood stimulates parathyroid gland chief cells to release more PTH. CALCITONIN inhibits osteoclasts, thus decreasing blood Ca2+ level. PARATHYROID HORMONE (PTH) promotes release of Ca2+ from bone extracellular matrix into blood and slows loss of Ca2+ in urine, thus increasing blood Ca2+ level. 3 4 2 5 1 High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT. CALCITONIN inhibits osteoclasts, thus decreasing blood Ca2+ level. 2 Copyright 2010, John Wiley & Sons, Inc.

Parathyroid Gland Disorders Hyperparathyroidism Caused by tumor Fatigue Muscular weakness Altered mental functions Bone weakening Hypoparathyroidism Caused by injury or removal of gland Muscle cramps Seizures Low blood calcium levels Copyright 2010, John Wiley & Sons, Inc. 13-28

Copyright 2010, John Wiley & Sons, Inc. Adrenal Glands Location: on top of kidneys Two separate gland structures Adrenal cortex: 3 zones make steroids Outer zone  mineralocorticoids Middle zone  glucocorticoids Inner Zone  androgens Adrenal medulla: produces epinephrine (adrenalin) and norepinephrine Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Adrenal Glands Copyright 2010, John Wiley & Sons, Inc. 13-29

Copyright 2010, John Wiley & Sons, Inc. Mineralocorticoids Aldosterone - major form Action Stimulates Na+ and H20 reabsorption from urine Stimulates excretion of K+ into urine Part of renin-angiotensin-aldosterone pathway Decreased BP  release of renin from kidney Renin causes angiotensinogen  angiotensin I In lungs angiotensin converting enzyme (ACE) causes angiotensin I  angiotensin II Angiotensin II stimulates aldosterone release Copyright 2010, John Wiley & Sons, Inc.

Adrenal Cortex Hormones Copyright 2010, John Wiley & Sons, Inc. 13-31

Copyright 2010, John Wiley & Sons, Inc. Mineralocorticoids Copyright 2010, John Wiley & Sons, Inc.

Glucocorticoid (Cortisol) Actions Increases rate of protein breakdown Stimulates liver formation of glucose Breaks down triglycerides in adipose Anti-inflammatory effects Inhibit white blood cells Depresses immune system Regulated by negative feedback: CRH and ACTH Copyright 2010, John Wiley & Sons, Inc.

Adrenal Cortex Hormones Copyright 2010, John Wiley & Sons, Inc. 13-32

Copyright 2010, John Wiley & Sons, Inc. Androgens Small amount in both females and males Puberty Stimulate axillary and pubic hair growth Contribute to adolescent growth spurt In females Contribute to libido Are converted to estrogens by other body tissues Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Adrenal Medulla Inner portion of adrenal glands Part of sympathetic nervous system Releases epinephrine and norepinephrine Increases heart rate and blood pressure Increases blood glucose, dilates airways Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pancreas Flattened organ in curve of duodenum Mostly exocrine - secretes digestive enzymes Endocrine - Islets of Langerhans Alpha cells  glucagon Beta cells  insulin Delta cells  somatostatin Requlate carbohydrates Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pancreas Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pancreas Copyright 2010, John Wiley & Sons, Inc. 13-34

Copyright 2010, John Wiley & Sons, Inc. Pancreas Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pancreas Copyright 2010, John Wiley & Sons, Inc.

Actions of Insulin and Glucagon Low blood glucose  glucagon release stimulates liver to release glucose High glucose levels  insulin release increases glucose  into skeletal muscle and adipose cells promotes amino acid uptake, protein synthesis, and lipid storage ANS also modulates hormone release Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Insulin acts on various body cells to: • accelerate facilitated diffusion of glucose into cells • speed conversion of glucose into glycogen (glycogenesis) • increase uptake of amino acids and increase protein synthesis • speed synthesis of fatty acids (lipogenesis) • slow glycogenolysis • slow gluconeogenesis Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal If blood glucose continues to rise, hyperglycemia inhibits release of glucagon Low blood glucose (hypoglycemia) stimulates alpha cells to secrete High blood glucose (hyperglycemia) stimulates beta cells to secrete INSULIN GLUCAGON 1 5 2 3 4 6 Insulin acts on various body cells to: • accelerate facilitated diffusion of glucose into cells • speed conversion of glucose into glycogen (glycogenesis) • increase uptake of amino acids and increase protein synthesis • speed synthesis of fatty acids (lipogenesis) • slow glycogenolysis • slow gluconeogenesis Blood glucose level falls Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal If blood glucose continues to rise, hyperglycemia inhibits release of glucagon Low blood glucose (hypoglycemia) stimulates alpha cells to secrete High blood glucose (hyperglycemia) stimulates beta cells to secrete INSULIN GLUCAGON 1 5 2 3 4 6 7 Insulin acts on various body cells to: • accelerate facilitated diffusion of glucose into cells • speed conversion of glucose into glycogen (glycogenesis) • increase uptake of amino acids and increase protein synthesis • speed synthesis of fatty acids (lipogenesis) • slow glycogenolysis • slow gluconeogenesis If blood glucose continues to fall, hypoglycemia inhibits release of insulin Blood glucose level falls Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal If blood glucose continues to rise, hyperglycemia inhibits release of glucagon Low blood glucose (hypoglycemia) stimulates alpha cells to secrete High blood glucose (hyperglycemia) stimulates beta cells to secrete INSULIN GLUCAGON 1 5 2 3 4 6 7 8 Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal If blood glucose continues to rise, hyperglycemia inhibits release of glucagon Low blood glucose (hypoglycemia) stimulates alpha cells to secrete High blood glucose (hyperglycemia) stimulates beta cells to secrete GLUCAGON 1 5 2 3 4 INSULIN Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal If blood glucose continues to rise, hyperglycemia inhibits release of glucagon Low blood glucose (hypoglycemia) stimulates alpha cells to secrete GLUCAGON 1 2 3 4 Low blood glucose (hypoglycemia) stimulates alpha cells to secrete 1 GLUCAGON Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Low blood glucose (hypoglycemia) stimulates alpha cells to secrete GLUCAGON 1 2 Glucagon acts on hepatocytes (liver cells) to: • convert glycogen into glucose (glycogenolysis) • form glucose from lactic acid and certain amino acids (gluconeogenesis) Glucose released by hepatocytes raises blood glucose level to normal Low blood glucose (hypoglycemia) stimulates alpha cells to secrete GLUCAGON 1 2 3 Glucose/ Insulin Regulation Copyright 2010, John Wiley & Sons, Inc.

Homeostatic Imbalances Diabetes Mellitus - Type I absolute insulin deficiency Patients < 20 years Autoimmune disorder: Beta cells destroyed Hyperglycemia results Cells can’t use glucose fat is broken down releases ketone bodies (ketoacidosis) lowers blood pH causing death Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Treatments Artificial pancreas - releases insulin  falling glucose levels Transplant of pancreas or Beta cells Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Type II Patients > 40 years Overweight, hypertension Problem (usually) receptors on target cells Controlled diet, exercise, and weight loss Copyright 2010, John Wiley & Sons, Inc.

Gonads: Ovaries and Testes Produce gametes: sperm and oocytes Produce hormones Testosterone in males Estrogen and progesterone in females Inhibin that inhibits FSH release Relaxin during pregnancy: facilitates birth Regulated by GnRH from hypothalamus FSH + LH from anterior pituitary Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Pineal Gland Small gland attached to roof of third ventricle (brain) Produces melatonin Sets body’s biological clock More released in darkness, less in sunlight Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Other Hormones Thymus: thymosin GI tract Gastrin Glucose-dependent insulinotropic peptide (GIP) Secretin Cholecystokinin (CCK) Kidney: erythropoietin (EPO) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Other Hormones Heart: atrial natriuretic peptide (ANP) Adipose tissue: leptin Placenta: human chorionic gonadotropin (hCG) Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Other Hormones Prostaglandins (PG) and leukotrienes (LT) Derived from fatty acids Act locally in most tissues and released from most body cells LTs stimulate white blood cells and mediate inflammation PGs affect many visceral functions, modulate inflammation, promote fever, and intensify pain Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Stress Physical stress Injury – accidental Exercise – purposeful Psychological stress Emotions – automatic Overloaded – can be self induced Copyright 2010, John Wiley & Sons, Inc. 13-40

Copyright 2010, John Wiley & Sons, Inc. Responses to Stress General Stress Syndrome hypothalamic response to stress Activates adrenal medulla (sympathetic NS) – short term Activates adrenal cortex (cortisol) - long term Basic goal is to increase available nutrients to fight off stress Copyright 2010, John Wiley & Sons, Inc.

Copyright 2010, John Wiley & Sons, Inc. Responses to Stress Copyright 2010, John Wiley & Sons, Inc. 13-41

Copyright 2010, John Wiley & Sons, Inc. Aging Some decrease in function with aging endocrine glands shrink Loss of negative feedback sensitivity GH levels even out, muscular strength decreases changes in melatonin secretion affect the body clock PTH levels rise  loss of bone mass Slower release of insulin Thymus declines after puberty Ovarian response to gonadotropins stops Slow decline in testosterone production Copyright 2010, John Wiley & Sons, Inc.