Martini s Visual Anatomy and Physiology First Edition Martini Ober Chapter 16 - Endocrine System Lecture 16 1 Lecture Overview The Adrenal Glands The Pancreas Other Endocrine Tissues Stress and its effects Life-span changes 2 Location/Blood Supply of the Adrenal Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 3 1
Adrenal Glands Adrenal cortex and medulla are functionally distinct 4 Hormones of the Adrenal Medulla Epinephrine (80%) and Norepinephrine (20%) derived from amino acid tyrosine hormones of fight or flight are called catecholamines release controlled by sympathetic nervous system (neural control of hormone release) hormone releasing cells are considered equivalent to postganglionic sympathetic neurons increases heart rate and blood pressure dilates respiratory airways promotes glycogenolysis and gluconeogenesis activates reticular formation increases metabolic rates 5 Adrenal Cortex and its Hormones Yellowish appearance of cortex is due to stored lipids, especially cholesterol and various fatty acids Produces more than 25 steroid hormones Hormones of the Adrenal lcortex are Called adrenocortical steroids, or corticosteroids Carried in blood by transcortins Essential to life Affect cellular metabolism by determining the nature and concentration of cellular enzymes Not stored in cell 6 2
Adrenocortical Steroids - Aldosterone increases blood volume and pressure by promoting conservation of sodium ions and water (distal tubules of kidney) Activated by 1) the reninangiotensin system and by 2) changing concentrations of of Na + and K + Aldosterone is a mineralocorticoid Zona glomerulosa 7 Adrenocortical Steroids - Glucocorticoids Cortisol (hydrocortisone) a glucocorticoid protein synthesis, protein catabolism increases fatty acid release (glucose-sparing effect) stimulates gluconeogenesis controlled by CRH from hypothalamus and ACTH from Produced in the Zona Fasciculata Blood levels peak shortly after arising in morning Have antiinflammatory and anti-immune effects 8 Adrenocortical Steroids - Androgens Adrenal androgens (gonadocorticoids) supplement sex hormones from the gonads (release stimulated slightly by ACTH; inhibitory stimulus unknown). Mostly dehydroepiandrosterone (DHEA) may be converted to estrogen in the blood ( ) When secreted in normal amounts, neither adrenal androgens or estrogens affect sexual characteristics (may affect sex drive in ) Produced in the Zona Reticularis Tumors of this region can lead to androgenital syndrome (masculinization) 10 3
Endocrine Pancreas Figures from: Hole s Human A&P, 12 th edition, 2010 11 Cells of the Pancreatic Islets Alpha cells - Glucagon Betacells Insulin, amylin Delta cells Somatostatin (growth hormone-inhibiting o hormone, o GH-IH) Suppresses release of insulin and glucagon Slows rates of food absorption Fcells Pancreatic polypeptide (inhibits GB contractions exact physiological role is uncertain) 12 Insulin Insulin decreases blood glucose levels by allowing cells to take up glucose from the blood Binding enhances glucose uptake Brain, kidneys, liver, RBCs are insulin independent Insulin release is also affected by the ANS Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 13 4
Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001 Glucagon Raises blood glucose levels by: - stimulating breakdown of stored molecules - increasing release and formation of glucose 14 Insulin and Glucagon Example of a humoral stimulus for hormone secretion 15 Pineal Gland Pinealocytes synthesize melatonin from serotonin 16 5
Melatonin regulates circadian rhythms - daily changes in physiological processes that follow a regular pattern Light (eyes) retina hypothalamus reticular formation melatonin pineal sympathetic fibers spinal cord may control onset of puberty (melatonin levels decline at puberty) helps regulate female reproductive cycle may protect CNS against free radicals (antioxidant) 17 Other Endocrine Glands Reproductive Glands ovaries secrete estrogen and progesterone testes secrete testosterone placenta secretes estrogen, progesterone, and gonadotropins, e.g., hcg Thymus Gland secretes thymosins promotes development of T-lymphocytes Heart secretes natriuretic peptides (ANP, BNP) -Natri = sodium; uretic = in the urine - promote loss of water and Na + at the kidney - secreted when atria/ventricles are stretched - inhibit renin release - inhibit secretion of ADH and aldosterone 18 Stress Types of Stress physical stress psychological (emotional) stress (Stress is any condition, physical or emotional, that t threatens homeostasis) Stress Response (General Adaptation Syndrome [GAS]) hypothalamus triggers sympathetic impulses to various organs epinephrine is released cortisol is released to promote longer-term responses Three general phases of the GAS in response to stress A R E: Alarm phase Resistance phase Exhaustion phase 21 6
Responses to Stress Exhaustion - lipid reserves - production of glucocorticoids - electrolyte imbalance - damage to vital organs 22 GH Abnormalities Growth Hormone Ups and Downs Gigantism - hypersecretion of GH in children Acromegaly hypersecretion of GH in adults Dwarfism hyposecretion of GH in children Age 9 Age 16 Age 33 Age 52 23 Diabetes (= Overflow) Diabetes Mellitus (DM) Hyposecretion or hypoactivity of insulin Three P s of Diabetes Mellitus (mellitum = honey) Polyuria (increased urination) Polydipsia (increased thirst) Polyphagia (increased hunger) Hyperglycemia, ketonuria, glycosuria Renal Glycosuria excretion of glucose in the urine in detectable amounts normal blood glucose concentrations or absence of hyperglycemia Diabetes Insipidus (insipidus = tasteless) Hyposecretion or hypoactivity of ADH Polyuria Polydipsia 24 7
Hormone Summary Table I Tissue Name Origin Destination Action on Target Tissue Control of Release 1 Se(x) FOLLICLE STIMULATING HORMONE (FSH) LUETINIZING HORMONE (LH) males: semiiferous tubules of testes; females: ovarian follicle In males: interstitial cells in testes; in females: mature ovarian follicle males: sperm production females: follicle/ovum maturation males: testosterone secretion females: ovulation Gonadotropin Releasing Hormone (GnRH) Gonadotropin Releasing Hormone (GnRH) T THYROID STIMULATING HORMONE (TSH) thyroid secrete hormones Thyrotropin Releasing Hormone (TRH) G GROWTH HORMONE (GH) bone, muscle, fat growth of tissues Growth Hormone Rleasing Hormone (GHRH) A ADRENOCORTICO- TROPIC HORMONE (ACTH) adrenal cortex secrete adrenal hormones Corticotropin Releasing Hormone (CRH) P PROLACTIN (PRL) mammary glands produce milk Prolactin Releasing Hormone (PRH) ANTI-DIURETIC HORMONE (ADH) (VASOPRESSIN) posterior distal convoluted tubule (DCT) reabsorption of water; increases blood pressure increase in osmolarity of plasma or a decrease in blood volume OXYTOCIN (OT) posterior uterine smooth muscle; breast contraction during labor; milk letdown Stretching of uterus; infant suckling 26 Hormone Summary Table II Tissue Name Origin Destination Action on Target Tissue Control of Release TRIIODOTHYRONINE (T3) & THYROXINE (T4) Thyroid (follicular cells) all cells increases rate of metabolism (BMR) Thyroid Stimulating Hormone (TSH) CALCITONIN Thyroid (C cells) Intestine, bone, kidney Decreases plasma [Ca 2+ ] ( intestinal absorp of Ca; action of osteoclasts; excretion of Ca by kidney plasma [Ca 2+ ] PARATHYROID HORMONE (PTH) Parathyroids Intestine, bone, kidney Increases plasma [Ca 2+ ] ( intestinal absorp of Ca; action of osteoclasts; excretion of Ca by kidney plasma [Ca 2+ ] EPINEPHRINE/ NOREPINEPHRINE (Catecholamines) Adrenal Medulla cardiac muscle, arteriole and bronchiole smooth muscle, diaphragm, etc increases heart rate and blood pressure... (fight or flight) Sympathetic Nervous System ALDOSTERONE (Mineralocorticoids) Adrenal Cortex Kidneys; sweat glands; salivary glands; pancreas reabsorption of water and Na (increases blood pressure) and excretion of K (mineralocorticoid) Angiotensin II plasma [Na+] plasma [K+] CORTISOL (Glucocorticoids) Adrenal Cortex all cells Diabetogenic; anti-inflammatory (glucocorticoid) ACTH INSULIN β-cells of Pancreatic Islets all cells, liver and skeletal muscle pushes glucose into cells from blood, glycogen formation (decreases blood glucose) plasma [glucose] SNS GLUCAGON α-cells of pancreatic Islets liver and skeletal muscle breakdown of glycogen (increase in blood glucose) plasma [glucose] TESTOSTERONE Testes secondary sex organs development and maintenance LH ESTROGEN Ovaries secondary sex organs development at puberty and maintenance throughout life LH NATRIURETIC PEPTIDES atria and ventricles of heart adrenal cortex, kidneys increased excretion of sodium and water from kidneys, blood volume, blood pressure Stretching of atria and ventricles 27 Review Reaction to stress occurs in three stages Short term Alarm or fight or flight Reactions similar to sympathetic stimulation Mediated by hormones of the adrenal medulla Long term Resistance Long-term raising of blood glucose Mediated by hormones of the adrenal cortex Exhaustion Failure of compensatory mechanisms 28 8