The endocrine system

What is an endocrine gland? Endocrine: secretes substance into blood Exocrine: secretes substance into a duct (ex: sweat)

ENDOCRINE GLANDS PITUITARY GLAND

a. Growth Hormone (GH) Hypersecretion = gigantism (children) or acromegaly (adults)

Stimulates milk production after childbirth b. Prolactin (PRL) Stimulates milk production after childbirth c. Adrenocorticotropic hormone (ACTH) Tropic hormone Stimulates cortex of adrenal gland

Hormones of adrenal cortex (corticosteroids) 1. Mineral corticoids – regulate mineral content of blood, like sodium and potassium Glucocorticoids – regulate metabolism and resistance to stress Ex: cortisone Androgens (sex hormone) In puberty: stimulate axillary/pubic hair growth/growth spurt Insignificant effect in males after puberty In females: libido and converted into estrogens 6

d. Thyroid-stimulating hormone (TSH) Tropic hormone Growth & activity of thyroid gland: 1. Calcitonin (not influenced by TSH) Decreases blood calcium levels by causing calcium to be deposited in the bones. Stimulus? Target? 2. Thyroid hormone Controls rate at which glucose is “burned” (oxidized) Targets every cell

What is a tropic hormone? A synthetic (“man-made”) hormone Hormones that affect the gonads Hormones of the thyroid gland A hormone that triggers another endocrine gland to secrete its hormones

e. Gonadotropic hormones - tropic hormones a. function: regulate activity of gonads b. types: 1. Follicle-stimulating hormone (FSH): egg/sperm development 2. Luteinizing hormone (LH): sex hormone synthesis; ovulation

f. Oxytocin- causes contractions for birth g. Antidiuretic hormone (ADH) Diuresis = urine production causes kidneys to reabsorb water from the forming urine stimulus? caffeine inhibits ADH secretion

Which of the following is NOT a hormone secreted by the pituitary gland? Prolactin Adrenocorticotropic hormone Growth hormone Calcitonin

What does sterility mean? What effect would LH and FSH have on this?

summary Pituitary gland – considered the “master” gland We covered 7 hormones it produces Extra credit assignment: write a story about a character that does not have a pituitary gland. Due: by the 11th (Monday)

2. PARATHYROID GLAND POSTERIOR OF THYROID

2. PARATHYROID GLAND Found posterior side of thyroid Parathyroid hormone (PTH) Regulator of calcium homeostasis in blood. Responds to LOW levels of Ca2+ targets the skeleton Hyposecretion: muscles uncontrollably spasm  fatal Hypersecretion: massive bone destruction

ADRENAL GLANDS: SUPERIOR TO KIDNEYS

Hormones of adrenal cortex (corticosteroids) SKIP Hormones of adrenal cortex (corticosteroids) 1. Mineral corticoids – regulate mineral content of blood, like sodium and potassium Ex: aldosterones Glucocorticoids – regulate metabolism and resistance to stress Ex: cortisone Androgens (sex hormone) In puberty: stimulate axillary/pubic hair growth/growth spurt Insignificant effect in males after puberty In females: libido and converted into estrogens

Problems with adrenal cortex Hyposecretion  Addison’s disease, fatal without treatment Weight loss Muscle weakness Fatigue that gets worse over time Low blood pressure Patchy or dark skin Hypersecretion of glucocorticoids  Cushing’s syndrome, fatal without treatment Weight gain, particularly around your midsection and upper back Fatigue Rounding of your face (moon face) Fatty pad or hump between your shoulders (buffalo hump) Pink or purple stretch marks (striae) on the skin High blood pressure, diabetes, bone loss SKIP

Adrenal cortex – see pituitary notes

adrenal medulla a. Epinephrine b. Norepinephrine Augments fight-or-flight

4. PANCREAS

a. Insulin – Responds to rising blood glucose levels Hyposecretion high blood glucose levels …. Diabetes mellitus (classic symptoms: polyuria (frequent urination), polydipsia (increased thirst) and polyphagia (increased hunger) Type I – failure to make insulin Type 2 – insulin resistance Gestational – during pregnancy

b. Glucagon responds to low blood glucose levels. target: liver

5. PINEAL GLAND

a. Melatonin- regulates day-night cycles

Copyright 1997 Smithsonian Magazine All rights reserved.                                                                                                                                             Taken on a strict schedule, melatonin can help reduce jet lag. (But was that West Coast or London time?) Copyright 1997 Smithsonian Magazine All rights reserved.

6. THYMUS Produces thymosin – regulates maturation of some white blood cells; important for immune system

7. GONADS 7A) OVARIES 1. Estrogens – stimulate secondary sex characteristics in females brings about menstrual cycle

Hyposecretion of either: infertility Progesterone- brings about menstrual cycle. quiets muscles of uterus during pregnancy Hyposecretion of either: infertility

7b) Testes 1. Testosterone testes cause growth and maturation of reproductive system secondary sex characteristics; sperm production in adult Hyposecretion = infertility

                                                                                  

8. PLACENTA (Temporary organ) human chorionic gonadotropin (hCG) – stimulates ovary to continue producing estrogen and progesterone Estrogen & progesterone (3rd month) Relaxin – relaxes pelvis

Aging and the endocrine glands Late middle age: efficiency of ovaries begins to decline  menopause GH declines = muscles atrophy Mildly hypothyroid Less able to resist stress/infection (due to thymus, glucocorticoids of adrenal and melatonin from pineal) Some decline in insulin production  diabetes (not responsible for this slide)

How hormones work 2 categories of hormones Soluble in lipids Most attached to transport protein in blood Ex: Thyroid hormone, sex hormones Soluble in water Travel by themselves in blood Ex: epinephrine/norepinephrine, ADH, oxytocin, GH, insulin

Lipid-soluble hormones: stimulate synthesis of new proteins Diffuse through lipid bilayer (cell membrane) Binds to receptors in cytoplasm or nucleus Triggers gene on/off  synthesis of new protein that alters the cell’s activity

MECHANISM OF ACTION OF LIPID-SOLUBLE HORMONES VIDEO CLIP

Water-soluble hormones: modify existing proteins Binds to receptor on cell membrane Activates G protein (membrane protein) that eventually causes ATP to convert to cyclic AMP (the second messenger). Cyclic AMP activates one/more protein kinases (enzyme that adds a phosphate group – phosphorylates – to other cellular proteins). Phosphorylated proteins cause physiological response Enzyme phosphodiesterase inactivates AMP

Water-soluble hormone action

Water-soluble hormone action