Chapter 16: The Endocrine System

Objectives Define the terms endocrine and exocrine. Describe the physiology of hormones including the different types and the mechanisms of their actions. Compare endocrine and neural controls of physiology.

Functions System of glands and cells make hormones Alters metabolic activities of many tissues and organs simultaneously Regulates long-term processes: growth development reproduction

What is a Hormone? A chemical messenger that is produced at one site and carried by the blood to its site of action (target cells)

Mechanism of Hormone Action Hormones produce one or more of the following cellular changes: alter plasma membrane permeability stimulate protein synthesis activate or deactivate enzyme systems induce secretory activity stimulate mitosis

Homeostasis Homeostasis How we maintain homeostasis maintaining internal balance in the body organism must keep internal conditions stable even if environment changes also called “dynamic equilibrium” How we maintain homeostasis nervous system endocrine system

What is the functional significance of the differences between the two systems? Endocrine System Nervous System Chemical signals control body functions Is unable to handle split-second responses Nerve signals control body functions Handles crisis management

Endocrine vs. Exocrine Endocrine Glands Exocrine Glands Glandular secretory cells that release their secretions directly into the blood stream The glands are called ductless Secrete their products onto epithelial surfaces- (skin or mucosa) The glands that have ducts

Glands Hypothalamus Pituitary Thyroid Parathyroid Adrenal Pineal Pancreas Thymus Gonads

Hypothalamus

Hypothalamus Links the nervous system to the endocrine system Controls: body temperature hunger thirst fatigue sleep circadian cycles

Controlling Body Temperature nerve signals brain sweat dilates surface blood vessels high body temperature low constricts surface blood vessels shiver brain nerve signals

Pituitary Gland Functions: Hormone: Location: stimulates the elongation of bones in the body “master gland” since it regulates endocrine functions Hormone: growth hormone Location: base of the brain, below hypothalamus

Pituitary Gland

Pituitary Gland Hormones

Pituitary Gland Hormones

Pituitary Dwarfism

Gigantism

Andre the Giant At 7'4" and 500 pounds, Andre the Giant could have been famous for his size alone. His drive, talent and ambition, however, proved to be as big as Andre himself, and the wrestler became legendary for his achievements in and out of the ring.

Acromegaly Occurs in adults Bones of hands face and feet are enlarged Due to the release of growth hormone in adults

Thyroid Gland Functions: Location: controls metabolism regulates tissue growth maintains blood pressure glucose oxidation makes proteins Location: by the Adams apple largest gland in the body

Thyroid Gland

Goiter Not enough iodine in the diet (iodine deficiency) Causes swelling of the thyroid gland

Goiter

Graves Disease Overactive thyroid Excessive amounts of thyroid hormones are produced Inflammation of the eye muscles by attacking autoantibodies

Parathyroid Glands 4 Functions: Hormone: Location: breaks down bone to regulate blood calcium Hormone: secretes parathormone Location: embedded in the thyroid

Adrenal Glands Functions: Secretion: Location: raises heart rate increases breathing increases blood sugar level dilates blood vessels Secretion: adrenaline Location: on top of the two kidneys

Pineal Gland Function: Secretion: Location: modulates the wake/sleep patterns modulates photoperiodic (seasonal) functions Secretion: melatonin Location: near the center of the brain

Pancreas Functions: Secretions: Location: controls blood sugar breaks down carbohydrates, proteins, and fats Secretions: insulin glucagon hormones that control the blood sugar in the body Location: behind the stomach side of the small intestine

Pancreas Secretions Insulin Glucagon allows glucose to enter cells LOWERS blood glucose levels Glucagon stimulates liver to make glucose RAISES blood glucose levels

Islets of Langerhans Two cell types: Alpha () cells produces glucagon Beta () cells produce insulin

Diabetes Under-secretion of insulin High blood sugar

Regulation of Blood Sugar insulin body cells take up sugar from blood liver stores sugar reduces appetite pancreas liver high blood sugar level (90mg/100ml) low liver releases sugar triggers hunger pancreas liver glucagon

Thymus Function: Secretion: Location: controls the immune system development of T-lymphocytes Secretion: Thymosin Location: thorax anterior mediastinum

Ovaries Two main hormones: Estrogen create female secondary sex characteristics Progesterone thickens the uterus lining every month

Testes One main hormone: Testosterone (an androgen) affects the secondary sex characteristics in men

Hirsutism Caused by an increase in testosterone secretion

Aging Causes few functional changes Decline in concentration of: growth hormone reproductive hormones