CHAPTER EIGHT CHEMICAL BALANCE KING’S COLLEGE CORE273 HORMONE ACTION • The Endocrine System modulates chemical messengers called hormones. • Hormones come from specialized tissues and various endocrine glands. • They function to maintain homeostasis. • • Remember the feedback loop? They regulate every system of the body! • Two modes of action: • Steroid hormones: enter cell directly through membrane and into nucleus – activate genes. • Non-steroid hormones: bind to receptor on membrane, activate chain of events inside cells. HYPOTHALAMUS AND PITUITARY GLAND • Hypothalamus regulates the majority of what contributes to homeostasis. • Thirst, hunger, fatigue, body temperature, etc. • Directs the activity of the pituitary gland via nervous and endocrine signals. • Pituitary gland has two divisions: • Anterior pituitary: creates and secretes own hormones. • Responds to hypothalamic release hormones. • Posterior pituitary: stores and releases hypothalamic hormones. • Responds to nerve signals from hypothalamus. ANTERIOR PITUITARY • Growth hormone (GH): widespread effects on growth. • Highest in growing children and adolescents. • Stimulates protein synthesis, fat breakdown, and energy use (metabolism). • Antagonizes insulin. • Competitive GH uses associated with Type II Diabetes (insulin resistance). • Prolactin (PRL): targets mammary glands for breast milk production. • Adrenocorticotropic hormone (ACTH): activates adrenal cortex of the adrenal glands to make hormones. ANTERIOR PITUITARY • Thyroid stimulating hormone (TSH): activates the thyroid gland. • Gland just below larynx in the front of the throat region. • Thyroid then produces its own hormones. • Follicle stimulating hormone (FSH): stimulates growth of egg/sperm. • Stimulates follicle in ovaries, Sertoli cells in testes. • Luteinizing hormone (LH): stimulates testes and ovaries. • Ovulation and production of estrogen/progesterone in females. • Stimulates Leydig cells for production of testosterone in males. POSTERIOR PITUITARY • Antidiuretic hormone (ADH): saves water at the kidneys. • Stimulates nephron tubules to allow water to move back into body. • Oxytocin: uterine contractions and milk ejection in females, bonding. PINEAL GLAND • Synthesizes and secretes melatonin. • Communicates information about light. • Levels are low during the daylight. • Peak during the dark. • Trains biological rhythms. • Regulates release of LH and FSH. • Powerful antioxidant. • Higher levels when we’re younger. THYROID AND PARATHYROID • Thyroid Gland: releases T3 and T4, as well as calcitonin. • Thyroxine (T3) and Triiodothyronine (T4): regulate BMR. • • Basal Metabolic Rate: rate at which energy is expended in a basal condition. Calcitonin: lowers blood calcium levels. • Stimulates osteoblasts to put calcium from blood into bone. • Parathyroid Gland: parathyroid hormone which raises blood calcium. • Stimulates osteoclasts to release calcium from bone. • OPPOSES CALCITONIN TO MAINTAIN HOMEOSTASIS OF CALCIUM! CORTEX OF ADRENAL GLAND • True endocrine gland. • Aldosterone: saves sodium and potassium at kidneys. • Causes tubules to reabsorb them back into the body. • Often synergistic with ADH. • Cortisol: sugar production and suppresses inflammation. • Major hormone in stress response! MEDULLA OF ADRENAL GLAND • Modified nervous tissue. • Epinephrine/Norepinephrine: “Adrenaline” • Roles in metabolism, blood pressure, and heart activity. • Sympathetic nervous responses. • Both a hormone and a neurotransmitter. • Quick onset and sustained impact on the body. Recall what happens during “Fight or Flight” response to blood vessels, lungs, heart, digestion, etc.? KIDNEYS • Renin: works to increase blood pressure. • Erythropoietin: stimulates production of red blood cells. HEART AND THYMUS GLAND • Thymus: Thymosin and Thymopoietin aid in maturing T-cells. • Heart: Atrial natriuretic hormone reduces blood pressure. PANCREAS • Exocrine function: digestive secretions via ducts into other organ. • Endocrine function: secretes hormones into blood stream. • Insulin: lowers blood sugar levels. • Glucagon: raises blood glucose (sugar) levels. • Diabetes Mellitus: inability to process glucose in cells. • Type I: pancreas can’t produce insulin. • Type II: cells resistant to insulin produced. • Glucose channels remain closed. Worksheet Seven CORE273 SUM18 NAME: Chemical Balance HORMONE EX: Growth Hormone Prolactin Adrenocorticotropic H. Thyroid Stimulating H. Follicle Stimulating H. Luteinizing Hormone Antidiuretic Hormone Oxytocin Melatonin Thyroxine/Triiodothyronine Calcitonin Parathyroid Hormone Aldosterone Cortisol Epinephrine/Norepinephrine Renin Erythropoietin Atrial Natriuretic Hormone Thymosin/Thymopoietin Insulin Glucagon RELEASING GLAND FUNCTION Anterior Pituitary Widespread effects on growth.
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