© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Endocrine System

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-2 target tissues Introduction  The endocrine system includes the organs of the body that secrete hormones directly into body fluids such as blood Regulates chemical reaction in cells and therefore control functions of the organs, tissues, and other cells Glands secrete hormones into bloodstream to

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-3 Hormones  Endocrine glands Ductless Release hormones  Directly into target tissues  Into bloodstream to be carried to target tissues  Hormones – chemicals secreted by a cell that affect the functions of other cells

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-4 Hormones (cont.)  Many are derived from steroids that easily cross the cell membrane  Examples of steroid hormones Estrogen Progesterone Testosterone Cortisol hormones

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-5 Negative and Positive Feedback Loops  Control hormone levels  Negative feedback loop Hormone release stops in response to decrease in stimulus  A person becomes dehydrated  Brain signals the release of Antidiuretic Hormone (ADH)  Kidneys retain water.  Kidneys excrete more urine until the concentration of fluids returns to normal.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-6 Negative and Positive Feedback Loops (cont.)  Positive feedback loop As long as stimulus is present, action of hormone continues  Infant nursing at mother’s breast  stimulates hypothalamus  stimulates posterior pituitary  Oxytocin released  stimulates milk production and ejection from mammary glands  Milk release continues as long as infant continues to nurse

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-7 Hypothalamus  Hormones Oxytocin – Stimulates contractions of uterus during labor Antidiuretic hormone (ADH) – stimulates conservation of water during dehydration.  Hormones transported to the posterior pituitary for storage  Directs posterior pituitary to release hormones Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-8  Controlled by the hypothalamus  Located at the base of the brain  Anterior lobe secretes many hormones, including:  Growth hormone (GH) – controls cellular reproduction and regulates use of carbs and fats.  Thyroid-stimulating hormone (TSH) – stimulates the metabolism of ALL tissues in the body.  Folicle-stimulating hormone (FSH) – production of reproductive cells  Prolactin (PRL) – production of milk in mammals Pituitary Gland Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved 34-9 Posterior Lobe Antidiuretic hormone (ADH) Oxytocin Stimulates the kidneys to conserve water Females: causes contraction of the uterus and ejection of breast milk Males: stimulates contraction of the prostate and vas deferens during sexual arousal Pituitary Gland (cont.)

© 2009 The McGraw-Hill Companies, Inc. All rights reserved T 3 T 4 Thyroid Gland and Parathyroid Glands Thyroid Gland  Located below the larynx (houses vocal cords)  Divided into follicles that store some of the hormones Major hormones Stimulate protein synthesis and increase cellular energy production Lowers blood calcium levels by activating osteoblasts that build new bone tissue Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Thyroid Gland and Parathyroid Glands (cont.)  Parathyroid glands Four located on the posterior surface of the thyroid gland Secrete parathyroid hormone (PTH)  Raises blood calcium levels through activation of osetoclasts (dissolve bone) As bone dissolves, calcium levels in blood increase Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Adrenal Glands  Located on top of each kidney  Divided into the adrenal medulla and adrenal cortex  Adrenal medulla Central portion Hormones  Epinephrine – Adrenaline, response to stress  Norepinephrine – works with epinephrine during stress events to bring the body back to homeostasis Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Pancreas  Located behind the stomach  Both exocrine gland and endocrine gland Exocrine – secretes digestive enzymes into a duct leading to the small intestine Endocrine – secretes hormones into bloodstream Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Insulin Protein hormone secreted by the pancreas that stimulates cells to take up glucose  Glucose – primary source of cellular energy  Gives the brain energy for psychological processes.  Body converts the glucose into glycogen for long term storage of energy. What happens after you eat a large meal?  Pancreas secretes insulin, which results in a decrease in blood levels of glucose.

© 2009 The McGraw-Hill Companies, Inc. All rights reserved What is Diabetes? Diabetes insipidusKidneys fail to reabsorb water, resulting in excessive urination; hyposecretion of ADH Diabetes mellitus Type I Type II Gestational Chronic disease characterized by elevated blood glucose levels Insulin-dependent diabetes mellitus; usually develops in childhood Noninsulin-dependent diabetes mellitus; primarily in adults but increased incidence in teens Occurs during pregnancy; usually temporary

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Other Hormone-Producing Organs  Pineal body Small gland in the center of the brain Located between cerebral hemispheres Known by some cultures/religions as the “third eye”. Melatonin  Regulates circadian rhythms  May play a role in onset of puberty Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved Other Hormone-Producing Organs (cont.)  The gonads - a Ovaries (female)  Estrogen – stimulates secondary sex characteristics (breasts, hips, etc.)  Progesterone – controls menstrual cycles and supports pregnancy.  Both of these hormones are responsible for menstruation! Testes (male)  Testosterone – responsible for development of primary and secondary sex characteristics (primary – reproductive organs; secondary – body hair, lower voice, etc.) Glands

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Stress Response  Stressor Any stimulus that produces stress Types  Physical factors  Psychological factors  Positive stimuli

© 2009 The McGraw-Hill Companies, Inc. All rights reserved The Stress Response (cont.)  Physiologic response to stress caused by hormone release Hypothalamus acts as a connector from the nervous system to the endocrine system. Hypothalamus senses the “stress” stimulus The adrenal gland secretes epinephrine and norepinephrine The “fight or “flight” response is generated The body returns to homeostasis