Physiology of Endocrine System PDF

Physiology of Endocrine System The Endocrine System Collected By: Dr. Ebrahim Al- Samet The Endocrine System Second messenger system of the body Uses chemical messages (hormones) that are released into the blood Hormones con...

Physiology of Endocrine System The Endocrine System Collected By: Dr. Ebrahim Al- Samet The Endocrine System Second messenger system of the body Uses chemical messages (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.1 1  Hormone Overview Hormones are produced by specialized cells Cells secrete hormones into extracellular fluids Blood transfers hormones to target sites These hormones regulate the activity of other cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.2 The Chemistry of Hormones Amino acid-based hormones Proteins Peptides Amines Steroids – made from cholesterol Prostaglandins – made from highly active lipids Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.3 2  Mechanisms of Hormone Action Hormones affect only certain tissues or organs (target cells or organs) Target cells must have specific protein receptors Hormone binding influences the working of the cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.4 Control of Hormone Release Hormone levels in the blood are maintained by negative feedback A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.10 3  Hormonal Stimuli of Endocrine Glands Endocrine glands are activated by other hormones Figure 9.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.11 Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions stimulate hormone release Figure 9.2b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.12 4  Location of Major Endrocrine Organs Figure 9.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.14 Pituitary Gland Size of a grape (0.5 grams) Hangs by a stalk from the hypothalamus Protected by the sphenoid bone Has two functional lobes Anterior pituitary – glandular tissue Posterior pituitary – nervous tissue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.15 5  Hormones of the Anterior Pituitary Six anterior pituitary hormones Two affect non-endocrine targets Four stimulate other endocrine glands (tropic hormones) Characteristics of all anterior pituitary hormones Proteins (or peptides) Act through second-messenger systems Regulated by hormonal stimuli, mostly negative feedback Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.16 Hormones of the Anterior Pituitary Figure 9.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.17 6  Growth Hormone (GH) General metabolic hormone –Regulated by »growth hormone– releasing Major effects are directed to hormone (GHRH) »growth hormone–inhibiting growth of skeletal muscles and hormone (GHIH), long bones Causes amino acids to be built into proteins Causes fats to be broken down for a source of energy Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.18 Functions of Other Anterior Pituitary Hormones Prolactin (PRL) Stimulates and maintains milk production following childbirth Function in males is unknown –Regulated by »prolactin-releasing hormone (PRH) »negative feedback of prolactin-inhibiting hormone (PIH) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.19 7  Functions of Other Anterior Pituitary Hormones Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenal cortex –Regulated by »corticotropin-releasing hormone (CRH) »negative feedback of glucocorticoids (when it needs to be inhibited) Thyroid-stimulating hormone (TSH) Influences growth and activity of the thyroid –Regulated by »thyrotropin-releasing hormone (TRH) »negative feedback of thyroid hormone (when it needs to be inhibited) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.19 Functions of Other Anterior Pituitary Hormones Gonadotropic hormones Regulate hormonal activity of the gonads – Regulated by » gonadotropin-releasing hormone (GnRH) » negative feedback of gonadal hormones (when it needs to be inhibited) Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries Stimulates sperm development in testes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.20a 8  Functions of Other Anterior Pituitary Hormones Gonadotropic hormones (continued) Luteinizing hormone (LH) Triggers ovulation Causes ruptured follicle to become the corpus luteum Stimulates testosterone production in males Referred to as interstitial cell-stimulating hormone (ICSH) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.20b 9  Hormones of the Posterior Pituitary Oxytocin Stimulates contractions of the uterus during labor Causes milk ejection Antidiuretic hormone (ADH) Can inhibit urine production In large amounts, causes vasoconstriction leading to increased blood pressure (vasopressin) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.22 Hormones of the Posterior Pituitary Figure 9.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.22b 10  Thyroid Gland Found at the base of the throat Consists of two lobes and a connecting isthmus Produces two hormones Thyroid hormone Calcitonin Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.23a Thyroid Gland Figure 9.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.23b 11  Thyroid Hormone Major metabolic hormone Composed of two active iodine- containing hormones Thyroxine (T4) – secreted by thyroid follicles Triiodothyronine (T3) – conversion of T4 at target tissues Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.24 Calcitonin Decreases blood calcium levels by causing its deposition on bone Antagonistic to parathyroid hormone Produced by C (parafollicular) cells Figure 9.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.25 12  Parathyroid Glands Tiny masses on the posterior of the thyroid Secrete parathyroid hormone Stimulate osterclasts to remove calcium from bone Stimulate the kidneys and intestine to absorb more calcium Raise calcium levels in the blood Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.26 Adrenal Glands Two glands Cortex – outer glandular region in three layers Medulla – inner neural tissue region Sits on top of the kidneys Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.27 13  Hormones of the Adrenal Cortex Mineralocorticoids (mainly aldosterone) Produced in outer adrenal cortex Regulate mineral content in blood, water, and electrolyte balance Target organ is the kidney Production stimulated by renin and aldosterone Production inhibited by atrial natriuretic peptide Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.28a Hormones of the Adrenal Cortex Figure 9.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.28b 14  Hormones of the Adrenal Cortex Glucocorticoids (including cortisone and cortisol) Produced in the middle layer of the adrenal cortex Promote normal cell metabolism Help resist long-term stressors Released in response to increased blood levels of ACTH Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.29a Hormones of the Adrenal Cortex Sex hormones Produced in the inner layer of the adrenal cortex Androgens (male) and some estrogen (female) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.29b 15  Hormones of the Adrenal Medulla Produces two similar hormones (catecholamines) Epinephrine Norepinephrine These hormones prepare the body to deal with short-term stress Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.30 Pancreatic Islets The pancreas is a mixed gland The islets of the pancreas produce hormones Insulin – allows glucose to cross plasma membranes into cells from beta cells Glucagon – allows glucose to enter the blood from alpha cells These hormones are antagonists that maintain blood sugar homeostasis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.32a 16  Pancreatic Islets Figure 9.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.32b Pancreatic Hormones and Blood Sugar Figure 9.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.33 17  Pineal Gland Found on the third ventricle of the brain Secretes melatonin Helps establish the body’s wake and sleep cycles May have other as-yet-unsubstantiated functions Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.34 Thymus Located posterior to the sternum Largest in infants and children Produces thymosin Matures some types of white blood cells Important in developing the immune system Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.35 18  Hormones of the Ovaries Estrogens Produced by Graafian follicles or the placenta Stimulates the development of secondary female characteristics Matures female reproductive organs Helps prepare the uterus to receive a fertilized egg Helps maintain pregnancy Prepares the breasts to produce milk Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.36 Hormones of the Ovaries Progesterone Produced by the corpus luteum Acts with estrogen to bring about the menstrual cycle Helps in the implantation of an embryo in the uterus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.37 19  Hormones of the Testes Interstitial cells of testes are hormone- producing Produce several androgens Testosterone is the most important androgen Responsible for adult male secondary sex characteristics Promotes growth and maturation of male reproductive system Required for sperm cell production Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.38 Other Hormone-Producing Tissues and Organs Parts of the small intestine Parts of the stomach Kidneys Heart Many other areas have scattered endocrine cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.39 20  Endocrine Function of the Placenta Produces hormones that maintain the pregnancy Some hormones play a part in the delivery of the baby Produces HCG in addition to estrogen, progesterone, and other hormones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.40 Developmental Aspects of the Endocrine System Most endocrine organs operate smoothly until old age Menopause is brought about by lack of efficiency of the ovaries Problems associated with reduced estrogen are common Growth hormone production declines with age Many endocrine glands decrease output with age Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.41 21