Chapter 16 The Endocrine System PDF

Visual Anatomy & Physiology Third Edition Chapter 16 The Endocrine System Lecture Presentation by Chasity O’Malley, Palm Beach State College...

Visual Anatomy & Physiology Third Edition Chapter 16 The Endocrine System Lecture Presentation by Chasity O’Malley, Palm Beach State College with Notes by Lori Garrett, Parkland College Copyright © 2018 Pearson Education, Inc. All Rights Reserved Section 1: Hormones and Intercellular Communication (1 of 4) Learning Outcomes 16.1 Describe the similarities between the endocrine and nervous systems and their specific modes of intercellular communication. 16.2 Explain the chemical classification of hormones. 16.3 Identify the organs and tissues of the endocrine system and the key functions of the hormones they secrete. 16.4 Explain the general mechanisms of hormonal action. Section 1: Hormones and Intercellular Communication (2 of 4) Learning Outcomes (continued) 16.5 Describe how the hypothalamus controls endocrine organs. 16.6 Describe the location and structure of the pituitary gland, and identify pituitary hormones and their functions. 16.7 Describe the role of negative feedback in the functional relationship between the hypothalamus and the pituitary gland. Section 1: Hormones and Intercellular Communication (3 of 4) Learning Outcomes (continued) 16.8 Describe the location and structure of the thyroid gland, identify the hormones it produces, and specify the functions of those hormones. 16.9 Describe the location of the parathyroid glands, and identify the functions of the hormone they produce. 16.10 Describe the location, structure, and functions of the adrenal glands, identify the hormones produced, and specify the functions of each hormone. Section 1: Hormones and Intercellular Communication (4 of 4) Learning Outcomes (continued) 16.11 Describe the location and structure of the pancreas, identify the hormones it produces, and specify the functions of those hormones. 16.12 Describe the location of the pineal gland, and identify the functions of the hormone that it produces. 16.13 Clinical Module: Explain diabetes mellitus: its types, clinical manifestations, and treatments. Module 16.1: The Nervous and Endocrine Systems Release Chemical Messengers That Bind to Target Cells Similarities – Both systems rely on the release of chemicals that bind to specific receptors on their target cells – They share many chemical messengers ▪ Called neurotransmitters in the nervous system ▪ Called hormones in the endocrine system – Both regulated primarily by negative feedback mechanisms – Common goal of both is to preserve homeostasis by coordinating and regulating other cells, tissues, organs, and systems Mechanisms of Intercellular Communication (1 of 2) Mechanism Transmission Chemical Signals Distribution of Effects Direct Through gap junctions Ions, small solutes, Usually limited to communication lipid-soluble materials adjacent cells of the same type that are Two cells are touching. One cell communicates to another. interconnected by connexons Paracrine Through extracellular Paracrines Primarily limited to the communication fluid local area, where paracrine One cell communicates with 3 small cells beside it. concentrations are relatively high; target cells must have appropriate receptors (see Modules 3.3, 11.8) Autocrine Through extracellular Autocrines Limited to the cell that communication fluid secretes the chemical signal A chemical comes out of the center of a cell, then back to cell’s sides. Mechanisms of Intercellular Communication (2 of 2) Mechanism Transmission Chemical Signals Distribution of Effects Endocrine Through the Hormones Target cells are mainly communication bloodstream in other distant tissues and organs and must Three cells communicate with a blood vessel below. have appropriate receptors Synaptic Across synapses Neurotransmitters Limited to very specific communication area; target cells must have appropriate Grouped cells communicate to a part below and outside the group. receptors Similarities Between the Nervous and Endocrine Systems Both systems rely on the release of chemicals that bind to specific receptors on their target cells. The two systems share many chemical messengers; for example, norepinephrine and epinephrine are called hormones when released into the bloodstream, but they are called neurotransmitters when released across synapses. Both systems are regulated primarily by negative feedback control mechanisms. The two systems share a common goal: to preserve homeostasis by coordinating and regulating the activities of other cells, tissues, organs, and systems. Module 16.1: Review A. What is the common goal of the nervous and endocrine systems? Learning Outcome: Describe the similarities between the endocrine and nervous systems and their specific modes of intercellular communication. Module 16.2: Hormones May Be Amino Acid Derivatives, Peptides, or Lipid Derivatives Groups based on chemical structure 1. Amino acid derivatives 1. Thyroid hormones – Produced by the thyroid gland 2. ​Catecholamines – Includes epinephrine, norepinephrine, and dopamine 3. Tryptophan derivatives – Melatonin Secreted by the pineal gland Hormone Classes (1 of 4) Module 16.2: Hormone Classes (1 of 3) Groups based on chemical structure (continued) 2. Peptide hormones ▪ Include most hormones of body ▪ Synthesized as prohormones – Inactive precursor molecules that are converted to active form ▪ Range from short polypeptide chains of amino acids (such as ADH and oxytocin) to small proteins (such as insulin, G H, and prolactin) ▪ Glycoproteins may also function as hormones – Polypeptides with carbohydrate side chains – Examples: TSH, LH, FSH Hormone Classes (2 of 4) Module 16.2: Hormone Classes (2 of 3) Groups based on chemical structure (continued) 3. ​Lipid derivatives ▪ Consist of carbon rings and side chains built from either fatty acids (eicosanoids) or cholesterol (steroid molecules) ▪ Eicosanoids – Important paracrine factors that coordinate cellular activities and enzymatic processes (such as blood clotting) in extracellular fluids Leukotrienes (secondary roles as hormones) Prostaglandins (involved primarily in coordinating local cellular activities) Hormone Classes (3 of 4) Module 16.2: Hormone Classes (3 of 3) Groups based on chemical structure (continued) 3. ​Lipid derivatives (continued) ▪ Steroid hormones – Released by: Reproductive organs (androgens by testes in males; estrogen and progesterone by ovaries in females) Adrenal gland (corticosteroids) Kidneys (calcitriol) – Bound to specific transport proteins in blood Remain in circulation longer than peptide hormones Hormone Classes (4 of 4) Module 16.2: Review A. Describe the structural classification of hormones. Learning Outcome: Explain the chemical classification of hormones. Module 16.3: The Endocrine System Includes Organs and Tissues with Primary and Secondary Hormone- secreting Roles Endocrine system overview – Includes those organs whose primary function is the production of hormones or paracrines ▪ Hypothalamus, pituitary gland, thyroid gland, adrenal gland, pancreas (pancreatic islets), pineal gland, parathyroid glands – Many other organs contain tissues that secrete hormones, but endocrine function is secondary ▪ Heart, thymus, digestive tract, kidneys, and gonads The Endocrine System (1 of 3) Module 16.3: The Endocrine System (1 of 4) Endocrine system overview (continued) – Hypothalamus ▪ Secretes hormones involved in fluid balance, smooth muscle contraction, control of hormone secretion by anterior pituitary gland – Pituitary gland ▪ Secretes multiple hormones that regulate the endocrine activities of the adrenal cortex, thyroid gland, and reproductive organs, and a hormone that stimulates melanin production The Endocrine System (2 of 3) Module 16.3: The Endocrine System (2 of 4) Endocrine system overview (continued) – Thyroid gland ▪ Secretes hormones affecting metabolic rate and calcium ion levels in body fluids – Adrenal glands ▪ The two adrenal glands secrete hormones involved with mineral balance, metabolic control, and resistance to stress ▪ They also release epinephrine and norepinephrine during sympathetic activation The Endocrine System (3 of 3) Module 16.3: The Endocrine System (3 of 4) Endocrine system overview (continued) – Pancreas (pancreatic islets) ▪ Secretes hormones regulating rate of glucose uptake and utilization by body tissues – Pineal gland ▪ Secretes melatonin, which affects reproductive function and circadian (day/night) rhythms – Parathyroid glands ▪ Secrete hormone important to regulation of calcium ion levels in body fluids Module 16.3: The Endocrine System (4 of 4) Endocrine system overview (continued) – Other organs with endocrine function and what their hormones regulate ▪ Heart—blood volume ▪ Thymus—immune response ▪ Digestive tract—digestive function coordination, glucose metabolism, appetite ▪ Kidneys—blood cell production, rate of calcium and phosphorus absorption by digestive tract, and an enzyme involved in regulating blood pressure ▪ Gonads—growth, metabolism, sexual characteristics as well as activities of organs in reproductive system Module 16.3: Review A. Define endocrine system. B. Name the organs of the endocrine system. Learning Outcome: Identify the organs and tissues of the endocrine system and the key functions of the hormones they secrete. Module 16.4: Hormones Affect Target Cells after Binding to Receptors in the Plasma Membrane, Cytoplasm, or Nucleus Hormones and receptors – To respond to a hormone, a target cell must have the appropriate protein receptor ▪ Without the receptor, the circulating hormone has no effect – Cells have receptors for many different hormones ▪ Different combinations of receptors produce differential effects on specific tissues Module 16.4: Hormone Binding (1 of 5) Two possible receptor locations on target cells 1. Receptor in plasma membrane (extracellular receptors) ▪ Receptors for catecholamines and peptide hormones, and most eicosanoids ▪ Act as first messenger, relaying message to an intracellular intermediary (second messenger) ▪ Second messenger then affects enzyme activity and changes cellular metabolic reactions, exerting hormone’s effects in the cell ▪ Generally involves a G protein (enzyme complex coupled to receptor) G Protein–Coupled Receptors (1 of 2) Module 16.4: Hormone Binding (2 of 5) Two possible receptor locations on target cells (continued) 1. Receptor in plasma membrane (continued) ▪ Examples of second messengers – Cyclic AMP (cAMP) Derivative of ATP Increased levels may activate enzymes or open ion channels, accelerating cell metabolic activity Decreased levels has inhibitory effect on cell – Calcium ions Generally function in combination with intracellular protein called calmodulin to activate enzymes G Protein–Coupled Receptors (2 of 2) A&P Flix: Mechanism of Hormone Action: Second Messenger cAMP Module 16.4: Hormone Binding (3 of 5) Two possible receptor locations on target cells (continued) 2. Receptor in cytoplasm or nucleus (intracellular receptors) ▪ Steroid hormones – Lipid-soluble hormones diffuse through plasma membrane – Alter activity of specific genes – Affect DNA transcription rate, changing pattern of protein synthesis – Change synthesis of enzyme and structural proteins affecting cell’s metabolic activity and structure Module 16.4: Hormone Binding (4 of 5) Two possible receptor locations on target cells (continued) 2. Receptor in cytoplasm or nucleus (continued) ▪ Thyroid hormones – Transported across cell membrane by carrier-mediated processes – Bind to receptors on mitochondria Increase rate of ATP production Module 16.4: Hormone Binding (5 of 5) Two possible receptor locations on target cells (continued) 2. Receptor in cytoplasm or nucleus (continued) ▪ Thyroid hormones (continued) – Bind to receptors in nucleus Activate specific genes or change rate of transcription Affects cell’s metabolic activity and structure Module 16.4: Review A. Define hormone receptor. B. Differentiate between a first messenger and a second messenger. C. Which type of hormone diffuses across the plasma membrane and binds to receptors in the cytoplasm? Learning Outcome: Explain the general mechanisms of hormonal action. Module 16.5: The Hypothalamus Exerts Direct or Indirect Control Over the Activities of Many Endocrine Organs Hypothalamus – Provides highest level of endocrine function by integrating nervous and endocrine systems – Three mechanisms of integration 1. Hypothalamic neurons synthesize two hormones that are transported to and released by the posterior pituitary 1. Antidiuretic hormone (ADH) Synthesized by the supraoptic nuclei 2. ​Oxytocin (OXT) Synthesized by the paraventricular nuclei Regulation Through the Hypothalamus (1 of 2) Module 16.5: The Hypothalamus Exerts Direct or Indirect Control (1 of 4) Hypothalamus (continued) – Three mechanisms of integration (continued) 2. Secretes regulatory hormones that control anterior pituitary gland endocrine cells 3. Contains autonomic centers that directly stimulate the endocrine cells in the adrenal medulla – Stimulated in response to sympathetic division activation – In response, adrenal medulla releases epinephrine and norepinephrine into bloodstream Regulation Through the Hypothalamus (2 of 2) Module 16.5: The Hypothalamus Exerts Direct or Indirect Control (2 of 4) Hypophyseal portal system – Capillary networks and interconnecting vessels between the hypothalamus and the pituitary gland (hypophysis, pituitary gland) ▪ Regulatory hormones released from the hypothalamus at the median eminence of infundibulum ▪ Move from interstitial fluid into fenestrated capillaries ▪ Carried to anterior pituitary in portal vessels (portal veins) ▪ Form second capillary network within the anterior pituitary Module 16.5: The Hypothalamus Exerts Direct or Indirect Control (3 of 4) Hypophyseal portal system (continued) – Allows hypothalamic hormones to reach target cells in anterior pituitary directly, without mixing and diluting in general circulation Hypophyseal Portal System Module 16.5: The Hypothalamus Exerts Direct or Indirect Control (4 of 4) Hypophyseal portal system (continued) – Two classes of regulatory hormones 1. Releasing hormones (RH) – Stimulate synthesis and secretion of one or more hormones at anterior lobe 2. Inhibiting hormones (IH) – Prevent synthesis and secretion of one or more hormones at anterior lobe Module 16.5: Review A. Define regulatory hormone. B. Identify the three mechanisms by which the hypothalamus integrates neural and endocrine function. C. Name and describe the characteristics and functions of the blood vessels that link the hypothalamus with the anterior lobe of the pituitary gland. Learning Outcome: Describe how the hypothalamus controls endocrine organs. Module 16.6: The Anterior Lobe of the Pituitary Gland Produces and Releases 7 Tropic Hormones, While the Posterior Lobe Releases 2 Hormones Pituitary gland, or hypophysis – Small, oval gland nestled within sella turcica of sphenoid bone – Releases nine peptide hormones ▪ Seven from anterior lobe (adenohypophysis) – Called tropic (trope, a turning) hormones because they “turn on” other endocrine glands ▪ Two from posterior pituitary (neurohypophysis) ▪ All nine bind to membrane receptors and use c AMP as second messenger The Pituitary Gland Module 16.6: The Pituitary Gland (1 of 11) Hormones of the anterior lobe 1. Thyroid-stimulating hormone (TSH) ▪ Targets the thyroid gland ▪ Stimulates release of thyroid hormones ▪ Released in response to thyrotropin-releasing hormone (TRH) from hypothalamus ▪ Release is decreased when thyroid hormone levels rise (negative feedback) Module 16.6: The Pituitary Gland (2 of 11) Hormones of the anterior lobe (continued) 2. Adrenocorticotropic hormone (ACTH) ▪ Also known as corticotropin ▪ Stimulates release of steroid hormones from adrenal cortex – Specifically those that affect glucose metabolism ▪ Released in response to corticotropin-releasing hormone (CRH) from hypothalamus Module 16.6: The Pituitary Gland (3 of 11) Hormones of the anterior lobe (continued) – Gonadotropins ▪ Regulate activities of the gonads ▪ Released in response to gonadotropin-releasing hormone (GnRH) from hypothalamus 3. Follicle-stimulating hormone (FSH) – Females: promotes ovarian follicle development and (in combination with LH) stimulates secretion of estrogens – Males: promotes maturation of developing sperm – Inhibited by inhibin (peptide released by gonads) Module 16.6: The Pituitary Gland (4 of 11) Hormones of the anterior lobe (continued) – Gonadotropins (continued) 4. ​Luteinizing hormone (LH) – Females Induces ovulation Promotes secretion of estrogen and progesterone Prepares body for possible pregnancy – Males Stimulates interstitial cells of testes to produce sex hormones (androgens), primarily testosterone Module 16.6: The Pituitary Gland (5 of 11) Hormones of the anterior lobe (continued) 5. ​Growth hormone (GH) ▪ Stimulates cell growth and reproduction by accelerating rate of protein synthesis – Skeletal muscle and chondrocytes are particularly sensitive to GH ▪ Regulated by two hypothalamic hormones – Growth hormone–releasing hormone (GH–RH) – Growth hormone–inhibiting hormone (GH–IH) ▪ Actions of growth hormone can be direct or indirect Module 16.6: The Pituitary Gland (6 of 11) Hormones of the anterior lobe (continued) 5. ​Growth hormone (continued) ▪ Indirect action of growth hormone (primary mechanism) – Liver cells respond to GH by synthesizing and releasing somatomedins (compounds that stimulate tissue growth) or insulin-like growth factors (IGFs) Receptors for these on various cells in the body including skeletal muscle and cartilage Response is increased uptake of amino acids and incorporation into new proteins Module 16.6: The Pituitary Gland (7 of 11) Hormones of the anterior lobe (continued) 5. ​Growth hormone (continued) ▪ Direct actions of growth hormone – Epithelial and connective tissues Stimulates stem cell division and differentiation – Adipose tissue Stimulates breakdown of stored triglycerides, releasing fatty acids into blood Tissues use these fatty acids instead of glucose to generate ATP (called glucose-sparing effect) – Liver Stimulates breakdown of glycogen reserves, releasing glucose into bloodstream Module 16.6: The Pituitary Gland (8 of 11) Hormones of the anterior lobe (continued) 6. Prolactin (pro-, before + lac, milk) (PRL) ▪ Works with other hormones to stimulate mammary gland development ▪ In pregnancy and nursing period, stimulates milk production by mammary glands ▪ Released in response to several prolactin-releasing factors ▪ Inhibited by prolactin-inhibiting hormone (PIH) ▪ Stimulated by prolactin-releasing hormones (PRH) Module 16.6: The Pituitary Gland (9 of 11) Hormones of the anterior lobe (continued) 7. ​Melanocyte-stimulating hormone (MSH) ▪ Possibly released from the pars intermedia of anterior lobe ▪ Stimulates melanocytes of skin to increase melanin production ▪ In adults, that portion of the anterior lobe is almost nonfunctional – Usually no MSH in circulation Module 16.6: The Pituitary Gland (10 of 11) Hormones of the posterior lobe 1. Antidiuretic hormone (ADH) ▪ Also known as vasopressin (VP) ▪ Released in response to a variety of stimuli – Main stimulus is an increase in solute concentration of blood (sensed by osmoreceptors) or a decrease in blood pressure or volume ▪ Primary function is to act on kidneys to retain water and decrease urination – Also causes vasoconstriction (helps increase blood pressure) ▪ Release is inhibited by alcohol Module 16.6: The Pituitary Gland (11 of 11) Hormones of the posterior lobe (continued) 2. ​Oxytocin (okytokos, swift birth) (OXT) ▪ Released in response to sensory input – Example of a neuroendocrine response ▪ Stimulates: – Smooth muscle contraction in wall of uterus Promotes labor and delivery – Contraction of myoepithelial cells in the mammary glands Promotes ejection of milk ▪ Also has unclear functions in sexual activity – Circulating levels rise during sexual arousal Hormones of the Posterior Lobe Module 16.6: Review A. Name the two lobes of the pituitary gland. B. Identify the nine pituitary hormones and their target tissues. C. In a dehydrated person, how would the amount of ADH released by the posterior lobe of the pituitary change? Learning Outcome: Describe the location and structure of the pituitary gland, and identify pituitary hormones and their functions. Module 16.7: Negative Feedback Mechanisms Control the Secretion Rates of the Hypothalamus and the Pituitary Gland Negative feedback – Typical control mechanism for hormone secretion – Example ▪ Hypothalamic releasing hormone triggers release of hormone by anterior pituitary gland, which triggers release of a second hormone by the target gland Module 16.7: Negative Feedback Between Hypothalamus and Pituitary Gland (1 of 3) Negative feedback (continued) – Example (continued) ▪ Second hormone suppresses secretion of both hypothalamic releasing hormone and pituitary hormone Module 16.7: Negative Feedback Between Hypothalamus and Pituitary Gland (2 of 3) Negative feedback (continued) – In some cases, both releasing and inhibiting hormones are part of the regulatory process – Growth hormone ▪ Somatomedins released by the liver influence hypothalamic hormones – Inhibit release of GH–RH – Stimulate release of GH–IH Module 16.7: Negative Feedback Between Hypothalamus and Pituitary Gland (3 of 3) Negative feedback (continued) – In some cases, both releasing and inhibiting hormones are part of the regulatory process (continued) ▪ Prolactin (PRL) – PRL inhibits release of PRH (prolactin-releasing hormone) – PRL stimulates release of PIH (prolactin- inhibiting hormone) Negative Feedback Regulation Hormone Relationships With the Hypothalamus Module 16.7: Review A. List the hypothalamic releasing hormones. B. The release of which pituitary hormone would lead to an increased level of somatomedins in the blood? C. What effects would increased circulating levels of glucocorticoids have on the pituitary secretion of ACTH? Learning Outcome: Describe the role of negative feedback in the functional relationship between the hypothalamus and the pituitary gland. Module 16.8: The Thyroid Gland Contains Follicles and Requires Iodine to Produce Hormones That Stimulate Tissue Metabolism Thyroid gland gross anatomy – Located on the anterior surface of the trachea, inferior to the thyroid cartilage – Composed of two lobes connected by a narrow isthmus – Size is variable ▪ Easily felt with fingers Module 16.8: The Thyroid Gland (1 of 9) Thyroid gland histology – Contains large numbers of thyroid follicles ▪ Hollow spheres lined by simple cuboidal epithelium ▪ Follicle cavity holds viscous colloid (fluid packed with dissolved proteins) ▪ Into that colloid, follicle cells secrete a globular protein called thyroglobulin – Molecule containing the amino acid tyrosine (building block of thyroid hormones) ▪ Network of capillaries surrounds each follicle, transporting nutrients, wastes, and secretory products Module 16.8: The Thyroid Gland (2 of 9) Thyroid gland histology (continued) – C (clear) cells ▪ Found between basement membrane of follicle cells ▪ Secrete hormone calcitonin (CT) – Helps to regulate calcium ion concentrations in body fluids Module 16.8: The Thyroid Gland (3 of 9) Thyroid hormone production and storage 1. Iodide ions from diet delivered to thyroid gland and taken up by follicle cells Module 16.8: The Thyroid Gland (4 of 9) Thyroid hormone production and storage (continued) 2. Enzymes convert iodide ions to iodine atoms and attach them to tyrosine portions of thyroglobulin molecule Module 16.8: The Thyroid Gland (5 of 9) Thyroid hormone production and storage (continued) 3. ​Thyroxine with four iodine atoms and triiodothyronine with three iodine atoms are produced and stored in thyroglobulin Module 16.8: The Thyroid Gland (6 of 9) Thyroid hormone production and storage (continued) 4. Follicle cells remove thyroglobulin from follicle by endocytosis Module 16.8: The Thyroid Gland (7 of 9) Thyroid hormone production and storage (continued) 5. Lysosomal enzymes break down thyroglobulin, releasing thyroid hormones and amino acids into cytoplasm ▪ Amino acids used to synthesize more thyroglobulin Module 16.8: The Thyroid Gland (8 of 9) Thyroid hormone production and storage (continued) 6. percent of thyroid secretions) and (