Human Anatomy and Physiology PDF

Human Anatomy and Physiology Eleventh Edition Chapter 16 Part A The Endocrine System PowerPoint® Lectures Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College...

Human Anatomy and Physiology Eleventh Edition Chapter 16 Part A The Endocrine System PowerPoint® Lectures Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Endocrine system acts with nervous system to coordinate and integrate activity of body cells Influences metabolic activities via hormones transported in blood Responses slower but longer lasting than nervous system responses Endocrinology: study of hormones and endocrine organs Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 16.1 Comparison of Nervous and Endocrine Systems Table 16.1 Comparison of Nervous and Endocrine Systems. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Endocrine system controls and integrates: – Reproduction – Growth and development – Maintenance of electrolyte, water, and nutrient balance of blood – Regulation of cellular metabolism and energy balance – Mobilization of body defenses Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Exocrine glands – Produce nonhormonal substances (examples: sweat, saliva) – Have ducts to carry secretion to membrane surface Endocrine glands – Produce hormones – Lack ducts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Hypothalamus is neuroendocrine organ Some have exocrine and endocrine functions – Pancreas, gonads, placenta Other tissues and organs that produce hormones – Adipose cells, thymus, and cells in walls of small intestine, stomach, kidneys, and heart Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Chemical messengers of endocrine system: – Hormones: long-distance chemical signals; travel in blood or lymph – Autocrines: chemicals that exert effects on same cells that secrete them – Paracrines: locally acting chemicals that affect cells other than those that secrete them – Autocrines and paracrines are local chemical messengers; not considered part of endocrine system autocrine paracrine Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Two main classes of hormones: – Amino acid–based hormones ▪ Amino acid derivatives, peptides, and proteins – Steroids ▪ Synthesized from cholesterol ▪ Gonadal and adrenocortical hormones A possible third class, eicosanoids, is considered a hormone by some scientists, but most classify it as a paracrine Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Though hormones circulate systemically, only cells with receptors for that hormone are affected Target cells: tissues with receptors for a specific hormone Hormones alter target cell activity Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Hormone action on target cells may be to: – Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels – Stimulate synthesis of enzymes or other proteins – Activate or deactivate enzymes – Induce secretory activity – Stimulate mitosis Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.1 Endocrine System Overview Hormones act in one of two ways, depending on their chemical nature and receptor location – Water-soluble hormones (all amino acid–based hormones except thyroid hormone) ▪ Act on plasma membrane receptors ▪ Act via G protein second messengers ▪ Cannot enter cell – Lipid-soluble hormones (steroid and thyroid hormones) ▪ Act on intracellular receptors that directly activate genes ▪ May act on plasma membrane receptors ▪ Can enter cell Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems Amino acid–based hormones, except thyroid hormone, exert effects through second- messenger systems Two main second-messenger systems: – Cyclic AMP – PIP2-calcium Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems Cyclic AMP (cAMP) signaling mechanism 1. Hormone (first messenger) binds to receptor 2. Receptor activates a G protein 3. G protein activates or inhibits effector enzyme adenylate cyclase 4. Adenylate cyclase then converts ATP to cAMP (second messenger) 5. cAMP activates protein kinases that phosphorylate (add a phosphate) other proteins Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems Cyclic AMP (cAMP) signaling mechanism (cont.) – Phosphorylated proteins are then either activated or inactivated – cAMP is rapidly degraded by enzyme phosphodiesterase, stopping cascade – Cascades have huge amplification effect Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Cyclic AMP Second-Messenger Mechanism of Water-Soluble Hormones Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems PIP2-calcium signaling mechanism – Hormone-activated G protein activates a different effector enzyme: phospholipase C – Activated phospholipase C splits membrane protein, PIP2, into two second messengers: ▪ Diacylglycerol (DAG) activates protein kinases ▪ Inositol trisphosphate (IP3) causes Ca2+ release from intracellular storage sites Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems PIP2-calcium signaling mechanism (cont.) – Calcium ions act as another second messenger ▪ Ca2+ alters enzyme activity and channels, or binds to regulatory protein calmodulin ▪ Calcium-bound calmodulin activates enzymes that amplify cellular response Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second-Messenger Systems (PIP2-calcium) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Plasma Membrane Receptors and Second- Messenger Systems Other signaling mechanisms – cGMP (cyclic guanosine monophosphate) is second messenger for selected hormones – Other hormones work without second messenger system ▪ Example: insulin receptor is a tyrosine kinase enzyme that autophosphorylates upon insulin binding – Activated tyrosine kinases provide docking sites for relay proteins that trigger cell responses Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Intracellular Receptors and Direct Gene Activation Lipid-soluble steroid hormones and thyroid hormone can diffuse into target cells and bind with intracellular receptors Receptor-hormone complex enters nucleus and binds to specific region of DNA Helps initiate DNA transcription to produce mRNA mRNA is then translated into specific protein – Proteins synthesized have various functions – Examples: metabolic activities, structural purposes, or exported from cell Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Direct Gene Activation Mechanism of Lipid-Soluble Hormones Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved A&P Flix: Mechanism of Hormone Action: Second Messenger cAMP Click here to view ADA compliant Animation: A&P Flix: Mechanism of Hormone Action: Second Messenger cAMP https://mediaplayer.pearsoncmg.com/assets/apf-mech-hormone-action Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.4 Hormone Release Blood levels of hormones – Controlled by negative feedback systems ▪ Increased hormone effects on target organs can inhibit further hormone release – Levels vary only within narrow, desirable range – Hormone release is triggered by: ▪ Endocrine gland stimuli ▪ Nervous system modulation Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endocrine Gland Stimuli Endocrine glands are stimulated to synthesize and release hormones in response to one of three stimuli: – Humoral stimuli – Neural stimuli – Hormonal stimuli Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Figure Animation: Regulation of Hormone Release Click here to view ADA compliant Animation: Regulation of Hormone Release https://mediaplayer.pearsoncmg.com/assets/sci-ap-regulation-of-hormone-release Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endocrine Gland Stimuli Humoral stimuli – Changing blood levels of ions and nutrients directly stimulate secretion of hormones – Example: Ca2+ in blood ▪ Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone) ▪ PTH causes Ca2+ concentrations to rise, and stimulus is removed Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endocrine Gland Stimuli Neural stimuli – Nerve fibers stimulate hormone release ▪ Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Endocrine Gland Stimuli Hormonal stimuli – Hormones stimulate other endocrine organs to release their hormones ▪ Hypothalamic hormones stimulate release of most anterior pituitary hormones ▪ Anterior pituitary hormones stimulate targets to secrete still more hormones ▪ Hypothalamic–pituitary–target endocrine organ feedback loop – Hormones from final target organs inhibit release of anterior pituitary hormones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Nervous System Modulation Nervous system can make adjustments to hormone levels when needed – Can modify stimulation or inhibition of endocrine glands Nervous system can override normal endocrine controls – Example: under severe stress, hypothalamus and sympathetic nervous system override insulin to allow blood glucose levels to increase ▪ Prepare body for “fight or flight” Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.5 Target Cell Specificity Target cells must have specific receptors to which hormone binds – Example: ACTH receptors are found only on certain cells of adrenal cortex, but thyroxin receptors are found on nearly all cells of body Target cell activation depends on three factors: 1. Blood levels of hormone 2. Relative number of receptors on/in target cell 3. Affinity (strength) of binding between receptor and hormone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.5 Target Cell Specificity Amount of hormone can influence number of receptors for that hormone – Up-regulation: target cells form more receptors in response to low hormone levels – Down-regulation: target cells lose receptors in response to high hormone levels ▪ Desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Ligand-receptor binding Number of receptors on a cell can change Target cells with higher # of receptors (up-regulated) are more sensitive Adenosine - neurotransmitter that produces calming effects Caffeine - antagonist to adenosine receptors – acts as stimulant Brain responds by increasing # of adenosine receptors Outcome: coffee drinkers over time need a lot more coffee for the same effect Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Ligand-receptor binding Number of receptors on a cell can change e.g. down-regulation Opiates induce pleasure and block pain i.e. morphine (agonist of endorphins) Regular consumers have # of opiate receptors decrease as an attempt to maintain homeostasis (down-regulation) What happens when drug is no longer taken? Results: need to Less receptors = Reduced consume more drug to Less response to natural sensitivity Endorphins = pain, achieve the same effects Nausea (withdrawal) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 16.2 Comparison between Lipid- and Water-Soluble Hormones Table 16.2 Comparison between Lipid- and Water-Soluble Hormones. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 16.6 The Hypothalamus Hypothalamus is connected to pituitary gland (hypophysis) via stalk called infundibulum Pituitary secretes at least eight major hormones It has two major lobes: – Posterior pituitary: composed of neural tissue that secretes neurohormones ▪ Posterior lobe, along with infundibulum make up the neurohypophysis – Anterior pituitary: (adenohypophysis) consists of glandular tissue Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Pituitary-Hypothalamic Relationships Posterior lobe is neural tissue derived from a downgrowth of brain – Maintains neural connection to hypothalamus via hypothalamic-hypophyseal tract ▪ Tract arises from neurons in paraventricular and supraoptic nuclei in hypothalamus ▪ Runs through infundibulum – Secretes two neurohormones (oxytocin and ADH) ▪ Hormones are stored in axon terminals in posterior pituitary and are released into blood when neurons fire Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Pituitary-Hypothalamic Relationships Anterior lobe is glandular tissue derived from an outpocketing of oral mucosa – Vascularly connected to hypothalamus via hypophyseal portal system consisting of: ▪ Primary capillary plexus ▪ Hypophyseal portal veins ▪ Secondary capillary plexus Hypothalamus secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved The Hypothalamus Controls Release of Hormones From the Pituitary Gland in Two Different Ways FOCUS FIGURE 16.1 Hypothalamus and Pituitary Interactions. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Posterior Pituitary and Hypothalamic Hormones Posterior pituitary consists of axon terminals of neurons from hypothalamic neurons: – Paraventricular neurons produce oxytocin – Supraoptic neurons produce antidiuretic hormone (ADH) Oxytocin and ADH – Each composed of nine amino acids – Almost identical but differ in two amino acids Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Posterior Pituitary and Hypothalamic Hormones Oxytocin – Strong stimulant of uterine contractions released during childbirth – Also acts as hormonal trigger for milk ejection – Both are positive feedback mechanisms – Acts as neurotransmitter in brain ▪ Uses PIP2-calcium second messenger system Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Posterior Pituitary and Hypothalamic Hormones Antidiuretic hormone (ADH) – Hypothalamus contains osmoreceptors that monitor solute concentrations – If concentration too high, posterior pituitary triggered to secrete ADH – Targets kidney tubules to reabsorb more water to inhibit or prevent urine formation – Release also triggered by pain, low blood pressure, and drugs Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Posterior Pituitary and Hypothalamic Hormones Antidiuretic hormone (ADH) (cont.) – Inhibited by alcohol, diuretics – High concentrations cause vasoconstriction, so also called vasopressin Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones All six hormones are peptide hormones All but growth hormone (GH) activate target cells via cAMP second-messenger system All but two are tropic hormones (tropins) that regulate secretion of other hormones – Growth hormone (GH) – Thyroid-stimulating hormone (TSH) (tropic) – Adrenocorticotropic hormone (ACTH) (tropic) – Follicle-stimulating hormone (FSH) (tropic) – Luteinizing hormone (LH) (tropic) – Prolactin (PRL) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Growth hormone (GH) – Also called somatotropin as it is produced by somatotropic cells – Has direct actions on metabolism and indirect growth-promoting actions – Direct actions on metabolism ▪ Glucose-sparing actions decrease rate of cellular glucose uptake and metabolism (anti-insulin effects) ▪ Triggers liver to break down glycogen into glucose ▪ Increases blood levels of fatty acids for use as fuel and encourages cellular protein synthesis Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones – Indirect actions on growth: ▪ GH triggers liver, skeletal muscle, and bone to produce insulin-like growth factors (IGFs) ▪ IGFs then stimulate: – Cellular uptake of nutrients used to synthesize DNA and proteins needed for cell division – Formation of collagen and deposition of bone matrix ▪ GH stimulates most cells to enlarge and divide, but major targets are bone and skeletal muscle Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones – Regulation of secretion ▪ GH release or inhibition chiefly regulated by hypothalamic hormones on somatotropic cells – Growth hormone–releasing hormone (GHRH) stimulates GH release Triggered by low blood GH or glucose, or high amino acid levels – Growth hormone–inhibiting hormone (GHIH) (somatostatin) inhibits release Triggered by increase in GH and IGF levels ▪ Ghrelin (hunger hormone) also stimulates GH release Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Growth-Promoting and Metabolic Actions of Growth Hormone (GH) Figure 16.5 Growth-promoting and metabolic actions of growth hormone (GH). Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical – Homeostatic Imbalance 16.2 Hypersecretion of GH is usually caused by anterior pituitary tumor – In children results in gigantism ▪ Can reach heights of 8 feet – In adults results in acromegaly ▪ Overgrowth of hands, feet, and face Hyposecretion of GH – In children results in pituitary dwarfism ▪ May reach height of only 4 feet – In adults usually causes no problems Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Disorders of Pituitary Growth Hormone Figure 16.6 Disorders of pituitary growth hormone. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Thyroid-stimulating hormone – Tropic hormone that is also called thyrotropin as it is produced by thyrotropic cells – Stimulates normal development and secretory activity of thyroid – Release triggered by thyrotropin-releasing hormone from hypothalamus – Inhibited by rising blood levels of thyroid hormones that act on both pituitary and hypothalamus ▪ Also inhibited by GHIH Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Regulation of Thyroid Hormone Secretion Figure 16.7 Regulation of thyroid hormone secretion. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Adrenocorticotropic hormone (ACTH) – Also called corticotropin as it is secreted by corticotropic cells ▪ Precursor to corticotropin is pro- opiomelanocortin – ACTH stimulates adrenal cortex to release corticosteroids – Regulation of ACTH release ▪ Triggered by hypothalamic corticotropin-releasing hormone/factor (CRH or CRF) in daily rhythm – Highest levels in morning ▪ Internal and external factors that alter release of CRH include fever, hypoglycemia, and stressors Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Gonadotropins (FSH and LH) – Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are secreted by gonadotropic cells of anterior pituitary – FSH stimulates production of gametes (egg or sperm) – LH promotes production of gonadal hormones ▪ In females, LH helps mature follicles of egg, triggers ovulation and release of estrogen and progesterone ▪ In males, LH stimulates production of testosterone Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Gonadotropins (FSH and LH) (cont.) – LH and FSH both are absent from blood in prepubertal boys and girls – Regulation of gonadotropin release ▪ Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty ▪ Suppressed by gonadal hormones (feedback) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Prolactin (PRL) – Secreted by prolactin cells of anterior pituitary – Stimulates milk production in females; role in males not well understood – Regulation primarily controlled by prolactin-inhibiting hormone (PIH), which is dopamine – PIH prevents release of PRL until needed, with decreased levels leading to lactation Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Prolactin (PRL) (cont.) – Increased estrogen levels stimulate PRL ▪ Reason behind breast swelling and tenderness during menstrual cycle – Blood levels rise toward end of pregnancy – Suckling stimulates PRL release and promotes continued milk production Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Anterior Pituitary Hormones Tropic Hormones Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 16.3-1 Pituitary Hormones: Summary of Regulation and Effects Table 16.3-1 Pituitary Hormones: Summary of Regulation and Effects. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 16.3-2 Pituitary Hormones: Summary of Regulation and Effects Table 16.3-2 Pituitary Hormones: Summary of Regulation and Effects. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved