Copyright © 2010 Pearson Education, Inc. Marieb Chapter 16 Part A: The Endocrine System
Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Acts with the nervous system to coordinate and integrate the activity of body cells Influences metabolic activities by means of hormones transported in the blood Responses occur more slowly but tend to last longer than those of the nervous system Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands
Copyright © 2010 Pearson Education, Inc. Endocrine System: Overview Some organs produce both hormones and exocrine products (e.g., pancreas) The hypothalamus has both neural and endocrine functions Secondary endocrine tissues include adipose cells, thymus, cells in the walls of the small intestine, stomach, kidneys, and heart
Copyright © 2010 Pearson Education, Inc. Figure 16.1 Pineal gland Hypothalamus Pituitary gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Thyroid gland Adrenal glands Pancreas Ovary (female) Testis (male)
Copyright © 2010 Pearson Education, Inc. Chemical Messengers: Review Hormone: Autocrines: Paracrines: Autocrines and paracrines are local chemical messengers and are not considered part of the endocrine system
Copyright © 2010 Pearson Education, Inc. Chemistry of Hormones Three main classes 1.Peptides Examples include: 2. Catecholamines Examples include: 3. Steroids Examples include:
Copyright © 2010 Pearson Education, Inc. Peptides/Proteins
Copyright © 2010 Pearson Education, Inc. Catecholamines, Biogenic Amines, Amines
Copyright © 2010 Pearson Education, Inc. Steroids
Copyright © 2010 Pearson Education, Inc. Target Cell Activation Target cell activation depends on three factors 1.Blood levels of the hormone 2.Relative number of receptors on or in the target cell 3.Affinity of binding between receptor and hormone
Copyright © 2010 Pearson Education, Inc. Hormones in the Blood Hormones are removed from the blood by Degrading enzymes Kidneys Liver These factors influence a hormone’s half-life
Copyright © 2010 Pearson Education, Inc. Half-Life Definition:
Copyright © 2010 Pearson Education, Inc. Interaction of Hormones at Target Cells Multiple hormones may interact in several ways! Permissiveness: Synergism: Antagonism:
Copyright © 2010 Pearson Education, Inc. Control of Hormone Release Blood levels of hormones Are controlled by negative feedback systems Vary only within a narrow desirable range Hormones are synthesized and released in response to 1.Humoral stimuli 2.Neural stimuli 3.Hormonal stimuli
Copyright © 2010 Pearson Education, Inc. Humoral Stimuli Changing blood levels of ions and nutrients directly stimulates secretion of hormones Example: Ca 2+ in the blood Declining blood Ca 2+ concentration This hormone causes Ca 2+ concentrations to
Copyright © 2010 Pearson Education, Inc. Figure 16.4a (a) Humoral Stimulus Capillary (low Ca 2+ in blood) Parathyroid glands Thyroid gland (posterior view) PTH Parathyroid glands 1 Capillary blood contains low concentration of Ca 2+, which stimulates… 2 …secretion of parathyroid hormone (PTH) by parathyroid glands*
Copyright © 2010 Pearson Education, Inc. Neural Stimuli Nerve fibers stimulate hormone release Example:
Copyright © 2010 Pearson Education, Inc. Figure 16.4b (b) Neural Stimulus CNS (spinal cord) Medulla of adrenal gland Preganglionic sympathetic fibers Capillary 1 Preganglionic sympathetic fibers stimulate adrenal medulla cells… 2 …to secrete catechola- mines (epinephrine and norepinephrine)
Copyright © 2010 Pearson Education, Inc. Hormonal Stimuli Hormones stimulate other endocrine organs to release their hormones Involve feedback loops
Copyright © 2010 Pearson Education, Inc. Figure 16.4c (c) Hormonal Stimulus Hypothalamus Thyroid gland Adrenal cortex Gonad (Testis) Pituitary gland 1 The hypothalamus secretes hormones that… 2 …stimulate the anterior pituitary gland to secrete hormones that… 3 …stimulate other endocrine glands to secrete hormones
Copyright © 2010 Pearson Education, Inc. Feedback Loops and Hormone Regulation
Copyright © 2010 Pearson Education, Inc. Feedback Loops and Hormone Regulation
Copyright © 2010 Pearson Education, Inc. The Pituitary Gland and Hypothalamus The pituitary gland (hypophysis) has two major lobes 1.Posterior pituitary (lobe) (neurohypophysis): Glial-like cells and nerve fibers 2.Anterior pituitary (lobe) (adenohypophysis) Glandular tissue
Copyright © 2010 Pearson Education, Inc. Basic Anatomy of the Pituitary & Hypothalamus
Copyright © 2010 Pearson Education, Inc. Posterior Pituitary & Hypothalamus
Copyright © 2010 Pearson Education, Inc. Anterior Pituitary & Hypothalamus
Copyright © 2010 Pearson Education, Inc. Figure 16.5a Hypothalamic neurons synthesize oxytocin and ADH. Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary. Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Oxytocin and ADH are released into the blood when hypothalamic neurons fire. Paraventricular nucleus Supraoptic nucleus Optic chiasma Hypothalamus Inferior hypophyseal artery Oxytocin ADH Infundibulum (connecting stalk) Hypothalamic- hypophyseal tract Axon terminals Posterior lobe of pituitary (a) Relationship between the posterior pituitary and the hypothalamus Neurohypophysis
Copyright © 2010 Pearson Education, Inc. Figure 16.5b When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior pituitary. Anterior pituitary hormones are secreted into the secondary capillary plexus. Hypothalamus Hypothalamic neuron cell bodies Hypophyseal portal system Superior hypophyseal artery (b) Relationship between the anterior pituitary and the hypothalamus Anterior lobe of pituitary TSH, FSH, LH, ACTH, GH, PRL Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Adenohypophysis
Copyright © 2010 Pearson Education, Inc. Posterior Pituitary Hormones - Oxytocin Oxytocin is released during labor (stimulates uterine contractions); Pitocin is synthetic oxytocin Also released when an infant suckles at the breast, starts breast feeding NEWS FLASH! Called the :”cuddle hormone”; thought to be involved in parent child bonding, autism, trust, and empathy Gee,it fixes everything! (NOT!)
Copyright © 2010 Pearson Education, Inc. Posterior Pituitary Hormones - ADH ADH stands for Its other names are vasopressin or AVP Action =
Copyright © 2010 Pearson Education, Inc. Posterior Pituitary Hormones - ADH ADH Actions Drink a 44 oz diet coke Work out without fluid intake
Copyright © 2010 Pearson Education, Inc. Posterior Pituitary Hormones - ADH Too much ADH? You have SIADH Too little ADH? You have diabetes insipidus
Copyright © 2010 Pearson Education, Inc. Anterior Pituitary Hormones Growth hormone (GH) Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL)
Copyright © 2010 Pearson Education, Inc. Anterior Pituitary Hormones All are proteins All except GH activate cyclic AMP second- messenger systems at their targets TSH, ACTH, FSH, and LH are all _________ hormones (regulate the secretory action of other endocrine glands)
Copyright © 2010 Pearson Education, Inc. Hypothalamic and AP Hormones Hypo AP
Copyright © 2010 Pearson Education, Inc. Growth Hormone (GH) Stimulates most cells, but primarily targets bone and skeletal muscle Causes protein synthesis and use of fats for fuel Most effects are mediated indirectly by insulin-like growth factors (IGFs) = hormones GH release is regulated by (GHRH) (GHIH) (AKA: somatostatin)
Copyright © 2010 Pearson Education, Inc. Actions of Growth Hormone Direct action of GH Stimulates liver, skeletal muscle, bone, and cartilage to produce insulin-like growth factors Mobilizes fats, elevates blood glucose by decreasing glucose uptake and encouraging glycogen breakdown (anti-insulin effect of GH)
Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Growth Hormone Hypersecretion In children results in gigantism Andre the Giant Robert Wadlow In adults results in acromegaly
Copyright © 2010 Pearson Education, Inc. Homeostatic Imbalances of Growth Hormone Hypersecretion Hyposecretion In children results in pituitary dwarfism
Copyright © 2010 Pearson Education, Inc. Figure 16.6 Growth hormone Feedback Inhibits GHRH release Stimulates GHIH release Inhibits GH synthesis and release Anterior pituitary Liver and other tissues Indirect actions (growth- promoting) Direct actions (metabolic, anti-insulin) Insulin-like growth factors (IGFs) Extraskeletal SkeletalFat Carbohydrate metabolism Increased cartilage formation and skeletal growth Increased protein synthesis, and cell growth and proliferation Increased fat breakdown and release Increased blood glucose and other anti-insulin effects Effects Produce Hypothalamus secretes growth hormone—releasing hormone (GHRH), and somatostatin (GHIH) Initial stimulus Physiological response Result Increases, stimulates Reduces, inhibits
Copyright © 2010 Pearson Education, Inc. Thyroid-Stimulating Hormone (Thyrotropin) Regulation of TSH release Stimulated by thyrotropin-releasing hormone (TRH) Inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus
Copyright © 2010 Pearson Education, Inc. Figure 16.7 Hypothalamus Anterior pituitary Thyroid gland Thyroid hormones TSH TRH Target cells Stimulates Inhibits
Copyright © 2010 Pearson Education, Inc. Adrenocorticotropic Hormone (ACTH) Secreted by glandular cells of the anterior pituitary Stimulates the adrenal cortex to release corticosteroids
Copyright © 2010 Pearson Education, Inc. Adrenocorticotropic Hormone (ACTH) Regulation of ACTH release Triggered by hypothalamic corticotropin- releasing hormone (CRH) in a daily rhythm Internal and external factors such as fever, hypoglycemia, and stressors can alter the release of CRH
Copyright © 2010 Pearson Education, Inc. Gonadotropins Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Secreted by glandular cells of the anterior pituitary FSH stimulates gamete (egg or sperm) production LH promotes production of gonadal hormones Absent from the blood in prepubertal boys and girls
Copyright © 2010 Pearson Education, Inc. Gonadotropins Regulation of gonadotropin release Triggered by the gonadotropin-releasing hormone (GnRH) during and after puberty Suppressed by gonadal hormones (feedback)
Copyright © 2010 Pearson Education, Inc. Prolactin (PRL) Secreted by glandular cells of the anterior pituitary Stimulates milk production Regulation of PRL release Primarily controlled by prolactin-inhibiting hormone (PIH) (dopamine) Blood levels rise toward the end of pregnancy Suckling stimulates PRH release and promotes continued milk production