Endocrine System PDF

The Endocrine System Endocrine System Includes all cells and endocrine tissues that produce hormones or paracrine factors Endocrine vs Nervous System Nervous system performs short term crisis management Controls and coordinates bodily activities that require rapid responses Endocrine system reg...

The Endocrine System Endocrine System Includes all cells and endocrine tissues that produce hormones or paracrine factors Endocrine vs Nervous System Nervous system performs short term crisis management Controls and coordinates bodily activities that require rapid responses Endocrine system regulates long term ongoing metabolic activity management Endocrine communication is carried out by endocrine cells (glands) that release hormones into the bloodstream in order to alter metabolic activities Paracrine communication involves chemical messengers between cells within one tissue STIMULUS: Deviation from homeostasis Endocrine System – long term, slow response Nervous System – short term, rapid response GOAL: Return to homeostasis Endocrine System Functions Endocrine system functions include: Maintenance of an optimal biochemical environment within the body Influences metabolic activities Integration and regulation of growth and development Control, maintenance, and instigation of sexual reproduction Endocrine System: Overview Endocrine glands: hypothalamus pituitary (adenohypophysis) pineal thyroid Pineal gland parathyroid thymus adrenal pancreas gonads The hypothalamus has both neural and endocrine functions The pancreas and gonads produce both hormones and exocrine products Other tissues and organs that produce hormones – adipose cells, cells of the small intestine, stomach, kidneys, and heart Hypothalamu s Pituitary gland Thyroid gland Parathyroid glands Thymus gland Adrenal glands Pancrea s Ovary Testis Hormones Hormones are chemicals secreted by cells into the bloodstream for transport to distant target tissues Hormones bind to their corresponding receptors, inducing events within the cell that ultimately change its behavior Hormones produce one or more of the following cellular changes in target cells: Alter plasma membrane permeability Stimulate gene activation & protein synthesis Activate or deactivate enzyme systems Induce secretory activity Stimulate mitosis & cytokinesis Hormone Classification Amino Acid Based Amino Acid Derivatives Protein Derivatives Based on a single amino acid Based on peptides of ≥ 3 amino acids Lipid Derivatives Based on fatty acids Eicosanoids Tyrosine Based Tryptophan Based Serotonin Melatonin Catecholamin es Epinephrine Norepinephrine Dopamine Thyroid Hormones Triiodothyronine (T3) Thyroxine (T4) Glycoproteins carbohydrate + protein Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Thyroid-stimulating hormone (TSH) Human chorionic gonadotropin (hCG) Erythropoietin (EPO) Identify One in each group describe Short Polypeptides/ Small Proteins < 200 amino acids Leukotrienes Prostaglandins Thromboxanes Prostacyclins Vasopressin (ADH) Oxytocin Adrenocorticotropic hormone (ACTH) Growth Hormone (GH) Melanocyte-stimulating hormone (MSH) Prolactin (PRL) Insulin Glucagon Parathyroid hormone (PTH) Calcitonin (CT) Atrial natriuretic peptide (ANP) Brain natriuretic peptide (BNP) Gastrin Secretin Cholecystokinin (CCK) Gastric Inhibitory Peptide (GIP) Steroid Based Androgens Estrogens Progestins Mineralocorticoids Glucocorticoids Calcitriol (Vitamin D) Classification of Hormones based on chemical composition Amino Acid Derivatives Tyrosine Based – Catecholamines (Epi, NE, Dopa) & Thyroid hormones Tryptophan Based – Serotonin & Melatonin Protein Derivatives (most hormones belong to this class) Glycoproteins – carbohydrate + protein Short Polypeptides – chains of less than 200 amino acids Lipid Derivatives Steroids – gonadal and adrenocortical hormones Eicosanoids – lipid based hormones that act locally on the same cell that released it or nearby cells (autocrine and paracrine mediators) Classification of Hormones based on receptors Hormones can also be classified based on location of receptors: Membrane Receptors Second messengers systems (G protein-linked) Tyrosine kinase-linked receptors Hormone-gated ion channels Intracellular and intranuclear receptors Most amino acid based-hormones use G protein-linked receptors for signal transduction Most steroid hormones can diffuse through the membrane and, therefore, bind to receptors found in the cytosol and nucleus, with the goal of activating or repressing genes AA-Based Hormone Action: cAMP-2nd Messenger AA-Based Hormone Action: PIP2-Calcium Ip3 MOA + pathway Know IP3 MOA G Proteins and Hormone Activity Hormone G proteins may decrease cAMP AC G PDE PLC PKC IP3 AMP cAMP cAMP AMP Smooth ER Ca2+ G G-Linked G Ca++ Channel G-Linked G-Linked G proteins may increase Ca2+ levels DAG G Proteins may increase cAMP G DAG G-Linked Ca++ IP3 Ca++ activates Protein Kinases decreases Protein Kinases Ca++ Opens Ion Channels Activates Enzymes CELLULAR RESPONSE Ex: Glucagon hormone releases glucose from glycogen polymers by increasing cAMP Ca++ CELLULAR RESPONSE Ex: Insulin hormone decreases glycogen breakdown by decreasing cAMP /Calmodulin Complex Enzyme Inhibition CELLULAR RESPONSE Ex: Oxytocin hormone causes influx of Ca2+ and excitation of smooth muscle in myometrium of uterus Steroid Hormones Steroid hormones diffuse into target cells to bind and activate a specific intracellular receptor Target Cell Characteristics Specificity Hormones circulate to all tissues but only activate target cells Target cells must have specific receptors to which the hormone binds Activation dependent on: Blood levels of the hormone How many hormones and how many receptor Affinity (think diabetes) Relative number of receptors on the target cell The affinity of those receptors for the hormone Sensitivity Up-regulation – target cells form more receptors in response to the hormone Down-regulation – target cells lose receptors in response to the hormone Hormone Concentrations in the Blood Concentrations of circulating hormone reflect: Rate of release Speed of inactivation and removal from the body Hormones are removed from the blood by: Degrading enzymes Kidney filtration Liver enzymes 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 humoral, hormonal, and neural stimuli Humoral – detects blood [solutes] Hormonal – detects blood [hormone] Neural – stimulated by AP from CNS Humoral Stimuli Humoral Stimulus Humoral = of body fluids (i.e.: blood) Secretion of hormones in direct response to changing blood levels of ions, nutrients, and gases Capillary blood contains low concentration of Ca2+, which stimulates… Low [Ca2+] in blood Thyroid gland (posterior) Example: [Ca2+] in the blood ↓ [Ca2+] in blood stimulates parathyroid glands to secrete PTH (parathyroid hormone) ↑ PTH causes [Ca2+] in blood to rise (Ca2+ is reabsorbed in kidneys and leached from bones) and the stimulus is removed Parathyroid glands PTH …secretion of parathyroid hormone (PTH) by parathyroid glands. PTH acts to increase blood Ca2+ Neural Stimuli Neural Stimulus Hormones are released in response to neural stimulation originating from the CNS (brain, spinal cord) Preganglionic sympathetic fibers stimulate adrenal medulla cells…. CNS (spinal cord) Example: Action potential travels along sympathetic nerve fibers that synapse at the adrenal medulla Chromaffin cells in adrenal medulla respond by releasing catecholamine hormones (EPI and NE) into the blood Preganglionic sympathetic fibers Medulla of adrenal gland Capillary …to secrete catecholamines (epinephrine, norepinephrine, and a small amount of dopamine) Hormonal Stimuli Hormonal Stimulus Hormones are released in response to hormones produced by other endocrine organs Example: The hypothalamus secrets hormones that… Hypothalamus …stimulate the anterior pituitary gland to secrete hormones that…. Pituitary gland Hypothalamic “releasinghormones” stimulate the anterior pituitary to release hormones Anterior pituitary’s tropic hormones stimulate target glands to secrete still more hormones Thyroid gland Adrenal cortex Gonads Note: Tropic vs Trophic Tropic – a hormone that stimulates release of another hormone Trophic – a hormone that stimulates growth and nourishment of a gland ….stimulate other endocrine glands to secrete hormones Feedback Control of Endocrine Secretion Hypothalamus Releasing hormone Releasing Hormone (from Adenohypophysis Endocrine organ Negative Feedback Loop Hormone 1 Hormone 1 Target Endocrine Organ Hormone 1 Hypothalamus) (from Anterior Pituitary) TRH TSH Thyroid Gland Thyroid hormones (T3 & T4) CRH ACTH Adrenal Cortex Glucocorticoids (cortisol) Testes Inhibin Ovaries Inhibin Estrogens Testes Androgens Ovaries Progestins Estrogens FSH GnRH Hormone 2 TEST!!!!!!! LH (from target organ) Hormonal NFbL Hypothalamic-Pituitary-Adrenal axis (HPA Axis) Hypothalamus Adenohypophysis of pituitary gland E1 ACTH E2 Long-loop negative feedback CRH KEY Integrating center: Hypothalamus CorticotropinReleasing Hormone (CRH) E1 Adrenocorticotropic Hormone (ACTH) Cortisol E2 Adrenal Cortex T E1 = Endocrine 1 Adenohypophysis E2 = Endocrine 2 Adrenal Gland Glucocorticoids (Cortisol) Response T Target cells Nervous System Modulation Sensory Stimuli The nervous system can modify the stimulation of endocrine glands and their negative feedback mechanisms The nervous system can override normal endocrine controls Example: Neural control of BGL under stress (stress) Cerebral Cortex Integrated information Limbic System creates emotions overrides Hypothalamus & Brain stem initiates Autonomic Responses Endocrine Responses Lack of Humoral & Hormonal Stimuli Control of Endocrine Activity Endocrine reflexes are the counterparts of neural reflexes Hypothalamus regulates the activity of the nervous and endocrine systems Secreting regulatory hormones that control the anterior pituitary gland Releasing hormones at the posterior pituitary gland Exerts direct neural control over the endocrine cells of the adrenal medullae Three Methods of Hypothalamic Control over the Endocrine System Anything RH comes from hypothalamus Hypothalamic Control of Adenohypophysis Hypothalamus regulates secretion of hormones Secretes releasing factors to release hormones Secretes inhibiting hormones to turn off secretion of hormones Hypothalamic Control of Pituitary Anything RH comes from hypothalamus Hypothalamus • • • • • • • >The Hypothalamus sends releasing/inhibiting hormones to the Adenohypophysis via the Hypophyseal portal system • • TRH PRH PIH (Dopamine) GHRH GHIH (Somatostatin) CRH GnRH Infundibulum HypothalamicHypophyseal Tract MSH >The Hypothalamus sends neural stimuli to the neurohypophysis via the Hypothalamic hypophyseal tract Hypophyseal Portal System Adenohypophysis (aka anterior pituitary aka pars distalis) Know this!!!! Inhibiting hormones not tested Oxytocin Vasopressin (aka Antidiuretic hormone aka ADH) • • • • • • TSH PRL GH ACTH FSH LH Neurohypophysis (aka posterior pituitary pars nervosa) • • Oxytocin Vasopressin (aka Anti-diuretic hormone aka ADH) Hypophysis (Pituitary Gland) Adenohypophysis (Anterior lobe) synthesizes and releases six hormones that regulate activity of other endocrine glands: Hypothalamic neurons in paraventricular nuclei Hypothalamic neurons in supraoptic nuclei Neurons in ventral hypothalamus TSH PRL GH ACTH FSH LH Infundibular stalk Superior hypophyseal artery Hypothalamohypophyseal nerve tract Primary capillary plexus Axon terminals Hypophyseal portal veins Secondary capillary plexus Neurohypophysis (Posterior lobe) stores and releases two hormones from hypothalamus Hypophyseal venule Secretory cells of adenohypophysis TSH ACTH GH FSH LH PRL Hypophyseal venule Inferior hypophyseal artery Oxytocin ADH Oxytocin ADH Describe relationship between hypothalamus and pituitary Adenohypophysis (anterior lobe) Neurohypophysis (posterior lobe) The Hypothalamus The hypothalamus sends a chemical stimulus to the anterior pituitary to releasing hormones stimulate the synthesis and release of hormones TRH - Thyrotropin Releasing Hormone (TRH) >> release of TSH Thyroid Stimulating Hormone from Anterior Pituitary Gland >> stimulate release of T3, T4 from Thyroid Gland (in neck) CRH - Corticotropin Releasing Hormone (CRH) from Hypothalamus >> release of ACTH Adrenocorticotropic Hormone from Anterior Pituitary Gland GnRH - Gonadotropin Releasing Hormone (GnRH) from Hypothalamus >> release of FSH and LH from the Anterior Pituitary >> Gonads GHRH - Growth Hormone Releasing Hormone >> release of GH Growth Hormone PRH - Prolactin Releasing Hormone from Hypothalamus >> release of PRL Prolactin Hormone from Anterior Pituitary Hypothalamic Hormones Hypothalamic Releasing/Inhibiting Hormones and Adenohypophysis Hypothalamic Hormone Effect on Adenohypophysis Thyrotropin-releasing hormone (TRH) release of Thyroid stimulating hormone (TSH) Prolactin Inhibiting Hormone/Dopamine (PIH) inhibits release of Prolactin (PRL) Growth hormone-releasing hormone (GHRH) release of Growth Hormone (GH) Growth hormone-inhibiting hormone/ Somatostatin (GHIH) inhibits release of GH Corticotropin-releasing hormone (CRH) release of Adrenocorticotropic Hormone (ACTH) Gonadotropin-releasing hormone (GnRH) release of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) Hypothalamus and Neurohypophysis Two neurohormones are synthesized in the hypothalamus and released by the neurohypophysis ADH (vasopressin) Oxytocin Hypothalamic Control of Anterior Pituitary Hypothalamic hormones PRFs Adenohypophyseal hormones Prolacti n Endocrine targets and secreted hormones Nonendocrine targets Breast Hypothalamus GHIH (Somatostatin ) PIH (Dopamine ) TRH CR H TSH ACTH Thyroid gland Adrenal gland T3 T4 Cortisol GHR H GH Liver IGFs Various tissues GnRH FS H LH Gonadal endocrine cells Androgen s Estrogen s Gonadal germ cells Adenohypophysis of pituitary gland The Pituitary Gland - Hypophysis Attached to the hypothalamus by the infundibulum Two basic divisions of the pituitary gland Anterior pituitary or Adenohypophysis Posterior pituitary or NeurohypophysisPars distalis (low density Pars nervosa(highdennsity) and infadibulum The Pituitary Gland - Hypophysis Releases nine important peptide hormones All nine bind to membrane receptors and use cyclic AMP as a second messenger Anterior Pituitary Pars distalis – largest division of the adenohypophysis Contains five different types of endocrine cells Somatotropic cells – secrete growth hormone (GH) Mammotropic cells – secrete prolactin (PRL) Thyrotropic cells – secrete thyroid-stimulating hormone (TSH) Corticotropic cells – secrete adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (MSH) Gonadotropic cells – secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Tropic hormones TSH, ACTH, FSH, and LH Regulate the secretion of hormones by other endocrine glands Hormones of the Adenohypophysis Thyroid stimulating hormone (TSH) triggers the release of thyroid hormones (T3 & T4) from thyroid gland Thyrotropin-Releasing Hormone ( TRH) from Hypothalamus promotes the release of TSH from the anterior pituitary Adrenocorticotropic Hormone (ACTH) stimulates the release of glucocorticoids from the adrenal gland Corticotropin-Releasing Hormone (CRH) from Hypothalamus causes the secretion of ACTH from the anterior pituitary Hormones of the Adenohypophysis Follicle stimulating hormone (FSH) – stimulates follicle development and estrogen secretion in females and sperm production in males Luteinizing hormone (LH) causes ovulation and progestin production in females and androgen production in males Gonadotropin-Releasing Hormone (GnRH) from the Hypothalamus promotes the release of FSH and LH Hormones of the Adenohypophysis Prolactin (PRL) – stimulates the development of mammary glands and milk production Prolactin-Releasing Hormone (PRLH) from Hypothalamus promotes the release of Prolactin (PRL) Growth Hormone (GH or Somatotropin) – stimulates cell growth and replication Growth Hormone-Releasing Hormone (GHRH) from Hypothalamus promotes the release of Follicle stimulating hormone (FSH) and Luteinizing hormone (LH) Melanocyte-Stimulating Hormone (MSH) – stimulates melanocytes to produce melanin Thyroid Stimulating Hormone (TSH) Triggered by TRH from hypothalamus Rising blood levels of thyroid hormones act on the pituitary and hypothalamus to block the release of TSH Hypothalamus TRH Adenohypophysis of pituitary gland Thyroid gland E1 TSH E2 T3 T4 T Response Long-loop negative feedback Tropic hormone that stimulates the normal development and secretory activity of the thyroid gland Adrenocorticotropic Hormone (ACTH) Triggered by CRH from hypothalamus Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH Stress Hypothalamus CRH Adenohypophysis ACTH Adrenal cortex Cortisol Long-loop Negative Feedback Stimulates the adrenal cortex to release corticosteroids Circadian rhythm Immune System Liver Muscle Adipose tissue Function suppressed Gluconeogenesis Protein catabolism Lipolysis Gonadotropins - FSH, LH Regulate the functions of the ovaries and testes Triggered by GnRH during and after puberty Two Gonadotropins: Follicle-stimulating hormone (FSH) FSH stimulates gamete (egg or sperm) production Luteinizing hormone (LH) LH In females: Stimulates maturation of the ovarian follicle Triggers ovulation Stimulates release of estrogens and progesterone LH in males: LH stimulates testes to produce testosterone These hormones not tested Growth Hormone (GH) (Somatotropin) Produced and released by the anterior pituitary Regulated by GHRH and GHIH from hypothalamus Function: Stimulates liver, skeletal muscle, bone, and cartilage to release insulin-like growth factors (IGFs) Increases cell metabolism and blood glucose level Promotes use of fats for fuel (lipolysis & gluconeogenesis) and protein synthesis No IGF on test or prolactin Prolactin Stimulates milk production in breasts of females Triggered by PRH Inhibited by PIH Blood levels rise toward the end of pregnancy Suckling stimulates PRH release and encourages continued milk production hormones not tested Neurohormones ➢Neurohormones are hormones released and secreted by neurons into the bloodstream, targeting distant cells. ➢Example: ➢Oxytocin ➢ADH Hormones (ADH & oxytocin) are made and packaged in neuron soma Vesicles are transported down axons Vesicles containing hormones are stored in neurohypophysis Neurohormones are released into blood when stimulated by APs from hypothalamus Posterior Pituitary Structurally part of the brain Contains axons of hypothalamic nerves where hormones are manufactured Releases Antidiuretic Hormone (ADH) Decreases the amount of water lost at the kidneys Elevates blood pressure Releases Oxytocin Stimulates contractile cells in mammary glands Stimulates smooth muscle cells in uterus Not in-depth just focus on anatomy Oxytocin Oxytocin is a strong stimulant of uterine contraction Regulated by a positive feedback mechanism to oxytocin in the blood This leads to increased intensity of uterine contractions, ending in birth Oxytocin Oxytocin triggers milk ejection (“letdown” reflex) in women producing milk Synthetic and natural oxytocic drugs are used to induce or hasten labor Plays a role in sexual arousal and satisfaction in males and nonlactating females Antidiuretic Hormone (ADH) Antidiuretic Hormone (ADH) reduces urine formation in order to avoid dehydration Solute concentration of blood is measured by osmoreceptors: With high solutes, ADH is synthesized and released, thus preserving water With low solutes, ADH is not released, thus allowing water loss from the body Alcohol inhibits ADH release and causes copious urine output Collecting Duct cells 4 3 Fusion of vesicles with membrane Storage vesicles cAMP ADH 2 Aquaporins ADH cAMP 1 ADH receptor G-word Review Glucose – a six carbon sugar that is a major energy source for the body C6H12O6 Glucose ! cellular respiration Glycolysis – breakdown of glucose to 2 pyruvate and 2 ATP Gluconeogenesis – formation of glucose from noncarbohydrate precursors, especially amino acids Glycogen – polysaccharide of glucose that serves as energy storage in animals Glycogenesis – the synthesis of glycogen from glucose Glycogenolysis – the breakdown of glycogen into glucose Glucagon – hormone produced by pancreas, by alpha cells (α cells), to increase your blood glucose levels (BGL) Glucagon produces glycogenolysis Thyroid Gland The largest endocrine gland, composed of circular follicles Colloid fills the lumen of the follicles and is the precursor of thyroid hormones Parafollicular cells (C cells) produce the hormone calcitonin Produces calcetonin opposite of the parathyroid Don’t worry about parafollicular cells Thyroid Follicles and Thyroid Hormones Thyroid gland contains numerous follicles Release several hormones such as thyroxine (T4) and triiodothyronine (T3) that regulate metabolism increases protein synthesis promotes glycolysis, gluconeogenesis, glucose uptake C cells produce calcitonin - helps regulate calcium concentration in body fluids Thyroid hormones T3 (Triiodothyronine) and T4 (Thyroxine) are two closely related iodinecontaining compounds T3 is ten times more active than T4 Bind to thyroid binding globulins (TBG) or albumin for transport in the blood Mechanisms of activity are similar to steroids – they are transported across cell membrane Hormones chemical structure not tested Thyroid hormones Regulate metabolism Promote glycolysis, gluconeogenesis, glucose uptake Glucose oxidation Increase metabolic rate Heat production Regulate growth and development Regulate tissue growth Increase protein synthesis Developing skeletal and nervous systems Maturation and reproductive capabilities Lipid soluble attach to albumin because they ccoagules Regulation of Thyroid Hormones Hypothalamus Stimulus: Low circulating T3, T4 detected by hypothalamus and adenohypophysis Hypothalamic ThyrotropinReleasing Hormone (TRH) can override the short-loop negative feedback TRH Adenohypophysis of pituitary gland Thyroid gland TSH E2 T3 T4 T Know this!!!! Short-loop E1 Response Long-loop negative feedback Regulated by negative feedback loop (NFbL) Four Parathyroid Glands Embedded in the posterior surface of the thyroid gland Chief cells produce parathyroid hormone (PTH) in response to lower than normal calcium concentrations Parathyroid hormones are regulators of calcium levels in healthy adults Homeostatic Regulation of Calcium Ion Concentrations Osteo blast hormone vs osteoclast Thyroid gland produces calcitonin Increased excretion of calcium in kidneys Calcium deposition in bone Inhibition of osteoclasts >> Calcium levels decline Parathyroid gland secretes parathyroid hormone (PTH) Release of stored calcium from bone Stimulation of osteoclasts Enhanced reabsorption of calcium in kidneys Stimulation of final conversion of vitamin D to calcitriol in kidneys; causes enhanced Ca2+ & PO4-3 absorption by GI tract >> Calcium levels rise *Normal calcium levels: 8.5 – 11 mg/dL Adrenal (Suprarenal) Glands Pyramid-shaped organs atop the kidneys Structurally and functionally, they are two glands in one Adrenal medulla – Nervous tissue that functions as part of the Sympathetic Nervous System Secretes catecholamines: Epinephrine (~75 – 80%) Norepinephrine (~25 – 30%) Adrenal cortex – Glandular tissue Secretes corticosteroids: Mineralocorticoids Glucocorticoids Gonadocorticoids Capsule Zona glomerulosa Aldosterone Regulated by: ACTH & K+ Adrenal Cortex Zona fasciculata Regulated by: ACTH Know the picture Mineralocorticoids Adrenal Medulla Glucocorticoids Cortisol Zona reticularis Gonadocorticoids Regulated by: ACTH Testosterone, Estrogen Innervation of sympathetic nervous system Catecholamines Epinephrine Norepinephrine Mineralocorticoids Maintain electrolyte balance Aldosterone is the most important mineralocorticoid Stimulates reabsorption of Na+ by the kidneys, reducing its excretion from the body Aldosterone secretion is stimulated by: Rising blood levels of K+ Low blood Na+ Decreasing blood volume or pressure Aldosterone Glucocorticoids Help the body resist stress by sparing glucose and reducing inflammation Cortisol is the most important glucocorticoid Stimulates gluconeogenesis Is glucose-sparing: conserves glycogen in liver while stimulating lipolysis & gluconeogenesis Increases blood glucose, fatty acids, and amino acids Cortisol Gonadocorticoids (Sex Hormones) Most gonadocorticoids secreted are androgens (male sex hormones), and the most important one is testosterone Androgens contribute to: The onset of puberty The appearance of secondary sex characteristics Sex drive in females Androgens can be converted into estrogens after menopause Estrogen Not emphasiZed Testosterone Structure of the Pancreas Figure 16.21 Anatomy and histology of the pancreas. Anatomy not important yet Pancreas Pancreatic islets – clusters of endocrine cells within the pancreas (islets of Langerhans) α-cells secrete Glucagon β-cells secrete Insulin Islets of Langerhans Pancreas 80x Acinar cells (exocrine) Duct Insulin and Glucagon Insulin lowers blood glucose by increasing the rate of glucose uptake and utilization Glucagon raises blood glucose by increasing the rates of glycogen breakdown and glucose manufacture by the liver Know this!!!! Regulation of Blood Glucose Concentrations Normal Blood Glucose Level (BGL): 70 – 110 mg/dL When BGL rises >> β cells respond by secreting insulin: Increased rate of glucose transport into target cell Increased rate of glucose utilization and ATP generation Increased conversion of glucose to glycogen (liver, skeletal muscle) Increased amino acid absorption and protein synthesis Increased triglyceride synthesis (adipose tissue) >> Blood glucose concentration declines back to normal range When BGL drops >> α cells respond by secreting glucagon: Increased breakdown of glycogen to glucose (liver, skeletal muscle) Increased breakdown of fats to fatty acids (adipose tissue) Increased synthesis and release of glucose (liver) >> Blood glucose concentration rises back to normal range Know this!!!! Regulation of Glucose Metabolism During Exercise Glucagon secretion increases during exercise to promote liver glycogenolysis Epinephrine and Norepinephrine further increase glycogenolysis Cortisol levels also increase during exercise for protein catabolism for later gluconeogenesis Cortisol is glucose-sparing Growth Hormone mobilizes free fatty acids Thyroxine (T4) promotes glucose catabolism Regulation of Glucose Metabolism During Exercise Insulin is usually required for cell uptake of glucose but exercising skeletal muscle does not! Exercise may enhance insulin’s binding to receptors Up-regulation of GLUT receptors occurs after 4 weeks of exercise! Know this!!!! Insulin -> RTK>GLUT4….diabetese could be cured via exercise Regulation of Fat Metabolism During Exercise When low plasma glucose levels occur, the catecholamines are released to accelerate lypolysis Triglycerides are reduced to free fatty acids (lipolysis) by lipase which is activated by: Cortisol Epinephrine Norepinephrine Growth Hormone Hormonal Effects on Fluid and Electrolyte Balance Reduced plasma volume leads to release of Aldosterone from adrenal cortex, which increases Na+ and H2O reabsorption by the kidneys and renal tubes. Osmoreceptors in hypothalamus sense dehydration, Antidiuretic Hormone (ADH) is released from the posterior pituitary, and water is then reabsorbed by the kidneys. Know this!!!! Hormones and Stress Stress – any condition that threatens homeostasis GAS (General Adaptation Syndrome) is our bodies response to stress-causing factors Three phases to GAS: Alarm phase (immediate, fight or flight, directed by the sympathetic nervous system) Resistance phase (dominated by glucocorticoids) Exhaustion phase (breakdown of homeostatic regulation and failure of one or more organ systems) Stress and the Adrenal Gland SHORT-TERM STRESS PROLONGED STRESS Stress Nerve impulses Hypothalamus Spinal cord CRH Corticotroph cells of adenohypophysis Preganglionic sympathetic fibers Adrenal cortex ACTH Know this!!!! Catecholamines Short-term stress response 1) Increased HR 2) Increased BP 3) Liver converts glycogen to glucose and releases glucose into blood 4) Bronchodilation 5) Changes in blood flow patterns leading to decreased GI and GU activity 6) Increased metabolic rate Mineralocorticoids Glucocorticoids Long-term stress response 1) Retention of Na+ and H2O by kidneys 2) Increased BV and BP 1) Proteins and fats converted to glucose or broken down for energy 2) Increased BGL 3) Suppression of immune system General Adaptation Syndrome Resistance Phase Long-term metabolic adjustments GH Circulatory system and body tissues Mobilization of remaining energy reserves: Lipolysis: Lipids are released from adipose tissue Proteolysis: Amino acids are released from skeletal muscle Cortisol ACTH ADH Conservation of glucose Peripheral tissue (except neural) breaks down SNS lipids to obtain energy RAS Aldosterone Glucagon Elevation of blood glucose level (BGL) Gluconeogenesis: Liver synthesizes glucose from other carbohydrates, amino acids, and lipids Conservation of Na+ and H2O; loss of K+ and H+ KEY: GH ATCH ADH SNS RAS = = = = = Growth Hormone Adrenocorticotropic hormone Antidiuretic hormone Sympathetic Nervous System Renin-Angiotensin System