The Endocrine System final

The Endocrine System final - The Endocrine System The...

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Unformatted text preview: The Endocrine System The Endocrine System: Overview Overview Endocrine system – the Endocrine body’s second great controlling system controlling which influences metabolic activities of cells by means of hormones hormones Endocrine System: Overview Overview Endocrine glands – Endocrine pituitary Endocrine System: Overview Endocrine Endocrine glands – thyroid, thyroid, Endocrine System: Overview Endocrine Endocrine glands – parathyroid, parathyroid, Endocrine System: Overview Endocrine Endocrine glands –, adrenal, Endocrine Endocrine System: Overview Overview Endocrine glands –pineal, Endocrine Endocrine System: Overview Endocrine Endocrine glands –pineal, Endocrine Endocrine System: Overview Endocrine Endocrine glands – thymus Hormone Hormone The term hormone, derived from a Greek The hormone derived phrase meaning "to set in motion," aptly describes the dynamic actions of these circulating substances as they elicit cellular responses and regulate physiologic processes through feedback mechanisms. Endocrine System: Overview Endocrine The pancreas and gonads produce both hormones and The exocrine products exocrine Endocrine System: Overview Overview The hypothalamus has The both neural functions and releases hormones and Thank GOD we had ADH Endocrine System: Overview Endocrine Other tissues and Other organs that produce hormones – adipose cells, Endocrine System: Overview Endocrine Other tissues and organs that produce hormones –pockets Other of cells in the walls of the small intestine, Endocrine System: Overview Overview Other tissues and Other organs that produce hormones –stomach Endocrine System: Overview Endocrine Other tissues and organs Other that produce hormones –kidneys –kidneys Endocrine System: Overview Endocrine Other tissues and organs Other that produce hormones –heart –heart Major Endocrine Organs Organs Autocrines and Paracrines Autocrines Autocrines – Autocrines chemicals that exert their effects on the same cells that secrete them that Autocrines and Paracrines Autocrines Paracrines – locally acting chemicals that affect cells Paracrines other than those that secrete them other Autocrines and Paracrines Paracrines These are not These considered hormones since hormones are long-distance chemical signals signals Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Hormones Hormones Hormones – chemical Hormones substances secreted by cells into the extracellular fluids extracellular Regulate the Regulate metabolic function of other cells other Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Have lag times ranging from seconds to hours Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Have lag times ranging from seconds to hours Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Tend to have prolonged effects Hormones Hormones Hormones – chemical Hormones substances secreted by cells into the extracellular fluids extracellular Are classified as Are amino acid-based hormones, or steroids hormones, Hormones Hormones Eicosanoids – Eicosanoids biologically active lipids with local hormone–like activity activity Hormones Hormones Eicosanoids – biologically active lipids with local Eicosanoids hormone–like activity hormone–like leukotrienes and prostaglandins Types of Hormones Types Amino acid based – Amino most hormones belong to this class, including: including: Amines, thyroxine, Amines, peptide, and protein hormones hormones Types of Hormones Types Amino acid based – most hormones belong to this class, Amino including: including: Amines, thyroxine, peptide, and protein hormones Types of Hormones Hormones Steroids – Steroids gonadal and adrenocortical hormones hormones Types of Hormones Types Steroids – gonadal and adrenocortical hormones Hormone Action Hormone Hormones alter target cell activity by one of two Hormones mechanisms mechanisms Second messengers involving: Regulatory G proteins Amino acid–based hormones Hormone Action Hormone Hormones alter target Hormones cell activity by one of two mechanisms two Direct gene activation Direct involving steroid hormones hormones Hormone Action Hormone The precise response depends on the type of The the target cell the Mechanism of Hormone Action Mechanism Hormones produce one or more of the following cellular Hormones changes in target cells changes Alter plasma membrane permeability Mechanism of Hormone Action Mechanism Hormones produce one or more of the following Hormones cellular changes in target cells cellular Stimulate protein synthesis Stimulate Mechanism of Hormone Action Mechanism Hormones produce one Hormones or more of the following cellular changes in target cells target Activate or deactivate Activate enzyme systems enzyme Mechanism of Hormone Action Mechanism Hormones produce Hormones one or more of the following cellular changes in target cells changes Induce secretory Induce activity activity Mechanism of Hormone Action Mechanism Hormones produce one Hormones or more of the following cellular changes in target cells target Stimulate mitosis Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Hormone (first messenger) binds to its receptor, which then binds to a G Hormone protein protein Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP The G protein is then activated as it binds GTP, displacing GDP Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Activated G protein activates the effector enzyme adenylate cyclase Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Adenylate cyclase generates cAMP (second messenger) from ATP Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP cAMP activates protein kinases, which then cause cellular effects Amino Acid-Based Hormone Action: cAMP Second Messenger Second Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Hormone binds to the receptor and activates Hormone G protein protein Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium G protein binds and activates a phospholipase enzyme protein Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Phospholipase splits the phospholipid PIP2 into diacylglycerol (DAG) and IP3 (both act as second diacylglycerol messengers) messengers) Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium DAG activates protein kinases; IP3 triggers release of Ca2+ stores Ca Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Ca2+ (third messenger) alters cellular responses Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Steroid Hormones Steroid Steroid hormones and thyroid hormone diffuse easily into their Steroid target cells target Steroid Hormones Steroid Once inside, they bind and activate a specific intracellular Once receptor receptor Steroid Hormones Steroid The hormone-receptor complex travels to the nucleus and binds The a DNA-associated receptor protein DNA-associated Steroid Hormones Steroid This interaction prompts DNA transcription to produce mRNA Steroid Hormones Steroid The mRNA is translated into proteins, which bring about a The cellular effect cellular Steroid Hormones Figure 16..3 Target Cell Specificity Specificity Hormones circulate to Hormones all tissues but only activate cells referred to as target cells to Target Cell Specificity Target Target cells must have specific receptors to which the Target hormone binds hormone Target Cell Specificity Specificity These receptors may be These intracellular or located on the plasma membrane membrane Target Cell Specificity Target Examples of hormone Examples activity activity ACTH receptors are only ACTH found on certain cells of the adrenal cortex the Target Cell Specificity Specificity Examples of hormone Examples activity activity Thyroxin receptors are Thyroxin found on nearly all cells of the body the Target Cell Activation Activation Target cell activation depends on three Target factors factors Blood levels of the hormone Target Cell Activation Target Target cell activation depends on three factors Relative number of receptors on the target cell Target Cell Activation Target Target cell activation depends on Target three factors three The affinity of those receptors The for the hormone for Target Cell Activation Target Upregulation: The hormones Upregulation: increases the number or sensitivity of the receptors sensitivity Thyroid hormone increases the Thyroid number of cardiac β1 receptors Clinical relevance: During thyrotoxicosis, Propranolol During can be used for treating tachycardia tachycardia why? Because propranolol will have why? enough β1 receptors Target Cell Activation Target Downregulation: A hormone Downregulation: decreases the number or affinity of receptors for itself or other hormones or prolonged use of propranolol prolonged can DECREASE the number of β1 receptors Clinical relevance: A patient’s response to drug patient’s therapy may change over time therapy Rats! Where did they all go?!? Hormone Concentrations in the Blood the Hormones circulate in Hormones the blood in two forms – free or bound free Hormone Concentrations in the Blood Blood Steroids and thyroid Steroids hormone are attached to plasma proteins to All others are All unencumbered unencumbered Hormone Concentrations in the Blood Blood Concentrations of circulating hormone reflect: Concentrations Rate of release Speed of inactivation and removal from the body Hormone Concentrations in the Blood Blood Hormones are removed Hormones from the blood by: from Degrading enzymes Hormone Concentrations in the Blood Blood Hormones are removed Hormones from the blood by: from The kidneys Hormone Concentrations in the Blood Blood Hormones are removed from the blood by: Liver enzyme systems Interaction of Hormones at Target Cells Target Three types of hormone interaction Permissiveness – one hormone cannot Permissiveness exert its effects without another hormone being present e.g. Absence of Thyroid hormone e.g. results in Cretinism Interaction of Hormones at Target Cells Target Three types of hormone Three interaction interaction Synergism – more than Synergism one hormone produces the same effects on a target cell cell e.g. Glucagon, GH and e.g. Norepinephrine all cause Glycogenolysis Glycogenolysis Interaction of Hormones at Target Cells Target Three types of hormone interaction Antagonism – one or more hormones opposes the action of Antagonism another hormone another Control of Hormone Release Control Blood levels of hormones: Blood Are controlled by negative feedback systems Vary only within a narrow desirable range Control of Hormone Release Control Hormones are Hormones synthesized and released in response to: in Humoral stimuli Neural stimuli Hormonal stimuli Humoral Stimuli Humoral Humoral stimuli – secretion of hormones in direct Humoral response to changing blood levels of ions and nutrients response Humoral Stimuli Stimuli Humoral stimuli – Humoral secretion of hormones in direct response to changing blood levels of ions and nutrients of Neural Stimuli Neural Neural stimuli – nerve Neural fibers stimulate hormone release release Preganglionic Preganglionic sympathetic nervous system (SNS) fibers stimulate the adrenal medulla to secrete catecholamines Hormonal Stimuli Hormonal Hormonal stimuli – Hormonal release of hormones in response to hormones produced by other endocrine organs endocrine Hormonal Stimuli Stimuli The hypothalamic The hormones stimulate the anterior pituitary In turn, pituitary In hormones stimulate targets to secrete still more hormones more Nervous System Modulation Nervous The nervous system The modifies the stimulation of endocrine glands and their negative feedback mechanisms Nervous System Modulation Nervous The nervous system can The override normal endocrine controls controls For example, control of For blood glucose levels blood Normally the endocrine Normally system maintains blood glucose Nervous System Modulation Modulation For example, control For of blood glucose levels levels Under stress, the Under body needs more glucose The hypothalamus The and the sympathetic nervous system are activated to supply ample glucose glucose Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Pituitary gland – two-lobed organ that secretes nine major Pituitary hormones hormones Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Neurohypophysis – posterior lobe (neural Neurohypophysis tissue) and the infundibulum tissue) Receives, stores, and releases hormones Receives, from the hypothalamus from Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Adenohypophysis – anterior lobe, made up of glandular tissue Adenohypophysis Synthesizes and secretes a number of hormones Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Pituitary-Hypothalamic Relationships: Posterior Lobe Posterior The posterior lobe is a downgrowth of hypothalamic neural tissue Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract) Pituitary-Hypothalamic Relationships: Posterior Lobe Posterior Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone Nuclei (ADH) (ADH) These hormones are transported to the posterior pituitary Level Pituitary-Hypothalamic Relationships: Anterior Lobe opment of Pituitary Anterior 5­6 wks The anterior lobe of the pituitary is an The outpocketing of the oral mucosa outpocketing There is no direct neural contact with There the hypothalamus the Level Pituitary-Hypothalamic Relationships: Anterior Lobe opment of Pituitary Anterior The anterior lobe of the The pituitary is an outpocketing of the oral mucosa of There is no direct neural There contact with the hypothalamus hypothalamus Pituitary-Hypothalamic Relationships: Anterior Lobe Anterior There is a vascular There connection, the hypophyseal portal system, consisting of: portal The primary capillary plexus The hypophyseal portal veins The secondary capillary plexus Pituitary-Hypothalamic Relationships: Anterior Lobe Anterior Adenophypophy Adenophypophy seal Hormones The six hormones of the The adenohypophysis: adenohypophysis: Are abbreviated as GH, Are TSH, ACTH, FSH, LH, and PRL and Regulate the activity of Regulate other endocrine glands other Adenophypophyseal Hormones Adenophypophyseal The six hormones of the The adenohypophysis: adenohypophysis: Are abbreviated as GH, Are TSH, ACTH, FSH, LH, and PRL and Regulate the activity of Regulate other endocrine glands other Adenophypophyseal Hormones Adenophypophyseal In addition, pro-opiomelanocortin (POMC): Has been isolated from the pituitary Is enzymatically split into ACTH, opiates, and MSH Is Activity of the Adenophypophysis Activity The hypothalamus sends a chemical stimulus to the The anterior pituitary anterior Releasing hormones stimulate the synthesis and release of Releasing hormones hormones Activity of the Adenophypophysis Activity The hypothalamus sends a chemical stimulus to the anterior The pituitary pituitary Inhibiting hormones shut off the synthesis and release of hormones Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Thyroid-stimulating hormone (TSH) Thyroid-stimulating Activity of the Adenohypophysis Activity The tropic hormones The that are released are: that Adrenocorticotropic Adrenocorticotropic hormone (ACTH) hormone Activity of the Adenophypophysis Adenophypophysis The tropic hormones The that are released are: that Follicle-stimulating Follicle-stimulating hormone (FSH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Follicle-stimulating hormone (FSH) Follicle-stimulating Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are The released are: released Follicle-stimulating hormone Follicle-stimulating (FSH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones The that are released are: that Luteinizing hormone Luteinizing (LH) (LH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Luteinizing hormone (LH) Growth Hormone (GH) Growth Produced by somatotropic Produced cells of the anterior lobe that: that: Stimulate most cells, but Stimulate target bone and skeletal muscle muscle Promote protein synthesis Promote and encourage the use of fats for fuel for Growth Hormone (GH) (GH) Produced by Produced somatotropic cells (acidophils) of the anterior lobe that: anterior Most effects are Most mediated indirectly by somatomedins somatomedins Anterior pituitary Growth Hormone (GH) Growth Antagonistic hypothalamic Antagonistic hormones regulate GH hormones Growth hormone–releasing Growth hormone (GHRH) stimulates GH release GH Growth hormone–inhibiting Growth hormone (GHIH) inhibits GH release GH Metabolic Action of Growth Hormone Hormone GH stimulates liver, GH skeletal muscle, bone, and cartilage to produce insulin-like growth factors factors Metabolic Action of Growth Hormone Metabolic Metabolic Action of Growth Hormone Metabolic Direct action promotes lipolysis and inhibits glucose uptake Metabolic Action of Growth Hormone Hormone Ponce de Leon Ponce Fountain of Youth Acromegaly Acromegaly Acromegaly Acromegaly Acromegaly Acromegaly Gigantism Gigantism Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Tropic hormone Tropic that stimulates the normal development and secretory activity of the thyroid gland thyroid Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Triggered by Triggered hypothalamic peptide thyrotropin-releasing hormone (TRH) hormone Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Rising blood levels of Rising thyroid hormones act on the pituitary and hypothalamus to block the release of TSH the Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Stimulates the adrenal Stimulates cortex to release corticosteroids corticosteroids Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Triggered by Triggered hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm daily Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Internal and external Internal factors such as fever, hypoglycemia, and stressors can trigger the release of CRH release Gonadotropins Gonadotropins Gonadotropins – folliclestimulating hormone stimulating (FSH) and luteinizing hormone (LH) hormone Regulate the function of Regulate the ovaries and testes the Gonadotropins Gonadotropins Gonadotropins – folliclestimulating hormone (FSH) stimulating and luteinizing hormone (LH) (LH) FSH stimulates gamete (egg FSH or sperm) production or What would be the blood levels of FSH in this group of students? FSH Gonadotropins Gonadotropins Gonadotropins – follicle-stimulating hormone (FSH) Gonadotropins and luteinizing hormone (LH) and Absent from the blood in prepubertal boys and girls Gonadotropins Gonadotropins Gonadotropins – Gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (LH) Triggered by the Triggered hypothalamic gonadotropin-releasing hormone (GnRH) during and after puberty and Functions of Gonadotropins Functions In females LH works with FSH to LH cause maturation of the ovarian follicle ovarian Functions of Gonadotropins Functions In females LH works alone to LH trigger ovulation (expulsion of the egg from the follicle) follicle) Functions of Gonadotropins Functions In females LH promotes LH synthesis and release of estrogens and progesterone progesterone Functions of Gonadotropins Gonadotropins In females LH promotes synthesis LH and release of estrogens and progesterone and Functions of Gonadotropins Functions In females LH promotes LH synthesis and release of estrogens and progesterone progesterone Functions of Gonadotropins Functions In males LH stimulates LH interstitial cells of the testes to produce testosterone testosterone Functions of Gonadotropins Functions In males LH is also referred to as interstitial cell-stimulating hormone LH (ICSH) (ICSH) Prolactin (PRL) Prolactin In females, stimulates milk production by the breasts Triggered by the hypothalamic prolactin-releasing hormone Triggered (PRH) (PRH) Prolactin (PRL) Prolactin Inhibited by prolactin-inhibiting hormone (PIH) Blood levels rise toward the end of pregnancy Suckling stimulates PRH release and encourages continued Suckling milk production milk The Posterior Pituitary and Hypothalamic Hormones The Posterior pituitary – made of axons of hypothalamic Posterior neurons, stores antidiuretic hormone (ADH) and oxytocin oxytocin The Posterior Pituitary and Hypothalamic Hormones The ADH and oxytocin are synthesized in the hypothalamus The Posterior Pituitary and Hypothalamic Hormones The ADH influences water balance The Posterior Pituitary and Hypothalamic Hormones The Oxytocin stimulates Oxytocin smooth muscle contraction in breasts and uterus and Oxytocin Synthetic and natural oxytocic drugs are used Synthetic to induce or hasten labor to Oxytocin Plays a role in sexual arousal and satisfaction Plays in males and nonlactating females in Antidiuretic Hormone (ADH) ADH helps to ADH avoid dehydration or water overload water Prevents urine Prevents formation formation Vasopressin regulates water permeability stimuli for release 1- ECF osmolarity (osmoreceptors in hypothalamus) osmolarity >280 mOsm vasopressin release 2- decreases in blood pressure/blood volume carotid/aortic baroreceptors/atrial stretch receptors vasopressin: released from posterior pituitary called antidiuretic hormone (ADH) for its ability to inhibit diuresis with vasopressin present mOsm water 100 900 collecting duct 500 1000 1200 300 vasa recta 1200 urine 1200 mOsm 100 300 600 600 700 800 mOsm water 300 300 600 NO vasopressin present 900 collecting duct 100 collecting duct impermeable to water 900 1200 1200 100 urine 100 mOsm response is GRADED (not all-or-none): amount of water reabsorbed depends upon amount of vasopressin present vasa recta: peritubular capillaries that dip into the medulla and go back up to the cortex Antidiuretic Hormone Antidiuretic (ADH) (ADH) Osmoreceptors monitor Osmoreceptors the solute concentration of the blood of Antidiuretic Hormone Antidiuretic (ADH) (ADH) With high solutes, ADH is With synthesized and released, thus preserving water thus With low solutes, ADH is With not released, thus causing water loss from the today water Antidiuretic Hormone (ADH) Alcohol inhibits ADH release and causes copious Alcohol urine output urine The Posterior Pituitary and Hypothalamic Hormones The Both use PIP-calcium second-messenger mechanism Thyroid Gland The largest endocrine gland, located in the anterior The neck, consists of two lateral lobes connected by a median tissue mass called the isthmus median Thyroid Gland Composed of follicles that produce the glycoprotein thyroglobulin Thyroid Gland Other endocrine cells, the parafollicular cells, Other produce the hormone calcitonin produce Effects of Thyroid Hormone TH is concerned with: Increasing metabolic rate Increasing Heat production Effects of Effects Thyroid Hormone Hormone TH plays a role in: Regulating tissue Regulating growth growth Calcitonin Produced by the parafollicular, or C, cells Lowers blood calcium levels in children Antagonist to parathyroid hormone (PTH) Calcitonin Inhibits osteoclast activity (and thus bone resorption) Inhibits and release of calcium from the bone matrix and Stimulates calcium uptake and incorporation into the Stimulates bone matrix bone Parathyroid Glands Parathyroid Tiny glands embedded Tiny in the posterior aspect of the thyroid of Chief (principal) cells Chief secrete PTH secrete PTH (parathormone) PTH regulates calcium balance in the blood balance Effects of Parathyroid Hormone Effects PTH release PTH increases Ca2+ in increases the blood as it: the Stimulates Stimulates osteoclasts to digest bone matrix Effects of Parathyroid Hormone PTH release PTH increases Ca2+ in the increases blood as it: blood Enhances the Enhances reabsorption of Ca2+ reabsorption and the secretion of phosphate by the kidneys kidneys Effects of Parathyroid Hormone Effects PTH release PTH increases Ca2+ in increases the blood as it: the Increases Increases absorption of Ca2+ absorption by intestinal mucosal cells Effects of Parathyroid Hormone Effects Rising Ca2+ in the blood inhibits PTH release Adrenal (Suprarenal) Glands Adrenal glands – paired, pyramid-shaped Adrenal organs atop the kidneys organs Adrenal (Suprarenal) Glands Structurally and functionally, they are two glands in Structurally one one Adrenal medulla – nervous tissue that acts as part of the Adrenal ANS ANS Adrenal (Suprarenal) Glands Structurally and functionally, they are two glands in Structurally one one Adrenal cortex – glandular tissue derived from Adrenal embryonic mesoderm embryonic Adrenal Cortex Synthesizes and Synthesizes releases steroid hormones called corticosteroids corticosteroids Adrenal Cortex Different corticosteroids are produced in each of Different the three layers the Zona glomerulosa – mineralocorticoids Zona (chiefly aldosterone) (chiefly Adrenal Cortex Different corticosteroids are produced in each of Different the three layers the Zona fasciculata – glucocorticoids Zona (chiefly cortisol) (chiefly Adrenal Cortex Different corticosteroids are produced in each of Different the three layers the Zona reticularis – gonadocorticoids Zona (chiefly androgens) (chiefly Mineralocorticoids Regulate the Regulate electrolyte concentrations of extracellular fluids fluids Mineralocorticoids Aldosterone – most important mineralocorticoid Aldosterone Maintains Na+ balance by reducing excretion of sodium from the body from Stimulates reabsorption of Na+ by the kidneys Mineralocorticoids Aldosterone secretion is stimulated by: Rising blood levels of K+ Low blood Na+ Decreasing blood volume or pressure The Four Mechanisms of Aldosterone Secretion Aldosterone Renin-angiotensin mechanism – kidneys release Renin-angiotensin renin, which is converted into angiotensin II that in turn stimulates aldosterone release The Four Mechanisms of The Aldosterone Secretion Aldosterone Plasma concentration of sodium and potassium Plasma – directly influences the zona glomerulosa cells cells ACTH – causes small increases of aldosterone ACTH during stress during Atrial natriuretic peptide (ANP) – inhibits Atrial activity of the zona glomerulosa activity The Four Mechanisms of Aldosterone Secretion Secretion Glucocorticoids (Cortisol) Help the body resist stress by: Keeping blood sugar levels relatively constant Maintaining blood volume and preventing water Maintaining shift into tissue shift Glucocorticoids Glucocorticoids (Cortisol) (Cortisol) Cortisol provokes: Gluconeogenesis Gluconeogenesis (formation of glucose from noncarbohydrates) noncarbohydrates) Rises in blood Rises glucose, fatty acids, and amino acids and Excessive Levels of Excessive Glucocorticoids Glucocorticoids Excessive levels of glucocorticoids: Depress cartilage and bone formation Inhibit inflammation Depress the immune system Promote changes in cardiovascular, neural, and Promote gastrointestinal function gastrointestinal Gonadocorticoids (Sex Hormones) Most gonadocorticoids secreted are androgens (male Most sex hormones), and the most important one is testosterone testosterone Gonadocorticoids (Sex Hormones) Hormones) Androgens contribute to: The onset of puberty The appearance of secondary sex characteristics Sex drive in females Sex Adrenal Medulla Made up of chromaffin cells that secrete epinephrine and norepinephrine Secretion of these hormones causes: Blood glucose levels to rise Blood vessels to constrict The heart to beat faster Blood to be diverted to the brain, heart, and skeletal muscle Adrenal Medulla Epinephrine is the more potent stimulator of Epinephrine the heart and metabolic activities the Norepinephrine is more influential on Norepinephrine peripheral vasoconstriction and blood pressure peripheral Stress and the Adrenal Gland Stress Pancreas A triangular gland, which has both exocrine triangular and endocrine cells, located behind the stomach Acinar cells produce an enzyme-rich juice Acinar used for digestion (exocrine product) used Pancreatic islets (islets of Langerhans) produce Pancreatic hormones (endocrine products) hormones The islets contain two major cell types: Alpha (α) cells that produce glucagon Beta (β) cells that produce insulin Glucagon A 29-amino-acid polypeptide hormone that is a 29-amino-acid potent hyperglycemic agent potent Its major target is the liver, where it promotes: Glycogenolysis – the breakdown of glycogen to Glycogenolysis glucose glucose Gluconeogenesis – synthesis of glucose from lactic Gluconeogenesis acid and noncarbohydrates acid Release of glucose to the blood from liver cells Insulin A 51-amino-acid protein consisting of two 51-amino-acid amino acid chains linked by disulfide bonds amino Synthesized as part of proinsulin and then Synthesized excised by enzymes, releasing functional insulin insulin Insulin: Lowers blood glucose levels Enhances transport of glucose into body cells Counters metabolic activity that would enhance Counters blood glucose levels blood Effects of Insulin Binding The insulin receptor is a tyrosine kinase The enzyme enzyme After glucose enters a cell, insulin binding After triggers enzymatic activity that: triggers Catalyzes the oxidation of glucose for ATP Catalyzes production production Polymerizes glucose to form glycogen Converts glucose to fat (particularly in adipose Converts tissue) tissue) Regulation of Blood Glucose Levels Regulation The The hyperglycemic effects of glucagon and the hypoglycemic effects of insulin insulin Diabetes Mellitus (DM) Results from hyposecretion or hypoactivity of Results insulin insulin The three cardinal signs of DM are: Polyuria – huge urine output Polydipsia – excessive thirst Polyphagia – excessive hunger and food Polyphagia consumption consumption Hyperinsulinism – excessive insulin secretion, Hyperinsulinism resulting in hypoglycemia resulting Diabetes Mellitus (DM) Figure 16.18 Gonads: Female Paired ovaries in the abdominopelvic cavity Paired produce estrogens and progesterone produce They are responsible for: They Maturation of the reproductive organs Appearance of secondary sexual characteristics Breast development and cyclic changes in the Breast uterine mucosa uterine Gonads: Male Testes located in an extra-abdominal sac Testes (scrotum) produce testosterone (scrotum) Testosterone: Initiates maturation of male reproductive organs Causes appearance of secondary sexual Causes characteristics and sex drive characteristics Is necessary for sperm production Maintains sex organs in their functional state Pineal Gland Small gland hanging from the roof of the third Small ventricle of the brain ventricle Secretory product is melatonin Melatonin is involved with: Day/night cycles Physiological processes that show rhythmic Physiological variations (body temperature, sleep, appetite) variations Thymus Lobulated gland located deep to the sternum in Lobulated the thorax the Major hormonal products are thymopoietins Major and thymosins and These hormones are essential for the These development of the T lymphocytes (T cells) of the immune system the Other Hormone-Producing Other Structures Structures Heart – produces atrial natriuretic peptide Heart (ANP), which reduces blood pressure, blood volume, and blood sodium concentration volume, Gastrointestinal tract – enteroendocrine cells Gastrointestinal release local-acting digestive hormones release Placenta – releases hormones that influence the Placenta course of pregnancy course Other Hormone-Producing Other Structures Structures Kidneys – secrete erythropoietin, which Kidneys signals the production of red blood cells signals Skin – produces cholecalciferol, the precursor Skin of vitamin D of Adipose tissue – releases leptin, which is Adipose involved in the sensation of satiety, and stimulates increased energy expenditure stimulates Developmental Aspects Hormone-producing glands arise from all three Hormone-producing germ layers germ Endocrine glands derived from mesoderm Endocrine produce steroid hormones produce Endocrine organs operate smoothly throughout Endocrine life life Most endocrine glands show structural Most changes with age, but hormone production may or may not be affected may Developmental Aspects Exposure to pesticides, industrial chemicals, Exposure arsenic, dioxin, and soil and water pollutants disrupts hormone function disrupts Sex hormones, thyroid hormone, and Sex glucocorticoids are vulnerable to the effects of pollutants pollutants Interference with glucocorticoids may help Interference explain high cancer rates in certain areas explain Developmental Aspects Ovaries undergo significant changes with age Ovaries and become unresponsive to gonadotropins and Female hormone production declines, the Female ability to bear children ends, and problems associated with estrogen deficiency (e.g., osteoporosis) begin to occur osteoporosis) Testosterone also diminishes with age, but Testosterone effect is not usually seen until very old age effect Developmental Aspects GH levels decline with age and this accounts GH for muscle atrophy with age for Supplemental GH may spur muscle growth, Supplemental reduce body fat, and help physique reduce TH declines with age, causing lower basal TH metabolic rates metabolic PTH levels remain fairly constant with age, PTH and lack of estrogen in women makes them more vulnerable to bone-demineralizing effects of PTH effects ...
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