Endocrine System Chapter 9 PDF

The Endocrine System Modified from: 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Learning Outcomes  Hormones and Intercellular Communication Explain the classification of hormones, identify key functions of hormones secreted by organs of the endocrine...

The Endocrine System Modified from: 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Learning Outcomes  Hormones and Intercellular Communication Explain the classification of hormones, identify key functions of hormones secreted by organs of the endocrine system, and list organs with secondary endocrine functions. Compare the mechanism of action for nonsteroid and steroid hormones. Describe how the hypothalamus controls other endocrine organs.  Endocrine Organs Describe the location and structure of the pituitary gland, and identify pituitary hormones, their target tissues, and functions. Describe the location and structure of the thyroid gland, identify the hormones it secretes, and list the effects of thyroid hormones on peripheral tissues. Describe the location and structure of the parathyroid glands, identify the hormone they produce, and list the effects of Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Learning Outcomes Describe the location, structure, and general functions of the adrenal glands, identify the hormones produced by the adrenal cortex and the adrenal medulla, and list the effects of each hormone. Identify the location and structure of the pancreas, identify key pancreatic cells, and the hormones they produce, specify the functions of each hormone, and summarize blood glucose homeostasis. Identify the location of the pineal gland, and identify the functions of melatonin. Define the stress response and summarize the events for each phase. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Endocrine System  Homeostasis is regulated by two systems: Nervous Endocrine  Together they control most of the organs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Endocrine and Nervous Systems  Features in common Release chemicals that bind to specific receptors Share some of same chemical messengers (e.g., norepinephrine, epinephrine) Regulate activity by negative feedback Common goal to preserve homeostasis Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Hormones control several major processes: Reproduction Growth and development Maintains electrolyte, water, nutrient balance of the blood Regulates cellular metabolism and energy balance Mobilization of body defences Maintenance of much of homeostasis Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormone Overview  Hormones are produced by specialized cells  Cells secrete hormones into extracellular fluids  Blood transfers hormones to target sites  These hormones regulate the activity of other cells Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of Hormone Action  Hormones affect only certain tissues or organs (target cells or target organs)  Target cells must have specific protein receptors  Hormone-binding alters cellular activity Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Effects Caused by Hormones  Changes in plasma membrane permeability or electrical state  Synthesis of proteins, such as enzymes  Activation or inactivation of enzymes  Stimulation of mitosis  Promotion of secretory activity Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs of Endocrine System  Organs or glands of the endocrine system are small and not often talked about Located throughout the body Produce and secrete hormones Ductless so secrete hormones directly into the blood  Hormones circulate to all organs of the body BUT affect only certain cells or organs – these are called target cells or target organs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Each target cell has a specific protein receptor on the cell membrane or inside the nucleus  This allows only specific hormones to act on the target cell  Once the right hormone finds the right cell with the right protein receptors, then the hormone will bind to the cell Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Chemistry of Hormones  Hormones are classified chemically as Amino acid based (non-lipid soluble), which includes  Proteins  Peptides  Amines Lipid based - made from cholesterol (lipid soluble)  Sex hormones  Corticosteriods  Prostaglandins - made from highly active Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Chemistry of Hormones  Two mechanisms in which hormones act 1. Second-messenger system (for aa-based) 2. Direct gene activation (for lipid-based) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Action  Hormone binds to a receptor on the target cell membrane  Activates an enzyme  The activated enzyme produces a 2nd messenger  The 2nd messenger causes intercellular changes. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 2. Steroid Hormones Mechanism of Action  Hormone enters directly into the cell into the nucleus  Binds to a receptor protein  This complex binds to the cell’s DNA  Results in formation of mRNA Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Control of Hormone Release  Hormone levels in the blood are mostly maintained by negative feedback. Example: A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached  The only main exception is oxytocin, which is controlled by positive feedback during the labour/ childbirth process. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Stimuli of Endocrine Glands  Most common stimuli  Endocrine glands are activated by other hormones  Examples: Anterior pituitary hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Humoral Stimuli of Endocrine Glands  Changing blood levels of certain ions stimulate hormone release  Humoral indicates various body fluids such as blood  Examples: Parathyroid hormone Calcitonin Insulin Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Neural Stimuli of Endocrine Glands  Nerve impulses stimulate hormone release  Most are under the control of the SNS  Examples include the release of norepinephrine and epinephrine by the adrenal medulla Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Secretion  Biorhythms  rhythmic alteration in hormone’s rate of secretion Ex: reproductive hormones - secrete in a monthly pattern  Circadian rhythm  refers to a 24-hour rhythm Ex: cortisol - high in am, low in pm Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Major Endocrine Organs  Hypothalamus  Pituitary gland  Thyroid gland  Parathyroid glands  Adrenal glands  Pineal gland  Thymus gland  Pancreas  Testes (Gonads)  Ovaries (Gonads) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Secondary Endocrine Organs  Contain tissues that secrete hormones, but endocrine functions are secondary Heart hormones - Regulate blood volume Digestive tract hormones - Coordinate digestive system functions, glucose metabolism, and appetite Adipose tissue hormones - Regulate appetite and fat metabolism Kidney hormones - Regulate blood cell production and rates of Ca2+ and HPO Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings - Hypothalamus – A few things to note….  The hypothalamus is responsive to: Light: daylength and photoperiod for regulating circadian and seasonal rhythms Olfactory stimuli, including pheromones Steroids, including gonadal steroids and corticosteroids Neurally transmitted information arising in particular from the heart, the stomach, and the reproductive tract Autonomic inputs Blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc. Stress Invading microorganisms by increasing body temperature, resetting the body's thermostat upward. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 1. Hypothalamus  The hypothalamus is not considered formally considered a gland (i.e. no endocrine or exocrine function), but it is the major controller of the pituitary gland.  Integrates activities of nervous and endocrine systems through three mechanisms 1. Synthesis and transport of two hormones to posterior pituitary 2. Secretion of regulatory hormones to anterior pituitary 3. Autonomic centers Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hypothalamic Regulatory Hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Autonomic Centers  Exert direct neural control over endocrine cells in adrenal medulla Active when sympathetic division stimulated Adrenal medulla responds by releasing epinephrine (EPI) and norepinephrine (NE or NOREPI) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 1 2 3 Antidiuretic Regulatory and Autonomic centers hormone and inhibitory hormones exert direct neural oxytocin are target the anterior control over synthesized lobe of the pituitary endocrine cells in by hypotha- gland. the adrenal lamic neurons. medulla. HYPOTHALAMUS Preganglionic motor fibers Adrenal cortex Hypophyseal Adrenal medulla portal system Adrenal gland Posterior lobe of pituitary gland Anterior lobe of pituitary gland Upon direct neuronal stimulation, the adrenal Hormones from anterior lobe ADH and oxytocin are medullae secrete epinephrine of the pituitary gland target released into circulation and norepinephrine into the the thyroid, adrenal cortex, from posterior lobe of circulation. and reproductive organs. the pituitary gland. 2. Pituitary Gland  Roughly the size of a grape, hangs from the infundibulum from the hypothalamus Controlled by hypothalmus  Called the master gland because it controls the activity of so many endocrine glands  Has two functional lobes Anterior pituitary - glandular tissue (75% of pituitary) Posterior pituitary - nervous tissue (25% of pituitary) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Anterior Pituitary  Six anterior pituitary hormones Two affect non-endocrine targets  Growth hormone (GH)  Prolactin (PRO) Four stimulate other endocrine glands (tropic hormones)  Thyroid-stimulating hormone (thyrotropic hormone) (TSH)  Adrenocorticotropic hormone (ACTH)  Luteinizing hormone (LH) (gonadotrophin)  Follicle stimulating hormone (FSH) (gonadotrophin) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Anterior Pituitary Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Pituitary Gland Hormones 1. Growth hormone Major effects are growth of skeletal muscles and long bones  Plays a role in determining final body size Also affects liver function  Causes amino acids to be built into proteins and fats to be broken down for energy Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Pituitary Gland Hormones 2. Prolactin (PRL) Stimulates growth of the mammary glands during pregnancy Stimulates and maintains milk production following childbirth Function in the males unknown Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Pituitary Gland Hormones 3. Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenal cortex 4. Thyrotropic (thyroid) stimulating hormone (TSH) Influences growth and activity of the thyroid gland Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anterior Pituitary Gland Hormones  5. and 6. Gonadotropic hormones Regulate hormonal activity of the gonads  Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries Stimulates sperm development in testes  Luteinizing hormone (LH) Triggers ovulation of an egg in females Stimulates testosterone production in males Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings How to remember? PRO Prolactin ATHletes ACTH GOt Gonadotrophins (FSH, LH) To Thyroid Stimulating Hormone GROW Growth Hormone Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pituitary–Hypothalamus Relationship  Hormonal release from the anterior pituitary is regulated by releasing and inhibiting hormones produced by the hypothalamus  Hypothalamus also produces two hormones which are transported to neurosecretory cells of the posterior pituitary  Oxytocin  Antidiuretic hormone  The posterior pituitary is not strictly an endocrine gland, but does release hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Posterior Pituitary 1. Antidiuretic hormone (ADH) Neurons stimulated by osmoreceptors release ADH in response to:  Fall in blood volume or decreased blood pressure  Rise in solute concentration in blood  Purpose is to conserve water and prevent urine production to prevent dehydration  target gland is the kidney H2O reabsorption will decrease urine output and increases blood volume (and thus BP) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  In large amounts, ADH causes vasoconstriction of the arterioles leading to increased blood pressure Vasopressin is also used as another name for ADH Thus, a vasopressor agent is one that elevated blood pressure Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Posterior Pituitary 2. Oxytocin (OXT) Stimulates contractions of the uterus during labour Causes milk ejection (let-down reflex)  Synthetic oxytocin (Pitocin) may be used to stimulate labor, control post partum bleeding or stimulate milk ejection  Bonding hormone – makes us feel safe, cooperative Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Posterior Pituitary Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 3. Thyroid Gland  Largest endocrine gland - on anterior surface of trachea  Two lobes connected by narrow isthmus (looks like a butterfly)  Produces two hormones 1. Thyroid hormone 2. Calcitonin Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Follicular Cells and C Cells Thyroid gland filled with C cells to secrete calcitonin, and thyroid follicles to secrete two hormones into the bloodstream (collectively known as Thyroid Hormone (TH)) 1. T3 (Triiodothyronine) 2. T4 (Thyroxine) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Thyroid Hormone  Inside cell: Bind to receptors on mitochondria and within the nucleus to increase rate of ATP production In nucleus, activate specific genes or changes rate of transcription  Affect concentration of enzymes and so metabolic activities of cell Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Effects of TH on Peripheral Tissues  Raises metabolic rate – rate of which glucose is burned and converted to energy  Increase heart rate and force of contraction  Increase sensitivity to SNS stimulation  Maintains sensitivity of respiratory centers to changes in CO2 and O2  Stimulate RBC formation  Necessary for regulating reproductive system Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings TH Regulation  Hypothalmus secretes thyroid releasing hormone (TRH)  stimulates the anterior pituitary  secretes thyroid stimulating hormone (TSH)  stimulates the thyroid gland to secrete thyroid hormone (TH; T3 and T4)  Negative feedback controls TRH release Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Calcitonin and C Cells  C cells - also called Parafollicular cells  Produce calcitonin (CT) which decreases blood Ca2+ levels by targeting: 1. Bones 2. Kidneys  Calcitonin secretion is controlled by humoral levels - negative feedback  Elderly – may have decreases levels of Calcitonin Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 4. Parathyroid Glands  Four parathyroid glands Embedded in posterior surface of thyroid gland Shaped like small peas Produce parathyroid hormone (PTH) Secreted in response to low Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  PTH has 3 target organs 1. Bone 2. Kidney 3. Intestines Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Calcitonin and PTH  Calcitonin and PTH act antagonistically  both controlled by blood Ca2+ levels Calcitonin – decreases blood Ca2+ PTH – increases blood Ca2+ Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 5. Adrenal Glands  Sit on top of the kidneys  Two regions 1. Adrenal cortex - outer glandular region  Mineralocorticoids  Glucocorticoids  Sex hormones 2. Adrenal medulla - inner neural tissue region  Epinepherine  Norepinepherine Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex  Adrenal cortex produces the three major steroid hormones (lipid soluble) – known as the corticosteroids 1. Minerocorticoids 2. Glucocorticoids 3. Sex hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex 1. Mineralocorticoids (mainly aldosterone) Target organ is the kidney Aldosterone reabsorbs Na+ and H2O and eliminates K+ in urine  Regulates electrolytes (especially Na+ and K+)  Regulates blood volume and blood pressure Production stimulated by renin (main Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  As aldosterone rises, the kidneys reabsorb more Na+ ions and expel K+ ions in the urine Water follows Na+  therefore, if kidneys reabsorb more Na+ then it will keep more water within in the body  Purpose is to keep the body hydrated and balance electrolytes – result is a lower urine output  Summary – mineralocorticoids regulate water and electrolyte balances in the body Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Renin: Hormone produced by the kidneys when BP drops Causes release of aldosterone to raise BP and BV Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Atrial Natriuretic Peptide (ANP) Prevents aldosterone release  released by the heart Performs the opposite of renin – reduces BP and blood volume Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex 2. Glucocorticoids (including cortisone and cortisol) Converts fats and amino acids into glucose (gluconeogenesis), thus helping to maintain blood glucose levels between meals  Ensures a steady supply of glucose for brain and other cells (otherwise will lead to death) These hormones assist the body to resist long-term stress by increasing blood glucose levels Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Glucocorticoids causes fats and proteins to be broken down and converted to glucose which is released into the blood When the levels of these hormones are low then hypoglycemia may occur Furthermore, low level results in difficulty dealing with stress (burnout)   causes suppression of their immune system Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cortisol  Also known as the stress hormone  Secreted in times of stress: Physical injury, hemorrhage Disease, infection Emotional stress (anger, worry)  Helps to increase BP & blood sugar, also has an anti-inflammatory effect  In drug form - Prednisone Reduces inflammation (redness, heat, swelling, pain) Used in treatment of inflammatory Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Hypothalmus releases CRH  stimulates the anterior pituitary gland to secrete ACTH  ACTH in turn stimulates the adrenal cortex to secrete cortisol Controlled by negative feedback – cortisol inhibits further secretion of CRH and ACTH Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex 3. Sex hormones Produced in the inner layer of the adrenal cortex Mostly androgens (male sex hormones) are made but some estrogens (female sex hormones) are also formed Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Remember -- Steroid CAT !!!!!!!!!!!!  Cortisol  Aldosterone  Testosterone  These hormones are essential for life If the adrenal cortex is removed or it’s function is lost then death occurs unless steroids are administered Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Medulla  Produces two similar hormones (catecholamines) 1. Epinephrine (adrenaline) 2. Norepinephrine (noradrenaline)  Catecholamines only prepare the body for brief or short-term (“fight or flight”) stressful situations It is the glucocorticoids that assist the body with long term stress Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hormones of the Adrenal Cortex Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Roles of the Hypothalamus and Adrenal Glands in the Stress Response Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 6. Pancreas  The pancreas (long, slender) is located close to the stomach in the upper abdominal cavity  Functions as both an endocrine gland and a exocrine gland (digestion of food) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pancreas  Two purposes: 1. Contains the pancreatic islets which are involved in glucose regulation (endocrine function) 2. Secretes enzymes for digestive system (exocrine function) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Contains the pancreatic islets known as the Islets of Langerhands – located throughout the pancreas  These islets produce cells: α-cells glucagon β-cells  insulin PIG: Pancreas - Insulin - Glucagon Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pancreatic Islets  Hormones of the pancreatic islets: Insulin – moves glucose from blood into skeletal muscle, liver and fat cells (adipose cells) Glucagon—allows glucose to enter the from the liver and fat cells (adipose cells) These hormones are antagonists that maintain blood sugar homeostasis Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Insulin  High levels of glucose in the blood (after a meal) stimulate the β-cells of the islets to secrete insulin  Insulin helps transport glucose into most cells (muscle, adipose, liver) – then used for energy or converted to fat for storage  Without insulin, the glucose Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  You need insulin to move glucose from the blood into the cells If the pancreas is not working, synthetic insulin is necessary  Normal blood glucose is 4-7 mmol Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Glucose-dependent insulin secretion from β cells, by analogy to excitation–contraction coupling in muscle, is referred to as stimulus-secretion coupling. Glucose stimulation elicits depolarization of the cell membrane and electrical activity in β cells. Opens calcium ion (Ca2+) channels in the membrane that respond to changes in voltage (voltage-dependent calcium channels (VDCCs)) Allows Ca2+ entry and action potential firing to stimulate fusion of insulin-containing vesicles with the plasma membrane (exocytosis into the blood stream). Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Diabetes Mellitus  Due to: Inability of pancreas to produce insulin (Type I) Reduced insulin production (Type II) Resistance of cells to insulin (Type II)  Because the cells are not getting the glucose they need, they break down fats and protein for energy Some cells (ex: RBC, neurons), require glucose for ATP  with insulin, these cells become energy deficient and die  If blood glucose is high, glucose spills out of blood into the urine Water will follow the glucose, thus the client voids frequently, becomes dehydrated and thirsty Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  When the cells are not being nourished properly then the cells lose their ability to fight infections  When fats instead of glucose is used for energy, the blood becomes acidic – this is referred to ketacidosis or ketosis If not corrected, will result in coma and death  If blood glucose is high, glucose moves into the urine as kidneys cannot reabsorb large Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 3 classic signs of diabetes mellitus 1. Polyphagia 2. Polyuria 3. Polydipsia Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Clinical Problems Caused by Diabetes Mellitus Diabetic retinopathy Increased risk of heart attack Diabetic nephropathy Diabetic neuropathy Reduced blood flow to distal portions of limbs, damaging peripheral tissues Glucagon  Helps to regulate blood sugar levels by increasing blood glucose levels  acts opposite to insulin  Released by the α-cells of the islets  Stimulated by low levels of blood glucose – hypoglycemia Occurs during periods of fasting Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  Target organ is the liver  Glucagon raises the blood glucose two ways: Stimulates the conversion of glycogen to glucose in the liver (glycolysis) Stimulates the release of glucose from the liver into the blood  This ensure the cells have enough glucose Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 7. Pineal Gland  Small (pea-sized), close to thalamus  Cells produce melatonin (derivative of serotonin)  Rate of melatonin production influenced by visual pathway Highest production at night Lowest production during day  Main function is to set circadian rhythms Daily changes in physiological processes following a regular day-night pattern Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 8. Thymus Gland  Located posterior to the sternum in thoracic cavity  Largest in infants and children – decreases in size with aging  Produces thymosin, which acts to: Mature some types of white blood cells Aid in development of the immune system  Removed in some autoimmune diseases (ex: myasthenia gravis) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 9. Testes  Interstitial cells of testes produce the androgens  Testosterone (most important androgen) is responsible for: Adult male secondary sex characteristics Stimulates male sex drive Promotes growth and maturation of male reproductive system Required for sperm cell production Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 10. Ovaries  Produce two different hormones: 1. Estrogen  Produced by follicles or the placenta  Stimulates the development of secondary female characteristics  Matures female reproductive organs  Helps prepare the uterus to receive a fertilized egg  Promotes breast development Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 2. Progesterone  Produced by the corpus luteum and eventually placenta if pregnant  Helps maintain pregnancy  quieting of myometrium  Helps prepare breast tissue for lactation  Acts with estrogen to bring about the menstrual cycle Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Placenta  Produces hormones that maintain pregnancy and play a part in the delivery of the baby Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones Human placental lactogen (hPL) prepares the breasts for lactation Relaxin relaxes pelvic ligaments and pubic symphysis for childbirth Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs  Parts of the small intestine  Parts of the stomach  Kidneys  Heart  Bones  Many other areas have scattered endocrine cells Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Organs Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings STRESS Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Stress Response  Any condition that threatens homeostasis is a form of stress (may be physical or emotional) Several mechanisms in body to oppose general and specific disruption Pattern of hormonal and physiological adjustments called stress response or general adaptation syndrome (GAS) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Three Stages of Stress Response 1. Alarm phase 2. Resistance phase 3. Exhaustion phase Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Alarm Phase  "Fight or flight“ – SNS activation 1. Energy reserves mobilized, primarily as glucose 2. Body prepares through "fight or flight" responses  EPI and NOREPI are dominant hormones Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Resistance Phase  If stress is longer than a few hours, body moves into the second phase (resistance phase)  Glucocorticoids are dominant with help from epinephrine, GH, and thyroid hormone Energy demands are still higher than normal (especially neural tissue) Glycogen reserves that were adequate in alarm phase are nearly exhausted  Body's metabolic reserves are mobilized and tissue metabolism is shifted away from glucose where possible Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Exhaustion Phase  Lipid reserves can maintain resistance phase for weeks or months  When reserves are depleted, body enters third phase (exhaustion phase)  Mineral (Na+, K+) imbalances are involved causing neuron and muscle fiber malfunction  Without immediate corrective action, organ systems fail causing death Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings System  In the absence of disease, efficiency of the endocrine system remains high until old age  Decreasing function of female ovaries at menopause leads to such symptoms as osteoporosis, increased chance of heart disease, and possible mood changes Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings System  Efficiency of all endocrine glands gradually decreases with aging, which leads to a generalized increase in incidence of: Diabetes mellitus Immune system depression Lower metabolic rate Cancer rates in some areas Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Review  Define endocrine system.  Describe the structural classification of hormones.  Name the primary organs of the endocrine system and those organs and tissues with secondary endocrine functions.  Describe two mechanisms of hormone action.  Which type of hormone binds to a plasma membrane receptor and why?  Which type of hormone diffuses across the plasma membrane and binds to receptors in the cytoplasm?  Identify the three mechanisms by which the hypothalamus integrates neural and endocrine function.  Define regulatory hormone.  Contrast releasing hormones with inhibiting hormones.  Name the two lobes of the pituitary gland and the cellular sources of their secreted hormones.  Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Review  In a dehydrated person, how would the amount of ADH released by the posterior pituitary change?  Name the three hormones secreted by the thyroid gland.  List five effects that thyroid hormones have on peripheral tissues.  After a thyroidectomy (surgical removal of the thyroid gland), symptoms of decreased thyroid hormone concentrations take about a week to appear. Why?  Describe the locations of the parathyroid glands.  Explain how parathyroid hormone raises blood calcium levels.  Increased blood calcium levels would result in increased secretion of which hormone?  Identify the two regions of an adrenal gland, and the hormones secreted by each.  Identify the target tissue for aldosterone.  How would elevated cortisol levels affect blood glucose levels?  Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Chapter 9 Review  The secretion of which hormone lowers blood glucose concentrations?  How do rising glucagon levels affect the amount of glycogen stored in the liver?  Define diabetes mellitus.  Identify and describe the two types of diabetes mellitus.  Describe three clinical problems caused by diabetes mellitus.  Describe the location of the pineal gland.  How would longer hours of daylight, as during the summer, affect the production of melatonin?  List the three phases of the stress response.  Describe the resistance phase.  During which phase of the stress response is there a collapse of vital systems? Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings