Endocrine System PDF

Endocrine System 2  The Endocrine System Endocrine system – Composed of glands and cells that secrete hormones – Helps coordinate functions between cells – Critical for maintaining homeostasis – Helps regulate growth and development metabolism and...

Endocrine System 2  The Endocrine System Endocrine system – Composed of glands and cells that secrete hormones – Helps coordinate functions between cells – Critical for maintaining homeostasis – Helps regulate growth and development metabolism and water balance reproduction and stress responses 3  Overview of the Endocrine System: Hormones and Endocrine Glands Hormones – Chemical messengers – Secreted by endocrine glands or tissues into blood – Travel everywhere blood goes – Affect only target cells, cells with receptors – May affect very distant organs or cells 4  Overview of the Endocrine System: Hormones and Endocrine Glands Endocrinology – Study of endocrine system – Diagnosis and treatment of its disorders 5  Functions 1. Controls homeostasis 2. Maintains water balance 3. Controls uterine contractions 4. Controls milk production 5. Regulates ions (calcium, sodium, potassium) 6. Regulates metabolism and growth 7. Regulates heart rate and blood pressure 8. Monitors blood glucose levels 9. Aids the immune system 10. Reproductive functions  Major Organs of the Endocrine System (Figure 11.1) 7  Overview of the Endocrine System: Hormones and Endocrine Glands Exocrine versus endocrine glands – Exocrine glands release secretions to tissue by ducts – Endocrine glands ductless, release into blood other organs not usually considered endocrine glands – e.g., brain and heart, releasing important substances 8 Overview of the Endocrine System: Comparison of the Nervous and Endocrine Systems Endocrine System – Chemical signals only Nervous System – Slower to respond and – Chemical and stop electrical signals – Hormones go everywhere – Responds and stops – Adapts relatively slowly quickly – Sometimes widespread – Targets specific organ effects – Adapts quickly – Usually local effects 9  Components of Endocrine System Endocrine glands: secrete their product directly into blood stream Chemical signal: molecules that are released from one location, move to another location, and produce a response 10  Types of Chemical Signals Intracellular: produce in one of part a cell and move to another part of same cell Intercellular: released from one cell and bind to receptors on another cell 11  Types of Intercellular Signals Autocrine: - released by cells and a have local effect on same cell type - Ex. Eicosanoids (released in response to inflammation) Paracrine: - released by cells that affect other cell types in close proximity - Ex. Somatostatin (inhibits insulin secretion)12  Neurotransmitter and neuromodulators: - secreted by nerve cells - Ex. Nervous system function Pheromones: - secreted into env’t and modify behavior and physiology of other individual in same species - Ex. Women and menstrual cycles Hormones and neurohormones: - secreted into blood and bind to receptor sites - Ex. Epinephrine and insulin 13  Overview of the Endocrine System What is the classical distinction made between endocrine and exocrine glands? Endocrine glands are ductless, and release their secretions directly into the bloodstream. Exocrine glands release their products into ducts. 15 Endocrine Physiology: Hormone Structure Hormone classification – Classified into three groups based on structure Steroid hormones – Lipids synthesized from cholesterol – Share structure four organic rings with varied side groups – E.g., testosterone and estradiol 16 Endocrine Physiology: Hormone Structure Monoamines – Small molecules – Synthesized from amino acids tyrosine and tryptophan – E.g., thyroxine and epinephrine 17 Endocrine Physiology: Hormone Structure Peptide hormones – Chains from 3 to more than 200 amino acids – Considered proteins if > 50 amino acids – Oxytocin, small peptide hormone – Insulin, a protein 18 The Chemical Classes of Hormones (Figure 11.3) 19  Endocrine Physiology: Hormone Receptors and Effects Hormone receptor – Given hormone fits receptor like key fits lock – Insulin “key” fits only insulin receptor “lock” does not stimulate other receptor types – Cell only responds if has proper receptors 20  Endocrine Physiology: Hormone Receptors and Effects Peptide hormones and most monoamines – Hydrophilic, unable to pass into target cell – Bind to receptor at cell surface – Hormone, first messenger – Receptor associated with membrane enzyme respond by producing second messenger inside cell often cyclic adenosine monophosphate (cAMP) 21  Endocrine Physiology: Hormone Receptors and Effects Cyclic AMP – Made by removing two phosphates from ATP – Activates or reactivates cytoplasmic enzymes – Leads to various metabolic effects e.g., wake up certain genes, producing new enzymes e.g., change permeability of plasma membrane e.g., glucagon activating certain metabolic pathways 22  Endocrine Physiology: Hormone Receptors and Effects Steroid hormones – Hydrophobic, readily pass into cell – Bind receptor associated with DNA – Causes gene to be transcribed – Specific protein produced alters metabolism in various ways 23  Components of Hormones Receptor site: location on a cell where hormone binds (lock) Target tissues: group of cells that respond to specific hormones Specificity: specific hormones bind to specific receptor sites 24  How does this work? 1. Hormones are secreted by endocrine glands directly into bloodstream 2. Hormones travel to all parts of body 3. Hormones (key) bind to receptor site (lock) on target tissue 4. Response occurs 27  How do hormones cause change? Alter cell activity of target tissues by increasing or decreasing cell’s normal processes Change permeability of cell membrane by opening or closing ion channels Synthesis of proteins 28  Types of Hormones Water soluble: - includes proteins, peptides, amino acids - most common - Ex. Growth hormone, antidiuretic, prolactin, etc. Lipid hormones: - includes steroids and eicosanoids - Ex. LH, FSH, androgens 30  Regulation of Hormones Blood levels of chemicals: Ex. Blood glucose levels (insulin) Other hormones: Ex. TSH signals thyroid gland to release thyroid hormone Nervous system: Ex. Epinephrine and fight or flight response Negative Feedback: tells body when homeostasis is reached 32 Pituitary Gland Small gland in brain Controlled by hypothalamus Divided into 2 regions: anterior and posterior Secretes at least 6 hormones 33 Figure 10.11 Anterior Pituitary Gland Growth Hormone: - Target tissues: most - Functions: stimulates growth of bones, muscles, and organs - Abnormalities: Too much GH causes giantism Too little GH causes pituitary dwarfism 35  Thyroid-Stimulating Hormone (TSH): - Target tissues: thyroid gland - Functions: regulates thyroid gland secretions - Abnormalities: Too much TSH, thyroid gland enlarges Too little TSH, thyroid gland shrinks 36 Figure 10.14 GONADOTROPINS LH (Luteinizing) for females: - Target tissue: ovaries - Function: promotes ovulation and progesterone production LH for males: - Target tissue: testes - Function: sperm production and testosterone 38  FSH (Follicle-Stimulating) for females: - Target tissue: follicles in ovaries - Function: follicle maturation and estrogen secretion FSH for males: - Target tissue: seminiferous tubules (testes) - Function: sperm production 39  Prolactin: - Target tissues: mammary glands and ovaries - Functions: milk production 40 Posterior Pituitary Gland Antidiuretic Hormone (ADH): - Target tissues: kidneys - Functions: conserve water - Abnormalities: Diabetes insipidus: - low ADH - kidneys to produce large amounts of dilute (watery) urine - can lead to dehydration and thirst 41  Oxytocin: - Target tissues: uterus - Functions: increases uterine contractions during labor 42 Thyroid Gland One of largest glands Requires iodine to function Thyroid hormones: - Target tissues: most - Functions: regulates metabolic rates and is needed for growth 45  Abnormalities of Thyroid Gland Hypothyroidism: Hyperthyroidism: – Decreased metabolism – Increased metabolism – Weight gain, reduced – Weight loss, increased appetite, fatigue appetite, nervousness – Low temp. and pulse – Higher temp. and pulse – Dry, cold skin – Warm, flushed skin – Myxedema in adults – Graves’ disease (leads to – Cretinism in infants goiter) 46  Calcitonin: - Target tissues: bones - Functions: secreted when blood Ca2+ levels are high 48 49 Parathyroid gland Parathyroid hormone (PTH): - Target tissues: bones and kidneys - Functions: regulates blood Ca2+ levels (more than calcitonin) If Ca 2+ is low then osteoclasts break down bone matrix and less Ca 2+ is lost in urine. If Ca 2+ is high then osteoclasts don’t break down bone matrix and more Ca 2+ is lost in urine. 50 Adrenal Glands On kidneys 2 regions medulla and cortex Adrenal Medulla (inner portion): Epinephrine/Norepinephrine: - Target tissues: heart, blood vessels, liver, fat cells - Functions: released as part of fight or flight response 53 Adrenal Cortex (outer portion): Aldosterone: - Type of mineralocorticoids - Target tissues: kidneys - Functions: causes Na+ and H2O to be retained and K+ to be secreted, indirectly involved with blood pressure and blood volume 55  Cortisol: - Type of glucocorticoids - Target tissues: most - Functions: increases breakdown of fat and protein for energy uses reduces inflammatory and immune responses 57  Androgens: - Target tissues: most - Functions: Males: secondary sexual characteristics Females: sex drive 59 Pancreas Organ in abdomen Insulin: - Target tissues: liver, skeletal muscle, adipose tissue - Functions: - regulates blood glucose levels - after a meal glucose levels are high and insulin is secreted - extra glucose is stored in form of glycogen 60 - Abnormalities: Diabetes mellitus: - Causes: too little insulin or faulty insulin receptors - Symptoms: exaggerated appetite, excess urine, dehydration, thirst, fatigue - Type I: insulin dependent (daily injections required) - Type II: insulin independent, often found in obese people, can be treated with diet but can turn into type I 62  Glucagon: - Target tissues: liver - Function: - regulates blood glucose levels - between meals glucose levels drop and glucagon is secreted - glucagon allows glycogen to be broken down into glucose 63 Testes Testosterone: - Target tissues: most - Functions: aids in sperm and reproductive organ development and function 65 Ovaries Estrogen/Progesterone: - Target tissues: most - Functions: involved in uterine and mammary gland development and menstrual cycle 66 Thymus gland Thymosin: - Target tissues: immune system tissues - Functions: promotes immune system development and function 67 Pineal Body (Gland) Melatonin: Target tissues: hypothalamus Functions: plays a role in onset of puberty and controls circadian rhythms. Light affects its function. 68 69