Endocrine System PDF

6. The Endocrine System Human Anatomy & Course Physiology Status Complete Materials 5. Endocrine System - Slides Date @October 1, 2024...

6. The Endocrine System Human Anatomy & Course Physiology Status Complete Materials 5. Endocrine System - Slides Date @October 1, 2024 Table of Contents Endocrine System Endocrine vs Exocrine Gland Comparison of Regulatory Systems Endocrine System Nervous System Chemical signals coordinate cell activities Binding of hormone and receptor Molecular action of hormones Steps in second messenger signaling Steps in steroid hormone signaling Pituitary gland System largely regulated by Hypothalamus Hormones of the pituitary 6. The Endocrine System 1  Tropic Hormones Thyroid Gland Thyroid Hormone Pineal Gland Adrenal Gland Pancreas Diabetes Many organs have secondary endocrine functions Types of Hormone Interactions Hormonal Response to Stress: The General Adaption Syndrome Endocrine System Functions: Growth and development Metabolism (energy) Fluid composition and volume of ECF (glucose, sodium, potassium, calcium) Environmental changes (temperature, infection, dehydration, hemorrhage) Controls all aspects of reproduction (spermatogenesis, maternal lactation, sexual response) Components: Gland: group of cells that synthesize and secrete the hormone close to capillary Hormone: chemical signal that alters target cell activities Target cell: cell with specific receptor for that hormone 6. The Endocrine System 2  Endocrine vs Exocrine Gland Endocrine Exocrine Ducts Ductless Has a Duct Into interstitial space/blood Secretes products Onto body surface vessel Comparison of Regulatory Systems Endocrine System Nervous System Chemical signal Chemical and electrical signal Target is reached via blood stream Target is adjacent Slow to react Fast acting Long lasting Short in duration Involved in growth, development, Involved in movement, crisis reproduction management metabolism, fluid composition & volume Chemical signals coordinate cell activities 6. The Endocrine System 3  Neural synapse: neurotransmitter alters adjacent cell Intercalated discs: allow ion movement between cells ensuring that cells contract as a unit Autocrine & Paracrine: are local chemical signals between same cell or adjacent cells (oordinates tissues) Hormone: are chemical signals travel through blood stream to target cells (coordinates organs & systems) Binding of hormone and receptor Alters cell activity by altering a protein (enzyme, regulatory factor or membrane channel) Stimulus for hormone secretion can be: 1. a change in a chemical (humoral) 2. nervous system (adrenal medulla) or 3. another hormone Response depends on target cell Can act on many different cells Any cell will have many different receptors can be up or down regulated Inactivated by enzymes, binding, liver or kidney removal (half life: minutes, hours or days) Type or classification of a hormone is based on chemical structure amino acid derived polypeptide derived glycoprotein steroid: derived from cholesterol eicosanoid: derived from arachidonic acid (20 carbon fatty acid) 6. The Endocrine System 4  Molecular action of hormones Types of hormones are either water or lipid soluble bind to specific receptors receptors are membrane bound or intracellular Water soluble hormones: act through second messenger signaling cascade Lipid soluble hormones: bind to intracellular receptors Steps in second messenger signaling 1. Hormone binds to cell surface receptor 2. Hormone-receptor complex activates G protein 3. G protein activates adenylate cyclase 4. Adenyl cyclase forms cyclic AMP from ATP 5. cAMP activates protein kinases 6. The Endocrine System 5  6. Phosphorylation results in turning on or off a protein (and or pathway) or membrane channel Steps in steroid hormone signaling 1. Steroid hormone binds to receptor either in cytoplasm or nucleus 2. Hormone-receptor complex turns on or off transcription Pituitary gland The anterior portion: is glandular containing cell populations that secrete 7 tropic hormones Regulatory factors from the hypothalamus are released into the Hypophyseal Portal System Portal system (two capillary beds connected by vein) gives hypothalamus a direct connection or control 6. The Endocrine System 6  The posterior portion: is neural containing axons & synaptic knobs that secrete ADH & oxytocin is an extension of the hypothalamus neurons has a separate circulation Secretes ADH & oxytocin (NT → Hormone) System largely regulated by Hypothalamus 1. Secretes regulatory factors that act on the anterior pituitary 2. posterior pituitary releases from axon terminal ADH and oxytocin into blood stream 3. neural pathways control sympathetic output of adrenal medulla Hormones of the pituitary 6. The Endocrine System 7  ACTH: adrencortico tropic GH: growth hormone hormone stimulates protein synthesis in TSH: thyroid stimulating hormone all cells particular bones and muscles PRL: prolactin FSH: follicle stimulating hormone stimulates mammary gland milk production sperm and egg formation LH: lutenizing stimulating hormone MSH: melanocyte stimulating hormone hormone production ADH: Antidiuretic hormone Oxytocin: labor contractions, lactation, sexual response increases BP and volume Hypothalamus: Hypothalamic Tropic Hormones regulatory (releasing and inhibitory) Function: turn on and off glands hormones act on anterior Location: Anterior Pituatary Gland pituitary glands Thyroid Gland 6. The Endocrine System 8  has two cell populations: follicle and C cells Function: synthesizes and secretes two hormones 1. Thyroid hormone: increases metabolism a. acts on cell respiration (mitochondria) b. made by the follicles 2. Calcitonin: decreases blood calcium levels a. Acts on bones (increasing deposition) b. Made by the C cells c. Antagonistic to parathyroid hormone (secreted by parathyroid gland Thyroid Hormone Acts on nearly all cells 6. The Endocrine System 9  Function: Important in growth and development Increases metabolism (cellular respiration) Increases basal metabolic rate Increases O2 consumption & ATP synthesis Increases NaK ATPase mobilizes energy reserves Increases enzymes involved in metabolism Increases the number of mitochondria Generates heat Regulated by negative feed back Stimulus is decrease in temperature & Response is increase in temperature Path: hypothalamus & TRH → anterior pituitary & TSH → thyroid & thyroid hormone → all cells Increase in Thyroid hormone: inhibits TSH secretion, increase in temp stops regulatory factor release (TRH) from hypothalamus Pineal Gland Function: Synthesizes melatonin or “dark hormone” Melatonin functions: 1. Body rhythms or day:night cycle 6. The Endocrine System 10  2. Antioxidant 3. Timing of sexual maturity Serotonin is converted to melatonin in the dark (direct link to retina) may be responsible for SAD: seasonal affected disorder Adrenal Gland Adrenal Cortex: 3 zones that Adrenal Medulla: Secretes synthesize 3 types of hormones epinephrine (80%) and norepinephrine (20%) 1. Mineralocorticoids: synthesize Aldosterone Neural in origin a. Aldosterone: increases BP Part of Sympathetic response and volume (conserves or Alarm phase 6. The Endocrine System 11  sodium in exchange for Mobilization of energy potassium, water follows) reserves 2. Glucocorticoids: synthesize Increases heart rate and force Cortisol Epinephrine & Norepinephrine: a. Cortisol: stress hormone stress response (alarm) (long term) increases heart rate and i. provides energy by blood pressure mobilizing energy provides energy (mobilizes reserves reserves) ii. anti-inflammatory suppressing immune system 3. Androgens: synthesize Testosterone Pancreas Structure: is both an endocrine & exocrine gland Function: secretes insulin & glucagon hormones Insulin: reduces blood sugar levels by using & storing glucose (increased uptake, formation of lipids & glycogen, proteins, ATP) Glucagon: increases blood glucose levels by mobilizing energy reserves & gluconeogenesis 6. The Endocrine System 12  Insulin: glucose removal from blood through uptake, storage and use Glucose is used to generate ATP needed in anabolic reactionsliver & muscles store glucose as glycogen (glycogenesis) Stimulates protein & fat synthesis (anabolic) Glucagon: glucose release into blood Glycogenolysis Gluconeogenesis: synthesis of glucose from C3 units 6. The Endocrine System 13  Lipolysis: aids in gluconeogenesis and ATP synthesis Diabetes occurs when glucose is not utilized instead fats are mobilized fat metabolism: ketone bodies and acid pH appear in urine excess sugar causes polyuria excess glucose is in urine, pulls water with it polydipsia thirst polyphagia hunger (cannot utilize glucose) Type I: inadequate insulin production Type II: insulin levels are normal or high but peripheral tissues fail to respond (insulin resistance) controlled by weight loss, exercise and diet 6. The Endocrine System 14  Many organs have secondary endocrine functions Intestines: many Gonads: testosterone, estrogen, progesterone Kidneys: AgII, EPO Adipose: leptin, resistin Heart: ANP Skin: calcitriol Thymus: thymosin Types of Hormone Interactions Antagonistic or opposing i.e. insulin and glucagon, Calcitonin and parathyroid hormone Synergistic or additive i.e. growth hormone (glucose sparing)and glucocorticoids Permissive: one hormone is needed for function of second hormone i.e. epinephrine and thyroid hormones Integrative: different but complementary effects i.e. calcitriol and parathyroid hormone Hormonal Response to Stress: The General Adaption Syndrome 1. ALARM or Short term phase: Flight or Flight response (Sympathetic nervous system) is dominated by Epinephrine 2. RESISTANCE or chronic or long term stress phase: is dominated by Cortisol and aldosterone, ADH, glucagon & epinephrine to maintain BP and mobilize energy reserves. Inhibits immune system. 3. EXHAUSTION: electrolyte imbalance, exhausted reserves, inhibition of immune system causes organ damage and failure 6. The Endocrine System 15 6. The Endocrine System 16