Endocrine System Ch. 17 PDF

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Summary

Lecture notes for Chapter 17 Endocrine System. Dr. Pal ...

Description

Endocrine System

Nervous System

Both Systems

Stimulus/message

Receptor, integrate, response

Regulatory

Secrete hormone

Secrete neurotransmitter

Chemical signals

Slow communication

Rapid communication

Neg. Feedback Loop

Prolonged response

Short lived response

Effects precise cells/organs

Circulate body = more widespread

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Endocrine System ○ Chemical messengers sent into the blood ○ Hormones bind to specific cell receptors ○ Lag period for action

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Hormone ○ Only affects cells w/ specific receptor ○ Travels in blood to act long distance

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Cell Signaling ○ Autocrine - effect on same cell that secretes it ○ Endocrine - hormone secretion into blood by endocrine gland ○ Paracrine - acts locally but on different cell type

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Target Cell Modulation ○ Up regulation - target cell increases number of hormone receptors ■ Target cell more sensitive to hormone ● Stronger response ○ Down regulation - target cell reduces receptor population ■ Target cell less sensitive to hormone ● Diminished response

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Hormone Structure ○ Protein Based - peptides & monoamines ■ Water ○ Lipid Based - steroids & eicosanoids ■ Steroid

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Steroid Hormones ○ Cholesterol based ○ Protein carrier needed for blood travel/prevent degradation ■ Bound hormone = protein attached to protein carrier ■ Unbound (free) hormone = able to leave blood ○ Slower to act ○ No amplification ○ Longer duration of action than peptide hormone ● Induction Sequence 1. Binds to receptors inside cell 2. transcription/translation 3. New protein is made

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Non Steroid Hormones ○ Water soluble so easily transported ○ CAN NOT cross the plasma membrane to enter the cell ○ Receptor binding linked to 2nd messenger ■ Four types 1. Glycoproteins: FSH, LH/ICSH 2. Amino Acid Derivatives: Epi, norepi, T3/T4 3. Peptides: ADH, oxytocin 4. Proteins: Insulin, glucagon, GH

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Kinase - enzyme ○ Catalyzes transfer of phosphate group from high energy phosphate donating molecules to specific substrates ■ Known as phosphorylation

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G Proteins - guanine nucleotide binding proteins ○ Act as molecular switches inside cells ○ Needs to be activated ○ Involved in transmitting signals from variety of stimuli outside cell to interior

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Cyclic AMP Production ○ Binding of hormone to its receptor activates a G protein ○ Activated G protein activates adenylyl cyclase ○ cAMP is synthesized from ATP by action of adenylyl cyclase ■ cAMP is second messenger ● Causes cellular response

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Cyclic AMP as Second Messenger ○ Non-steroid hormone

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Phospholipase C ○ Membrane associated enzyme ○ Cleaves phospholipids just before the phosphate group ○ Produces two 2nd messengers

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Signal Amplification ○ Each hormone triggers multiples reactions at each stage of metabolic pathway ■ Cascade of reactions ensues ■ Very small amount of hormone can result in large changes/effects ● Occurs only with NON-STEROID hormones

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Eicosanoid Hormones ○ Paracrine (local) signaling molecules ○ Production can be blocked by anti-inflammatory drugs ■ Leukotrienes - proinflammatory ■ Prostaglandins - uterine smooth muscle contraction ■ Thromboxanes - promote platelet aggregation (1st part of blood clot)

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Hormone Release 1. Humoral - blood level of something 2. Neural - nerve fibers 3. Hormonal - hormone chain

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Adrenal Medulla ○ Sympathetic ganglion ○ 10-20% of the gland (inner cose) ○ Releases 80% epinephrine & 20% norepinephrine with trace dopamines ■ Released into the bloodstream with widespread effect all over body ● Alarm reaction ○ Acts as non-steroid hormones

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Catecholamine Effects ○ Aka ‘Fight or Flight’ ■ Increase heart rate, increase metabolic rate, smooth muscles in airways dilate

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Hormone activity ○ Secretion controlled via negative feedback ○ Secretion continues until set point reached & target cells provide messages to stop ■ Maintains homeostasis

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Neg. Feedback Loop - maintains homeostasis Pos. Feedback Loop - moves away from homeostasis

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Other Hormones ○ Thymus - Immune Cells ○ Pineal Gland - Melatonin ○ Pancreas - Insulin & Glucagon ○ Adrenal Gland - Fight or flight ■ Epi,, nor, dop ○ Parathyroid - PTH

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Calcitonin ○ Lowers blood calcium levels 1. Increased calcium loss in urine 2. Osteoblasts stimulated = calcium deposited in bone 3. Osteoclasts inhibited = prevents bone resorption (no bone breakdown)

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Parathyroid Hormones ○ Raises blood calcium levels 1. Osteoclasts stimulated = calcium releases 2. Decreased osteoblast activity (no calcium in bone) 3. Increased calcium reabsorption in kidneys 4. Increased calcium absorption in the intestines a. Can’t do without proper amount of Vitamin D

Calcium Homeostasis = humoral

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Hypothalamus ○ 8 hormones produced ■ 6 in anterior pituitary ● FLAT PIG ■ 2 in posterior pituitary 1. ADH 2. Oxytocin

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Neurohypophysis ○ Posterior lobe of pituitary gland ■ Cells of neurohypophysis don’t make hormones. ■ Neurons in the hypothalamus have axons w/ axon terminals in the posterior lobe of the pituitary gland ■ Neuron stores hormone in neurohypophysis ■ Hormones released from neuron vesicles in venous blood ● Two hormones: 1. Antidiuretic Hormone (aka Vasopressin) a. High blood sodium = ADH released into blood b. Kidneys conserve water = blood becomes dilute i. Decreased salt conc. c. Helps prevent dehydration 2. Oxytocin a. Uterine contraction to expel contents b. Milk ejection i. Pos. Feedback Loop 1. Labor, birth & delivery

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Adenohypophysis ○ Anterior lobe of pituitary gland ■ Hypothalamus releasing / inhibiting hormones ○ Hypophyseal Portal System ■ Venous blood travels from hypothalamus → adenohypophysis (thr/ veins) ○ “Releasing” & “inhibiting” hormones secreted by hypothalamus

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Endocrine Control ○ Hypothalamus secretes hormones which make other endocrine glands secrete hormones ■ stimulate/inhibit hormones from adenohypophysis

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FLAT PIG (6 hormones of the anterior pituitary) ○ F - FSH - Follicle Stimulating Hormone ○ L - LH - Luteinizing Hormone ○ A - ACTH - Adrenocorticotropic Hormone ** ○ T - TSH - Thyroid Stimulating Hormone ** ○ P - PRL - Prolactin ○ I - ICSH - Interstitial Cell Stimulating Hormone ○ G - GH - Growth Hormone ** ● Hypo → aden → 3rd location → secrete hormone

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Hormone Secretion ○ Hyposecretion ■ Inadequate ■ Due to trauma to secreting organ ■ Can be autoimmune disease ○ Hypersecretion ■ Excessive ■ Can be tumor production ■ Can be autoimmune disease

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Growth Hormone (somatropin) - not tropic ○ Produced most by adenophysis ○ Targets cells widespread : muscle, bone, liver, adipose tissue ■ Stimulates cellular growth & mitosis ■ Results in protein synthesis & fat metabolism ■ Carbohydrate metabolism ■ Electrolyte balance

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Pituitary Dwarfism ○ Insufficient GH production ○ Perfect proportion but small ○ Easily treated with HGH ■ Hormonal disease Gigantism ○ Hypersecretion of GH ○ Long bone growth occurs via epiphyseal plate before they are depleted Acromegaly ○ Excessive GH production in adults ○ No long bone, just thickness/width

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Thyroid Gland Hormones 1. Calcitonin 2. Thyroid Hormones

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Thyroid Hormones ○ Iodine binds to tyrosine molecules ■ Forms T3 & T4 ■ Stored until signal for releases ● 90% is T4 yet converted to active form (T3) to bind to target tissue ○ effects ■ CRITICAL for development of fetal & neonatal brain ■ Increases heart rate & cardiac contractility ■ Promotes vasodilation ■ Activates sodium-potassium pump ■ Generates heat = increases basal metabolic rate

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Hypothyroidism ○ Not enough T3 or T4 ○ Rapid decline of blood Ca2+ levels ■ Decreased metabolism ■ Weight gain ■ Thick hair ■ Low pulse ■ Dry skin ■ Goiter Hyperthyroidism ○ Usually caused by PT tumor ○ Raises blood Ca2+ levels ■ High pulse ■ Thin hair ■ Weight loss ■ Insomnia ■ Heat intolerance ■ Exophthalmos (bulging eyeballs)

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Adrenal Cortex ○ 80-90% of gland ○ Outer core ■ 3 layers 1. Glomerulosa a. Mineralocorticoids i. Salt hormones b. Aldosterone i. Kidneys retain water 2. Fasciculata a. Glucocorticoids i. Sugar hormones b. Cortisol i. Treat inflammation 3. Reticularis a. Androgens i. Sex hormones b. testosterone/estrogen

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Mineralocorticoid ○ Aldosterone ■ Low BV & BP → aldosterone released into blood → kidneys reabsorb sodium & water → decreased water in urine (reabsorbed in blood) → increased BV & BP

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Glucocorticoid ○ Cortisol = blood sugar goes up everywhere in body ■ Hyperglycemia ■ Decreased inflammation due to increased capillary permeability ■ Altered immune response ■ Inhibits vitamin D → decreases dietary calcium absorption ■ Impaired collagen synthesis → poor wound healing ■ Decreased protein production & protein catabolism ● Decreases muscle mass ● Increase glucose in blood ● Suppresses immune response ● Decreases tissue repair

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Cortisol Production ○ Increased cortisol release = ■ Caffeine consumption ■ Exercise ■ Infection ■ Mental anxiety ■ Extreme heat or cold ■ Physical exhaustion ○ Hypothalamus → Corticotropin Releasing Hormone (CRH) → Anterior Pituitary → ACTH → Adrenal Cortex → Cortisol

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Cushing Syndrome ○ Excess of cortisol ○ Muscle & bone mass lost rapidly as protein is metabolized (breakdown) ■ Can be from exogenous or endogenous causes ● If due to pituitary tumor = Cushing Disease (increased ACTH) ○ Disrupts carbohydrate & protein metabolism

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Addison Disease ○ Cortisol deficient ■ Very easy to die during times of stress ○ Direct loss of adrenal cortex function Signs & symptoms ○ Look tan ■ First 13 AA of ACTH same as MSh ○ No epi effects = hypotension ○ Hypoglycemia ○ No increase in cortisol production (even in times of stress) ■ JFK ○ Profound fatigue ○ Dehydration

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Pancreatic Secretions ○ Insulin ○ Glucagon

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Glucagon ○ Alpha cells ○ Only on perimeter of pancreatic islets ○ Raises blood glucose levels ■ Effects ● Liver … ○ Stimulates gluconeogenesis ○ Liver glycogenolysis = AA used ● Adipose tissue … ○ Stimulates fat breakdown ■ Ketones produced ■ FA released into circulation Insulin ○ Beta cells ○ Scattered thr/out islet ○ Lower blood glucose levels ■ Effects … 1. Muscle (myocyte) 2. Liver (hepatocyte) 3. Adipose Tissue (adipocyte) a. Glucose enters when insulin reaches receptor transmembrane channel that insulin opens

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Insulin Formation ○ Glucose rapidly ↑ translation of insulin mRNA ○ Slowly ↑ transcription of insulin gene

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Metabolic Syndrome ○ 5 risk factors 1. Visceral Obesity 2. Low HDL Cholesterol 3. High Triglycerides 4. Insulin Resistance 5. Hypertension a. Only need three for diagnosis b. Increased chance of heart disease, diabetes & stroke i. A mere lack of sleep increases death risk 1. Even at healthy weight one can have it

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Insulin Resistance ○ Cells in muscle, body fat & liver start resisting/ignoring signal that hormone insulin trying to send out ■ Hyperinsulinemia ● Body sends more insulin ● Down regulation ■ Only way to get rid of excess insulin is to decrease insulin resistance Hyperglycemia ○ Increase blood glucose

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Diabetes Mellitus ○ Type 1 ■ No insulin produced ■ Glucose can’t enter cells (lose weight) ○ Type 2 ■ Insulin resistance ● Cells fail to respond to insulin properly Diabetes Signs & symptoms ○ Crave extra liquids ○ Frequent urination ■ Osmotic pull ● Water from blood to urine ○ Always hungry ○ Numbness (feet) ○ Weight loss ○ Blurred vision

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Hb A1C ○ Rate of formation depends of [glu] ○ Forms irreversible bond ■ Glucose bond w/ hemoglobin ○ RBC circulates about 120 days ○ Serum (Hb A1C) indicates glucose values previous 3 months

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Stress ○ Adrenal medulla releases catecholamines ○ Adrenal Cortex releases glucocorticoids ○ Neural input effect on hypothalamus ■ Effect .. ● Increases glucose in blood ● Suppresses immune response ● Affects many organ systems

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Hormones of Stress ○ Increased Aldosterone =↓UO → ↑BV → ↑CO ○ Increased ADH = ↑BV → ↑CO ○ Increased epi/norepi = ↑PRV →↑ BP ○ Increased glucagon = ↑Blood glucose ○ Increased beta endorphins = pain suppression

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Chronic Stress ○ Chronic stress leads to significant hormonal imbalance ■ In bet/ no problem & death

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Review of Hormone Release ○ Stimuli to manufacture/release 1. Humoral - not hormone, blood levels a. Water, glucose, calcium, sodium 2. Neural - sympathetic Nervous system a. Epi & norepi 3. Hormonal - hormones a. FLAT PIG...