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Human Anatomy and Physiology

Human Anatomy and Physiology. Endocrinology. Overview. Nervous system electrochemical impulses regulate muscles and glands quick response Endocrine system influences metabolism via chemical messages prolonged response Endocrine versus exocrine glands. Endocrine glands. Major glands

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Human Anatomy and Physiology

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  1. Human Anatomy and Physiology Endocrinology

  2. Overview • Nervous system • electrochemical impulses regulate muscles and glands • quick response • Endocrine system • influences metabolism via chemical messages • prolonged response • Endocrine versus exocrine glands

  3. Endocrine glands • Major glands • Pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands • Other glands • Pancreas, gonads • Organs/tissues producing hormones • Adipose tissue, intestine, stomach, kidneys, heart

  4. Hormones • Steroidal • Gonads, adrenal glands • Amino acid based • Works by a secondary messenger system • Cyclic AMP : cAMP signaling mechanism • PIP-Calcium signaling mechanism • cAMP components • Receptor, G protein, adenylate cyclase, cAMP, protein kinase

  5. Cyclic AMP signaling

  6. Cyclic AMP signaling • Steps • First messenger • GDP displaced by GTP • Activation of G-protein • Activation of adenylate cyclase • Hydrolysis of GTP to GDP • Inactivation of G-protein • Second messenger cAMP from ATP • Activation of protein kinase • Activation of metabolism

  7. PIP calcium signaling

  8. PIP calcium signaling • Steps • First messenger • GDP displaced by GTP • Activation of G-protein • Activation of phospholipase • Hydrolysis of GTP to GDP • Inactivation of G-protein • Phospholipase splits PIP2 into DAG and IP3 • DAG and IP3 act as secondary messengers • DAG activates protein kinases, IP3 triggers Ca++ release from ER • Ca++ activates channels on plasma membrane or binds to calmodulin which activates metabolism

  9. Steroidal hormones

  10. Steroidal hormones • Steps • Diffuse into cell and enter nucleus • Bind to receptors to form receptor complexes • Complexes bind to DNA • Production of mRNA • mRNA + ribosomes make proteins • Proteins include enzymes that stimulate metabolism

  11. Hormones • Hormones travel in blood free or bound to protein carriers • Blood hormone concentration decreases • Degraded by target organs • Removal by kidneys and liver • Half-life (seconds to 30 min.)

  12. Hormone release • Three major stimuli • 1. Humoral • Ca++ lowering causes PTH release • 2. Neural • SNS stimulates adrenal gland to release epinephrine • 3. Hormonal (common) • Hypothalamus releases hormones that cause pituitary to release other hormones (e.g. GnRH to FSH)

  13. Growth hormone • Site of release • Anterior pituitary • Target organ • All body organs especially bones and skeletal muscle • Stimulation • Primarily in adolescence, low levels of GH • Feedback mechanism • High levels of GH, hyperglycemia, obesity

  14. Thyroid hormone precursors Hypothermia TRH TSH T3 & T4 Increase in metabolism & body temperature

  15. Thyroid hormone • Stimulation • Falling levels of T3 (triiodothyronine) and T4 (thyroxine). TH raise BMR and heat production • Feedback mechanism • Increase in BMR and body heat (i.e., exercise)

  16. Parathyroid hormone • Site of release • Parathyroid glands • Target organ • Bone, intestine, kidneys • Stimulation • Falling Ca++ blood levels • Feedback mechanism • Increase in Ca++ blood levels

  17. Parathyroid hormone • Ca++ needed for nerve impulses, muscle contraction and blood clotting

  18. Adrenocorticotropic hormone • Site of release • Anterior pituitary • Target organ • Adrenal cortex (glucocorticoids) • Stimulation • Stress (i.e., fever, hypoglycemia) • cortisol • Feedback mechanism • Increase levels of blood glucocorticoids

  19. Adrenal gland hormones • Mineralocorticoids (aldosterone) • Site of release • Adrenal cortex • Target organ • Kidneys • Stimulation • Decrease in blood volume, pressure, Na+ level • Feedback mechanism • Increase in blood volume, pressure, Na+ level

  20. Adrenal gland hormones • Epinephrine and norepinephrine • Site of release • Adrenal medulla • Target organ • Heart, vasculature, bronchioles • Stimulation • Sympathetic nervous system (SNS) • Feedback mechanism • None. SNS stimulation decreases when needed

  21. Pancreatic hormones • Insulin and glucagon

  22. Other hormones • Renal • Arginine vasopressin (antidiuretic hormone - ADH) • Reproduction • Follicle-stimulating hormone (FSH) • Luteinizing hormone (LH) • Oxytocin

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