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Endocrine Physiology Part 1 of 4

Endocrine Physiology Part 1 of 4. Dr. Meg- angela Christi M. Amores. Coordination of body functions. Chemical messenger systems: Neurotransmitters released by axon terminals of neurons into the synaptic junctions; act locally to control nerve cell functions Endocrine hormones

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Endocrine Physiology Part 1 of 4

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  1. Endocrine Physiology Part 1 of 4 Dr. Meg-angela Christi M. Amores

  2. Coordination of body functions • Chemical messenger systems: • Neurotransmitters • released by axon terminals of neurons into the synaptic junctions; act locally to control nerve cell functions • Endocrine hormones • released by glands or specialized cells into the circulating blood ; influence the function of cells at another location in the body • Neuroendoctrine hormones • secreted by neurons into the circulating blood • influence the function of cells at another location

  3. Coordination of body functions • Chemical messenger systems • Paracrines • secreted by cells into the extracellular fluid ; • affect neighboring cells of a different type • Autocrines • secreted by cells into the extracellular fluid ; • affect the function of the same cells that produced them • Cytokines • peptides secreted by cells into the extracellular fluid • can function as autocrines, paracrines, or endocrine hormones

  4. Endocrine hormones • carried by the circulatory system to cells throughout the body • they bind with receptors and initiate many reactions • Some affect many different cell types • Others affect a specific target tissue • multiple hormone systems play a key role in regulating almost all body functions

  5. Hormones • 3 general classes • Proteins and polypeptides • Are Stored in Secretory Vesicles Until Needed • Steroids • Usually Synthesized from Cholesterol and Are Not Stored • Derivatives of AA Tyrosine • Thyroid hormones • Adrenal medullary hormones: epinephrine, norE

  6. Hormone Secretion, Transport, Clearance from body • each of the different hormones has its own characteristic onset and duration of action • norepinephrine and epinephrine, are secreted within seconds after the gland is stimulated • thyroxine or growth hormone, may require months for full effect

  7. Control • Negative Feedback Prevents Overactivity of Hormone Systems • ensure a proper level of hormone activity at the target tissue • to prevent oversecretion of the hormone or overactivity at the target tissue • Positive Feedback • occurs when the biological action of the hormone causes additional secretion of the hormone • surge of luteinizing hormone (LH) that occurs as a result of the stimulatory effect of estrogen on the anterior pituitary before ovulation

  8. Cyclical Variations Occur in Hormone Release • periodic variations in hormone release that are influenced by seasonal changes, various stages of development and aging, the diurnal (daily) cycle, and sleep • Example: secretion of growth hormone is markedly increased during the early period of sleep • due to changes in activity of neural pathways involved in controlling hormone release

  9. Pituitary Hormones • Pituitary Gland • Anterior Lobe (adenohypophysis) • Growth hormone • Adrenocorticotropin • Thyroid-stimulating hormone • Prolactin • FSH and LH • Posterior Lobe (neurohypophysis) • Antidiuretic hormone • Oxytocin

  10. Anterior Pituitary Hormones

  11. Hypothalamus and Pituitary • Almost all secretion by the pituitary is controlled by either hormonal or nervous signals from the hypothalamus • hypothalamic releasing and hypothalamic inhibitory hormones • Regulates secretion from anterior pituitary

  12. Hypothalamus and Pituitary

  13. Abnormalities in Growth Hormone Secretion • Panhypopituitarism • decreased secretion of all the anterior pituitary hormones • Dwarfism • generalized deficiency of anterior pituitary secretion • all the physical parts of the body develop in appropriate proportion to one another • Age 10 years – looks like 4-5 years

  14. Abnormalities in Growth Hormone Secretion • Gigantism • growth hormone-producing cells of the anterior pituitary gland become excessively active • All body tissues grow rapidly, including the bones • person becomes a giant-up to 8 feet tall • Acromegaly • after the epiphyses of the long bones have fused • bones can become thicker and the soft tissues can continue to grow • bones of the hands and feet and in the membranous bones, including the cranium, nose, bosses on the forehead, supraorbital ridges, lower jawbone, and portions of the vertebrae

  15. Posterior Pituitary • do not secrete hormones • a supporting structure for large numbers of terminal nerve fibers and terminal nerve endings • nerve endings are bulbous knobs that contain many secretory granules • Granules secrete the hormones

  16. Posterior pituitary gland

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