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ENDOCRINE SYSTEM

ENDOCRINE SYSTEM. Chapter 16. Endocrine vs Nervous System. NERVOUS. ENDOCRINE. Uses chemical hormones released from glands into the blood. Uses action potentials along axons & chemical neurotransmitters at synapses. Receptors are on the plasma membranes of target cells or intercellular.

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ENDOCRINE SYSTEM

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  1. ENDOCRINE SYSTEM Chapter 16

  2. Endocrine vs Nervous System NERVOUS ENDOCRINE • Uses chemical hormones released from glands into the blood • Uses action potentials along axons & chemical neurotransmitters at synapses • Receptors are on the plasma membranes of target cells or intercellular • Receptors are on post-synaptic membrane • Signals are very fast (milliseconds) • Signals are slower (seconds to days) • Response is immediate but short-lived • Response is delayed but more sustained

  3. HORMONES • Hormones – chemical substances secreted by cells into blood stream • Regulate metabolic function of other cells • Are either peptides or steroids

  4. Hormone - Target Cell Specificity • circulate to all tissues but affect activity of only certain cells, these are their target cells • specificity of effect governed by hormone receptors

  5. Characteristics of Hormones • Hormones: • exert effects some distance from where produced • active at very low (pg to ng) concentrations in the blood • have short half-life in body - secs to mins

  6. Characteristics of Hormones • their effect is to alter cell activity. The precise response depends on the target cell type. Typical cellular effects include: • Altering plasma membrane permeability • Stimulating protein synthesis • Activating enzymes • Inducing secretory activity • Stimulating mitosis

  7. Control of Hormone Release • Synthesis & release of most hormones are regulated by negative feedback. • As hormone levels rise, they cause target organ effects that inhibit hormone release.

  8. Chemical Classes of Hormones • Amines - Derived from tyrosine or tryptophan. Includes: epinephrine, T4, & melatonin. • Proteins & peptides - Made from amino acid chains. Includes: antidiuretic hormone, growth hormone, & insulin. • Glycoproteins- A polypeptide chain bound to one or more carbohydrates.Includes: follicle-stimulating hormone & luteinizing hormone. • Steroids- Lipids derived from cholesterol.Includes: testosterone, estradiol, & cortisol.

  9. Mechanisms of Hormone Action • Hormones: • Diffuse through the cell membrane & bind to intracellular receptors (steroid hormones & T4) or bind to receptors on the membrane of distant cells (amino-acid based hormones). • Carry out their effects by direct gene activation (steroids) or through signal transduction systems (amino-acid based).

  10. Distribution of Endocrine Tissue • Specialized organs (pituitary, adrenal, thyroid) • Discrete clusters within other organs (pancreas, gonads) • Cells dispersed singly within other tissues (enteroendocrine cells)

  11. REGULATION OF RELEASE TARGET ORGAN GLAND HORMONE EFFECTS OF HYPER- & HYPOSECRETION NORMAL EFFECTS OF HORMONE

  12. Neurohypophysis (posterior pituitary) Adenohypophysis (anterior pituitary)

  13. GROWTH HORMONE • Gigantism - a hypersecretion of growth hormone during infancy, childhood or adolescence, while epiphyseal growth plates remain open. 12 year-old with mother

  14. GROWTH HORMONE • Acromegaly - GH hypersecretion in adulthood, when epiphyseal plates are closed. Large, spade-like hands of acromegaly

  15. GROWTH HORMONE • Dwarfism - GH deficiency in childhood, leading to a maximum height of 4 feet with normal body proportions. Dwarfed brothers with researcher in India

  16. THYROID HORMONE • Cretinism - results from severe hypothyroidism in children. The children are mentally retarded, with a short body & a thick neck & tongue.

  17. THYROID HORMONE • Myxedema - Due to hypothyroidism in adults. Symptoms of low metabolic rate, chills, lethargy, mental sluggishness, & swelling of body tissues. Swelling associated with myxedema

  18. THYROID HORMONE • If myxedema results from a lack of iodine, the thyroid enlarges & protrudes into a condition called goiter.

  19. THYROID HORMONE • Grave’s Disease - The most common hyperthyroid pathology is characterized by elevated metabolic rate (rapid heartbeat, sweating, nervousness) & exophthalmos (protrusion of the eyeballs). Exophthalmos typical of Grave’s

  20. ANTIDIURETIC HORMONE • Diabetes insipidus is a result of ADH deficiency, a syndrome marked by intense thirst & very high urine output

  21. Routes of Aldosterone Stimulation

  22. GLUCOCORTICOIDS • At high concentrations, cortisol has pronounced anti-inflammatory & anti-immune effects including: • Depressing cartilage & bone formation • Inhibiting inflammation by stabilizing lysosomal membranes

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