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Chapter 9 The Endocrine System

Chapter 9 The Endocrine System. Functions of Endocrine System. Second messenger system of the body Uses chemical messages (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development Mobilization of body defenses

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Chapter 9 The Endocrine System

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  1. Chapter 9The Endocrine System

  2. Functions of Endocrine System • Second messenger system of the body • Uses chemical messages (hormones) that are released into the blood • Hormones control several major processes • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of much of homeostasis • Regulation of metabolism

  3. Hormone Overview • Hormones produced by specialized cells • Cells secrete hormones into extracellular fluids • Blood transfers hormones to target sites • Hormones regulate activity of other cells

  4. The Chemistry of Hormones • Amino acid-based hormones • Proteins • Peptides • Amines • Steroids – made from cholesterol • Prostaglandins – made from highly active lipids

  5. Mechanisms of Hormone Action • Hormones affect only certain tissues or organs (target cells or organs) • Target cells must have specific protein receptors • Hormone binding influences the working of the cells

  6. Effects Caused by Hormones • Changes in plasma membrane permeability or electrical state • Synthesis of proteins, such as enzymes • Activation or inactivation of enzymes • Stimulation of mitosis

  7. Steroid Hormone Action • Diffuse through membrane of target cells • Enter the nucleus • Bind to a specific protein • Bind to specific sites on DNA • Activate genes that result in synthesis of new proteins

  8. Nonsteroid Hormone Action • binds to membrane • does not enter cell • Sets off a series of reactions that activates an enzyme • Catalyzes a reaction that produces a second messenger molecule • Oversees additional intracellular changes to promote a specific response

  9. Control of Hormone Release • Most hormone levels in the blood are maintained by negative feedback • A stimulus or low hormone levels in the blood triggers the release of more hormone • Hormone release stops once an appropriate level in the blood is reached

  10. Positive Feedback

  11. Humoral Stimuli of Endocrine Glands Hormonal Stimuli of Endocrine Glands - changing blood levels of certain ions stimulate hormone release - activated by other hormones

  12. The main hormones ACTH – adrenocorticotropic hormone ADH – anti-diuretic hormone, or vasopressin FSH – follicle-stimulating hormone GH – growth hormone LH – luteinizing hormone PRL – prolactin TSH – thyroid-stimulating hormone Pituitary Hormones

  13. Neural Stimuli of Endocrine Glands • Nerve impulses stimulate hormone release • Most are under control of the sympathetic nervous system

  14. Other Hormone-Producing Tissues • Parts of the small intestine • Parts of the stomach • Kidneys • Heart • Placenta • Many other areas have scattered endocrine cells

  15. Developmental Aspects Most endocrine organs operate smoothly until old age, but here are some changes: • Menopause is brought about by lack of efficiency of the ovaries • Problems associated with reduced estrogen are common • Growth hormone production declines with age • Many endocrine glands decrease output with age

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