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

Humoral Stimuli of Endocrine Glands

Hormonal Stimuli of Endocrine Glands

- changing blood levels of certain ions stimulate hormone release

- activated by other hormones

pituitary hormones
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
Neural Stimuli of Endocrine Glands
  • Nerve impulses stimulate hormone release
  • Most are under control of the sympathetic nervous system
Other Hormone-Producing Tissues
  • Parts of the small intestine
  • Parts of the stomach
  • Kidneys
  • Heart
  • Placenta
  • Many other areas have scattered endocrine cells
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