Mechanisms of Hormone Action

April 18, 2012 | By | Reply More

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 function 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

 Mechanism of  Action of Steroid Hormones(DNA or “Gene Expression”)

Hormones diffuse through the plasma membrane of target cells
Enter the nucleus
Bind to a specific protein within the nucleus
Hormone-protein complex binds to a specific site on the cell’s DNA
Activates genes that result in synthesis of new proteins
New protein influences cell function

Nonsteroid Hormone Action: “Second Messenger System”

Hormone binds to a membrane receptor
Hormone does not enter the cell
Sets off a series of reactions that activates an enzyme
Catalyzes a reaction that produces a second messenger molecule
↓Cyclic AMP (cAMP)
cAMP  activates additional intracellular changes to promote a specific response

Control of Hormone Release

  • Hormone levels in the blood are maintained by negative feedback
  • A stimulus (like low hormone levels in the blood) triggers the release of more hormone
  • Hormone release stops once an appropriate level in the blood is reached

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Category: Medical, Physiology

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