CHAPTER 10'3 Hormone in mammals

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BIOLOGY SB017

• CHAPTER 10.3 Hormone in mammals

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OBJECTIVES

• Describe the endocrine system and the main
  endocrine glands
• List the types and characteristics of hormones
• Explain the mechanism of hormone action ( gene
  activation and cAMP )
• Compare the two mechanism of hormonal action

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ENDOCRINE SYSTEM

• The endocrine system is made up of glands
  called ENDOCRINE GLANDS.

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ENDOCRINE SYSTEM

• Characteristics of endocrine glands
• secretes chemicals called hormones
• a ductless gland i.e. the hormone is secreted
  directly into the bloodstream
• it has a rich supply of blood with a
• relatively large number of blood vessels

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MAIN ENDOCRINE GLANDS

• THE HYPOTHALAMUS AND PITUITARY GLAND
• PARATHYROID AND THYROID GLANDS
• ADRENAL GLAND
• PANCREAS
• GONADS

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HORMONE DEFINITION

• A chemical secreted by cells in one part of the
  body that is transported in the bloodstream to
  other parts of the body where it affects
  particular target cells

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Characteristics of hormone

• A small soluble organic molecule
• Travels in blood
• Fits into precise target molecule
• Specific for a particular target
• Effective in low concentration

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TYPES OF HORMONE

• Non steroid
• Amine and peptide hormone

• Steroid

• Soluble in water

• Soluble in lipid

• Response within a few minutes

• Long term response

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Major chemical groups of hormones
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Major chemical groups of hormones
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Major chemical groups of hormones
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• TABLE 1

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MECHANISM OF HORMONE ACTION
i. Gene activation
ii. Second messenger (cAMP)
Steroid hormone
Non- steroid hormone
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MECHANISM OF HORMONE ACTION

• A. GENE ACTIVATION
• e.g. steroid hormones by adrenal cortex
• Steps
• Steroid hormones pass through the cell surface
  membrane
• Bind to a receptor protein in the cytoplasm or
  in the nucleus

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• 3) The complex formed passes to the cell nucleus
  where the hormone exert a direct effect upon the
  chromosomes by switching on genes and
  stimulating transcription (mRNA formation)
• 4) The mRNA enters the cytoplasm
• 5) and is translated into new proteins such as
  enzyme

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MECHANISM OF HORMONE ACTION

• B. cyclic AMP
• e.g. adrenaline (epinephrine)
• These hormones being insoluble in lipid, cannot
  pass through the plasma membrane. 
• Hormone diffuses through the blood, into the
  interstitial fluid, and then reaches the target
  cell.

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MECHANISM OF HORMONE ACTION cyclic AMP

• It binds to the receptors present on the surface
  of the cell.
• This binding activates G protein which in turn
  activate adenylyl cyclase

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MECHANISM OF HORMONE ACTION cyclic AMP

• Adenylyl cyclase in turn converts ATP into cAMP
• cAMP in turn activates a variety of protein
  kinase in the cell
• Activated protein kinase phosphorylates one or
  more enzymes

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MECHANISM OF HORMONE ACTION cyclic AMP

• In this mechanism, the hormone acts as the first
  messenger which brings information to the plasma
  membrane.
• A second messenger (cAMP) then relays the message
  of the hormone inside the cell.
• Adrenaline (epinephrine) stimulate the glycogen
  breakdown

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COMPARISON BETWEEN THE TWO MECHANISMS OF
HORMONAL ACTION
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COMPARISON BETWEEN THE TWO MECHANISMS OF
HORMONAL ACTION
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COMPARISON BETWEEN THE TWO MECHANISMS OF
HORMONAL ACTION
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