Homeostasis and Thermoregulation

Introduction to Homeostasis

• Definition: An organizing principle to maintain a constant internal environment.
• Internal Environment: Tissue fluid in the human body.
• Importance: Necessary to maintain equilibrium for cell functionality.

Organs Involved in Homeostasis

• Lungs: Regulate carbon dioxide and oxygen with the help of the brain's respiratory center.
• Skin: Regulates temperature controlled by the hypothalamus.
• Liver: Regulates glucose levels via insulin control.
• Kidneys: Regulate urea and excess minerals through urine and water excretion, influenced by antidiuretic hormone.

Thermoreceptors

• Definition: Sensory receptors sensitive to temperature changes.
• Location: Found in the skin.
• Function: Connected to the hypothalamus for temperature regulation.

Feedback Mechanism

• Negative Feedback: Key process in regulating body temperature.

  • When Hot:

    • Thermoreceptors detect temperature rise.
    • Hypothalamus stimulates neurons resulting in:
      • Increased sweat production
      • Relaxation of hair erector muscles
      • Dilation of blood capillaries
      • Decrease in metabolic reaction
    • Outcome: Body temperature decreases.

  • When Cold:

    • Thermoreceptors detect temperature drop.
    • Hypothalamus stimulates neurons resulting in:
      • Shivering
      • Contraction of hair erector muscles
      • Constriction of blood capillaries
      • Increase in metabolic reaction
    • Outcome: Body temperature increases.

Endotherms vs Ectotherms

• Endotherms (Homeotherms):

  • Ability to generate their own body heat.
  • Includes mammals and birds.
  • Enables colonization of cold regions.

• Ectotherms (Poikilotherms):

  • Cannot generate their own heat.
  • Depend on external heat sources like sunlight.
  • Includes reptiles and amphibians, found in warmer regions.

Importance of Maintaining Body Temperature

• Essential for enzyme-catalyzed reactions to occur at optimal levels.