Mammalian homeostasis

• To function properly and efficiently, organisms have different control systems to ensure internal conditions are kept relatively constant
• Homeostasis


  The process of maintaining constant internal body conditions
• Homeostasis is critically important for organisms to ensure the maintenance of optimal conditions for enzyme action and cell function
• Conditions monitored by sensory cells

  • Core body temp
  • Metabolic waste (CO2 and Urea)
  • Blood pH
  • Concentration of glucose in blood
  • Water potential of the blood
  • Concentration of respiratory gases, CO2 and O2 in the blood
• Homeostasis


  The regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• Homeostasis


  The maintenance of stable internal conditions in an organism
• Majority in organisms use negative feedback to maintain homeostatic balance
• Negative feedback control loops

  • Involve a receptor
  • Coordination system (nervous and endocrine)
  • Effector (muscles and glands)
• Receptor


  Detects stimuli involved with condition/physiological factor
• Coordination system


  Transfers information between different parts of the body
• Effector


  Carries out response
• Outcome of negative feedback loops

  1. Factor/stimuli is continuously monitored

  2. Increase in factor = body response to decrease it

  3. Decrease in factor = body response to increase it
• Negative feedback loop diagram

  
• Homeostasis in mammals relies on two different coordination systems to transfer information between different parts of the body
• Nervous system


  • Information transmitted as electrical impulses that travel along neurons
• Endocrine system


  • Information is transmitted as chemical messengers called hormones that travel in the blood
• Impulses


  Short lived and required for fast but short responses
• Hormones


  Involved in slower activation but longer lasting responses
• Some hormones can act very quickly
• Many metabolic reactions within the body produce waste
• Excretion


  Removal of waste
• Excretory products formed in humans

  • Carbon
  • Urea
• Urea


  Produced by the liver from excess amino acids
• More protein eaten than required results in excess that cannot be stored in the body
• Amino acids within protein can still provide useful energy
• Deamination


  1. Amino group removed from acid

  2. Extra hydrogen removed

  3. Form ammonia

  4. Remaining keto acid may enter the Krebs cycle and be respired

  5. Converted to glucose or glycogen
• Deamination of amino acids

  
• Ammonia is soluble and highly toxic 

  • Dissolves in blood to form alkaline ammonium hydroxide, disrupting blood pH 
  • Can impact reactions of cell metabolism such as respiration 
  • Interferes with cell signaling  processes 

   

  • Can be avoided by converting to urea 
  • Urea is less soluble and less toxic than ammonia 
  • Ammonia Combined with co2 to form urea 
• Urea formation