Homeostasis

• Homeostasis


  The maintenance of a constant internal environment independent of external environment conditions

  
• Internal conditions that should be kept constant

  • Temperature
  • pH
  • Water potential
  • Concentration of metabolic wastes
  • Blood glucose concentration
  • Carbon dioxide concentration
• Negative feedback process

  • Occurs when the body reacts to bring about an opposite effect to the changes detected
• Components of negative feedback

  • A normal or set point that needs to be maintained
  • A stimulus which is a change from normal condition in the internal environment
  • Receptors that detect the stimulus
  • A corrective mechanism that brings about reverse effect of the stimulus

  
• What happens when a condition rises above normal

  1. Receptors detect the change

  2. Corrective mechanism is activated

  3. Condition returns to normal

  
• Osmoregulation


  • The process of maintaining the water potential of blood plasma
  • Changes in the amount of water and solutes in the body above or below the normal level are detected
  • Antidiuretic hormones (ADH) act on the kidneys to regulate the blood water potential
  • ADH affects the reabsorption of water in the kidneys and keeps the water potential of the body constant
• Regulating water potential of blood plasma when it increases above normal

  1. Hypothalamus in brain stimulated

  2. Pituitary gland releases less anti-diuretic hormone (ADH) into bloodstream

  3. Decreases the permeability of cells of the wall of the collecting duct to water and collecting duct of the kidney tubules reabsorbs less water into the blood capillaries

  4. More water loss in the urine, volume of urine produced is larger and less concentrated

  5. Water potential of blood plasma returns to normal
• Regulating water potential of blood plasma when it decreases below normal

  1. Hypothalamus in brain stimulated

  2. Pituitary gland releases more anti-diuretic hormone (ADH) into bloodstream

  3. Increases the permeability of cells of the wall of the collecting duct to water and collecting duct of the kidney tubules reabsorbs more water into the blood capillaries

  4. Less water loss in the urine, volume of urine produced is smaller and more concentrated

  5. Water potential of blood plasma returns to normal
• Hormone


  A chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs
• Type 2 diabetes mellitus


  A persistently higher than normal blood glucose concentration due to the body's resistance to insulin or insufficient production of insulin
• Risk factors for type 2 diabetes mellitus

  • Unhealthy diet
  • Sedentary lifestyle
• Ways to manage type 2 diabetes

  • Dietary control
  • Regular exercise
• Homeostatic mechanism


  1. Stimulus from change in internal environment

  2. Corrective mechanism

  3. Negative feedback

  
• Hormone


  A chemical substance produced by a gland, carried in the bloodstream, that alters the activity of one or more specific target organs
• Structures in the skin involved in thermoregulation

  • Blood vessels (arterioles and capillaries)
  • Sweat glands
  • Sensory receptors (temperature receptors)
• Regulation of body temperature on a hot day

  1. Increased sweat production

  2. Vasodilation of arterioles

  3. Relaxation of hair erector muscles

  4. Reduced metabolic rate

  
• Regulation of body temperature on a cold day

  1. Decreased sweat production

  2. Vasoconstriction of arterioles

  3. Contraction of hair erector muscles

  4. Increased metabolic rate

  5. Shivering

  
• Vasodilation and vasoconstriction refer to the dilation and constriction of blood vessels, not shunt vessels
• Endocrine glands are ductless glands that transport their secretion through the bloodstream
• Exocrine glands have ducts to transport secretions to target organs
• Example of exocrine glands

  sweat gland, salivary gland And pancreas
• Example of endocrine gland

  pituitary gland, pancreas, adrenal gland
• negative feedback is a corrective mechanism to restore normal conditions in response to a stimulus and when there is a change from the normal conditions