MOD 5 & 6

• Digestion of carbohydrates


  1. Glucose absorption

  2. Excess carbohydrate digestion

  3. Skipping a meal
• Homeostasis


  The body's ability to function well despite the ever-changing external environment
• Organisms with efficient homeostasis systems

  • Can tolerate a wide range of external factors
• Substances maintained in the body

  • Glucose
  • Water
  • Carbon dioxide
  • Oxygen
  • Mineral salts (sodium, chlorine)
• Internal conditions regulated


  • Temperature
  • Blood pressure
  • Hormone concentration
• Homeostasis


  The condition during which a system like the physical body is maintained in a more-or-less steady state
• Maintaining homeostasis


  • Requires continuous monitoring of the internal environment and constantly adjusting to keep things in balance
• Organs/systems involved in homeostasis

  • Liver
  • Pancreas
  • Kidneys
  • Brain (hypothalamus, autonomic nervous system, endocrine system)
• Liver's role in homeostasis

  Metabolizing toxic substances, maintaining carbohydrate metabolism, managing lipid metabolism, cholesterol production
• Kidneys' role in homeostasis

  Regulating blood water levels, re-absorption of drugs, maintaining salt and ion levels, regulating blood pH, excreting urea and waste
• Hypothalamus' role in homeostasis

  Regulation of blood heat, pulse, blood pressure, circadian rhythms (wake/sleep cycles)
• Cell membrane


  Serves as the gatekeeper of the cell, allowing only selected substances to go in and out
• Cell membrane structure


  • Highly specialized to allow efficient movement of substances in and out of the cell
  • Contains signal receptors to identify substances to be transported
• Maintaining homeostasis


  1. Stimulus

  2. Sensor

  3. Control center

  4. Effector
• Stimulus


  The variable being regulated, indicates the value has moved away from the set point
• Sensor


  Monitors the values of the variable and sends data to the control center
• Control center


  Matches the data with normal values and sends a signal to the effector if the value is not at the set point
• Effector


  An organ, gland, muscle, or other structure that acts on the signal from the control center to move the variable back toward the set point
• The hypothalamus is the most important example of an integrating center or control center for homeostasis
• Negative feedback loop


  Feedback serves to reduce an excessive response and keep a variable within the normal range
• Processes controlled by negative feedback

  • Body temperature regulation
  • Control of blood glucose
• Setpoint


  The physiological optimum value for a variable
• Normal range


  The spread of values within which fluctuations around the setpoint are considered insignificant
• Regulation of body temperature - Cooling down

  1. Blood vessels in skin dilate to allow more blood flow

  2. Sweat glands activated to increase sweat output

  3. Breathing becomes deeper and through mouth
• Regulation of body temperature - Heating up

  1. Blood vessels in skin contract to prevent heat loss

  2. Shivering generates heat

  3. Thyroid gland secretes more hormones to increase metabolism

  4. Adrenal glands secrete adrenaline to break down glycogen for energy
• Positive feedback loop


  Feedback serves to intensify a response until an endpoint is reached
• Processes controlled by positive feedback

  • Blood clotting
  • Childbirth
• Blood clotting


  1. Injured blood vessel releases substances

  2. Platelets cling to site and release chemicals

  3. More platelets attracted, accelerating clot formation
• Childbirth


  1. Infant's head pushes against cervix

  2. Nerve impulses to hypothalamus

  3. Hypothalamus releases oxytocin

  4. Oxytocin stimulates uterine contractions

  5. Contractions push baby harder against cervix, causing more dilation
• Regulation of glucose concentration

  1. Pancreatic beta cells release insulin when blood glucose is high

  2. Pancreatic alpha cells release glucagon when blood glucose is low
• Homeostasis


  Maintaining stable conditions in the human body
• Homeostatic mechanisms fail


  Homeostatic imbalance may result
• Homeostatic imbalance


  Cells may not get everything they need or toxic wastes may accumulate in the body
• Homeostasis not restored


  Imbalance may lead to disease or even death
• Diabetes


  Disease caused by homeostatic imbalance where blood glucose levels are no longer regulated and may be dangerously high
• Medical intervention


  Can help restore homeostasis and possibly prevent permanent damage
• Normal aging


  Reduction in efficiency of body's control systems, making body more susceptible to disease
• Older people


  • Harder time regulating body temperature, more likely to develop heat-induced illnesses
• Diabetes


  Metabolic disorder caused by excess blood glucose levels, disease caused by failed homeostasis
• Homeostatic control mechanisms do not work efficiently enough or amount of blood glucose is too great


  Medical intervention necessary to restore homeostasis and prevent permanent organ damage