Homeostasis

• Organism tolerance states that organisms survive most effectively within tolerance limits for a given abiotic factor
• Tolerance limits is where maximum and minimum amounts of a given abiotic factor that individuals can tolerate
• Zone of physiological stress

  members of a specific population are rare due to limiting abiotic factors – approaching tolerance limits
• Zone of intolerance

  Members of a specific population are non-existent due to the absence of the necessary abiotic factors – beyond tolerance limits.
• although environmental conditions may change drastically, the internal body temperature must remain within its tolerance limit
• body temperature refers to an organism's tolerance range of internal temperature.
• the regulation of body temperature is known as thermoregulation
• optimum body temperature encourages optimum metabolic activity (enzyme activity)
• organisms must adapt to control body temperature within a narrow range
• the consequence of having a body temperature below the tolerance limit

  The rates of enzyme-catalysed metabolic reactions are too slow to maintain the life processes in the cell.
• the consequence of having a body temperature above the tolerance limit


  The structures of the active sites of enzymes are altered which decreases the rates of enzyme-catalysed metabolic reactions.
• water availability is essential for all life processes within and organisms
• osmoregulation is the maintenance of solute concentration by movement of water
• what is the consequence of transport

  material transported are in solution
• what is the consequence of metabolism

  Enzyme-catalysed reaction occur in solution
• What is the consequence of thermoregulation

  With a high heat capacity, water is good at regulating temperature – lots of energy is needed to alter cell temperature.
• What is the consequence of movement

  Muscle movement, movement in plants/flowers.
• what is the consequence of sexual reproduction

  production of gametes
• what is the consequence of support

  Structural support in various tissues – animals and plants.
• if water availability is below the tolerance limit then:

  • Cells and tissues shrink.
  • Increase in solute concentrations.
  • Can affect folding of polypeptides and enzyme function.
• if water availability is above the tolerance limit then:

  • Cells and tissues can burst.
  • Solutes become too dilute.
  • Can reduce rate of some life processes.
• glucose is primary sugar used as a substrate for respiration in humans
• the concentration of glucose in blood is very carefully controlled
• homeostasis is the maintenance of a stable internal environment by regulation factors
• the regulation factors of homeostasis include

  • thermoregulation
  • osmoregulation
  • glucoregulation
  • chemoregulation
• the maintenance of the internal environment remains even if external environmental factors change
• detectable changes in the internal or external environment is called a stimulus
• homeostasis requires constant monitoring and adjusting of internal factors and responding to environmental changes
• what is the first step in the process of the stimulus response model:

  1)     Imbalance induced due to stimulus.
• what is the second step in the process of the stimulus response model:

  2)     Sensory receptors detect and respond to a stimulus that transmits messages as nerve impulses from receptors to the control centre and intensity of message linked to intensity of stimulus.
• what is the third step in the process of the stimulus response model:

  3)     The control centre receives and processes signal from sensory receptors, signals transmitted by nerve impulses (fast and short) or hormones (slow and long lasting) – the hypothalamus in the brain is the control centre for thermoregulation.
• what is the fourth and final step in the process of the stimulus response model:

  4)     The effector then responds to nerve impulses or hormones, initial stimulus has resulted in a response to either oppose or enhance the stimulus.
• thermoregulation is where thermoreceptors respond to changes in temperature
• Many thermoreceptors are in the skin and within the hypothalamus of the brain (which is the control centre).
• Hypothalamus is part of the central nervous system.
• Changes in temperature are detected by thermoreceptors.
• Stimulus signal transmitted by nerve impulses to control centre.
• Control centre sends signal to effectors at skin, muscles, and endocrine glands to return body temperature to normal.
• Organisms must use self-regulating mechanisms to ensure they remain within tolerance limits
• self-regulation leads to negative feedback