Coordination

• Homeostasis

  The maintenance of a constant internal environment despite to maintain optimum conditions for function in response to internal and external changes
• How and why coordination is needed in multicellular organisms

  To coordinate the functions of different cells and systems to operate effectively.

  • Organisms need to respond to in/external changes to survive.
  • Responses occur by electrical responses and chemical responses in animals and by hormones in plants
  • Cells rely on each other for removal of waste such as CO2
  • Cells communicate via cell signalling
• Internal factors which cause a response

  • Blood glucose concentration
  • Internal temperature
  • Water potential
  • Cell pH
• External factors which cause a response

  • Humidity
  • External temperature
  • Light intensity
  • New or sudden sound
• Cell signalling

  The communication makes sure that the activities of different organs are coordinated to keep the organism working effectively. This occurs through one cell releasing a chemical which has an effect on another cell, known as a target cell.
• The hormonal system works by cells releasing hormones which travel in the blood and act as signals to distant cells
• The nervous system transfers signals locally by secreting neurotransmitters
• Cell surface receptors allow cells to recognise the chemicals involved in cell signalling
• It is important to maintain core body temperature to control the rate of metabolic reactions

  • If body temperature is too high, enzymes may becomes denatured. Increased kinetic energy breaks hydrogen bonds holding molecule in 3D shape.
  • Shape of active site is changed and no longer works as a catalyst. Metabolic reactions are less efficient.
  • If body temperature is too low enzyme activity is reduced, slowing the rate of metabolic reactions.