5.1.1 - the need for communication systems

• define homeostasis

  maintaining a constant internal environment despite external and internal changes
• why do multicellular organisms require communication systems?

  • they need to respond (through behaviour/physiology ) to changes in external environment (stimulus)
  • needed for homeostasis to excrete waste/toxic substances from metabolic reactions in cells which affect the environment cells are in. (e.g- co2 and tissue fluid)
• What are the reasons for keeping the internal environment constant for:

  • blood glucose concentration
  • internal temperature
  • water potential
  • Cell pH
  • blood glucose concentration - glucose present for respiration and ensured constant water potential
  • internal temperature - enzyme can catalyse reactions at optimum temperature
  • water potential - prevents cells bursting/shrinking and not functioning
  • Cell pH- enzyme can catalyse reactions at optimum temperature
• what are some examples of external environmental changes?

  • temperature
  • light intensity
  • sound
• what does a good communication system look like?

  • should cover the whole body
  • should enable cell signalling
• what are the two types of communication systems?

  • Nervous system - allows neuronal signalling via synapses for rapid response
  • Endocrine system - uses blood to transport signals for longer term response
• what is cell signalling?

  the way in which cells communicate with each other.

  
  

  this is the process in which one cell will release a chemical that is detected by another cell. second cell will respond to the signal released by the first cell.

  
  

  cell signalling involves molecules with complementary shape to receptor on target cell.
• what is the response pathway?

  • stimulus -> receptor -> cell signalling -> effector -> response
• what is a stimulus

  change in the internal/external environment
• what do receptors do and what are its properties?

  • receptors detect stimuli
  • they are specific
  • some receptors are cells, some are proteins on cell surface membranes
• what are effectors?

  are cells that bring about a response to the stimulus to produce an effect
• how do you produce a response

  • receptors need to communicate with effectors and effectors may need to communicate with other cells - cell signalling.
• How do communications systems organisms respond to changes in the internal environment?

  • they respond to changes in their internal environment to make sure that the conditions are always optimal for their metabolism (chemical reactions)
• how does cell signalling occur by adjacent + distant cells - provide examples?

  • adjacent (nearby cells), when in the nervous system communicate by secreting chemicals called neurotransmitters, which send signals to adjacent cells such as nerve/muscle cells.
  • distant cells, the hormonal systems work by cells releasing chemicals called hormones, which travel in the blood and all as signals to distant cells