- Multicellular organisms need a communication system in order to:
- Respond to changes in the internal and external environment
- Coordinate the activities of different organs
- Cells communicate with eachother via cell signalling. This can be
- A good communication system will
- Cover the whole body
- Enable cells to communicate with eachother
- Enable specific communication
- Enable rapid communication
- Enable both short-term and long-term responses
- Homeostasis is the maintenance of the internal environment in a constant state despite external changes. Things that organisms need to maintain include:
- Body temperature
- Blood glucose concentration
- Blood salt concentration
- Water potential of the blood
- Blood pressure
- Carbon dioxide concentration
Negative feedback: a process that brings about a reversal of any change in conditions. It ensures an optimum steady state can be maintained. It is essential for homeostasis.
Stimulus > receptor > communication pathway (signalling) > effector > response
A number of structures are required for this pathway to work:
- Sensory receptors e.g temp or glucose conc receptors.
- Monitor internal conditions. If they detect a change they will be stimulated to send a message
- A communication system e.g nervous or hormonal.
- Used to transmot a message from the receptor cells to effectors. Message may pass through a coordination centre such as the brain.
- Effector cells e.g. liver or muscles.
- These bring about a response that reverses the change by the receptors.
Less common that negative. Acts to increase…