• “The maintenances of a constant internal environment”

    • The internal environment is made up of tissue fluid
    • Maintaining the features of this fluid at the optimum levels protect the cells from changes in the external environment which gives the organism a degree of impendence
    • Homeostasis includes the maintaining of the chemical makeup, volume and other features of blood and tissue fluids within restricted limits
    • It ensures that all cells meet their needs to function normally despite external changes
    • Homeostasis is the ability to return to a set point and so maintain organisms in a balanced equilibrium


    • Enzymes controlling biochemical reaches within cells and proteins are sensitive to changes in pH and temperature, resulting in lower effectiveness or denaturing if requirements are not met
    • Changes to the water potential of the blood and tissue fluids may cause cells to shrink/expand as a result of water leaving/entering by osmosis. Therefore, the cell cannot function normally.
    • Maintenance of blood glucose levels is essential in ensuring a constant water potential and for respiration of the cells
    • Enables the organisms to be less dependent on the environment

    Control Mechanisms

    • Set Point: The desired level for optimum performance
    • Receptor: Detects any deviations from the set point and informs the controller
    • Controller: Coordinates information from various receptors and seconds instructions to an effector
    • Effector: Brings about the change required to return the system back to set point
    • Feedback Loop: Informs the receptors of the change to the system brought about by the effector