Princ & FM

• ·       Homeostasis is the process by which the internal environment is maintained in a steady state (within tolerance limits).
• ·       Conditions that must be kept around an optimum in the human body include: temperature, pH, blood glucose, oxygen and carbon dioxide concentrations, water levels and blood pressure.
• ·       Homeostasis is important to allow protein and enzyme action, to stop vast changes in cell water potentials and to make organisms more independent of their external environment.
• ·       Control of any system includes the features of: the optimum point, receptors, a coordinator, effectors and a feedback mechanism.
• ·       The main two types of feedback mechanism are positive and negative feedback.
• ·       Positive feedback is where a deviation from an optimum results in changes that result in even further deviation, such as in the creation of an action potential.
• ·       Negative feedback is where a response neutralises or reverses the original stimulus, bringing a condition back to the optimum.
• ·       Homeostasis is shown in thermoregulation, when we are too warm changes include vasodilation, increased sweating and lowering of body hair, whereas when we are too cold changes include shivering, raising of hair, increased metabolic rate, decreased sweating and vasoconstriction.
• ·       Temperature control is an example of negative feedback, where a deviation from the optimum causes the hypothalamus to send more or less nerve impulses to the skin, and thermoreceptors then change the number they send back based on what response has occurred.