Homeostasis Maintaining the internal environment Homeostasis Homeostasis is the state of steady internal physical and chemical conditions maintained by living systems, despite changes in the external environment. • Some simple examples of homeostasis: When it is cold you shiver, when it is hot you sweat to maintain the optimum body temperature of 37.5 degrees Celsius. • There are a number of different body systems that work together to maintain the balance across the entire organism. Feedback • In order to keep internal conditions (eg. Temperature or nutrient concentration) stable, organisms must have a feedback mechanism to quickly identify and control all changes to homeostasis. • Draw a diagram of the stimulus response in your notes Feedback Negative Feedback • Mechanisms that counteract the stimulus are referred to as Negative Feedback. • An example is temperature, when your core body temperature increases the body will counteract the increase by activating sweat glands throughout the body. Negative Feedback • This process can be compared to the air conditioning systems you see so often in homes and offices. • There is a sensor (thermometer) in an air conditioner you input the desired temperature and the control centre (computer) in the air con will send info to the effector, to release cold air. Negative Feedback Negative Feedback Conditions in the body are constantly fluctuating, negative feedback is constantly working to maintain the internal environment. The figure below shows how homeostasis operates to continually readjust body conditions to maintain them within tolerance limits. QUESTIONS Complete Biozone worksheet p175, 178, 179
