September 8 2015 BSC 215 READING pages 21 27 Core Principles in Anatomy and Physiology Four Principles Feedback loops The relationship of structure and function Gradients Cell cell communication Homeostasis all core principles relate to homeostasis Maintenance of the body s internal environment Homeostatic imbalances can result in diseases or even death Variables body s internal environment is the result of wide range of these coordinated processes most variables are regulated to stay at a particular normal value including temperature chemical composition of blood etc Feedback Loops are a Key Mechanism Used to Maintain Homeostasis Feedback Loops are homeostatic control mechanisms a change in a regulated variable causes effects the feedback and in turn affect that same variable can be either negative opposing the initial change reducing output or positive reinforcing the initial change increasing output when change in a regulated variable is detected actions are triggered that will bring it back to normal Negative a change in a regulated variable in one direction results in actions that cause changes in the variables in the opposite direction each variable has a set point or normal value o ex temperature 98 6 F mostly it is a normal range though when value is outside normal range a stimulus is picked up by a receptor or sensor The receptor then sends info to the control center often the brain Control center realizes the variable is off and sends signals to organs cells called effectors These cause physiological responses that return value to normal Positive effector s activity actually increases reinforce the initial stimulus often found w in a negative feedback loop to produce a quicker response Structure and Function are Related at All Levels of Organization Form follows function form of a structure always best suits its function Gradients Drive Many Physiological Processes Gradient present any time more of something exists in one area than another and the two are connected concentration gradient present when the amount of a substance changes over a range temperature and pressure also have gradients drive most processes Cell Cell Communication is Required to Coordinate Body Functions Cells must work together to achieve homeostasis communication is typically b w electrical signals or chemical messengers ex nerve cells