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Unformatted text preview: od Necessary Life Functions II Necessary Life Functions II Metabolism – all the chemical reactions that occur in the body Excretion – removal of wastes from the body Reproduction – cellular and organism levels Cellular – an original cell divides and produces two identical daughter cells Organism – sperm and egg unite (fertilization) make possible the formation of a new person Growth – increase in size of a body part or of the organism Metabolism Metabolism Metabolism: A broad term used for all the chemical reactions that occur within cells of the body Catabolism ­ breaking down substances into simpler components Anabolism – synthesizing more complex substances or structures from simpler substances Homeostasis Homeostasis Homeostasis is the ability of the body to maintain a relatively stable internal environment The internal environment of the body is in a dynamic state of equilibrium (internal conditions vary, but within relatively narrow limits) A wide variety of chemical, thermal, and neural factors act and interact in complex ways to maintain homeostasis Homeostatic Control Homeostatic Control Mechanisms Variable – the factor or event being regulated Receptor monitors the environment and responds to changes (stimuli) Control center determines the set point at which the variable is maintained Effector provides the means to respond to the stimulus Homeostatic Control Mechanisms Homeostatic Control Mechanisms Negative Feedback Negative Feedback In negative feedback systems, the output “turns down” or “shuts off” the original stimulus Example: Regulation of blood glucose levels Positive Feedback Positive Feedback In positive feedback systems, the output enhances or “turns up”...
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