Homeostasis - Study notes.pdf

Homeostasis Learning Objectives Define homeostasis and describe importance of homeostasis Define and describe positive and negative feedback mechanisms and give examples of each Negative feedback systems: temperature regulation, glucose regulation, blood pressure regulation Positive feedback syste...

Homeostasis Learning Objectives Define homeostasis and describe importance of homeostasis Define and describe positive and negative feedback mechanisms and give examples of each Negative feedback systems: temperature regulation, glucose regulation, blood pressure regulation Positive feedback systems: blood clotting and labour Homeostasis Homeo: like, similar Stasis: standing still or in a state of equilibrium Equilibrium: a state of rest or balance due to the equal action of opposing forces Maintenance of a relatively stable internal environment despite continuous outside changes Requires optimum: concentration of O2 & CO2, nutrients such as glucose and fats, Ions such as Na+, Ca+, Water, temperature, pressure Fluid Compartments Total body water = 40 L Intracellular fluid (ICF) compartment: 2/3 or 25 L in cells Extracellular fluid (ECF) compartment: 1/3 or 15 L Extracellular Fluid (ECF) Plasma: 3 L Interstitial fluid (IF): in spaces between cells Other: lymph, CSF, humors (eye), synovial fluid, serous fluid, and gastrointestinal secretions Homeostasis Control mechanisms: Involve continuous monitoring and regulation of many factors (variables) Nervous and endocrine systems accomplish the communication via nerve impulses and hormones Disturbance (imbalance) of homeostasis: Increases risk of disease Contributes to changes associated with aging May allow destructive positive feedback mechanisms to take over (heart failure) Components of a Control Mechanism Receptor (sensor) Monitors the environment Responds to stimuli (changes in controlled variables) Control center Determines the set point at which the variable is maintained Receives input from receptor Determines appropriate response Effector Receives output from control center Provides the means to respond Response acts to reduce or enhance the stimulus (feedback) Negative Feedback The response reduces or shuts off the original stimulus e.g. Temperature Regulation Negative Feedback The response reduces or shuts off the original stimulus e.g. Glucose Regulation Negative Feedback The response reduces or shuts off the original stimulus e.g. Blood Pressure Regulation Positive Feedback The response enhances or exaggerates the original stimulus May exhibit a cascade or amplifying effect Usually controls infrequent events: e.g. Platelet plug formation and blood clotting Positive Feedback The response enhances or exaggerates the original stimulus. May exhibit a cascade or amplifying effect Usually controls infrequent events: e.g. Enhancement of labor contractions by oxytocin