Homeostasis and Thermoregulation PDF

HOMEOSTASIS Maintaining Balance HOMEOSTASIS  Homeostasis: maintenance of a steady internal state, despite changes in the external environment  For example: Blood pressure Body Temperature Blood glucose Blood pH Fluid bal...

HOMEOSTASIS Maintaining Balance HOMEOSTASIS  Homeostasis: maintenance of a steady internal state, despite changes in the external environment  For example: Blood pressure Body Temperature Blood glucose Blood pH Fluid balance MAINTAINING HOMEOSTASIS  Balance is obtained by maintaining a dynamic equilibrium.  Made possible by 3 functional components: 1. Receptor or Sensor:  receives the stimulus or information 2. Control Centre or Coordinating Centre:  Puts the information together (integrates) and determines (coordinates) the sequence of events that follow 3. Effector or Regulator:  Performs a response FEEDBACK SYSTEMS  A cycle of events in which a variable (body temperature; blood glucose; blood pH; etc) is continually monitored, assessed and adjusted  Uses a sensor; a control centre and an effector TYPES OF FEEDBACK SYSTEMS: 1. Negative Feedback:  Process by which a mechanism is activated to restore conditions to their original state NEGATIVE FEEDBACK EXAMPLE: TYPES OF FEEDBACK SYSTEMS: 2. Positive Feedback:  Process by which a small effect is amplified (moves the controlled variable even further from a steady state)  Reinforces the change POSITIVE FEEDBACK EXAMPLE: AMEOBA SISTERS: THERMOREGUL ATION THERMOREGULATION  Thermoregulation: the maintenance of body temperature within a range that enables cells to function efficiently  Ectotherms:  Organisms that depend on air temperature to regulate metabolic rates  Body temperature is often regulated through sun exposure  E.g. invertebrates, fish, amphibians, reptiles  Endotherms:  Organisms that are able to maintain a constant body temperature regardless of their surroundings (within reason)  Regulation can occur through adjusting respiration rate, vasoconstriction and vasodilation, sweating, adjusting heart rate, shivering  E.g. mammals and birds CORE TEMPERATURE  Core Temperature: the temperature of the internal body including organs such as the liver, heart and blood  Human Temperatures: Core Temperature Peripheral Temperature Most Constant Fluctuates Between 36.5˚C and 37.5˚C Can be 4˚C lower than 37˚C on cold days Chest cavity, abdominal cavity Fingers, toes HEAT & COLD STRESS  The body is constantly exposed to heat stress & cold stress  E.g. exercise, environmental temperatures REGULATING TEMPERATURE  The HYPOTHALAMUS is the key to regulation!  Gland in the vertebrate brain that coordinates nerve and hormone function RESPONSE TO EXTREME COLD 1. HYPOTHERMIA  Core temperature drops below normal range  Can lead to coma or death  Body responds by diverting heat from the periphery to the core 2. METABOLISM OF BROWN FAT  Brown fat: dark adipose tissue with many blood vessels involved in the production of heat in hibernating animals and human babies  Converts chemical energy to heat  Studies show it is present in some capacity in adults; stimulated by cold  FREEZING CELLS  The body will do as much as it can to prevent cells or organs from freezing due to: 1. Formation of Ice crystals  Act like microscopic knives and pierce cell membranes, causing cells to lose important nutrients and organelles 2. Thawing of cells  Ice crystals will melt together, causing cells to fill with water and push against one another