Thermoregulation & Feedback How do different organisms maintain temperature balance? Warm-blooded (endotherms) Cold-blooded (ectotherms)
Temp Regulation - Homeostasis Why must organisms maintain internal temp balance? Enzymes!! Enzymes speed up chemical rxns in your body Enzymes only work under certain conditions
Thermostat Temperature set on thermostat Too cool? Heater kicks on and temperature goes up Too warm? Stays off until house cools down Constant checking and turning on and off
Control of homeostasis through feedback Feedback system- cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re- monitored, re-evaluated, etc.
1) receptor sensor that responds to changes (stimuli) 2) control center sets range of values, evaluates input and sends output 3) effector receives output from control center and produces a response 3 basic components of a feedback system
Body Temperature Control The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermoreceptors in the skin. There are also receptors in the hypothalamus- called central thermoreceptors. These detect changes in blood temperature.
Summary What is the difference between an ectotherm and an endotherm? What are the components of a feedback system?
Correction of overheating 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasodilation. 3. Sweating
Sweating How does it work? Heat energy in the body is used to convert the water in sweat to vapour cooling down the body.
Heat Loss Radiation: Transfer of heat via infrared rays 60% heat loss at rest Conduction: Heat loss due to contact with another surface Convection: Form of conductive heat loss
Heat Loss Evaporation Heat transferred via water (sweat) on skin surface Evaporation rate depends on Temperature and relative humidity Amount of skin surface exposed 25% heat loss at rest Most important means of cooling off during exercise
Correction of overcooling 1. Detected by thermoreceptors in the hypothalamus. 2. Causes vasoconstriction. 3. Decreased sweating 4. Shivering
Keeping warm When it's cold, the muscle contracts pulls the hair up. A layer of warm air accumulates around the hair and insulates the organism. Heat retained
Voluntary responses In humans the cerebrum “makes” people feel cold or hot. They can then e.g. put on more clothes, eat a hot meal, exercise etc as appropriate.
Summary Describe the specific pathway that is used to keep us warm. Start with the temperature receptors in the skin. Describe the specific pathway that is used to cool us off. Start with the temperature receptors in the skin.