Topic 8- Homeostasis Flashcards
What is Homeostasis?
Regulation of an internal environment in the face of changes in the external environment.
What parameters do organisms need to control?
pH, water, solutes, temperature, O2/CO2, heart rate, and volume and pressure of cells and blood plasma, osmoregulation.
What are negative feedback mechanics?
A change in a variable under homeostatic control trigger a response that opposes the change.
What components make up negative feedback mechanics?
Sensor- detects environmental conditions.
Integrator- Analyzes signal from sensor, compares conditions to the set point and activates an appropriate effector.
Effector- Causes a physiological change that opposes the deviation from the set point.
What is a common integrator?
The brain, specifically the hypothalamus.
What is a common sensor?
Nerve receptors, or other sensory organs.
What are positive feedback mechanisms?
A change in a variable under homeostatic control triggers a response that amplifies the change. Ex, baby preparing for delivery during labor. Baby puts pressure on cervix, which signals pituitary to release oxytocin which causes the uterus to contract, this continues as long as there is continual pressure on the cervix.
Thermoregulation
Regulating the internal body temperature. Temperature has a huge impact on energy budgets.
What is Ambient Temperature (Ta)?
An environments actual air temperature.
What is Body Temperature (Tb)?
Avg Human temp is 37 degrees celsius, for ectotherms, it will be the temperature of their environment.
What is body heat?
Heat generated by metabolism, heat can be exchanged with the environment by conduction, convection, evaporation and radiation. Body heat can be regulated by changing the rate of heat gain and loss. The rate of heat exchange is called conductance.
How does conductance work? (Exchange of heat)
Small animals have greater conductance. Large organisms have lower conductance due to smaller SA/V ratios. (Beneficial for large animals.)
What is a homeotherm?
Maintains constant body temperature independent of ambient temperature. Can be both an endotherm or ectotherm. Stable environment allows for ectotherm to be a homeotherm.
What is a heterotherm?
Tb will fluctuate with Ta, changes according to ambient temperature.
What is an endotherm?
Uses metabolism to generate body heat.(Internal heat generation.)
What is an ectotherm?
Acquires body heat from environment. They do generate heat from metabolism but don’t keep it.
Body Temperature regulation strategies
What is regional heterothermy?
Demonstrated by certain tuna and sharks, it is an adaptation: countercurrent heat-exchange system. Different parts of the body will have different temperatures, it is not uniform throughout.
What are the metabolic consequences of endothermy vs. ectothermy?
As body mass increases mass specific RMR decreases. Ectotherms develop similar scaling in much lower terms.
What effect does increasing temperature have on metabolism?
As temperature increases, metabolism increases, which in turn enzyme activity. If temperature goes past optimum temperature too much it will cause a crash enzyme activity.
Ambient Temp. And RMR in a Homeothermic Endotherm
Ta and RMR in Heterothermic Extotherm
Ectotherms activity will reduce to survive temperature, temperature will dictate whether or not it will be in an active or lethargic state.
Thermal Zones of Homeotherms
Energy spent to cope with specific temperatures.
Acclimation Graph
How does fur/feather thickness help?
Thicker fur has better insulator power and arctic animals change fur thickness seasonally. The opposite occurs in tropical climates, as temperature increases fur gets thinner or shorter.
