Homeostasis Flashcards
What is homeostasis?
Keeping the internal environment constant despite changes to the external environment
What are the 6 conditions which are to be kept constant?
-Body temperature
-Blood glucose concentration
-Blood salt concentration
-Water potential of blood
-Blood pressure
-CO2 concentration
What is the feedback loop of homeostasis?
Conditions in body change (stimulus) -> Change detected -> Corrective mechanism activated (response) ->Conditions returned to set point -> Corrective mechanism switched off
What are the two types of feedback loops?
Negative and Positive
Which type of feedback loop is used by most systems?
Negative
What is a negative feedback loop?
Deviation from the set point that causes changes that bring the level back towards set point
Examples of a negative feedback loop.
-Temperature
-Water Potential
-Blood Glucose
What is a positive feedback loop?
Deviation from the set point that causes changes that result in an even greater deviation from the normal.
Examples of a positive feedback loop.
-Excitation of Neurons
-Onset of Uterine Contraction at Birth
What are Endothermic animals?
Animals which are able to maintain their body temperature within very tight limits (humans)
What are Ectothermic animals?
Animals that have a core body temperature that fluctuates with ambient and are reliant on external sources to heat to keep warm
What are advantages of endotherms?
-Constant body temperature
-Activity possible in cold environments
-Ability to inhabit colder areas of the planet
What are disadvantages of endotherms?
-High proportion of food energy used in thermoregulation
-Need to eat more food
-Less energy for growth
How do endotherms regulate their temperatures?
-Sweat glands in skin
-Mouth/Nose/Lungs
-Hairs on skin
-Arteriole vasodilation/vasoconstriction
-Liver cell metabolism
-Skeletal muscles
-Behavioural methods
What are advantages of ectotherms?
-Use less food for respiration
-Can survive long periods without eating
-More energy from food can be used for growth
What are disadvantages of ectotherms?
-Less active in colder areas/times so at risk of predation
-May not be active all winter so need sufficient stores of energy
How do ectotherms regulate their temperatures?
-Use behavioural methods to adjust heat exchange with the environment
-Some are more specifically adapted to help
What happens if there is a rise in core temperature in order to create the temperature to fall back to optimum?
-Thermoregulatory centre in hypothalamus detects change -> Nervous system and hormonal system carry signals to skin, liver and muscles -> Less heat generated and more heat lost
What happens if there is a fall in core temperature in order to create the temperature to fall back to optimum?
-Thermoregulatory centre in hypothalamus detects change -> Nervous system and hormonal system carry signals to skin, liver and muscles -> More heat generated and less heat lost
