Homeostasis Flashcards
Homeostasis
- Maintenance of a constant internal environment
Internal conditions to carry out functions in biological molecules
- Enzymes - control biochemical reactions
- Transport proteins - Move substances
How enzymes denature and change shape - result
- Small fluctuations in temperature and pH
- Can’t transport substances any longer
Why is homeostasis important?
- Constant water potential in blood and tissue fluid
- Cells don’t shrivel or swell and burst
- Prevent cell from functioning correctly
- Constant blood glucose concentration - reliable source of fuel for respiration
Organisms with homeostatic mechanisms
- Survive in more extreme environments
- May have a wider geographical range - greater chance of finding food and shelter
How do mammals prevent cells from freezing?
1 - Antifreeze proteins
2 - AFP bind to ice crystals - preventing them from growing into larger crystals
3 - As ice forms in extracellular space - water from inside the cell rush out through aquaporins to dilute higher concentrations of solutes
4 - Cyroprotectants - glycerol and urea, increase the concentration of solutes inside the cell to help prevent a harmful outflux of water
5 - Aquaporin
Control mechanisms in homeostasis
1 - Stimulus produces change variable
2 - Changed detected by receptor
3 - Input; information sent along afferent pathway to the control centre
4 - Output; Information sent along efferent pathway to effector
5 - Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis
Negative feedback
- Change produced by the control system leads to change in the stimulus detected by the receptor.
- System is turned off - regulation of blood glucose
Body temperature rises
- Blood vessels dilate = heat loss to environment
- Sweat gland secretes fluid
- Fluid evaporates - heat is lost from the body
- Heat is lost to environment
- Normal body temperature
Body temperature falls
- Blood vessels constrict - heat is conserved
- Sweat gland do not secrete fluid
- Shivering (involuntary) generates heat - warms body
- Heat is retained
- Normal body temperature
What does the hypothalamus do when body is too hot
Mechanisms to gain or save heat;
- Respiration increases
- Muscles work
- Hair stands up
- Surface blood vessels contract
What does the hypothalamus do when body it too cold
Mechanisms to lose heat;
- Respiration slows
- Hair lie flat
- Surface blood vessels dilate
- Sweating
Positive feedback
- Change from optimum causes changes that result in even greater deviation from the normal level
- Stimulus causes a small influx of Na+ - changes permeability of of the neurone to Na+ so that more ions enter
Thermoregulation
Maintenance of body temperature
Endotherms
- Gain heat from metabolic processes within the body
eg/ Respiration in shivering muscles
