Homeostatsis Flashcards
Homeostasis
maintainance of a constant internal environment
Importance of homeostasis
- consistency of temperature and pH, as it can affect enzyme activity;
- if blood glucose too high, water moves out by osmosis leading to dehydration
Describe how thermoregulation can combat a large decrease in external temperature
- thermoreceptors in hypothalamus detect temperature changes of blood;
- thermorecepters in skin detect temperature changes of skin
- Impulse is sent to the heat gain centre of hypothalamus
- nerve impulses transmitted from hypothalamus results in:
- vasoconstriction of arterioles, leading to less blood to skin;
- Shivering,which generates heat via respiration;
- Piloerector muscles contract, causing hair to rise (insulator)
- negative feedback occurs to regulate increase
Why is a tall,thin person more likely to lose heat than a small and stout one?
- larger surface area to volume ratio;
- more heat loss by radiation;
Advantages of endothermy over ectothermy
- endotherms maintains its body at a metabolically favourable temp
- enzymes can work at optimum temperature;
- so metabolic reactions proceed more quickly;
- more independent of environment so better able to survive in different environment;
Why do reptiles seek shade when the temperature increases abover 40 degrees
- body will ‘overheat’ in very hot environments;
- they have no physiological cooling mechanism
- may lead to enzyme dentaturation
Role of insulin
- secreted when blood sugar increases
- it binds to specific receptors on liver cells;
- binding of insulin activates enzymes** in liver which encourages **glycogenesis
- increases permeability to glucose, leading to more glucose entering cells from blood
- so the glucose entering the cell is converted to glycogen, reducing blood glucose conc
Even with no insulin, why does the blood glucose conc still decrease
- glucose is used in cell respiration
- glucose enters cells and is converted to glycogen
- glucose is excreted in urine;
Differences in nervous and hormonal systems in mammals
Nervous vs Hormones:
- Fast vs Slow acting
- Localised vs Broadcast
- short lived vs long term effects
- electrical via nerves vs chemical delivered by blood vessels
How can diet and exercise maintain low glucose conc in type 2 diabetics?
- feeding on polysaccharides e.g starch slower digestion** therefore **no surge in blood sugar level;
- exercise - increased respiration which uses glucose
Describe the role of the hormone glucagon in the control of blood sugar concentration.
- Binds to specific receptor;
- On muscle and liver cell;
- Activates adenylate cyclase**, which converts **ATP into cAMP
- This activates enzymes in liver
- These catalyse the hydrolysis of glycogen;
- Also leads to glyconeogenesis
- Glycogensis inhibited
- Glucose facilitatedly diffused of out of liver cell cells into blood
- This Increases blood glucose levels;
Describe the physiological responses to a fall in temp
- Reduction in sweating;
- Hair erection;
- Rapid contraction of skeletal muscles;
- Vasoconstriction
- Release adrenaline and thyroxine which increases resp;
Describe three physiological responses to a rise in temp
- More sweating
- Vasodialation
- Hair lowers
How does shivering and having raised hair help to increase heat
- Shivering generates heat by respiration;
- Hair has tendency to keep air trapped thereby reducing air movement;
- This gives insulation so less heat loss
Role of blood vessels in skin when conserving heat
- Vasoconstriction of arterioles, which leads to less blood to surface
- Less heat loss by radiation
