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
Differences between hormones and local chemical mediators
Hormones:
- have widespread effect
- affect distant organs
- only affect cells with right receptor;
- are transported in the blood whereas mediators spread by diffusion
How does panting reduce body temp
- Evaporation of water from lining of mouth
- Heat transferred from blood;
Explain how Increased exercise intensity leads to an increased heart rate.
- More resp by muscle tissue
- More CO2 released, this lowers pH
- Decreased pH detected by chemoreceptors in carotid arteries
- This send impulses to the Medulla Oblangata involved;
- MORE impulses to SAN along sympathetic nerve
- Leads to increased HR, so more blood flow leads to more CO2 moved to lungs
Explain how increased cardiac output is advantageous during exercise
- Increases glucose and O2 supply to muscles
- Increases lactate, heat and CO2 removal from muscles
- More aerobic respiration can therefore take place for muscles;
Why can a successful diabetic still have high glucose conc
- Recently eaten food high in carbohydrates
- Glucose absorbed from intestine into blood;
- Long time after insulin injection
- Insulin does not convert glucose to glycogen
Why does oxygen consumption increase with temperature?
- Increases kinetic energy
- More respiration occurs so more oxygen used up
- More energy in the form of ATP made
Why do diabetics have higher blood glucose
In Diabetic person:
- Lack of insulin /reduced sensitivity of cells to insulin;
- Reduced uptake of glucose by liver cells
- Reduced conversion of glucose to glycogen;
How does glycogenesis in liver cells lead to a reduced blood glucose
- Glucose concentration in cell is decreased so higher glucose conc in blood;
- This creates a diffusion gradient;
- Glucose enters cell from blood by facilitated diffusion through a channel protein
The body secretes a large number of different Hormones but only a few different neurotransmitters. Explain the importance of this
- Hormones reach all cells via blood
- Neurotransmitters secreted directly on to target cell;
- Different hormones are specific to different target cells;
Disadvantages of injection of insulin
- Pain of injections
- Short lived effect, so constant reinjection
- Need to consistently measure blood sugar
- Diet restriction
