The maintenance of a constant internal environment.
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Transcript of The maintenance of a constant internal environment.
Learning ObjectivesHow you keep conditions inside your body
constant
How cells get rid of waste products
How the body monitors its temperature
How blood sugar level is controlled
The main things that need to be controlled areBody temperatureWater contentSalt contentBlood sugar contentUreaCarbon dioxide
Cooling the Body DownToo hot- enzymes denature, can’t catalyse
cell reactionsCore temperature too high – skin capillaries
dilate More blood flows through skin - flush- lose
heat -radiationToo low- blood capillaries to skin constrict,
reduce blood flow to skin
BODY TEMPERATUREEnzymes in the human body work best at
about 37 C
The brain has a thermoregulator control centre to maintain this
It controls nerve receptors sensitive to blood temperature in the brain
It also receives information from the skin temperature receptors
WATER CONTENTKidneys control amount of water retained in
the body
Act as Filters to keep a balance of a) water, b) urea, c) ions in the blood
SALT CONTENTIons e.g., of sodium are taken into the blood
after digestion of food
This may cause the salt content of the blood to be too high, drawing water into the cells by osmosis
Excess ions are removed from the blood by the kidneys to maintain a correct body water balance
SweatRate goes up if too hotSweat mainly water, salt As water evaporates, it cools the skinHeat is lost from the body in sweatIn humid conditions, sweat does not evaporate very
easily
BLOOD SUGAR
Eating foods containing carbohydrate means the carbohydrates are digested into sugars which are absorbed into the blood
Levels of blood glucose must be controlled
Insulin is the hormone which controls the level of sugar in your blood.
Regulation of blood GlucoseThe pancreas detects sugar levels
If they are too high the cells in the pancreas secrete insulin
Insulin causes liver and muscles to take up glucose to form glycogen this is the form the energy is stored
Insulin causes the blood glucose levels fall
DiabetesA person who has this does not produce
enough of the hormone insulinSo their blood sugar levels can rise to a
fatally high levelThis can cause come and death
Experiments carried out by Frederick Banting and Charles BestThese were the first scientists to isolate
insulin
They removed a pancreas from a dog and took an extract from it
They injected this extract into diabetic dogs and observed the effects on blood sugar levels
They found that it caused the dogs blood sugar levels to drop dramatically
What was in this dogs pancreas?The chemical was isolated and it was
INSULIN
Today genetically modified bacteria are used to manufacture human insulin
Check your KnowledgeWhich organ detects blood sugar levels?What hormone does it secrete?What does this hormone convert blood sugar
toWhy is this such an important hormone? Where does this conversion of blood sugar to
glycogen take place?
UREA
Surplus amino acids from digestion are converted to fats and carbohydrates in the liver
The Liver produces the waste product – urea which travels in the blood to the kidneys.
The kidneys filter it out of the blood. It becomes concentrated, to be excreted as urine
CARBON DIOXIDECarbon dioxide is a waste product of
respiration
This is breathed out from the lungs, some dissolved in water vapour.