Homeostasis- mocks Flashcards
Homeostasis definition
-maintaining the same/constant internal environment (bodily functions are working well) by regulating water content level, temperature, ion content and blood glucose level/sugar.
Describe what happens to your body on a hot day
- The thermoregulatory centre (hypothalamus) in the brain and skin receptors will monitor and detect this change
- The blood vessels supplying the skin capillaries will dilate (vasodilation- diameter increases as it widens)
- More blood will flow to the surface of the skin (this is how it can become pink)
- More thermal energy/ heat will be radiated outwards and the body will cool down.
- Hair follicles on the skin will droop/ lie flat.
- Sweating (evaporation of water) also cools the body.
Describe what happens to the human body on a cold day.
- The thermoregulatory centre (hypothalamus) in the brain and skin receptors will monitor and detect this change
- The blood vessels supplying the skin capillaries will become narrower.constrict (vasoconstriction)
- Less blood will flow to the surface of the skin and less thermal energy will be radiated outwards.
- Shivering (muscular contractions) will release energy and hair follicles will stand upright/erect.
Describe what happens to the human body when the blood glucose/sugar level is high.
When the blood glucose level is high, the pancreas will detect this change. The pancreas will secrete more insulin which will convert the excess glucose into glycogen (insoluble) and this will be stored in the muscles and liver for further use.
Describe what happens to the human body when the blodd/sugar level is low
-When the blood glucose level is low, the pancreas will detect this change. The pancreas will secrete glucagon (hormone) and this will convert glycogen into soluble glucose which will flow into the bloodstream and restore homeostatic equilibrium (negative feedback).
What is the main job of the kidneys?
- to filter the blood
- to remove waste that we don’t want
urea
- it is made in the liver during the process of deamination which is where excess amino acids (that we don’t need) are converted to fats and carbohydrates
for storage.
Kidney other job
to regulate ions and water
Ions
Lost through sweat but mainly regulated through kidneys
How do we gain water?
from the foods and drinks that we consume
How do we lose water?
- partly through the skin when we sweat
- partly through the lungs when we breathe
- mostly through urine
Why is water regulation so important?
Because our cells can lose or gain water through osmosis
How do kidneys excrete things?
-They excrete excess water, excess salts and urea (formed in the liver from excess amino acids) by producing urine.
Deamination
- The digestion of proteins from the diet results in excess amino acids which need to be excreted safely, as they cannot be stored by the body in the same way that excess glucose can
- Deamination is the process of breaking down excess protein and it predominantly occurs in the liver
- Enzymes in the liver split up amino acid molecules, with the part containing carbon turned into glycogen and the other part containing nitrogen (the amino part) turned into ammonia (this is why we say the amino acid has been deaminated)
- Ammonia is toxic to cells and so it is immediately converted to urea which can be transported around the body via the blood safely for excretion by the kidneys
Structure and function of the kidney
- The kidneys help to control the water content of the body and the concentrations of substances (such as sodium and potassium ions) dissolved in the fluids of the body
- The kidney contains highly branched capillary networks that form filters which contain pores with an average radium of about 3 nanometers
- When blood passes through the kidneys, the pressure it is under increases as it is pushed into the filters
- This high-pressure mass flow forces molecules that are small enough to pass through the pores out of the bloodstream – this is called filtration
- Substances forced out of the blood include glucose, urea and water with ions dissolved in it. The liquid formed is called filtrate
- Larger molecules (such as RBCs or proteins) are too big to pass out of the filter and so remain in the blood plasma
- The kidneys then selectively reabsorb substances needed by the body back into the bloodstream (this is an active process)
- In a healthy kidney, this includes all of the glucose and some ions from the filtrate
- Anything not reabsorbed forms urine, which is then stored in the bladder until it is excreted
- Urea, formed from the deamination of amino acids in the liver, is not selectively reabsorbed
- The concentration of urea in the urine is far higher than that of the blood plasma
- Reabsorption of water from the filtrate back into the bloodstream is why the concentration of urea in the filtrate is so much higher
