Maintaining water and nitrogen in the body

3 ways water is lost:

  • exhalation

  • sweating

  • excretion

water amount can only be controlled through urine and drinking; can’t be controlled by sweating and exhalation

Urea - a waste product produced when proteins are broken down

Ions - includes sodium, potassium, calcium, nitrogen → need to be maintained for water balance: too much/little osmosis - can affect cell activity

Conc. of urine is controlled by ADH

process of water content regulation is controlled by negative feedback

Diet high in protein

Digestive system
proteins → amino acids

Liver
amino acids → ammonia (deaminated)
ammonia → urea

Kidneys
urea is filtered from the blood and excreted from the body in urine

processes the kidneys do:

  • filtration of all glucose, ions and water from blood

  • selective reabsorption of all glucose, some ions and some water into the blood

  • excretion of all urea, excess ions, and excess water into the urine

kidney parts:

  • cortex - outer layer

  • medulla - inner layer

  • nephrons (kidney tubules) - where blood is filtered

more water → less ADH → kidney tubules less permeable, less reabsorption → less conc. urine

less water → more ADH → kidney tubules more permeable, more reabsorption → more conc. urine