Negative feedback
A buffer can be defined as a substance
that help to resist or prevents a radical change in fluid pH by absorbing
excess hydrogen or hydroxyl ions. Thus, the kidneys help control acid-base
balance by excreting hydrogen ions and generating bicarbonate that helps
maintain blood plasma pH within a normal range. The kidney is said to
control pH by controlling the renal threshold of HCO3 . However, HCO3- level in the blood
cannot rise without changes in levels of other anions or cations in the blood.
To do so without effects on Na+,
Cl- or other ions would defy electrical neutrality, i.e. the
blood would become negatively charged and the urine positive.
