Download Kidneys and pH regulation During cellular respiration, cells produce

Kidneys and pH regulation
During cellular respiration, cells produce acids which eventually give off H+.
These H+ ions lower the pH of your blood.
In order to deal with the effects of H+ ions, the body uses an acid-base buffer system.
The following reaction occurs within the blood in order to maintain the proper blood pH:
H2O + CO2 H2CO3 HCO3- + H+
The water that is produced is used by the body or is released in urine or through sweating and the CO2
that is created can be exhaled from the lungs.
If this reaction continues to carry on through, the blood will run out of HCO3 (bicarbonate). Therefore
the kidneys carry out the reverse reaction in order to make more bicarbonate for the blood. The
bicarbonate that is needed for this reaction is produced through the reverse reaction which
requires water and carbon dioxide.
The reverse reaction also produces H+ ions, which is the problem in the blood to begin with. However,
since the H+ ions are produced in the kidneys they are simply excreted in the urine.
The HCO3- that is produced in the kidneys is transported out of the kidneys into the blood stream to
maintain the buffer system.
Regulation of Sodium and Water Balance
Three major hormones are involved in regulating sodium and water balance in the body at the level of
the kidney.
1.
2.
3.
ADH (antidiuretic hormone) from the posterior pituitary acts on the kidney to promote water
reabsorbtion, thus preventing its loss in the urine. (Blood Pressure goes up)
Aldosterone from the adrenal gland acts on the kidney to promote sodium reabsorption, thus
preventing its loss in the urine. (Blood Pressure goes up)
ANH (atrial natriuretic hormone) from the atrium of the heart acts on the kidney to promote
sodium excretion so that it is excreted in the urine. (Blood pressure goes down)
ADH (antidiuretic hormone)
 Acts mostly on collecting duct
 Makes walls of collecting duct more permeable to water so water is absorbed
 Secreted from posterior pituitary when blood becomes hypertonic (high solute, low water) or
blood volume drops (hypovolemia)
Aldosterone
 Acts mostly on distal tubule
 Stimulates Na+/K+ pumps to move Na+ out of nephron (into blood) and K+ into nephron (from
blood)
 Also stimulates other Na+ and K+ channels (reabsorption of Na+, loss of K+)
 Secreted from adrenal cortex when blood Na+ drops (hyponatremia)
Atrial Natriuretic Hormone
 Acts mostly on collecting duct and distal tubule
 Closes Na+ channels preventing Na+ reabsorption, inhibits aldosterone release, and reduces
proximal tubule Na+ reabsorption
 Secreted by atria when they sense increased blood volume (hypervolemia)
 By reducing Na+ reabsorption, more Na+ exits body and water follows lowering Blood Pressure
and blood volume
Need to know:
1. What is being regulated?
2. How it’s being done (where  nephron)?
3. What is releasing/causing the change?