Page 1818 - Saunders Comprehensive Review For NCLEX-RN

to normal; the stimulus for the secretion of renin then
is removed.

F. Homeostasis of potassium

1. Increases in the serum potassium level stimulate the
secretion of aldosterone.
2. Aldosterone stimulates the distal convoluted tubules
to secrete potassium; this action returns the serum
potassium concentration to normal.
G. Homeostasis of acidity (pH)
1. Blood pH is controlled by maintaining the
concentration of buffer systems.
2. Carbonic acid and sodium bicarbonate form the most
important buffers for neutralizing acids in the plasma.
3. The concentration of carbonic acid is controlled by the
respiratory system.
4. The concentration of sodium bicarbonate is controlled
by the kidneys.
5. Normal arterial pH is 7.35 to 7.45, maintained by
keeping the ratio of concentrations of sodium
bicarbonate to carbon dioxide constant at 20:1.
6. Strong acids are neutralized by sodium bicarbonate to
produce carbonic acid and the sodium salts of the
strong acid; this process quickly restores the ratio and
thus blood pH.
7. The carbonic acid dissociates into carbon dioxide and
water; because the concentration of carbon dioxide is
maintained at a constant level by the respiratory
system, the excess carbonic acid is rapidly excreted.
8. Sodium combined with the strong acid is actively
reabsorbed in the distal convoluted tubules in
exchange for hydrogen or potassium ions. The strong
acid is neutralized by ammonia and is excreted as
ammonia or potassium salts.
H. Adrenal glands (see Chapter 46 for information about the adrenal
glands)
1. One adrenal gland is on top of each kidney.
2. The adrenal glands influence BP and sodium and
water retention.
I. Bladder
1. The bladder detrusor muscle, composed of smooth
muscle, distends during bladder filling and contracts
during bladder emptying.
2. The ureterovesical sphincter prevents reflux of urine
from the bladder to the ureter.
3. The total bladder capacity is 1 L; normal adult urine
output is 1500 mL/day.
J. Prostate gland

1818