When the pH of the extracellular fluid declines:
1 the kidneys excrete more sodium ions.
2 the kidneys excrete more bicarbonate ions.
3 the kidneys reabsorb more potassium ions.
4 the kidneys reabsorb less water.
5 the pH of the urine increases.
The kidneys would increase the levels of bicarbonate ion to rise the pH of the blood.
The functional part of the kidney, the nephron is we're excretion and absorption takes place to concentrate urine. If the OUTSIDE environment of the nephron experiences a drop in pH, the neuron has to adjust to make the outside environment more pliable in order to continue excretion and absorption of water and NaCl. Excretion of bicarbonate is the only answer choice that could readjust the pH of the outside environment of the nephron.
To determine the correct answer, let's break down the given options and find the one that accurately describes what happens when the pH of the extracellular fluid declines.
1) The kidneys excrete more sodium ions: The excretion of sodium ions is not directly related to changes in extracellular fluid pH. Sodium excretion is primarily regulated by hormonal factors such as aldosterone.
2) The kidneys excrete more bicarbonate ions: This option is a plausible choice because bicarbonate ions play a crucial role in maintaining pH balance. When extracellular fluid pH declines (becomes more acidic), the kidneys increase the excretion of bicarbonate ions to help restore the pH balance.
3) The kidneys reabsorb more potassium ions: The reabsorption of potassium ions is not directly involved in compensating for changes in extracellular fluid pH. Potassium handling primarily occurs in response to other factors like blood pressure regulation and aldosterone levels.
4) The kidneys reabsorb less water: The reabsorption of water is not directly influenced by changes in extracellular fluid pH. Water reabsorption is primarily regulated through antidiuretic hormone (ADH) secretion in response to plasma osmolality and fluid balance.
5) The pH of the urine increases: This option seems unlikely because if extracellular fluid pH declines, the kidneys aim to excrete excess acid and maintain balance. Increased urinary pH would suggest alkalization, not acidity.
Based on this analysis, the correct answer is option 2: the kidneys excrete more bicarbonate ions.