Final answer:
The body would release a weak base as part of its buffering system to increase the pH from 4 back up towards the normal level of 7.4 by binding excess hydrogen ions.
Step-by-step explanation:
If the pH of the body dropped well below the normal range, to a pH of 4 for example, the body would need to increase the pH back to a normal level. To do this, the body would release a weak base into the bloodstream as part of its buffering system.
This weak base would bind to the excess hydrogen ions present, thereby raising the pH towards 7.4, which is the ideal pH for bodily fluids. The body's buffering systems are crucial for maintaining this balance, using substances like bicarbonate (HCO₃⁻) as buffers, which can react with both strong acids and strong bases to minimize extreme changes in pH.