Final answer:
Renal compensation is the secondary defense against changes in pH that takes minutes to be activated.
Step-by-step explanation:
The secondary defense against changes in pH that requires minutes to be activated is renal compensation.
When the body experiences changes in pH, the kidneys play a vital role in restoring the balance. The renal system can adjust blood pH through the excretion of hydrogen ions (H+) and the conservation of bicarbonate, but this process takes hours to days to have an effect. This is known as renal compensation.
Other compensatory mechanisms such as buffering of hydrogen ions and respiratory compensation work more quickly, but renal compensation is a slower but more long-lasting defense against changes in pH.