1. Decreases by 4. (B)
2. The atomic number changes. (B)
3. 56/26 Fe. (C)
4. Potassium-40;t1/2=25 days. (B)
5. Takes place in the upper atmosphere. (A)
Description of a nerve signal
The nerve signal, or action potential, is a coordinated movement of sodium and potassium ions across the nerve cell membrane. Here's how it works: As we discussed, the inside of the cell is slightly negatively charged (resting membrane potential of -70 to -80 mV).
