An action potential is initiated each time the membrane potential is raised to .............. potential.

Explanation

To answer the question regarding what potential is required to initiate an action potential, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Action Potential**:
- An action potential is a rapid change in the electrical membrane potential of a neuron that occurs when a nerve impulse is transmitted.

2. **Identifying the Key Term**:
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