Muscle twitch and tetanus

Explanation

### Step-by-Step Solution:

1. **Definition of Muscle Twitch**:
- A muscle twitch is defined as a single, quick contraction of a muscle fiber in response to a strong enough action potential. This contraction is noticeable and can be felt by an individual.

2. **Characteristics of Muscle Twitch**:
- It involves a brief contraction followed by relaxation.
- The contraction is strong enough to be perceived, indicating that the action potential has reached the threshold level.
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