The brief contraction of all the muscle fibres in a motor unit in response to a single action potential in its motor neuron is called

Options

A. muscle tone
B. treppe
C. rigor mortis
D. muscle twitch

Answer

To answer the question, "The brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor neuron is called," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question is asking for a specific term that describes a phenomenon in muscle physiology. It involves the contraction of muscle fibers in response to a single action potential.

2. **Identifying Key Terms**:
- **Motor Unit**: A motor unit consists of a motor neuron and the muscle fibers it innervates.
- **Action Potential**: This is an electrical signal that triggers muscle contraction.

3. **Analyzing Options**: The options provided are:
- Muscle Tone
- Treppe
- Rigor Mortis
- Muscle Twitch

4. **Defining Each Option**:
- **Muscle Tone**: Refers to the continuous and passive partial contraction of the muscles, which helps maintain posture.
- **Treppe**: This is a phenomenon where muscle contractions increase in strength with repeated stimulation, known as the staircase effect.
- **Rigor Mortis**: A postmortem condition where muscles become stiff due to biochemical changes after death.
- **Muscle Twitch**: This is the brief contraction of all muscle fibers in a motor unit in response to a single action potential.

5. **Choosing the Correct Answer**: Based on the definitions, the correct term that describes the brief contraction of all muscle fibers in a motor unit in response to a single action potential is **Muscle Twitch**.

6. **Components of Muscle Twitch**: A muscle twitch has three phases:
- **Latent Period**: The time between the action potential and the beginning of contraction.
- **Contraction Phase**: The period during which the muscle fibers are actively contracting.
- **Relaxation Phase**: The period during which the muscle fibers return to their resting state.

### Final Answer:
The brief contraction of all the muscle fibers in a motor unit in response to a single action potential in its motor neuron is called **Muscle Twitch**.

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