Which of the following statements is true regarding all or none principle?

Options

A. All stimuli irrespective of their strength can cause contraction of muscles
B. By increasing the strength of stimulus strength of muscle fibre's contraction increase
C. All stimuli which are above the threshold
D. Both (2) & (3)

Answer

To determine which statement is true regarding the all or none principle, we need to analyze the concept of muscle contraction and the nature of stimuli involved. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the All or None Principle
The all or none principle states that a muscle fiber will either fully contract or not contract at all. This principle is crucial in understanding how muscle fibers respond to stimuli.

### Step 2: Identify the Role of Threshold
For a muscle to contract, the stimulus must reach a certain threshold level. If the stimulus is below this threshold, the muscle will not contract. This means that there is a minimum level of stimulus required to initiate contraction.

### Step 3: Evaluate the Statements
Now, we will evaluate the provided statements against the all or none principle:
- **Statement A**: "All stimuli irrespective of their strength are going to cause contraction."
- This is incorrect because only stimuli above the threshold will cause contraction.

- **Statement B**: "By increasing strength of stimulus, strength of muscle fiber contraction increases."
- This is also incorrect. According to the all or none principle, once the threshold is reached, the muscle will contract fully, and increasing the stimulus strength does not lead to a stronger contraction.

- **Statement C**: "All stimuli which are above the threshold can cause contraction."
- This is correct. Once the stimulus exceeds the threshold, the muscle will contract fully.

### Step 4: Conclusion
Based on the analysis, the correct statement regarding the all or none principle is **Statement C**: "All stimuli which are above the threshold can cause contraction."