Action potential is

Options

A. Decremental phenomenon
B. Does not obey all or none
C. `K^(+)` goes from ECF to ICF
D. Always same for any one neuron

Answer

### Step-by-Step Solution:

1. **Definition of Action Potential**:
- Action potential refers to a rapid rise and fall in voltage or membrane potential across a cellular membrane. It is a key process in the functioning of neurons and muscle cells.

2. **Characteristics of Action Potential**:
- Action potentials are characterized by a specific pattern of change in voltage, which is crucial for the propagation of signals in the nervous system.

3. **Options Analysis**:
- **Option A**: "Decremental phenomenon" - This is incorrect because action potentials do not decrease in amplitude as they travel along the axon.
- **Option B**: "Does not obey all or none" - This is incorrect as action potentials follow the all-or-none principle; they either occur fully or not at all.
- **Option C**: "Potassium goes from extracellular fluid to intracellular fluid" - This is incorrect. During an action potential, potassium ions actually move from the intracellular fluid to the extracellular fluid.
- **Option D**: "Always same for any one neuron" - This is correct. The action potential has a consistent amplitude and shape for a given neuron.

4. **Conclusion**:
- Based on the analysis of the options, the correct answer is **Option D**: Action potential is always the same for any one neuron.