An investigator places an isolated neuron in a calcium-free medium, gives the neuron a suprathreshold stimulus and then performs an assay to test whether neurotransmitter is released into the medium.Which of the following outcomes would you predict ?

Options

A. No neurotransmitter is detected since influx of calcium into the synaptic knob is required for neurotransmitter release.
B. No neurotransmitter is detected since influx of calcium is required in order for the neurons to conduct an action potential
C. Neurotransmitters is detected since calcium is not required for action potential coduction and the initial stimulus was suprathreshold
D. We cannot predict the outcome without knowing whether the neuron was myelinated or not

Explanation

To solve the question regarding the outcome of placing an isolated neuron in a calcium-free medium and applying a suprathreshold stimulus, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of Calcium in Neurotransmitter Release:**
- Neurotransmitter release from a neuron is primarily triggered by the influx of calcium ions (Ca²⁺) into the presynaptic terminal. When an action potential reaches the nerve ending, it causes depolarization, which opens voltage-gated calcium channels.

2. **Effect of a Suprathreshold Stimulus:**
- A suprathreshold stimulus is strong enough to generate an action potential. However, the presence of calcium is crucial for the release of neurotransmitters. In a calcium-free medium, even if an action potential occurs, the necessary calcium influx will not happen.

3. **Predicting the Outcome:**
- Since the neuron is placed in a calcium-free medium, the voltage-gated calcium channels will not open upon depolarization. Therefore, there will be no calcium influx into the synaptic knob, which is essential for triggering the release of neurotransmitters.

4. **Conclusion:**
- Based on the above reasoning, we can conclude that no neurotransmitter will be released into the medium. Thus, the correct prediction is that **no transmitter is detected**.

### Final Answer:
- The outcome predicted is that **no neurotransmitter is detected** in the calcium-free medium after applying a suprathreshold stimulus.

---