Nor adrenaline secreted by sympathetic nervous system is inactivated by

Options

A. Acetylecholine
B. Acetylecholine esterase
C. Dopamine
D. Monamine oxidase

Answer

**Step-by-Step Solution:**

1. **Understanding Noradrenaline**:
- Noradrenaline is a neurotransmitter released by the sympathetic nervous system. It plays a crucial role in the "fight or flight" response, increasing heart rate and force of contraction.

2. **Identifying the Inactivation Mechanism**:
- The question asks how noradrenaline is inactivated after its release. Inactivation is essential to stop the action of noradrenaline and to reset the system for the next signal.

3. **Evaluating the Options**:
- **Option 1: Acetylcholine**: This neurotransmitter is primarily involved in memory and muscle activation, not inactivating noradrenaline.
- **Option 2: Acetylcholine Esterase**: This enzyme breaks down acetylcholine in the synaptic cleft, but it does not play a role in noradrenaline inactivation.
- **Option 3: Dopamine**: While dopamine is another neurotransmitter, it does not have a direct role in the inactivation of noradrenaline.
- **Option 4: Monoamine Oxidase**: This enzyme is responsible for breaking down monoamines, including noradrenaline. It helps terminate the action of noradrenaline by facilitating its degradation.

4. **Conclusion**:
- Based on the evaluation of the options, the correct answer is **Option 4: Monoamine Oxidase**. This enzyme is involved in the inactivation of noradrenaline through processes such as diffusion from binding sites or re-uptake into nerve endings.