Strength of heart muscles contraction and heart beat becomes faster on stimulation by

Options

A. Sympathetic nerves and adrenaline
B. Sympathetic and parasymapathetic nerves
C. Parasympathetic nerves and epinephrine
D. Parasympathetic nerves and acetylcholine

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about what causes the strength of heart muscle contraction and an increase in heart rate.

2. **Identifying the Options**: The options given include:
- Option 1: Sympathetic Nerves and Adrenaline
- Option 2: Sympathetic and Parasympathetic Nerves
- Option 3: Parasympathetic Nerves and Apinephrine
- Option 4: Parasympathetic Nerves and Acetylcholine

3. **Analyzing Option 1**:
- The sympathetic nervous system is responsible for the "fight or flight" response.
- It releases neurotransmitters that increase heart rate and the strength of heart contractions.
- Adrenaline (also known as epinephrine) is released during stress, which further enhances heart function.

4. **Analyzing Option 2**:
- This option mentions both sympathetic and parasympathetic nerves.
- While sympathetic nerves increase heart rate, parasympathetic nerves generally decrease heart rate.
- Therefore, this option is not correct.

5. **Analyzing Option 3**:
- This option mentions parasympathetic nerves and apinephrine (another name for adrenaline).
- The parasympathetic system does not stimulate the heart; it has the opposite effect.
- Thus, this option is incorrect.

6. **Analyzing Option 4**:
- This option mentions parasympathetic nerves and acetylcholine.
- Acetylcholine is a neurotransmitter that decreases heart rate when released by the parasympathetic nervous system.
- Therefore, this option is also incorrect.

7. **Conclusion**: Based on the analysis, the correct answer is **Option 1: Sympathetic Nerves and Adrenaline**, as they both work to increase the strength of heart muscle contractions and the heart rate.