Mammal's heart is

Options

A. myogenic
B. neurogenic
C. voluntary
D. sympathetic

Answer

To answer the question "Mammal's heart is," we need to analyze the options provided and understand the characteristics of the mammalian heart.

### Step-by-Step Solution:

1. **Understanding the Structure of the Mammalian Heart**:
- The mammalian heart, including that of humans, is a four-chambered organ. It consists of two atria (right and left) and two ventricles (right and left).
- This structure prevents the mixing of oxygenated and deoxygenated blood, which is crucial for efficient circulation.

2. **Identifying the Heart's Control Mechanism**:
- The heart's rhythmic contractions are controlled by the sinoatrial (SA) node, located in the right atrium.
- The SA node generates electrical impulses that stimulate the heart to contract rhythmically.

3. **Defining Myogenic vs. Neurogenic Hearts**:
- A **myogenic heart** is one where the heartbeat is initiated by the heart muscle itself (like in mammals).
- A **neurogenic heart** is controlled by the nervous system and is typically found in lower vertebrates.

4. **Evaluating the Options**:
- **Option 1: Myogenic** - This is correct because the mammalian heart beats due to impulses from the SA node.
- **Option 2: Neurogenic** - Incorrect, as this type of heart is found in lower vertebrates, not mammals.
- **Option 3: Voluntary** - Incorrect, as the heart's contractions are involuntary and not under conscious control.
- **Option 4: Sympathetic** - While the heart can respond to sympathetic nervous stimulation (increasing heart rate during stress), this does not define the heart's nature.

5. **Conclusion**:
- The correct answer is **Option 1: Myogenic**. The mammalian heart is myogenic because it generates its own rhythmic contractions through the SA node.