Which of the following is associated with decrease in cardiac output ?

Options

A. Sympathetic nerves
B. Parasympathetic neural signals
C. Pneumotaxic centre
D. Adrenal medullary hormon

Answer

To determine which of the following is associated with a decrease in cardiac output, we can analyze the options based on their physiological roles:

### Step-by-Step Solution:

1. **Understanding Cardiac Output**:
- Cardiac output (CO) is the amount of blood the heart pumps in a minute. It is influenced by heart rate and stroke volume.
- A decrease in cardiac output can lead to insufficient blood flow to organs and tissues.

2. **Role of the Autonomic Nervous System**:
- The autonomic nervous system (ANS) regulates involuntary bodily functions, including heart rate and blood pressure.
- It has two main components: the sympathetic nervous system and the parasympathetic nervous system.

3. **Sympathetic Nervous System**:
- The sympathetic nervous system prepares the body for stressful situations (fight or flight response).
- It typically increases heart rate and cardiac output during stress or emergencies.

4. **Parasympathetic Nervous System**:
- The parasympathetic nervous system is responsible for rest and digest functions.
- It decreases heart rate and can lead to a decrease in cardiac output. This is primarily mediated by the vagus nerve.

5. **Pneumotaxic Centers**:
- These centers are involved in the regulation of breathing and do not directly influence cardiac output.

6. **Adrenal Medullary Hormones**:
- Hormones such as adrenaline (epinephrine) released from the adrenal medulla typically increase heart rate and cardiac output during stress.

7. **Conclusion**:
- Among the options considered, the parasympathetic neural signals are associated with a decrease in cardiac output.

### Final Answer:
The correct option that is associated with a decrease in cardiac output is **parasympathetic neural signals**.

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