One of the example of the action of the autonomous nervous system is

Options

A. Knee-jerk response
B. Pupillary reflex
C. Swallowing of food
D. Peristalsis of the intestines

Answer

**Step-by-Step Solution:**

1. **Understanding the Autonomous Nervous System (ANS):** The ANS is responsible for controlling involuntary bodily functions, such as heart rate, digestion, and respiratory rate. It operates without conscious control.

2. **Identifying Examples of ANS Actions:** We need to evaluate the options provided in the question: knee-jerk response, pupillary reflex, swallowing, and upward peristalsis of the intestine.

3. **Analyzing Each Option:**
- **Knee-Jerk Response:** This is a monosynaptic reflex action, which is primarily controlled by the somatic nervous system. It involves a direct pathway from sensory neurons to motor neurons.
- **Pupillary Reflex:** This reflex is an unconditioned reflex that involves the autonomic nervous system, but it is not a primary example of the ANS's role in involuntary actions.
- **Swallowing:** This process is primarily controlled by the somatic nervous system, as it involves voluntary muscle actions.
- **Upward Peristalsis of the Intestine:** Peristalsis refers to the involuntary contractions of the smooth muscles in the gastrointestinal tract, which is controlled by the autonomic nervous system.

4. **Conclusion:** The action that is a clear example of the autonomous nervous system is the upward peristalsis of the intestine, as it involves involuntary muscle contractions that are not under conscious control.

5. **Final Answer:** The correct answer is **upward peristalsis of the intestine**.

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