Question

One of the examples of the action of the (a) swallowing of food (b) pupillary reflex (c) peristalsis of the intestine (d) all of these.

Short answer

All of the listed actions (swallowing of food, pupillary reflex, peristalsis of the intestine) involve involuntary components controlled by the autonomic nervous system, therefore the correct answer is (d) all of these.

Step-by-step solution

Understanding Autonomic Nervous System Functions

First, recognize that the actions listed: swallowing of food, pupillary reflex, and peristalsis of the intestine, are controlled by the autonomic nervous system. This system governs involuntary actions in the body, which do not require conscious effort.

Recognizing the Actions

Next, examine each action individually to determine if it's an involuntary action. Swallowing involves voluntary and involuntary muscle contractions, including a reflex coordinated by the autonomic nervous system once swallowing begins. The pupillary reflex is an involuntary reaction to light intensity changes. Peristalsis of the intestine is the involuntary muscle contractions that move food through the digestive tract.

Choosing the Correct Answer

Since all listed actions involve involuntary components controlled by the autonomic nervous system, the correct answer is that all of these are examples of the action of this system.

Key concepts

Swallowing of Food

The act of swallowing, or deglutition, is a complex process involving both voluntary and involuntary muscle contractions. Initially, when food is chewed and formed into a bolus, the decision to swallow voluntarily triggers the beginning of the process. However, once swallowing begins, the action transitions into an involuntary phase under the regulation of the autonomic nervous system.

The autonomic nervous system coordinates the various muscles and functions needed for the safe passage of the bolus from the mouth through the pharynx and esophagus and into the stomach. This coordination is crucial because it ensures that the airway is protected by temporarily halting breathing and closing off the trachea, preventing choking.

Pupillary Reflex

The pupillary reflex, also known as the pupillary light reflex, is an involuntary response controlled by the autonomic nervous system. It occurs in response to the intensity of light hitting the retina. In bright light, the pupils constrict to reduce the amount of light entering the eye, and in low light, they dilate to allow more light to enter. This reflex is vital for protecting the delicate retinal cells from damage due to excessive light and for optimizing vision.

Functionally, this response is a balance between the sympathetic and parasympathetic nervous systems. The parasympathetic nervous system is responsible for pupil constriction, while the sympathetic nervous system causes the pupil to dilate. The quick adjustment of pupil size demonstrates an incredibly refined autonomic process that takes place without conscious effort.

Peristalsis of the Intestine

Peristalsis of the intestine is an involuntary, rhythmic contraction of the intestinal muscles, which is essential for the movement of food through the digestive system. It is the primary mechanism that propels food along the digestive tract, starting from the esophagus and continuing down to the anus.

The peristaltic movement is coordinated by the enteric nervous system, a network of neurons that function independently but are modulated by the autonomic nervous system. When food stretches the walls of the gastrointestinal tract, this triggers a series of muscle contractions that create a wave-like motion, pushing the food through the intestines and ultimately aiding in digestion and absorption of nutrients.