Parasympathetic Nervous System

The Simple Science

The parasympathetic nervous system is like the chill-out component of your body’s control system. It helps you calm down and relax after stressful situations. Think of it as the opposite of the fight-or-flight response; it’s more of a “rest and digest” mode. When activated, it tells your body to slow down, take it easy, and conserve energy.

To make the parasympathetic nervous system work for you, try engaging in activities that naturally induce relaxation and a sense of calm. Deep, slow breathing is a powerful tool because it signals your body that it’s time to relax. When you take deep breaths, you’re essentially telling your brain to mellow out and activate the parasympathetic response.

Mindfulness and meditation are also great ways to kickstart this system. By focusing on the present and maintaining a state of calm awareness, you help shift your body into a relaxed state. Gentle physical activities like yoga or leisurely walks in nature can also stimulate the parasympathetic nervous system, promoting relaxation and reducing stress.

Eating slowly and mindfully can help too, as it activates the “rest and digest” response, aiding in better digestion and nutrient absorption. By regularly practicing these activities, you can strengthen your body’s ability to enter a state of calm and relaxation, counterbalancing the stress and hustle of daily life.

The Deeper Learning

The parasympathetic nervous system (PNS) is one of the two main subdivisions of the autonomic nervous system, the other being the sympathetic nervous system (SNS). While the SNS is associated with the body’s “fight or flight” response to stress or danger, the PNS is responsible for the “rest and digest” or “feed and breed” activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tearing), urination, digestion, and defecation.

Anatomical and Functional Characteristics

• Origin: The PNS originates in the brainstem and the lower part of the spinal cord (sacral region). Its fibers emerge from the cranial nerves (particularly the vagus nerve, which supplies the heart, lungs, and digestive tract) and sacral spinal nerves.
• Neurotransmitters and Receptors: The primary neurotransmitter of the PNS is acetylcholine (ACh), which binds to two types of receptors: nicotinic and muscarinic acetylcholine receptors. The action of ACh on these receptors promotes restful and restorative processes in the body.
• Effects on Organs: In general, the PNS slows down the heart rate, decreases respiratory rate, stimulates digestive processes, and promotes energy conservation and nutrient absorption in the body. It effectively counteracts the arousal state induced by the SNS, helping to maintain homeostasis.

Physiological Responses

• Cardiovascular System: The PNS reduces myocardial contractility and heart rate, leading to decreased cardiac output and lower blood pressure, facilitating a state of relaxation and recovery.
• Respiratory System: It constricts the bronchial tubes, leading to decreased airway diameter and reduced respiratory rate, which is conducive to rest.
• Digestive System: The PNS stimulates salivary gland secretion, increases peristalsis in the digestive tract, and enhances secretion of digestive enzymes, aiding in digestion and nutrient absorption.
• Eye: Activation of the PNS constricts the pupils (miosis), which is part of the body’s preparation for rest and protection of the eyes from bright light.

Regulatory Role

The PNS plays a critical role in the body’s restorative processes and helps to conserve energy. It is involved in regulating bodily functions when at rest, promoting healing, regeneration, and nourishment of the body. It is also crucial in managing stress responses, allowing the body to return to a state of calm and balance after periods of stress or emergency.

Understanding the parasympathetic nervous system’s functions and its balancing role in the body’s overall autonomic regulation is essential for appreciating how physiological processes contribute to health and well-being. Practices that stimulate the parasympathetic response, such as deep breathing, meditation, and relaxation techniques, can be beneficial in managing stress, reducing anxiety, and promoting overall health.