Parasympathetic Nervous System

Table of Contents

Other names

rest-and-digest system
craniosacral division of the autonomic nervous system

Synopsis

The parasympathetic nervous system (PNS) is one of the two branches of the autonomic nervous system (the other being the sympathetic nervous system). While the sympathetic branch is responsible for the “fight or flight” response, the parasympathetic branch governs the “rest and digest” functions. It promotes relaxation, recovery, and conservation of energy by slowing the heart rate, stimulating digestion, and facilitating repair and immune activity.

Originating from the brainstem (via cranial nerves such as the vagus nerve) and the sacral region of the spinal cord, the parasympathetic nerves innervate major organs including the heart, lungs, liver, stomach, intestines, pancreas, kidneys, and bladder. Unlike the sympathetic system, which prepares the body for action, the parasympathetic system restores balance by regulating involuntary functions during periods of calm and recovery.

The parasympathetic nervous system plays a crucial role in maintaining homeostasis. It regulates activities like:

  • Reducing heart rate and blood pressure

  • Stimulating salivary and digestive gland secretion

  • Increasing intestinal motility and nutrient absorption

  • Promoting urination and defecation

  • Supporting sexual arousal and reproductive organ function

  • Enhancing immune response during periods of rest

Dysfunction of the PNS may manifest as digestive issues (e.g., poor motility, constipation), chronic stress, anxiety, fatigue, and imbalanced heart rate variability (HRV). Vagal tone—an indicator of vagus nerve activity—is often used to assess the strength of parasympathetic function. Low vagal tone is associated with depression, inflammation, and poor stress recovery.

Parasympathetic activity is typically dominant during sleep, after meals, and during meditative or relaxed states. Its proper functioning is essential for healing, repair, hormonal balance, and mental clarity.

Natural Remedies

Deep breathing exercises: Diaphragmatic breathing increases vagal activity and slows the heart rate.

Meditation and mindfulness: Reduces sympathetic dominance and encourages parasympathetic balance.

Cold exposure: Brief exposure (e.g., face in cold water) stimulates vagus nerve function.

Laughter, singing, and humming: Activate vagal pathways through the throat and facial muscles.

Probiotics and gut health: A healthy gut supports vagal signaling and parasympathetic activity.

Massage therapy: Especially abdominal massage can stimulate parasympathetic responses.