Autonomic nervous system

Main

The autonomic nervous system (ANS) is a division of the nervous system that unconsciously controls vital bodily functions. It regulates internal organs, glands, and smooth muscles without any conscious effort. The ANS consists of three main parts:

1. Sympathetic nervous system (SNS): The SNS is responsible for the "fight or flight" response, which prepares the body for action in stressful situations. It increases heart rate, breathing rate, and blood pressure, diverts blood flow to skeletal muscles, and releases glucose from the liver for energy. The SNS originates from the thoracic and lumbar regions of the spinal cord.

2. Parasympathetic nervous system (PNS): The PNS is responsible for the "rest and digest" response, which promotes relaxation, digestion, and energy conservation. It slows heart rate, increases intestinal activity, and stimulates secretion of digestive enzymes. The PNS originates from the cranial nerves and the sacral region of the spinal cord, with the vagus nerve being the primary nerve of the PNS.

3. Enteric nervous system (ENS): The ENS is a subdivision of the ANS that directly controls the gastrointestinal system. It is embedded in the lining of the gastrointestinal tract and can function independently of the SNS and PNS. The ENS regulates motility, secretion, and blood flow in the gut, and communicates with the central nervous system through the vagus nerve.

Terms

• Nervous system: the complex network of neurons and fibers that transmits messages between different parts of the body and the brain, enabling sensation, movement, and regulation of bodily functions

Analogy

The ANS is like an autopilot for your body. Just as an autopilot controls a plane's speed, direction, and altitude without the pilot's constant input, the ANS controls your body's internal functions without you having to think about it. The sympathetic system acts like the throttle, increasing speed and altitude when needed, while the parasympathetic system acts like the landing gear, slowing the plane down for a smooth landing.

Misconception

A common misconception is that the sympathetic nervous system is always harmful and the parasympathetic system is always beneficial. In reality, both systems are essential for maintaining homeostasis and responding appropriately to different situations. Chronic activation of the sympathetic system can lead to health problems like hypertension and anxiety, but acute activation is necessary for dealing with stressors and challenges. Similarly, while the parasympathetic system promotes rest and relaxation, excessive activation can cause issues like bradycardia (slow heart rate) and hypotension (low blood pressure).

History

1. 1733 - James Johnstone first describes the "vegetative nervous system"

2. 1898 - John Newport Langley coins the term "autonomic nervous system" and proposes the division into sympathetic and parasympathetic systems

3. 1921 - Otto Loewi discovers acetylcholine, the first neurotransmitter, and demonstrates its role in the parasympathetic system

4. 1946 - Walter Bradford Cannon publishes "The Wisdom of the Body," emphasizing the role of the ANS in maintaining homeostasis

5. 2000s - Research expands on the role of the ANS in stress, emotion, and disease, and the concept of autonomic balance gains prominence

How to use it

1. When you feel anxious or stressed, take slow, deep breaths to activate the parasympathetic system and promote a sense of calm. Focus on exhaling for longer than you inhale to engage the vagus nerve.

2. Engage in regular exercise, particularly aerobic exercise, to help balance the ANS and reduce stress. Exercise can increase parasympathetic activity and decrease sympathetic overactivity over time.

3. When doing boring tasks like cleaning your apartment or washing dishes, use the time to practice mindfulness and engage your parasympathetic system. Focus on the sensations of the task, like the warmth of the water or the texture of the sponge, to promote a sense of calm and relaxation.

Facts

1. The ANS has over 100 million nerve cells, which is more than the number of stars in the Milky Way galaxy.

2. Autonomic disorders, such as postural orthostatic tachycardia syndrome (POTS) and multiple system atrophy (MSA), affect over 70 million people worldwide.

3. The longest nerve in the ANS, the vagus nerve, contains about 80% of parasympathetic fibers and interfaces with multiple organs, including the heart, lungs, and digestive tract.

4. Autonomic dysfunction can cause a wide range of invisible symptoms, such as fatigue, brain fog, digestive issues, and temperature regulation problems, which can significantly impact quality of life.

5. The ANS continues to mature and develop until around age 30, which may partly explain why some autonomic disorders emerge in young adulthood.