Week 11:

The Parasympathetic Nervous System and Brain Health

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Activating the Parasympathetic Nervous System for Brain Health

Objectives:

Understand the parasympathetic nervous system (PNS) and its role in relaxation and brain function.
Learn how activating the PNS benefits cognitive function, emotional regulation, and stress management.
Practice breathing exercises that stimulate the PNS for long-term brain health.

Introduction to the Autonomic Nervous System (ANS)

The Autonomic Nervous System (ANS) controls involuntary functions like heart rate, digestion, and respiratory rate. It has two main branches:

Sympathetic Nervous System (SNS): Responsible for “fight or flight” responses—heightened alertness, increased heart rate, and energy mobilization.

This image compares the parasympathetic and sympathetic nervous systems:

Parasympathetic (Rest and Digest):
- Slows heartbeat, constricts pupils, stimulates digestion, contracts bladder, and promotes sexual arousal. It helps the body relax and conserve energy.
Sympathetic (Fight or Flight):
- Increases heartbeat, dilates pupils, inhibits digestion, relaxes airways, and prepares the body for stress or emergency by releasing energy and redirecting resources.

Both systems regulate body functions to maintain balance.

Why is the PNS Important for Brain Health?

Reduces chronic stress: Chronic SNS activation can shrink the hippocampus (memory center) and impair cognitive function.
Enhances neuroplasticity: PNS activation supports the brain’s ability to rewire and adapt to new learning experiences.
Improves emotional regulation: A well-regulated PNS leads to better emotional stability and resilience.

🌿 Our nervous system has two parts: the sympathetic (activating, alerting) and the parasympathetic (calming, relaxing 🧘‍♀️) parts. In this video, we’ll show you a few ways to activate the parasympathetic nervous system to manage anxiety. 💆‍♂️✨

Discussion Prompt: What daily activities might unknowingly keep you in "fight or flight" mode?

📝 Journaling Reflection: Ways to Use the Information from This Video

Take a moment to reflect and journal about the following:

1️⃣ How can you use the techniques from the video to manage your anxiety in the future?
2️⃣ What specific situations do you think these methods could be helpful in?
3️⃣ Did any of the techniques surprise you or feel particularly effective?
4️⃣ How has watching this video changed your understanding of the fight or flight response?

Benefits of Activating the Parasympathetic Nervous System

Activating the PNS has scientifically backed benefits:

1. Stress and Anxiety Reduction

The vagus nerve, a key part of the PNS, helps lower cortisol levels and reduce inflammation.
Studies show slow breathing increases vagal tone, reducing stress-related amygdala hyperactivity.

Heart: It helps decrease heart rate and lowers vascular tone, which can contribute to relaxation and reduced stress.

Brain: The vagus nerve plays a role in regulating mood and reducing anxiety and depression. It helps balance the sympathetic response to stress, supporting a calming effect.

Liver: It helps regulate insulin secretion and maintain glucose balance, which is crucial for metabolic processes.

Blood Vessels: By reducing vascular tone, the vagus nerve also helps lower blood pressure, contributing to a calmer state overall.

Inflammation: One of its key functions is to suppress inflammation through the cholinergic anti-inflammatory pathway, which is critical for reducing chronic inflammation linked to many diseases.

The vagus nerve, as shown in the image, is an essential part of the parasympathetic nervous system (PNS) that helps regulate several vital functions in the body. The vagus nerve influences various organ systems in ways that contribute to reducing stress and promoting overall well-being:

🧠✨ Curious about the vagus nerve? Watch this video to discover its vital role! 🌟 From brainstem to colon, the vagus nerve handles essential functions in your body.

2. Improved Cognitive Function and Memory

When relaxed, the prefrontal cortex (decision-making, focus) functions optimally.
The hippocampus, crucial for memory, thrives in a parasympathetic state.

Prefrontal Cortex: When relaxed, the prefrontal cortex operates efficiently, as it is responsible for decision-making, focus, and cognitive flexibility. The vagus nerve plays a role in this by activating the parasympathetic nervous system, which helps bring the body into a relaxed state, allowing the prefrontal cortex to function optimally.

Hippocampus: This area of the brain is crucial for memory consolidation and retrieval. Under stress, the hippocampus may not function optimally, but when in a parasympathetic state (due to vagus nerve activation), the hippocampus operates more effectively, enhancing memory and cognitive functions.

3. Enhanced Sleep Quality

Activating the PNS before bedtime improves deep sleep, crucial for memory consolidation and learning.

Encoding: Information is taken in during the day. Activating the PNS before sleep helps your brain relax, making encoding more efficient.
Consolidation: During deep sleep (slow-wave sleep), your brain moves memories from short-term to long-term storage. The PNS helps trigger deep sleep, improving memory storage.
Recall: Stored memories are accessed when needed. Good sleep (helped by the PNS) makes it easier to recall information.

In short, activating the PNS before bed helps you sleep deeply, which is crucial for better memory and learning.

Breathing Techniques to Activate the PNS

How Breathing Affects the ANS

Breathing is the only voluntary way to influence the autonomic nervous system.

Slow, deep breaths activate the vagus nerve, shifting the body to a parasympathetic state.
Shallow, rapid breathing keeps the SNS activated, leading to stress.

Scientific Support: Slow breathing at 6 breaths per minute has been shown to increase heart rate variability (HRV), a marker of parasympathetic activation.

Heart Rate Variability (HRV): The variation in time between heartbeats reflects the communication between the heart and brain. A high HRV generally signals a flexible and adaptive cardiovascular system, associated with positive mental states and resilience to stress. In contrast, low HRV can indicate stress or potential health issues. This regulation of heart rate is controlled by the autonomic nervous system, which operates without conscious effort and includes the sympathetic and parasympathetic branches. The sympathetic system activates the "fight-or-flight" response, raising heart rate and blood pressure in stressful situations, while the parasympathetic system promotes relaxation, slowing the heart rate after stress. Together, these systems maintain a balanced, healthy response to changing conditions, with HRV serving as a valuable indicator of this balance.

HR is how many times your heart beats per minute.
HRV is the variation in time between those beats.

They’re related but not the same. A healthy heart doesn’t beat perfectly evenly—it adapts based on your nervous system. High HRV is usually a good sign of cardiovascular health, stress resilience, and recovery.

So while HR tells you your heart’s pace, HRV gives deeper insight into your body's adaptability and balance between stress and recovery—which is what all those listed habits help improve.

This image shows the tug-of-war between the parasympathetic and sympathetic nervous systems, which is what controls Heart Rate Variability (HRV).

HRV is like a balance meter between calm and stress. More parasympathetic activity = better HRV and health. More sympathetic activity = lower HRV and more stress load.

Meditation and slow breathing calm your nervous system, boosting HRV by reducing stress signals and increasing relaxation signals to your heart. This improves overall cardiovascular health and resilience to stress.

Meditation and slow breathing improve Heart Rate Variability (HRV) by engaging the nervous system, particularly the parasympathetic system.

🧠 (Brain)

The medulla and cerebrum coordinate how your body responds to breathing and heart activity.
The baroreflex (yellow path) is a reflex triggered by blood pressure changes, affecting HRV.

💓 (Heart and Nerves)

Parasympathetic nerve (blue): slows heart rate, increases HRV. This is the "rest and digest" side.
Sympathetic nerve (red): speeds up heart rate, lowers HRV. This is the "fight or flight" side.
SA node: where the heart’s rhythm is controlled.

🧘 (Meditation and Breathing)

Meditation + Slow, Deep Breathing stimulates the parasympathetic system.
This reduces sympathetic nerve activity and increases parasympathetic nerve activity.

Activity 1: Diaphragmatic Breathing

What It Does:

Strengthens the diaphragm (a key muscle in deep breathing).
Increases oxygen flow to the brain, promoting relaxation.

Instructions:

Sit in a comfortable position with one hand on your chest and the other on your belly.
Inhale deeply through the nose for 4 seconds, feeling the belly expand.
Exhale slowly through the mouth for 6 seconds, feeling the belly contract.
Repeat for 5 minutes.

Discussion: How does your body feel after the exercise?

Discover the power of your breath. Suzanne Smith, MSN, NP, from UCLA’s Integrative Digestive Health and Wellness Program, explains the benefits of diaphragmatic breathing and shows you how to do it—simple, effective, and easy to add to your daily routine.

After watching the "Diaphragmatic Breathing Demonstration" from Michigan Medicine, did you feel a difference? How did it feel to practice diaphragmatic breathing?

Activity 2: Alternate Nostril Breathing (Nadi Shodhana)

What It Does:

Balances left and right brain hemispheres.
Enhances focus and reduces stress.

Instructions:

Close your right nostril with your thumb and inhale through the left nostril for 4 seconds.
Close your left nostril and exhale through the right nostril for 6 seconds.
Inhale through the right nostril for 4 seconds, close it, and exhale through the left nostril for 6 seconds.
Repeat for 5 minutes.

Discussion: Did you feel calmer after this practice?

Clear your energy, calm your mind. Nadi Shodhana Pranayama is a powerful breathing technique that purifies blocked energy channels, balances the brain, and lowers your heart rate. Add it to your daily routine for a more focused, peaceful you.

Activity 3: 4-7-8 Breathing Technique

What It Does:

Calms the nervous system quickly.
Improves sleep and reduces anxiety.

Instructions:

Inhale through the nose for 4 seconds.
Hold the breath for 7 seconds.
Exhale slowly through the mouth for 8 seconds.
Repeat for 4 cycles.

Discussion: How did your stress level change before and after?

pdf: Dr.-Weil-4-7-8-Breathing-Exercise.pdf

Breathe your way to calm. Join Dr. Weil as he guides you through the 4-7-8 breathing technique—a simple yet powerful practice to relax your body and quiet your mind. Just 4 cycles a day can make a big difference. Watch to learn and find your own rhythm.

Reflection and Journal Activity

When do I feel most stressed or anxious?
What are three ways I can activate my PNS daily?
Describe a moment when I felt deeply relaxed and mentally clear.

Optional: Create a "relaxation playlist" with calming music that encourages PNS activation.

Summary

- The PNS counteracts stress, improving brain health.
- Breathing techniques offer instant stress relief.
- Daily relaxation practices enhance cognitive function.
Key Takeaway:
Practicing even 5 minutes of deep breathing daily can transform brain function and emotional resilience.

Refrence

McEwen, B. S. (2017). The role of the hippocampus in stress and resilience. Neuropsychopharmacology, 42(1), 177-199. DOI: 10.1038/npp.2016.120
Thayer, J. F., & Lane, R. D. (2009). A model of neurovisceral integration in emotion regulation and dysregulation. Journal of Affective Disorders, 112(1), 111-127. DOI: 10.1016/j.jad.2008.12.016
Davidson, R. J., & McEwen, B. S. (2012). Social influences on neuroplasticity: Stress and interventions to promote well-being. Frontiers in Neuroscience, 6, 125. DOI: 10.3389/fnins.2012.00125
Laborde, S., et al. (2017). Influence of slow-paced breathing on HRV and stress. Frontiers in Physiology, 8, 213. DOI: 10.3389/fphys.2017.00213

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