Chapter 1: Nervous System Basics

When we practice or teach yoga, we experience the effects on our muscular and skeletal systems in obvious ways. We experience tension, contraction, stretching, softening of our muscular system. The skeletal system supports our body in all of these poses. Our respiratory system we can experience in deeper ways when we are practicing various pranayama exercises. Our nervous system is impacted by all these activities either exciting it or calming it. We will start with a general overview of the brain, the regions of the nervous system called central and peripheral nervous systems, and the functional differences between the somatic and autonomic systems. We will explore how stress impacts this system and how yoga, pranayama, and meditation can support this system.

Three Parts of the Brain – The Triune Brain

Paul MacLean, a physician and neuroscientist, explored the evolutionary development of the human brain. He created a model that shows how the human brain evolved from a reptilian brain to our highest-level mammalian brain. Within the structure of our brain, he states, we have a primitive component, called the hindbrain, which is responsible for the basic physical and unconscious functions. This is the reptilian part of our brain. The midbrain, the early mammalian brain, is responsible for memory, emotion, bonding reactions, and fight or flight. One can consider it the emotional part of your brain. The highest level of our brain is the forebrain, or the rational brain. This comprises the neocortex, which is the largest part of the cerebral cortex. The cerebral cortex is the outer layer of the cerebrum. This area is for conscious activities such as reading,

Human Brain - Rational

Mammalian - Emotional

Reptilian - Survival writing, language, thought, cognition, and motor commands (Institute, 2019). Neuroscience has found that the often brain activates all three systems at once so this model is a simplification of how the brain functions.

When we are under stress, humans shift from using the cerebral cortex or forebrain to the midbrain and hindbrain. These evolutionary brain regions overlay the anatomical parts of the brain. The neocortex, cerebral cortex, and cerebrum are all in the forebrain.

General Structures of the Brain

Brain stem – basic needs. The gateway from the spinal cord to the rest of the brain

Cerebral cortex – the outer layer of the cerebrum. Neural integration in the central nervous system. Memory, attention, perception, awareness, thought, language, consciousness

Prefrontal Cortex – conscious thinking and emotional regulation

Neocortex – the largest part of the cerebral cortex. Sleep, memory, and learning processes

Cerebrum – integrates information the brain receives. The entire upper part of brain

Cerebellum – motor control, motion, memory. Underneath the cerebrum Thalamus – regulates the brain

Amygdala – prepares you to fight back before you can assess

An example of how yoga impacts the brain, is that yoga increases the activity in the prefrontal cortex. When you increase activity in the prefrontal cortex, your stress lowers (Swanson, 2020)

Another example of how the brain is impacted by yoga is that yoga decreases activity in the amygdala. The amygdala works with the prefrontal cortex to process and respond to fear (Swanson, 2020) (eco). If there is decreased activity in the amygdala, our sense of fear or hypervigilance can decrease. If yoga impacts parts of our brain, we are essentially training our brain to process and respond to fear and stress more effectively.

Branches of the Nervous System

The nervous system is divided into two main parts: the peripheral nervous system (PNS) and the central nervous system (CNS).

• PNS are the nerves that run down the limbs and out into tissues

» Somatic

» Autonomic

• CNS is the brain and the spinal cord

» Spinal cord protected by vertebrae

» Brain stem – primal part of the brain

» Hemispheres, left and right

Neurotransmitters are naturally occurring chemicals that send signals or messages between nerves. Each nerve has its own balance of neurotransmitters. There are two kinds, calming and stimulating, which keep us awake or prepare us for rest. We need stimulating neurotransmitters to think and react fast. We also need calming neurotransmitters to help recover from periods of stress, to calm down, and to sleep. All of these affect mood, energy, focus, sleep, and memory.

A Few Types of Neurotransmitters

• Serotonin – calming and made in the gut

• GABA – calming, counter exposure to chronic stress. Can become depleted

• Glutamate – stimulating, help you think, learn, and remember

• Dopamine – stimulating, ability to experience pleasure, mood, movement, mental process. Converts to adrenaline

• Adrenaline – (norepinephrine + epinephrine) gives bursts of energy, strength, and power. Increase heart rate, sweat, mood, and focus. Long term stress causes adrenaline depletion

When your students leave the studio feeling happy, relaxed, and blissful, you know that they were able to create those emotions through their yoga practice. Throughout their yoga, including asana, pranayama, and some level of meditation, they have released neurotransmitters eliciting these wonderful feelings.

Let’s Talk About Stress

Stress is defined as the ability of the body to adapt to changes in our environment. Note, stress is how we adapt to change. Stress is not inherently bad. Stress is unavoidable, it is how we handle and process it that matters. Stress can be good as it helps us prepare for a challenge. Stress can also be a positive thing, like preparing for a vacation or wedding. The body is preparing for a change.

• Increase neuroplasticity – brain change

• Increase synaptic connections – memory and recall

• Increase frontal lobe function – reasoning and decision-making

• Increase brain volume – memory

• Increase positive brain frequencies – theta and alpha

Yoga gets you into your body and has you focus on your breath. With controlled breathing, your heart rate may drop. Postures can help you release tension. Various styles of yoga, such as restorative, hatha, Iyengar, and yoga nidra, all can help release tension.

Before all this research, Iyengar taught a yoga approach intended to help release pain and heal the injury. He used props and modified poses. He believed supporting the body with props facilitates the body toward healing. The various poses can elicit physiological responses that can aid the healing process (Lasater, 1995). Today, we would probably term that the relaxation response. The relaxation response can be elicited through yoga.

Herbert Benson is a Harvard researcher who explored the mind/body connection. “The response is defined as your personal ability to encourage your body to release chemicals and brain signals that make your muscles and organs slow down and increase blood flow to the brain.” (Mitchell, 2013).

Yoga increases the body’s awareness and emotional intelligence so we can control our stress responses. Stress is not inherently bad, it’s our body reacting to change. Through posture, breath, and control of our monkey mind, we can help control how we perceive and respond to change.

Nervous System and Pranayama

We know that shifting our nervous system from fight/flight/freeze mode to our rest and digest mode will improve our well-being. We have all experienced the effects of our asana classes. After class, we have this post-yoga glow. This comes not only from the asanas but also from the enhanced breathing during class.

The first thing we do when we experience stress or stressors: we shift our breathing. Whether imagined or real, whether physical, emotional, or psychological stress, our nervous system responds the same way. The nervous system will shift to stress mode. If the stress becomes chronic, our nervous system forgets what is normal. If we stay in this constant state of stress, our bodies lose the ability to go back to baseline. Stress can interfere with our breathing patterns. There are various ways our breath can shift, such as chest, collapsed, hyperventilation, breath grabbing, and frozen chest breathing. (MacLean, 1990)

There is no real normal to breathing. Our rate or volume switch is based on need. We can develop patterns of irregular breathing, impacting rate, and volume. But we can use the breath to facilitate a de-stressing effect. Being aware of how we can control our breath will help to elicit a down regulation of the nervous system (Farhi, 1996). Mindful breathing can help you calm down. Each exhalation relaxes the heart muscle, resulting in increased parasympathetic activity (Institute, 2019).

When we breathe, the diaphragm directly stimulates the vagus nerve. This impacts the parasympathetic and sympathetic nervous systems. The vagus nerve, the tenth cranial nerve, is a primary nerve of the PNS. The vagus nerve is myelinated above the diaphragm and regulates the heart and lungs. Below the diaphragm, the vagus nerve is unmyelinated and regulates the gut and abdominal organs.

The “vagal break stops the sympathetic nervous system dominance and regulates the heart rate via vagal activation. This action promotes relaxation, self-soothing, growth , and repair. [This] activates the parasympathetic nervous system” (p.240) (Institute, 2019). The sympathetic (fight/flight/freeze) dominance can be released through vagal nerve toning/ activation such as belly breathing, extended exhales, and kapalabhati.

Nervous System and Meditation

When you go into Google Scholar and look up articles on meditation effects, there are 503,000 articles listed. To narrow all this down, we will summarize by stating that meditation calms the mind, slows racing thoughts, increases neuroplasticity, and decreases heart rate and blood pressure. Research has shown when people meditate for fifteen to twentyfive minutes, both brain hemispheres begin working together. People gain whole-brain functioning. Humans tend to be left- or right-side dominant, each side having different jobs. The left side is more logical, analytical, and detail-oriented. The right side is more intuitive, creative, and artistic. Meditation appears to strengthen both sides. Both sides are activated, displaying better focus and alertness, stronger memory, and better intellectual functioning. People report being happier, more peaceful, and balanced emotionally (eco).

Conclusions

When we teach yoga, pranayama, and meditation, we should be aware of how powerful these tools are to our nervous system. We should have a general understanding of how our nervous system works and then how outside factors can influence its functioning and health. Utilizing our tools skillfully can facilitate health and well-being in all of our students.