The nervous system, together with the endocrine system, coordinates all activities of the organ systems to maintain homeostasis (keeping the body healthy and into balance). With yoga we directly influence our nervous system by doing asanas, pranayama and meditation.
The nervous system reacts quickly on signals from outside the body, but these reactions don’t last very long. For instance: you put your hand on top of a burning stove. The receptors in your hand sent a signal to your brain telling that you are burning your hand. Your brain sent a signal to the muscles of the hand and arm. As a reaction you will withdraw your hand. All of this in a split of a second.
The endocrine system reacts slower, but these reactions take place over a longer period of time. For instance: you reach the age of puberty. Time to grow hair on your face. Your body starts to produce hormones that will stimulate hair growth.
Anatomically the nervous system can be divided in our central nervous system (CNS) and our peripheral nervous system. (PNS). Our CNS contains our brain and spinal cord. It coordinates all sensory information and gives impulses to our muscles. It also covers the ‘higher functions’, like intelligence, memory and emotions.
All communication between our CNS and the rest of our body runs through our peripheral nervous system (PNS). This includes all nervous tissue outside our CNS. Our spinal cord is the most important route to transfer information from the rest of our body to our brain and from our brain to the rest of our body. Our spinal cord can even handle and react on impulses without sending information to the brain.
All information (heat, pain etc) is collected by sensors of the PNS, sent through communication lines of our PNS to our CNS. Our CNS processes the information and sent and action (impulse) back.
We can divide our PNS into two parts:
Somatic nervous system and autonomic nervous system.
- We can control our Somatic nervous system. This is the system that coordinates the movement of our skeletal muscles.
- Our autonomic nervous system ‘does its own job’. It controls blood pressure, heart and breathing rates, body temperature, digestion, metabolism (thus affecting body weight), the balance of water and electrolytes (such as sodium and calcium), the production of body fluids (saliva, sweat, and tears), urination, defecation, sexual response, and other processes.
This autonomic nervous system can again be divided in two systems:
sympathetic nervous system and Parasympathetic nervous system
- The sympathetic nervous system is also called our ‘fight of flight system’. It prepares the body for stressful or emergency situations; fight or flight. Thus, it increases heart rate and the force of heart contractions and widens (dilates) the airways to make breathing easier. It causes the body to release stored energy. Muscular strength is increased. This division also causes palms to sweat, pupils to dilate, and hair to stand on end. It slows body processes that are less important in emergencies, such as digestion and urination.
- The parasympathetic system controls body processes during ordinary situations. Generally, it conserves and restores. It slows the heart rate and decreases blood pressure. It stimulates the digestive tract to process food and eliminate wastes. Energy from the processed food is used to restore and build tissues.
Our parasympathetic system has to be ‘active’ for about ten hours a day to prevent our body from depleting it selves of its energy. We sleep for 7 to 8 hours, so we still have to be ‘switched off’ for two more hours. When we watch television, surf on the internet or play with our phone, we think we are resting, but for our nervous system we don’t. We are still alert. We are still in a fight or flight reaction, trying to cope with all incoming impulses. So we end up wearing ourselves out, bringing us close to a burn-out.
Yoga (and walking in nature) are stimulating our parasympathetic nervous system. Switching our body ‘off’ and giving it the rest it needs to recover.