Читать книгу The Mind-Body Cure - Bal Pawa - Страница 34

The somatic nervous system sends messages from our central nervous system to our organs, muscles, and skin when we decide to do something. It controls our voluntary movement. For example, we use it every time we take a big bite out of a juicy hamburger. Our somatic nervous system sends the message from our brain to our body to pick up and bite into that burger. The somatic nervous system directs the nerves that coordinate this action. These are all choices we make; they are voluntary responses rather than automatic reactions.

But what starts our mouth watering when the food arrives? What stimulated our hunger in the first place? What gets our heart pumping when we jog? These functions are under the control of the ANS, which controls our involuntary, or automatic, reactions. We don’t always choose these actions. The ANS has two arms to regulate the involuntary functions in the body—the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS)—and their interaction forms the basis of the mind-brain-body connection.

Communication between the brain and the body occurs through nerve pathways, and an autonomic nerve pathway connects two nerve cells (neurons) (Figure 2.2). One cell is located in the brainstem or spinal cord and it is connected by nerve fibers to the second cell, which is located in a cluster of nerve cells called an autonomic ganglion (more than one are called ganglia). These ganglia are connected to a specific organ, gland, or muscle by a further set of nerve fibers. Signals travel from one cell to another along the nerve fibers, often down from the brain to the body and back up from the body to the brain.

The central nervous system communicates with the autonomic nervous system through the vagus nerve and autonomic ganglia, which run from the brainstem (pons and medulla oblongata) to organs such as the lungs, heart, and gut. The parasympathetic system uses both pathways for rest-and-digest responses, whereas the sympathetic system engages autonomic ganglia near the spine to manage fight-or-flight situations.

Figure 2.2. The connection between the autonomic nervous system and the brain

One of the main nerve pathways that connects the ANS to the body is the vagus nerve, which is also known as the “wandering nerve” because this long nerve has the widest distribution in the body. It travels from the brain into organs in the neck, chest, and abdomen. The tenth of twelve cranial nerves (meaning they originate in the brainstem), the vagus nerves come in a pair but we refer to them in the singular form.

Most of the time, the ANS works automatically, without conscious thought. It determines how fast our heart beats, how vigorously our stomach contracts, and how much air gets into our lungs. It also responds automatically to our subconscious thoughts, which communicate with the ANS at every instant, and determines whether our stress hormones are turned on or off. Although the ANS is an automatic system for the most part, our mind has dominance over the brain and can regulate the ANS to a great degree.