Читать книгу The Human Race – Too Smart to Survive онлайн

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But the nerve roots also integrate autonomic nerve fibers, which control metabolism and things like adapting to stress or resting conditions. The major vegetative centers connect at the thoracic spine to form longitudinal cords that run under the rib joints on the right and left to the upper lumbar spine, forming what is called the “sympathetic trunk”. This is our stress system and responds to stress by altering hormone production and energy supply to keep the body alive in emergency situations (increased heartbeat, increased blood sugar and cholesterol, faster breathing, increased muscle tone, dilation of bronchial tubes, reduction of digestive and thyroid function). Discrete changes, however, are physiological and change within a day, from day to day, and from week to week, automatically adjusting to external circumstances. From the brain stem and coccyx originate the large parasympathetic nerves, which act like an antagonist of the sympathetic nervous system. They promote sleep, digestion, and healing as well as growth by stimulating the thyroid gland.