All About The Nervous System

The Nervous System

The nervous system regulates your body's structures and processes in order to maintain homeostasis despite any fluctutations in the internal or external environment. For example, for someone who lives in Austrailia or a warmer climate, when they experience a cooler day their nervous system would respond by constricting blood flow to the extremeties in order to conserve body heat. This is one of the many ways your nervous system helps to maintain homeostasis.

The nervous system is organized into two main divisions: the central nervous system and the peripheral nervous system. Together, these two systems control sensory input, integration and motor output. The central nervous system, consisting of the brain and spinal cord, is responsible for integrating and processing the information sent by nerves. The peripheral nervous system consists of nerves that carry sensory messages to the central nervous system and nerves that send information from the central nervous system to the muscles and glands. The peripheral nervous system is further divided into two sections: the somatic system and the autonomic system. The somatic system controls all of your voluntary responses (ie. skating, running, jumping, etc.) and the autonomic system controls all of your involuntary responses (ie. breathing, digestive system, etc.). The autonomic system is then further divided into two more sections: the parasympathetic nervous system and the sympathetic nervous system. The parasympathetic nervous system is activated when your body is calm and at rest, and acts to restore and conserve energy. This system, sometimes referred to as the 'rest and digest' response, slows down your heart rate, reduces blood pressure, and promotes the digestion of food. The sympathetic nervous system is typically activated in stressful situations, and is often referred to as the 'fight or flight' response. Norepinephrine and epinephrine are released during this response, and norepinephrine has been known to have an excitatory effect on its target muscles. This 'fight or flight' response causes blood pressure and heart rate to increase and digestion to slow down.

The sympathetic nervous system is also directly related to why we blush! The epinephrine released by this response (adrenaline) causes your blood vessels to dilate to allow more oxygen delivery and blood flow. This is exactly what happens when you blush. The veins in your face respond to the signal from the chemical transmitter adenylyl cyclase, which signals the veins to allow the adrenaline to do its job. As a result, the veins in your face dilate allowing more blood flow to pass through your cheeks, accounting for the reddened appearance that shows others that you are embarrassed.