Let’s pretend for a minute that your body is a pirate ship. A captain is in charge of everything that happens on his or her ship. Your brain is the ship’s captain. It is in charge of everything that happens inside of your body. A captain gives orders to do important things like swab the deck or drop the anchor. The brain controls important functions like movement, breathing, and more! But how does the brain know what orders to give?
Neurons and the Division of the Nervous System
When you use your five senses, you are paying special attention to your body and to the world around it. We learn things about ourselves and our surroundings through internal and external sensations. These sensations are picked up by nerve cells called neurons. There are billions of neurons in the human body.
Neurons send signals to the brain through neurotransmitters, which are like messengers. The paths that these messengers take to deliver their signals are called synapses. Neurons fall into two categories. One category is the central nervous system (CNS) and the other is the peripheral nervous system (PNS). The CNS includes the brain and the spinal cord, while the PNS includes all the other neurons in the body.
The Peripheral Nervous System
The PNS has two subdivisions. The first is the somatic nervous system and the second is the autonomic nervous system. The somatic nervous system focuses on external signals. These signals are picked up by your five senses. Organs such as your eyes and ears are part of the somatic nervous system. The somatic nervous system is also called the voluntary nervous system. This is because you have some control over these organs. The autonomic nervous system is also called the involuntary nervous system. This is because you do not have control over its organs, such as the heart and intestines.
The autonomic nervous system is also divided into two parts. The sympathetic nervous system excites your body. The parasympathetic nervous system calms it down. What does this mean? When your body senses danger, the sympathetic nervous system kicks in. Have you ever noticed that your breathing or heartbeat is faster when you’re scared? This is your sympathetic nervous system. It prepares your body for “fight or flight,” which means it prepares you to confront the threat or run away from it.
While some organs become more active, others slow down. This includes digestive organs. After all, if you’re being chased by a lion, digesting your lunch isn’t your biggest concern! The parasympathetic nervous system has the opposite effect. It slows down the organs that are working extra hard and restarts the organs that have been paused. This returns your body to its normal functioning.
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