Your two major divisions: the central nervous system

Your nervous system allows you to experience the world around you and react to it.

It’s a complex system that’s split into two main parts, the central nervous system and the peripheral nervous system. Read on to learn the parts and functions of the system.

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Nervous System

A ball comes toward you and you swing your bat. A big dog jumps out in front of you and you begin to sweat. You walk past a bakery and the wonderful aroma makes your mouth water.

All of these functions are possible because you have a working nervous system. Your nervous system is a complex collection of nerves and cells that carry messages and control actions.It has three main functions.

First, it detects change going on inside and outside your body. This is possible thanks to sensory receptors found throughout your body and concentrated in your sensory organs, such as your eyes, ears, tongue, nose and skin. Your nervous system also interprets the information from the sensory receptors, and then effects a response by sending out an order to your muscles or glands. For example, when the pitcher winds up and throws the baseball toward you, your eyes see the ball, your brain says swing, and your arms move.

CNS & PNS

This is a nice, tidy way to look at the nervous system, but in reality it’s a very involved system made up of billions of cells that carry out countless functions every minute of the day. To best understand how the entire system works, we will consider the two major divisions: the central nervous system and the peripheral nervous system. The central nervous system, or CNS, consists of the brain and spinal cord.

It’s the part that interprets the incoming sensory information and then issues the orders, so I like to think of it as the boss.The peripheral nervous system, or PNS, is made up of nerves that travel to and from the central nervous system. It reports any sensory changes to the brain and spinal cord, and then carries out orders. So, you could say the PNS is like the workers.

Subdivisions of PNS

The peripheral nervous system is divided again, giving us two main subdivisions.

This is easy to understand if you remember that some of the nerves of the PNS travel toward the brain, while others travel away from it. The nerves traveling toward the brain make up the sensory division or afferent division. Nerves in this division take information from sensory receptors and carry it to the CNS, like the frightening sound of a dog barking or the wonderful smell of freshly baked bread. In other words, the sensory division allows you to sense the word around you.The nerves traveling away from the CNS make up the motor division, or efferent division, of the peripheral nervous system. The nerves in this division send messages to your muscles and glands to carry out the orders issued by the brain.

If you think about it, some of these orders are things you consciously decide to do, like swinging a bat to try to hit a home run. But other things, like your mouth watering or sweating, are done without your conscious input. Because there are some body reactions that are voluntary and some that are not, we can further divide the motor division of the PNS into two additional subdivisions.

Somatic & Autonomic NS

The somatic nervous system is a subdivision of the motor division that allows us to consciously control our skeletal muscles. This includes any voluntary movement, like brushing your teeth or swatting a fly off your arm.

The autonomic nervous system is a subdivision of the motor division that allows the body to perform tasks that are not under conscious control. In other words, it’s the system that regulates involuntary activities, like digestion, sweating and your heart beating even when you’re sound asleep.

Divisions of the Autonomic NS

Do you remember when that dog jumped out in front of us at the beginning of this lesson? Well, not only would that make you sweat, it would also make your heart race. That’s an example of an automatic function of the autonomic nervous system. You didn’t tell your heart to beat faster, it just did.

Once the dog runs off and the coast is clear, your heart rate returns to normal.Therefore, we see that the autonomic nervous system has the ability to speed up and slow down involuntary activities. So we have one more division to consider. The autonomic nervous system has two parts. The sympathetic nervous system gets you ready for fight or flight by doing things like speeding up your heart rate, constricting your blood vessels and raising your blood pressure. The parasympathetic nervous system calms you down once the threat is over, so it slows your heart rate and allows you to relax.

Lesson Summary

Let’s review.Your nervous system is a complex collection of nerves and cells that carry messages and control actions. It has three main functions. It detects change going on inside and outside your body, interprets the information from the sensory receptors, and then effects a response.

The system is divided into the central nervous system, or CNS, that consists of the brain and spinal cord, and the peripheral nervous system, or PNS, that is made up of nerves that travel to and from the central nervous system. The CNS receives information from the sensory division of the PNS, interprets that information, and then issues orders, which are carried out by the motor division of the PNS.The motor division can carry out voluntary or involuntary orders, so we see that the motor division has two subdivisions.

The somatic nervous system is a subdivision of the motor division that allows us to consciously control our skeletal muscles. The autonomic nervous system is a subdivision of the motor division that allows the body to perform tasks that are not under conscious control. The autonomic nervous system itself has two parts, which are the sympathetic nervous system that gets you ready for fight or flight and the parasympathetic nervous system that calms you down.

Nervous System Terms ; Definitions

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Terms Definitions
Nervous system a complex collection of nerves and cells that carry messages and control actions
Central nervous system consists of the brain and spinal cord and interprets the incoming sensory information and issues orders
Peripheral nervous system made up of nerves that travel to and from the central nervous system; reports any sensory changes to the brain and spinal cord, then carries out orders
Sensory division nerves in this division take information from sensory receptors and carry it to the CNS
Motor division nerves in this division send messages to the muscles and glands to carry out the orders issued by the brain
Somatic nervous system a subdivision of the motor division that allows us to consciously control our skeletal muscles
Autonomic nervous system a subdivision of the motor division that allows the body to perform tasks that are not under conscious control
Sympathetic nervous system gets one ready for fight or flight by doing things like speeding up the heart rate, constricting blood vessels and raising blood pressure
Parasympathetic nervous system calms one down once the threat is over, it slows heart rate and allows one to relax

Learning Outcomes

You should be prepared to accomplish the following at the end of this lesson:

  • Define the nervous system
  • Contrast the central and peripheral systems
  • Describe the division and sub divisions of the nervous system
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