Nervous System Overview: Central & Peripheral

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  • 0:04 Central Nervous System
  • 1:25 Peripheral Nervous System
  • 3:23 Lesson Summary
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Lesson Transcript
Instructor: Paul Bautista
What happens in your nervous system when you react to stimuli? Did you know that the brain is sometimes uninvolved with reflexes? Find out the answer to these questions, and more, in this lesson on the human nervous system.

Central Nervous System

Not everything we do is decided by our brains. There are some automatic reactions that don't involve your brain. I know that seems weird, but think about how your leg involuntarily kicks when the doctor taps your knee with a rubber mallet. Your spinal cord is responsible for this knee-jerk reaction, not your brain.

Your spinal cord is made up nerves, which are in turn made up of bundles of neurons. You can think of all of these neurons as baseball players passing balls, which are chemical signals.

Sometimes sensory neurons carry messages to the brain. Other times, like when you accidentally touch a hot burner on the stove, they only get as far as the spinal cord before producing a natural reflex. Your spinal cord sends signals to your motor neurons without any input from your brain so you can pull your hand back before you get burned. No time is wasted 'thinking' about what to do. When every moment counts, the nerves in your spinal cord take control!

Don't get me wrong, your brain gets involved most of the time when you touch something. For example, when you feel a mosquito land on your arm, your sensory neurons send signals to interneurons in your brain. Then, your brain sends signals to your motor neurons to swat the mosquito.

Together, your brain and your spinal cord make up your central nervous system. At the core of your body, they are the center of the control system.

The brain and spinal cord make up the central nervous system
central nervous system

Peripheral Nervous System

Your sensory neurons and your motor neurons make up your peripheral nervous system. Your central nervous system is like the coach and your peripheral nervous system is like the team. The coach calls the plays, but the team is on the front line of action, and sometimes players have to react on their own.

Your peripheral nervous system is made up of sensory neurons (which take in information about what you see, hear, taste, touch and smell) and motor neurons (which send information to your muscles and glands so you can react). The sensory neurons are the ones that tell your brain there's a mosquito biting you, and then your brain tells your motor neurons to swat it with your hand.

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