Nervous System

What does the nervous system do?
Answered by Susan Sherwood and Discovery Channel
  • Susan Sherwood

    Susan Sherwood

  • Discovery Channel

    Discovery Channel

  1. Blink. Breathe. Scratch. Sweat. Wave. You're using your nervous system. It's divided into two parts: the central nervous system (CNS) and the peripheral nervous system (PNS). Although they have different functions, they work cooperatively to help you do everything from grabbing a cup of coffee to dancing a waltz. Let's look at what the systems do and what could happen if they don't function properly.

    The brain and the spinal cord compose the CNS. Information about your world, both internal and external, is collected and goes to the spinal cord, where the data are transmitted to the brain. The brain receives the information, interprets it, determines a response and transmits that response through the spinal cord to the appropriate body part.

    The information collection and response is the responsibility of the PNS, which connects the rest of the body to the brain and spinal cord. Using sensory receptors and other neurons, the PNS gathers information, sends it to the spinal cord or brain and performs the reaction the brain has chosen. Two subsections of the PNS divide up this labor, the "somatic" and "autonomic" nervous systems. The somatic nervous system permits voluntary responses to environmental stimuli; it controls the skeletal muscles after the brain has given its orders.

    When a mosquito lands on your arm and meets an unhappy ending (for the insect, at least), there has been cooperation between the somatic nervous system and CNS.  Receptors in the PNS feel and see the bug, and a message goes to the spinal column, which transmits the sensation and sight to the brain. The brain retorts, "smack it" and sends the command to the PNS, which makes the arm swat the creepy-crawly.

    That's done quickly, but with consciousness. The "autonomic" nervous system is responsible for keeping the body running smoothly without conscious effort; it deals with information involving glands and organs. This system, for example, keeps your heart beating, food digesting and saliva flowing.

    The goal is to keep these systems working smoothly, and there can be serious consequences if they don't. Diseases such as multiple sclerosis and Parkinson's affect the CNS. Peripheral nerve disorders include carpal tunnel syndrome, diabetic nerve damage and Guillain-Barre syndrome. (The immune system injures the PNS, causing difficulty in transmitting information to the CNS.)

    So, then, what does the nervous system do? Almost everything. If something goes awry, symptoms can run the gamut from finger numbness to paralysis. That's a nerve-wracking prospect.

    spinal illustration
    (© iStockphoto/mstroz)

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  2. Your nervous system coordinates all of your movements, sensations and thoughts. For example, if you pick up something very hot, you will drop it without even thinking about it. Your nervous system senses the hot object and signals to your muscles to let it go. The nervous system senses your surroundings (both internal and external); communicates information between your spinal cord, brain and other tissues; coordinates your body's voluntary movements; and regulates and coordinates your body's involuntary functions such as heart rate, breathing and body temperature. In the same way a computer is run by its microprocessor, the nervous system is run by the brain: Where computer "wires" connect the parts of a computer to each other, the nerves and spinal cord connect the parts of the body to the brain. Nerves transmit electrochemical signals throughout the nervous system and also between the nervous system and parts of your body.

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