Nervous

[[image:nervous_pic.png width="800" height="252"]]﻿ By: Stephanie, Spencer, Connor, and Katerina
** __What is the nervous system?__ ** The nervous system is the body control center, and the most complex system. The nervous system interprets, detects, and responds to adjustments in external and internal conversions. This system brings together endless bits of data and sends reactions through the nerves to organs. The central nervous system is the brain and spinal cord. How do you dream at night? How do you blink without even thinking? How do you remember things like the way to your friend’s house, or a password to a computer? This is all done by the brain, which is the most important organ to the nervous system. The brain has 5 different parts: 1. Cerebrum (say: suh-ree-brum) 2. Cerebellum (say: sair-uh-bell-um) 3. Brain stem 4. Pituitary gland (say: puh-too-uh-ter-ee gland) 5. Hypothalamus (say: hy-po-thal-uh-mus)
 * __The Brain:__ **

The largest part of the brain is the cerebrum. Almost 85% of the brains weight is the cerebrum, because the cerebrum controls your voluntary muscles, which means you couldn’t play a sport or dance at a school dance without it. Your memory also comes from your cerebrum- both short-term memory and long-term memory. The cerebrum also has 2 halves, one on each side of your head. In theory, the right half lets you ponder abstract things while the left side is said to be more analytical. Scientists do not know for sure which side of your body the cerebrum controls.

Located at the back of the brain and under the cerebrum is the cerebellum, which is only 1/8 of the cerebrums size. The cerebellum controls coordination, balance, and movement. This means that you could not stand upright or ride a skateboard without it.

Right beneath the cerebrum and in front of the cerebellum is the brain stem. The rest of the brain is connected to the spinal cord through the brain stem. The brain stem controls the involuntary muscles like breathing air, digesting food, and circulating blood. Since there are involuntary muscles in the heart and stomach, the brain stem tells your heart to pump more blood when you’re running, or it tells your stomach to start digesting food when you are eating. Your brain sends over a million messages to your body, and the brain stem deals with some of them.

__**The Spinal Cord**__ The spinal cord is a long, thin, tubular clump of nervous tissue and support cells that extends from the brain. The spinal cord starts and goes down in between the first and second lumbar vertebrae; it doesn't go through the entire length of the vertebral column though. The relatively shorter spinal cord is protected by the vertebral column. The spinal cord functions mainly on the neural signals the brain sends. The spinal cord has three major functions: 1) Serve as a conduit for motor information, which travels down the spinal cord. 2) Serve as a conduit for sensory information, which travels up the spinal cord. 3) Serve as a center for coordinating certain reflexes.

Your eyes are one of the major system organs to the nervous system. Your eyes and brain convert light waves into an impression us humans call vision. Some of the many parts of the eye are listed below. **__Cornea:__** This outer layer of tissue covers the iris and the pupil. It acts as the eyes outer lens, and contributes to the eyes ability to focus.
 * __Eyes__ **

**__Iris:__** the opening that is located in the center of the eye is called the iris. The iris changes shape as light passes through the eye. **__Pupil:__** the pupil is an expanding and contracting window in the iris that passes light through the retina. **__Retina:__** the light sensitive layer of tissue in the back of the eye that consists of several layers, one of which containing the rods and cones that are sensitive to light. **__Lens:__** the lens is a small transparent structure in the eye that helps refract light by changing the shape of the eye so it can focus on objects close up and far away. That helps the retina form the image.

The nervous system is the body's information gatherer, storage center and control system. Its overall functions are to collect information about the body's internal/external states, and transfer this information to the brain, to analyze this information, and to send impulses out to initiate appropriate motor responses to meet the body's needs. At the most basic level, the function of the nervous system is to send signals from one cell to others or from one part of the body to others. There are multiple ways that a cell can send signals to other cells. One is by releasing chemicals called hormones into the internal circulation, so that they can diffuse to distant sites. When we talk about the nervous system sending "signals" to the brain, or synapses "firing," or the brain telling our hands to contract around a door handle, what we're talking about is electricity carrying messages between point A and point B. Also, your nerve cells have more potassium ions inside than outside which makes the cell slightly negative. Then, when the cell opens when receiving, say a bee sting, it opens at a rate where the potassium ions cross the sodium ones outside and create an electrical impulse. It does this and the signals are decoded by the brain and then you think "I just got a bee sting" and this happens in extremely small fractions of seconds.
 * __Other Major Functions of the Nervous System:__ **

**__Connections to other systems:__ ** The nervous system has connections to all the other systems: the respiratory system, muscular system , digestive system , circulatory system , and skeletal system. This is because the nervous system is the controlling organ of the body; it’s the center of consciousness and the emotional and behavioral functions that make up the personality of a human being. This system has ties to the respiratory and circulatory systems because of the fact that the nervous system controls them. The nervous system monitors respiratory volume and blood gas levels. It also regulates respiratory rate. Ties to the muscular system also take place because receptors in muscles provide the nervous system with information about your body’s position and movement. Since the muscular system connects to the digestive system, the nervous system regulates the speed at which food moves through the digestive tract. Finally, the nervous system connects to the skeletal system in a very important way: the bones provide calcium that is essential for proper functioning of the nervous system. The skull also protects the brain, which is the most essential organ to the nervous system. As you can see, many ties to many systems take place throughout the nervous system, and each connection is crucial for proper functions to take place.


 * __﻿Nervous System Fun Facts:__ **
 * If you could line up all the neurons in our body it would be around 600 miles long.
 * The total surface area of the human brain is about 25, 000 square cm.
 * There are about 13,500,00 neurons in the human spinal cord.
 * The Nervous System can transmit impulses as fast as 100 meters per second.
 * Only four percent of the brain's cells work while the remaining cells are kept in reserve.
 * There are 43 different pairs of nerves which connect the central nervous system to every part of our body. Twelve of these nerve pairs are connected to the brain, while the remaining 31 are connected to the spinal cord.
 * The spinal cord has around 135,000,000 neurons. If one could spread out the human brain like a cloth, its surface area would cover twenty-five thousand square centimeters.
 * There are more nerve cells in the human brain than there are stars in the Milky Way.
 * A newborn baby's brain grows almost 3 times during the course of its first year.
 * The left side of human brain controls the right side of the body and vice-versa.
 * A New born baby loses about half of their nerve cells before they are born.
 * As we get older, the brain loses almost one gram per year.
 * An average adult male brain weighs about 1375 grams, but an average adult female brain is about 1275 grams.
 * Nerve cells look like goldfish.
 * There are 100 billion neurons in your brain alone.
 * Nuerons are the largest cells in the human body.
 * The most sensitive nerves are found at the base of the spinal cord.
 * The nervous system is connected to all the body systems.

You can find more fun facts about the nervous system here: [| Nervous System Fun Facts]

You can also find more about the Nervous System on these websites: Your Gross and Cool Body BBC National Geographic Medtropolis Get Body Smart [|More Nervous System Fun Facts]