Which carry messages from the cell body

The mammalian brain contains between million and billion neurons, depending on the species. Each mammalian neuron consists of a cell body , dendrites , and an axon. When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch or centimeter to three feet about one meter or more.

Many axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia.

In the brain, the glia that make the sheath are called oligodendrocytes, and in the peripheral nervous system, they are known as Schwann cells. The brain contains at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place.

Current research is uncovering important new roles for glia in brain function. Explain the brain to your students with a variety of teaching tools and resources. Engage local scientists to educate your community about the brain. In young children, the brain is highly adaptable. In fact, when one part of a young child's brain is injured, another part often can learn to take over some of the lost function.

But as you age, the brain has to work harder to make new neural pathways, making it harder to master new tasks or change set behavior patterns. That's why many scientists believe it's important to keep challenging the brain to learn new things and make new connections — it helps keeps the brain active over the course of a lifetime.

Memory is another complex function of the brain. The things you've done, learned, and seen are first processed in the cortex. Then, if you sense that this information is important enough to remember permanently, it's passed inward to other regions of the brain such as the hippocampus and amygdala for long-term storage and retrieval.

As these messages travel through the brain, they too create pathways that serve as the basis of memory. Different parts of the cerebrum move different body parts. The left side of the brain controls the movements of the right side of the body, and the right side of the brain controls the movements of the left side of the body.

When you press your car's accelerator with your right foot, for example, it's the left side of your brain that sends the message allowing you to do it. Basic body functions. A part of the peripheral nervous system called the autonomic nervous system controls many of the body processes you almost never need to think about, like breathing, digestion, sweating, and shivering.

The autonomic nervous system has two parts: the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system prepares the body for sudden stress, like if you witness a robbery. When something frightening happens, the sympathetic nervous system makes the heart beat faster so that it sends blood quickly to the different body parts that might need it. It also causes the adrenal glands at the top of the kidneys to release adrenaline, a hormone that helps give extra power to the muscles for a quick getaway.

This process is known as the body's "fight or flight" response. The parasympathetic nervous system does the opposite: It prepares the body for rest. It also helps the digestive tract move along so our bodies can efficiently take in nutrients from the food we eat. Sight probably tells us more about the world than any other sense. Light entering the eye forms an upside-down image on the retina.

The retina transforms the light into nerve signals for the brain. The brain then turns the image right-side up and tells you what you're seeing.

Every sound you hear is the result of sound waves entering your ears and making your eardrums vibrate. These vibrations then move along the tiny bones of the middle ear and turn into nerve signals. The cortex then processes these signals, telling you what you're hearing. The tongue contains small groups of sensory cells called taste buds that react to chemicals in foods.

Taste buds react to sweet, sour, salty, bitter, and savory. The taste buds send messages to the areas in the cortex responsible for processing taste. Olfactory cells in the mucous membranes lining each nostril react to chemicals you breathe in and send messages along specific nerves to the brain.

The skin contains millions of sensory receptors that gather information related to touch, pressure, temperature, and pain and send it to the brain for processing and reaction. Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. Over half of all the nerve cells in your nervous system do not transmit any impulses. These supporting nerve cells are located between and around your neurons to insulate, protect and nourish them.

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