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Nervous System Facts
Learn some fun nervous system facts for kids. The nervous system of humans and other animals is a vital part of how the body functions.
Components of the nervous system including neurons, glial cells and axon all help send nerve signals around the body. Read on to find out about the two main parts of our body's nervous system and many other interesting facts.
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The nervous system is a complex structure of nerves of neurons that transmit signals around the body to coordinate actions. It is in effect our body's electrical wiring.
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The nervous system of vertebrates (which includes humans and animals that have backbones and spinal columns) has two parts, the central nervous system (CNS) and the peripheral nervous system (PNS).
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The CNS includes the brain, spinal cord and retina of the eyes. The brain is protected by the skull, and the spinal cord by the skeletal vertebrae.
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The PNS includes all other nervous system structures that sit outside the CNS but that help connect the CNS to areas of the body.
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Nerves are enclosed bundles of long fibers called axons which are made up of nerve cells. There are two types of nerve cells: neurons and glial cells.
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Glial (or glia) cells are derived from the Greek word "glue". They are specialized cells that provide structure and support to neurons. They help hold neurons in place, supply nutrients to neurons, destroy germs, remove dead neurons, and direct axons of neurons.
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Some types of glial cells generate a substance called myelin that coat axons and work as electrical insulation to help them quickly and efficiently transmit signals.
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Neurons quickly and precisely send signals as electrochemical waves along axons to other cells. There are two types of neurons, sensory neurons and motor neurons.
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Sensory neurons change light, touch and sound into neural signals which are sent back to our CNS to help our body understand and react to its surroundings.
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Motor neurons transmit neural signals to activate muscles or glands.
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There are approximately 100 billion neurons in the human brain and 13.5 million neurons in the human spinal chord.
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The nervous system can transmit signals at speeds of 100 meters (328 feet) per second.
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The field of science that focuses on the study of the nervous system is called neuroscience. Neurology is the medical branch of study and treatment, while doctors and surgeons in this field are called neurologists and neurosurgeons.
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Nerves in our body can be vulnerable to both physical damage and damage through diseases. Damage to nerves can cause great pain, loss of feeling, or loss of muscle control.
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Physiatrists help rehabilitate patients with nervous system damage.
The nervous system is the body’s main control system. It is made up of the central nervous system (or CNS) and a network ofnerves that extend from the CNS to all parts of the body. The nervous system regulates both voluntary activities, such as walking and talking, and involuntary activities, such as breathing, which you make no conscious decisions about.
The CNS consists of the brain and spinal cord. The rest of the nervous system, called the peripheral nervous system, consists of nerves. These include 12 pairs of nerves that branch from the brain (cranial nerves) and 31 pairs that branch from the spinal cord (spinal nerves).
The nervous system contains billions of neurons (nerve cells). A neuron has a cell body, arms called dendrites, and a long projecting fibre, the axon. Electrical signals – up to 2,500 per second – can pass along axons. They can also jump between neurons by means of chemicals that pass across the gaps in synapses (neuron junctions).
The main parts of the brain are the large folded cerebrum, the brainstem, which forms a stalk at the foot of the brain, the cerebellum behind it, and central structures, such as the thalamus.
Nerves are made up of bundles of the axons of nerve cells. Some of these carry information picked up by sensory receptors around the body to the CNS for processing. Other axons carry messages from the CNS to muscles, causing movement, or to the body’s glands, causing the release of hormones. Many axons are surrounded by a protective sheath containing a fatty substance called myelin. This acts to insulate the axons electrically.
Most nerves consist of several axon bundles, called fascicles. The speed at which individual nerves transmit signals varies depending on their thickness and whether or not their axons have myelin sheaths; fatter, myelinated axons transmit signals faster, at up to 350 kph (218 mph).
The CNS has two main tasks. It has to process information, both about the outside world (obtained by organs such as the eyes) and about the inside of the body (obtained by internal receptors). It also has to generate responses such as movement that will protect and maintain the body. Some activity within the CNS is quite simplereflex (automatic) activity. But much of its activity, particularly in the brain’s cerebrum, is complex and conscious.
FUNCTIONS OF THE CEREBRAL CORTEX
The cortex (outer layer) of the cerebrum has many functions. Different areas of the cortex are involved in processing or analysing sensory information, sending signals to direct muscle movements, or in other activities such as reasoning, memory, or creative thought.
The spinal cord’s main function is to transmit information between the brain and spinal nerves. It is also involved in some reflex activity. Its grey matter is made up of the cell bodies of neurons. Its white matter contains axons (neuronal fibres). These are arranged into groups called tracts and carry signals up and down the cord.
In its simplest sense, a reflex is an emergency reaction of the nervous system to a threat such as a hot object touching the skin. In a wider sense, reflexes are automatic responses to a wide range of situations in the body and are key to many internal activities, such as the heart beat. A division of the nervous system called the autonomic nervous system is in overall control of these internal activities.
In a simple reflex, information passes from the area affected, in this case the finger, to the central nervous system (red pathway). This triggers an immediate response, in this case the contraction of a muscle (blue pathway) to withdraw the finger. Here, the reflex action involves only two nerves and the spinal cord. However, a signal also passes to the brain, which registers the pain.
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