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May 16, 2013

The Peripheral Nervous System (PNS), the Cell and Their Natural Activity



It is made up of two types of nerves the Sensory or Afferent nerves that transmit information from the body organs, skin or muscles to the brain. The Motor or Efferent nerves carry orders and decisions down to the muscles and glands from the brain. The Motor Nerves are also a part of the Somatic or the Autonomic Nervous System.

Before discussing the structure and functions of the CNS and the PNS we will prefer to first explain some basics which are a part of these two systems as a complicated mechanism.
  
The Cells:

They are billions in number of which the human Nervous system is made of. These cells are of two types, called neurons and glia. The neurons or nerve cells perform the major task of receiving and sending information from and to other parts of the body. Glia cells or glia protect and support the neurons in different manners. The glia in the first place, cover parts of the neurons with a sheath or a covering made of a fatty tissue, myelin. Other types help remove dead nerve cells. There are more ways in which glia provide a support to the neurons. It is believed that at least 12 billion neurons and in the same number glia cells are present in the human nervous system. Neurons, which were seen for the first time in 1950 with an electronic microscope, vary widely in size and in shape. They, perform different functions according to their position and capacity in the nervous setting.

 Each, neuron has a cell body, a nucleus that contains the cells genetic information (programming the capacity) in DNA (deoxyribonucleic acid) and Dendrites. Dendrites are narrow, branching extensions of the cell body which receive the incoming signals. Most neurons have a tail like extension, called Axon which may be as short as a fraction of an inch for a brain neuron or long as 2 or 3 feet for an axon on a neuron in the spinal cord. A neuron receives information from other neurons through its dendrites and cell body, while it transmits information down its axon.

The Neural Activity:

The human body, as we know, has an amount of electricity in it which facilitates the sensation and feeling process. Our brain is an incredibly a busy centre of electrical activity for as long as we live even when we are asleep. Each neuron has, like a battery, a potential energy within it because the inside of the neuron has more negative than positive ions (charged particles) while it is surrounded by positive ions on the outside. This potential energy is known as the” Resting Potential”.

Now, Action Potential is sending a nerve impulse down its axon from one end of the neuron to the other. The action potential begins, near the cell body (the Axon Hillock) at a specific part of the axon, and the impulse travels all the way long the axon to the axon terminal. Impulses covered with myelin travel faster along axons. The action potential cannot accrue beneath the myelin Sheath as myelin acts as an insulator, but instead jumps rapidly between the nodes, or gaps in the myelin.

John S Lam is an IT Instructor at Examskey. He is 220-801 Certified Professional. Take the benefit of our 200-120 material and assure your success. Check out our free demo of all certifications Exams.

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