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Old Thursday, November 16, 2006
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Default The Nervous System

THE NERVOUS SYSTEM is divied into two main parts:

THE CENTRAL NERVOUS SYSTEM consists of the brain and spinal code,which lies within the bony cases of the skull and spine.THE parts of the nervous system outside the skull and spine made up the peripheral nervous system.THE PHERPHERIAL NERVOUS SYSTEM largely consists of the nerve fibers,or axon,which carry nervous impulses from the sensory recepter of the body inward to the nervous system and carry nervous impulses for the movement of the muscles and exication of certain glands outward from the central nervous system.THE PERIPHERAL NERVOUS SYSTEM has TWO DIVISION:

THE SOMANTIC NERVOUS SYSTEM motor fiber activtes the striped muscles of the body,such as those that move the arms and legs,while the sensory fiber of this system come from the major receptar organs of the body,the eyes the ears,the touch receptor,and so on.

THE AUTONOMIC NERVOUS SYSTEM MOTOR FIBERS activate the smooth muscles of the body such as the stomach,cause secretion from certain glands such as the salivery gland and regulate activity in the special type of muscles found in the is thus a smooth muscles, glanduater and heart muscles system.SENSORY FIBER in the autonamic system carry information from the internal bodily organs that is perceived as pain warmth cold or pressure.THE AUTOMAMIC SYSTEM in its turn has two subdivision:

IN GENERAL the sympathitcs system is active in state of arousal and in streesful situation:the parasympathitics system is active in resting and quiet states.

THE SPINAL CODE AND BRAIN STEM are like a long stalk protuding from the higher part of the central nervous system the forebrain,THE BRAIN STEM consists of the three division:the medulla,the pons,and the midbrain.THE SPINAL CODE AND BRAIN STEM control and regulate bodily functions such as breathing that are necessary for life. They also begin the processing of the sensory information from the enviorment and provide pathways by which this information can be carried to the forebrain.Furthermore no movement of the body can occure witout the activation of the certain neurones,called moto neurones,in the spinal code and brain stem.The forebrain sends nerve impulses down pathways in the spinal cord and brain stem to excites the motoneurones.

OFF TO THE back of the brain is a large complesx structure called the cereblum.This structure receive sensory and other outputs from the spinal code ,brain stem and forebrain;It process this information and then send outputs to many parts of the brain to help make our movement precise,coordinated and smooth.

in the centre AND CORR OF THE brain stem running from medulla up to the mid brain is a compex region containing many small clumps of neurones and numbers of long and short fibers.The appeareance of this regin reminded early anatomist of this region thus this region was called the reticuller formation.The fibers and nerve cells of the reticuler formation concernend with corticial arousal are therefore known as the ascending reticuller activating system.

NERVOUS CELLS OR NEURONS are the information carriers of the nervous system. neurones came in many sizes and shapes,but they have certain features in common.Each has a cell body that contain the machinery to keep the nervous cell alive,and each has two types of fiber ,DENDRITES AND AXON
The dendrites are usually relatively short and have many branches,which receive stimulation from other neurones.THE axon on the other hand is often quiet long and its function is to conduct nerve impulses to other neurones or to musles and glands.SInce the dendrites and axon receive information that is then conducted along the axon.
BY USING FINE WIRES OR or fluid filled glass tubes known as microelectrode,neurophysiologists have shown that nerves impulses are electrical events of very short duration that move along the axon.AS the electrical activity moving along the axon reaches and passes the microelectrodes The recording device receiving a quick sharp,electricial pulses this is the nerve impulse because it is brief and sharp,it is called the spike.when the neurone is resting and not conducting anerve impulse the inside of the cell has negative charge.A stimul which exicts the cell will make the inside charge a little less negative.
JUST ABOVE THE mid brain forming akind of expanded bulb on top of the brain stem, is the region of the forebrain known as thelamus. THE thelamus lies between the two cerabul hempashire and is covered by them.FOR this reason it cannot be seen from outside, and brain must be cut open to show it.THE talalmus contain many grouping of the nerve cell called nucles.SOME of these nucles received input from the seeing and heering and pressure pain temparture body position and tastes senses;
LYING BELOW THE thalamus is the small vital area of the brain known as the hypothalamus.ITS importance to psycologhist is that it contain nucles and fiber tracts whioch are related to the motivation behaviour of biologhicial sort.SO HYPOTHALAMUS is playing vital role inthe regulation of the eternal enviorment of the body.THE term internal enviorment refers to the condition inside the body. especially the chemicial compasition of the blood and other fluid that bath body cells.BLOD temparture,the concentration of salt in the blood and the concentration of the chemical messenger called harmones and other chemicial in the body are monitiored and sensed by different specialized neurones in the hypothalamus.THE hypothalamus also receive report about the state of the internal enviorment from other bodily organ.THE nerves system is linked to the glandular system of the body by the connection between the hypothalamus and the pituatry gland.
MOST OF WHAT WE SEE when we look at the brain is the outside of the large structure known as the cereblum.THE human cerebum waight about 1,400 grams.THE cerebulm is divided into two cereblu hempashire,one on each side of the head,by adeep cleft and fissure called the lognitidual fissure. each hempashire is covered by the cerebul cortex,a sheet of neurone averging aboutb one and half millimetersin thickness and contaning billion of neurones.AS you look out side the cereblum the cerebul cortex look likes rumpled piece of cloth with many ridges and valleys,ABOUT two third of the cerebal cortex is in the sulci and fissure of the brain and thus cannot be seen when we look at the brain.
SOME OF THE nules of the thalamus and hypothalamus and cerebum are interconnected to form the kind of ring and border around the lower portion of the forebrain.this group of structure is known as the limbic system.

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