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THE NERVOUS SYSTEM EXPLAINED

An Understanding of the Human Nervous System is necessary for the Traditional Martial Artist. So that he may apply Strikes or Pressure to certain points of the body for Self-Defense and Healing purposes.

Introduction:
The human system consists of a Brain and Spinal Cord which are the central receiving, integrating and sending components of a communications network that spreads to all parts of the body. Some of the nerve fibers that make up this "Network" carry information from the skin, such as touch, pain or temperature. Others transmit degree of stretch of a muscle, while others relate the condition of the various organs of the body. This information is continually fed into the spinal cord and the brain.
Nerve fibers relaying information to the brain and spinal cord are called Sensory Nerves.
Nerve fibers that transmit the commands of the brain to the tissues that perform the action are called Motor Nerves.

NOTES: Average adult male brain weighs approximately three lbs., while the adult female about 10% less.

The structural unit of the nervous system is the Neuron. The Neuron unit contains:

  • Cell body

  • Dendrites

  • Nucleus

  • Axon

  • Termination's

SEE DRAWING # 1

FIG.1


There are twelve (12) pairs of Cranial Nerves and Thirty-one (31) pairs of Spinal Nerves.
The Cranial nerves arise from the brain.
With the Spinal nerves, Eight (8) pairs arise from the Cervical part of the Spinal cord, Twelve (12) from the Thoracic, Five (5) from the Lumbar, Five (5) from the Sacral and One (1) from the Coccygeal segments of the cord.


SEE DRAWING # 2

FIG.2


The Spinal Nerves are named according to their relationship to a Particular Ventral Body. The First Cervical Nerve appears between the base of the skull and the Atlas or First Cervical Vertebra. The Eighth Cervical Nerve emerges between the Seventh Cervical Vertebra and the First Thoracic Vertebra.
Thereafter, a Spinal Nerve is named from the Vertebral that lies immediately above it as it exits from the Vertebral Canal.
For Example: The 11th Thoracic Spinal Nerve emerges between the 11th and 12th Thoracic Vertebra.
The spinal cord consists of a small Central Canal surrounded by masses of nerve cell bodies that are called, because of their color, Gray Matter. External to or outside of the Gray Matter is an area of White Matter which consists of Axons. These Axons are grouped into Tracts, which Ascend and Descend in the Spinal Cord. 

(SEE DRAW # 3)

FIG.3


Ascending fibers going to the brain are called Sensory Tracts. Descending fibers called Motor Tracts go from the brain to end in the gray matter of the spinal cord. The point of contact between the terminal ends of the axons and the muscle fiber or dendrite is called a Synapse.

Sensory fibers from the Periphery of the Body entering one side of the spinal cord will cross to the opposite side of the cord before they end in the brain. In a similar manner, motor fiber arising from one side of the brain, soon cross to descend in the opposite side of the spinal cord. Destruction of the Motor Areas in the Left Side of the Brain results in the Loss of Voluntary Movement in the Right Side of the Body.

KNEE REFLEX


From a sitting position, cross your legs at the knees and sharply tap the Tendon just below the knee cap. As the knee is already bent and the tendon somewhat stretched, the force of the tap further stretches the tendon, resulting in a sudden kick or extension of the leg that is impossible to control.
Specialized nerve endings in the tendon are stimulated when the tendon is stretched, and the impulse travels along the Sensory Axon in the spinal nerve to enter the spinal cord through the Dorsal Root. The axon synapses with a cell body in the Posterior Horn. This cell body is a component of the connecting neuron, which synapses in turn with a cell body in the Anterior or Ventral Horn. Stimulation of this motor cell results in an impulse that travels along it's axon through the Ventral Root to the spinal nerve, where it reaches the muscle and causes it to contract. Contraction of the muscle straightens the leg.


(SEE DRAW # 4)

FIG.4


This reflex, like most, is protective in nature. Protection against sudden and possibly injurious movements at a joint is afforded without conscious thought. If the sensory stimulus had to reach the brain and travel from the brain down the spinal cord before corrective action could be taken, the result of such delay might be disastrous.
Voluntary movement is the result of the constriction of striated muscle.
There is another motor system with a slightly different anatomical pattern that controls the functions of structures not under voluntary control. This is the Autonomic Nervous System. The autonomic system is subdivided into two systems that produce two different types of Physiological Responses. The Sympathetic and the Parasympathetic systems. The Sympathetic system consists of paired neurons that arise from all the Thoracic and the first two Lumbar Spinal cord segments. Another component of the system is a series of ganglia lying on either side of the vertebral bodies and extending from the bodies united vertically by nerve fibers like so many knots on a string. The ganglia, along with the intervening nerve fibers, form the Right and Left Sympathetic Trunks.
Parasympathetic motor fibers arise from two areas of the Central Nervous System:


(SEE DRAW # 5)

FIG.5


One from the brain and traveling in the Third(3rd), Seventh(7th), Ninth(9th), and Tenth(10th) Cranial Nerves; The other from the Second(2nd) and Third(3rd) Sacral segments of the Spinal cord.

The Sympathetic Nervous System prepares an individual for, Fight or Flight.
Stimulation of this system results in:

  • Dilation of the Pupils,

  • Increase in the Rate and Strength of Contraction of the Heart,

  • Decrease in peristalsis of the Gastro-Intestinal Tract,

  • Diminished blood flow in the skin and gastro-intestinal tract in order to increase the blood flow to voluntary muscles.


At the same time, the nerves of this system cause the Adrenal Gland to secrete Adrenaline into the blood stream. This reinforces the physiologic functions of the Sympathetic Fibers.

Parasympathetic Systems will produce somewhat of an Opposite Affect.
It produces:

  • Constriction of the Pupils,

  • Adjusts the Lens of the Eye so that Near Objects are more clearly defined,

  • Increases the flow of Saliva,

  • Decreases the Rate and Strength of Contraction of the Heart,

  • Increases the flow of digestive juices and peristaltic movements of the gastro-intestinal tract,

  • Permits emptying of the Bowel and Bladder.

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