THE NERVOUS SYSTEM
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.
Nerve fibers relaying information to the brain and spinal cord
are called Sensory Nerves.
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
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 unit contains:
SEE DRAWING # 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,
(5) from the Lumbar, Five (5) from the Sacral and One (1) from the
Coccygeal segments of the cord.
SEE DRAWING # 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)
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.
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)
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
(SEE DRAW # 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
Parasympathetic Systems will produce
somewhat of an Opposite Affect.
Constriction of the Pupils,
Adjusts the Lens of the Eye so that Near Objects are more clearly
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.