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| Sunday, August 06, 2006 |
| The Nervous System |
1. NERVOUS SYSTEM
1.1 The nervous system anatomy is divided into:
1. central nervous system : the brain and spinal cord
It processes incoming sensory information and sends outgoing motor commands.
2. peripheral nervous system: the nerve cells that control voluntary and involuntary movements, includes all neural tissue outside the central nervous system divided into motor and sensory systems
The motor system is divided into the somatic (or skeletal) nervous system and the autonomic nervous system.
o The skeletal motor system allows voluntary control over skeletal muscle with a few exceptions.
o The autonomic nervous system is largely involuntary and controls cardiac and smooth muscles and glands.
In addition to the brain and spinal cord, principal organs of the nervous system are:
Eyes, ears, sensory organs of taste, sensory organs of smell, sensory receptors in skin, joints, muscles, and other parts of the body
1.2 Nervous system physiology (function)
The nervous system is a complex, highly specialized network. It organizes, explains, and directs interactions between human and his environment.
The brain as the main central of the nervous system controls:
-Sight, hearing, taste, smell, and feeling (sensation).
-Voluntary and involuntary functions, such as movement, balance, and coordination.
-the actions of most other body systems, such as blood flow and blood pressure.
-The ability to think and reason by being conscious and have thoughts, memories, and language.
Brain cell are sensitive to oxygen depletion, which can cause irreversible damage to the brain.
Impulses go to the central nervous system through sensory nerves and are carried away from it by the motor nerves.
A nerve impulse is an electrical change within a nerve cell or fiber; measured in millivolts, it lasts a few milliseconds and can be recorded by electrodes.
Reflexes is movement occur in direct response to an outside stimulus; thus, a tap on the knee causes a jerk, and a light shone into the eye makes the pupil contract.
Various nerve terminals called receptors constantly send impulses into the central nervous system. These are of three classes:
-exteroceptors, which are sensitive to pain, temperature, touch, and pressure;
-interoceptors, which react to changes in the internal environment; and
-proprioceptors, which respond to variations in movement, position, and tension.
-These impulses terminate in special areas of the brain, as do those of special receptors concerned with sight, hearing, smell, and taste.
1.3 Possible complication to the system
The symptoms of a nervous system problem depend on which area of the nervous system is involved and what is causing the problem.
Nervous system problems may occur slowly and cause a gradual loss of function (degenerative), or they may occur suddenly and cause life-threatening problems (acute). Symptoms may be mild or severe.
Some serious conditions, diseases, and injuries that can cause nervous system problems include:
~Blood supply problems (vascular disorders).
~Injuries (trauma), especially injuries to the head and spinal cord.
~Problems that cause a gradual loss of function (degenerative) Parkinson's disease. .
~Infections that may occur in the eg: Brain (abscesses).
~Organ system failure. Examples include: Respiratory failure, Heart failure.
A sudden (acute) nervous system problem can cause many different symptoms, depending on the area of the nervous system involved. Stroke and transient ischemic attack (TIA) are common examples of acute problems. You may experience the sudden onset of one or more symptoms, such as:
~Numbness, tingling, weakness, or inability to move a part or all of one side of the body (paralysis).
~Dimness, blurring, double vision, or loss of vision in one or both eyes.
~Loss of speech, trouble talking, or trouble understanding speech.
~Sudden, severe headache.
~Dizziness, unsteadiness, or the inability to stand or walk, especially if other symptoms are present.
~Confusion or a change in level of consciousness or behavior.
~Severe nausea or vomiting.
Most headaches are not caused by serious central nervous system problems. The pain that comes with a headache can range from a throbbing or a piercing pain, such as with a migraine, to severe pain that comes and goes over several days, such as with cluster headaches. Headaches are usually caused by problems with the sinuses, scalp, or muscles of or around the head.
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posted at 12:59 AM   |
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| 8 Comments: |
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