In this article, I will give general features in the anatomy and function of the nervous system briefly. Anatomically speaking, the nervous system is divided to a central part and a peripheral part. The central part of the nervous system iscomprised of the brain and the spinal cord. The peripheral part of the nervous system is composed of the cranial nerves which are considered part of the peripheral nervous system although they originate in the brain.
In addition, the spinal nerves and the peripheral nerves are also part of the peripheral nervous system. Also neurons cell bodies which are called ganglia and which are located outside the central nervous system are considered part of the peripheral nervous system. The brain is situated in the cranial cavity covered by the cranial bone which gives it protection against trauma. The spinal cord is located in the spinal canal which also gives it protection against trauma.
From a functional point of view the nervous system is divided to a somatic nervous system and an autonomic nervous system. The somatic nervous system is comprised of somatic parts of the central and peripheral nervous system. In particular it supplies skeletal muscles with sensory and motor innervation.
The autonomic nervous system consists of autonomic nerves of the central and peripheral nervous system. It provides motor innervation that is involuntary to glands of the body as well as to smooth muscles inside the body such as the pancreas and the adrenal gland. The autonomic nervous system is further divided into two parts. These are the sympathetic and parasympathetic nevous systems.
Usually and with few exceptions the sympathetic division of the autonomic nervous system is stimulated in stressful conditions such as anxiety and panic attacks. The parasympathetic nervous system functions physiologically in the opposite direction. Its main stimulation is for the gastrointestinal system in which it enhances the process of digestion. When the sympathetic nervous system is functional usually the parasympathetic division is off and the reverse is true also.
The brain and spinal cord contains a liquid material that is called cerebrospinal fluid. This liquid gives support to the brain and spinal cord against sudden trauma such as shock. The cerebrospinal fluid in the brain is located in spaces within the brain and which are called ventricles.
These ventricles are four in number and communicate with each other through canals. Obstruction in these canals is of clinical significance as it can cause the medical condition which is called hydrocephalus or brain edema. The brain is the site where the muscles coordination occurs in the cerebellum and the basal ganglia. In addtion, emotional situations are processed in the limbic system of the brain.
Motor activities of muscles in the extremeties can be either controlled from the motor areas in the brain cortex or through sites in the spinal cord. A paralysis of the right hand for example can signify a disorder in the spinal cord in the cervical region or due to a disorder in the motor cortex of the opposite direction.
Another example is problems with walking manner or gaits can be ascribed to disorders in the lumar region of the spinal cord or due to a damage to the cerebral cortex in its motor area in the opposite side of the site of disorder in the legs. The spinal cord is especially important for the refexes it can make to muscles of the extremeties.
Hyporeflexia usually signifies a damage to in the spinal cord that supplies the muscles of the reflex by motor innervation. Hyperreflexia usually signifies upper motor neurons damage in the brain. Motor dysfunction in the extremeties can also sometimes signify damage to certain areas of the brain such as the cerebellum and the basal ganglia.
Examples include parkinson disease and huntington’s corea. Memory in humans is processed in a site in the limbic system which is called the hyppocampus. Damage to the brain can also occur due to accumulation of toxic compounds in the blood. In wilson disease the accumulation of copper in the basal ganglia of the brain can cause damage to this are of brain tissue.