-The nervous system is a very complex system in the body. It has many, many parts. The nervous system is divided into two main systems, the central nervous system (CNS) and the peripheral nervous system. The spinal cord and the brain make up the CNS. Its main job is to get the information from the body and send out instructions. The peripheral nervous system is made up of all of the nerves and the wiring. This system sends the messages from the brain to the rest of the body.
-The peripheral nervous system consists of the nerves that lie outside the brain and the spinal cord. These nerves carry impulses like sensations and information from the body to the spinal cord and from the spinal cord to the body. Thus, the peripheral nervous system connects the CNS to the muscles of the body.
-The central nervous system (CNS) is the processing center for the nervous system. It receives information from and sends information to the peripheral nervous system. The two main organs of the CNS are the brain and spinal cord. The brain processes and interprets sensory information sent from the spinal cord. Both the brain and spinal cord are protected by three layers of connective tissue called the meninges. -The function nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory.
Central Nervous System
the brain is one of the most important organs in the human body system. It is the center of all commands. It monitors all the conscious and unconscious processes of the body. The brain coordinates various organs of the body and controls all the voluntary movements in the body. The brain is the organ that helps you remember things, learn, understand, think, create, talk, hear, taste, etc. The brain is divided into three segments, that is, fore brain, mid brain and the hind brain. The fore brain consists of the cerebral hemispheres and olfactory lobes. The mid brain is the region that mostly contains optic lobes, and the hind brain is the region that includes the cerebellum and the medulla oblongata. The pituitary gland is present in the lower side of the fore brain. It is called the ‘master gland’ as it regulates the function of many other glands in the body.
The spinal cord is a bundle of nerves that run down the back from the brain in the spinal column. The spinal cord is about 40 cm in length and as wide as the thumb. The function of the spinal cord is to relay all the impulses, information and sensations from all around the body, internally and externally, to the brain. If the spinal cord gets affected due to an injury, it may sever some or most of the connections between the brain and other parts of the body, leading to paralysis in different parts of the body like the upper and lower limbs.
Peripheral Nervous System
The 31 pairs of spinal nerves branch off and reach out to different parts of the body and perform different functions. The nerves of the cervical region supply information to the back of the head, neck, shoulders, arms, hands and the diaphragm. The nerves of the thoracic region supply information to the chest and some parts of the abdomen. The lumbar region nerves cover the lower back, parts of the thighs and the legs. The nerves of the sacral region provide information to the buttocks, most of the leg, feet, anal and genital area.
Somatic and Autonomic Nervous System
The PNS is further divided into the somatic nervous system and the autonomic nervous system. The somatic nervous system contains sensory (afferent) neurons that carry information from organs/muscles to the CNS, and motor (efferent) neurons that carry information from the brain and spinal cord to muscles of the body. Sensory neurons provide the brain all the information regarding the environment. The somatic nervous system plays an important role in transmitting the information and controlling voluntary movement.
Sympathetic and Parasympathetic Nervous System
The autonomic system regulates the involuntary body functions like respiration, heartbeat, blood flow and digestion. It is further subdivided into the sympathetic nervous system which regulates your flight-or-fight responses, and the parasympathetic system that helps regulate various normal functions of the body, for example, sexual arousal, salivation, lacrimation (shedding tears), urination, digestion, and defecation. Functions of the parasympathetic nerves include constriction of eye pupils, increase in secretion of saliva, increased digestion, decrease in heartbeat, etc. The sympathetic nerve functions involve dilation of eye pupils, sweating, production of goose bumps, decrease in digestion, etc. One of the important nerves, the vagus nerve is divided into sympathetic and parasympathetic nerves.
The sensory system is also a part of the nervous system. Sensory systems for vision, hearing, somatic sensation (touch), taste and olfaction (smell) work with the help of the sensory receptors, neural pathways and certain parts in the brain that help process sensory information. When you feel cold or hot, it is the sensory neurons that are doing their work. The motor neurons are reactors, that help the body react to different environment. For example, the immediate pulling away of your hand when you touch a hot stove is a motor neuron reaction. The somatic motor neurons convey orders to the muscles.
A subsystem of the peripheral nervous system is the enteric nervous system. Normally, it communicates with the CNS but studies show that it works autonomously too. It regulates the gastrointestinal system in the body.
Multiple Sclerosis| A chronic disease of the nervous system that can affect young and middle-aged adults. The course of this illness usually involves recurrent relapses followed by remissions, but some patients experience a chronic progressive course.| The myelin sheaths surrounding nerves in the brain and spinal cord are damaged, which affects the function of the nerves involved.
Also associated with aging.| Tremor, rigidity and poverty of spontaneous movements.
The commonest symptom is tremor, which often affects one hand, spreading first to the leg on the same side then to the other limbs. It is most profound in resting limbs, interfering with such actions as holding a cup.
The patient has an expressionless face, an unmodulated voice, an increasing tendency to stoop, and a shuffling walk.| Sciatica| A common condition arising from compression of, or damage to, a nerve or nerve root.| Usually caused by degeneration of an intervertebral disc, which protrudes laterally to compress a lower lumbar or an upper sacral spinal nerve root.The onset may be sudden, brought on by an awkward lifting or twisting movement.| Pain felt down the back and outer side of the thigh, leg, and foot. The back is stiff and painful. There may be numbness and weakness in the leg.|
A. The cortex gets its name from the Latin word for “bark” (of atree).B. There are approximately 100 billion neurons in the human brain.C. The average human brain weighs about 3 pounds (1.4 kilograms).D. Unlike humans, the octopus does not have a blind spot.E. The average length of the adult spinal cord is 45 cm for men and 43 cmfor women.