Brain & The Nervous System

What is the Nervous System

The control centre of the human body lies within the nervous system. As the central processing unit operates for a computer, so does the brain and nervous system work for the human body.

Functions of Nervous System:

The functions of the nervous system are:
1. Keeps us informed of the surroundings through the various sense organs
2. Remembering, thinking & reasoning capability
3. Control & coordination of all voluntary muscular activities
4. Regulation of involuntary activities like breathing & heart beat.

Parts of the Nervous System

1. Central nervous system comprising of the brain & spinal cord
2. Peripheral nervous system comprising of nerves that enter & exit from brain & spinal cord.

Parts of the Central Nervous System

The Brain and Central Nervous System:

The human brain is what separates man from other living beings. The brain is protected within the cranium of the skull. The brain consumes nearly 20% of the oxygen intake of the body. {Yawning is due to lower percentage of oxygen}.

Parts of The Brain

The brain has 3 parts namely the cerebrum, cerebellum and medulla oblongata. The cerebrum is the largest portion and divided into 2 cerebral hemispheres. The outer surface is convoluted with ridges & grooves. These convolutions are basically cell bodies of neurons & gray in color. Higher the number of convolutions indicates higher intelligence & hence gray matter is referred to intelligence. This is also responsible for thinking, reasoning, inventing, planning and memorizing. This also houses the sub-conscious mind. The cerebellum is small in size, has no convolutions but coordinates all muscular activities. Alcohol tends to affect the cerebellum and hence the unnatural movements of an alcoholic. Medulla Oblongata is located at the bottom the brain and controls the activities of internal organs and is responsible for breathing, heart beat & all other involuntary actions. Any injury to this results in instant death.

Brain Functions

All the functions of the other organ systems are controlled and regulated by the brain. Voluntary movements, such as that of the muscles, as well as involuntary movements, like reflexes and the beating of the heart, are controlled by the brain and the other parts of the system.

The Spinal Cord:

This extends from medulla oblongata till down the rib cage. It contains the cerebrospinal fluid which acts like the shock proof cushion.{the shock absorber in our body!). The spinal cord basically controls the reflexes below the neck, conducts sensory impulses to the brain and conducts motor impulses to muscles of trunk & limbs.

Divisions of The Peripheral Nervous System

The peripheral nervous system is divided in two systems namely somatic nervous system & Autonomic nervous system.

The Somatic Nervous System:

This system consists of cranial nerves like the optic & auditory sensory nerves, motor nerves going to the eye muscles and mixed nerves entering & exiting the face & tongue. It also consists of spinal nerves which control & sense the various functions of the body under the neck.

The Autonomic Nervous System: This system consists of a pair of chains of nerves & ganglia on either side of the backbone. It controls the involuntary functions of the body. Autonomic nervous system is influenced by emotions like grief, anger, fear, sexual stimulation etc. This system is also responsible for our reflexes, both voluntary & involuntary. It is in 2 parts namely the Sympathetic & Parasympathetic systems.

The Sympathetic Nervous System and The Parasympathetic Nervous System

The sympathetic nervous system is stimulated by the hormone adrenaline. It prepares the body for violent actions against abnormal conditions. The parasympathetic system is basically concerned with re-establishing normal conditions after the violent act is over. For example- In a fear/anger situation the heart beats faster due to the sympathetic system but the parasympathetic nervous system starts retarding the heart beat to normal once the act is over.

Brain and Nervous System Disorders

There are diseases that are associated with the nervous system. Often, when this system is affected, there are consequent effects to the rest of the body. Disorders of the brain and nervous system may be acquired, while a number of them are congenital. There are mental and behavioral manifestations of brain disorders, like mental retardation, and there are also physical symptoms of such ailments, like cerebral palsy.

Cerebral palsy is one of the disorders of the nervous system which can be acquired by an unborn child during prenatal development. A person with this condition has problem with the motor areas of the brain, so his movements are uncoordinated. Partial paralysis is also a symptom. About 65% of patients with cerebral palsy may be also mentally retarded, with possible learning disabilities and communication problems. There is no treatment for the disease, but there is therapy to help the patient with movement. Nearly half a million persons in the United States are diagnosed with cerebral palsy. This is a central nervous system disorder.

Epilepsy is another disease of the nervous system which is characterized by seizures along with other symptoms that affect muscular movement. According to the Epilepsy Foundation, there are about 3 million persons in the United States who experiences seizures from epilepsy. This condition is 10% likely to occur in children who are diagnosed with mental retardation or cerebral palsy. Around 22% of stroke patients and 10% of persons with Alzheimer’s disease may experience epilepsy. Every year, an estimated 200,000 new cases of the condition are diagnosed, for both children and adults. This is also a central nervous system disease.

Paralysis may be temporary or permanent loss of sensation and motor control in specific parts of the body. This may be because of damage to major nerves or fatal injuries to the spinal cord. Paraplegia is when a person is unable to feel or move both his lower limbs. Hemiplegia is when the patient has no sensation on an arm or leg of the same side of the body. A quadriplegic patient has not sensation on the upper limbs and lower limbs. About 92 percent of sports-related injuries result in a person with quadriplegia, according to some studies.