The Human Nervous System

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The nervous system is a complex connection of nerves and unique cells (neurons) that are responsible for transmitting signals to and from various body parts.

Classification Of the Human Nervous System

The nervous system is basically classified into Central nervous system and Peripheral nervous system. The central nervous system manages the whole body and the nervous system. It is only because of the nervous system’s efficient coordination between the different organ systems that we can feel sensations like pain or cold.

The central nervous system (CNS) consisting of the brain, spinal cord.
The peripheral nervous system (PNS) consisting of sensory neurons, ganglia (a cluster of neurons) and nerves.

The Human Nervous System - Testbook

The nervous system is also classified on the basis of functionalityinto:

The somatic nervous system(SNS) responsible for conscious perception and voluntary motor response. For example, getting startled when someone sneaks up on you. That was not decided by you, nonetheless, it is a motor response involving skeletal muscle contractions.
The autonomic nervous system( ANS) responsible for involuntary body movements usually with the objective of maintaining body homeostasis. For example, sweating when your body is hot is to cool the body down.
The enteric nervous system(ENS) responsible for controlling smooth muscle and glandular tissue in the digestive system.

Let’s understand in detail the Central Nervous system and the Peripheral Nervous System –

Central Nervous System

So far you know that the nervous system is classified into Central and Peripheral nervous system. Neurons are the basic unit of the nervous system. These neurons are classified into three types – Sensory, motor and association/connecting neurons. The main function of the central nervous system is to keep control over the entire body and the nervous system. The Central Nervous consists of two main parts – Brain and Spinal Cord. These two parts are covered by three membranes mentioned below:

Durameter which is the outer layer/membrane.
Arachnoid membrane is the middle layer.
Piameter is the innermost membrane

Let’s study in details the two main parts of the central nervous system i.e. brain and spinal cord –

Human Nervous System - Testbook

Brain

It is entirely covered by a protective layer called meninges. To protect the brain from injuries it is covered by a bony box termed as the cranium. Furthermore, the brain is divided into three parts Forebrain, Midbrain, and Hindbrain.

Forebrain

The forebrain is made up of the Cerebrum, Thalamus, and Hypothalamus. The Cerebrum is associated with memory, wisdom, knowledge, will power and thinking. Thalamus regulates cold, heat and pain. Whereas, the Hypothalamus controls the sweat, blood pressure, secretion of hormones, thirst, hunger, etc.

Midbrain

Midbrain manages the main function of hearing and vision.

Hindbrain

Hindbrain includes parts like Cerebellum, Pons and Medulla. The human body posture is managed by Cerebellum. The Pons acts as a bridge between the spinal cord and brain. Medulla regulates important functions like respiration, heart rate, sneezing, and coughing, etc.

Spinal Cord

The spinal cord starts from the medulla oblongata and extends towards the neural canal of the backbone/vertebral column.
There are 31 pair of spinal nerves that arises from the side of the spinal cord.
The function of the Spinal cord is to control all the reflexes that take place below the neck.
Furthermore, the spinal cord conducts the sensory impulses arising from the muscles and skin to the brain.
Vertebrae protect the spinal cord from any kind of injuries.
The spinal cord also conducts the motor responses from the brain to the muscles present in the limbs and trunk area.

Peripheral Nervous

The peripheral nervous system consists of the nerves that arise from the brain and spinal cord. The human body has 31 pairs of spinal nerves and 12 pairs of cranial nerves. The peripheral nervous system is divided into the somatic nervous system and autonomic nervous system.

Somatic Nervous system

Somatic Nervous system includes the peripheral nerve fibers that convey the sensory information to the motor nerve fiber and central nervous system.

Autonomic Nervous system

The autonomic nervous system consists of three sections namely, the sympathetic, parasympathetic and the enteric nervous system. It regulates the smooth muscle of the viscera (internal organs) and glands.

What is the Function of the Nervous System?

Essentially, the primary function of the nervous system is to send signals either from one cell to another or from one body organ to another.
There is more than one way in which cells send signals. The broadcast method of signaling is done through the endocrine system where the hormones are released into the circulatory system. Through the nervous system, the signaling is done “point to point”. Hence, the nervous system entails advantages of being more specific, accurate and speedy.
The human nervous system controls the human body. The body reacts to stimulus because the nervous system extracts these external signals via sensory receptors and the central nervous system processes these signals and decides on an appropriate response and then sends an output signal to the concerned body part to activate the response.

Diseases Associated with the Nervous System

Diseases occurring in the nervous system are mainly due to a genetic defect, a result of traumatic experiences, infections, or ageing. Diseases associated with the peripheral nervous system are mainly due to stoppage in nerve conduction. Illustrated below is the list of diseases along with their symptoms, treatment and precautionary measures.

Name of disease	Symptoms	Treatment	Prevention
Alzheimer’s	Associated with failing memory and deterioration in reasoning ability.	Treatments exist only to slow down the symptoms because the death of brain cells cannot be reversed.	Regular physical exercise can reduce the risk of Alzheimer’s by at least 50%. We should keep a check on our thyroid and sex hormone levels and eat healthy fats.
Leprosy	– Infectious disease and is associated with skin lesions and no sensation to touch – numbness in hands, feet and legs – Muscle weakness, as evident from symptoms such as foot drop.	Early recognition is important as early treatment limits the damage. Medications exist to kill the microorganisms and reduce symptoms.	Doctors recommend annual examinations for at least five years after the last contact with an infectious person.
Polio	Fever, headache, vomiting, diarrhoea, fatigue, neck stiffness, muscle stiffness, abnormal sensations in an area, muscle spasms	The motive of the treatment is to control the growth of symptoms while the infection runs its course.	Polio can be completely prevented and immunised against through vaccination. The polio vaccine needs to be given at age 2 months, 4 months, and between 6 and 18 months of age with a booster between 4 and 6 years of age.
Rabies	Preliminary symptoms are mild and varied. The victim alternates between moods of agitation and calm; experiences muscle spasms of mouth and pharynx.	Injections or immunoglobulin vaccine.	Rabies can be prevented by vaccinating dogs and cats as required by law. We should not keep wild animals as pets and stay away from strays.
Epilepsy	Epilepsy is a sudden rush of electrical activity in the brain. Mild seizures may be difficult to recognise and could span a few moments wherein you lack awareness. Stronger seizures will lead to spasms and uncontrollable muscle twitches. Victims either become confused or lose consciousness.	The treatment plan depends on the severity of seizures. Some options are anti-epileptic medications, ketogenic diet, vagus nerve stimulator and even brain surgery of the affected area.	We should keep away from alcohol and drugs and maintain a regular sleep schedule. Vitamin D tablets can be consumed and regular exercising would also be beneficial. A head injury can be prevented by wearing helmets while riding at all times. Regularise your sleep cycle and ensure you stick to it.
Parkinson’s disease	Parkinson’s disease commences usually with a tremor in the hand. Other symptoms include slow movement, stiffness, loss of balance, speech impairment.	Treatments prevent symptoms from aggravating. In more advanced cases, surgery is advised. A speech pathologist will correct the problems associated with speech.	Consume organic products which do not contain pesticides and insecticides. Have green tea and also incorporate Vitamin D3 and Omega 3 Fatty Acids in our diet. Regular aerobic exercise can also be beneficial.
Cerebral Palsy	Symptoms of cerebral palsy start to show in the first three years of life. These include overdeveloped or underdeveloped muscles, leading to stiff or floppy movements; crawling abnormally, limited movement, preferring one side of the body to another, lying down awkwardly.	The treatment varies from individual to individual. A care plan addresses the needs of the child and the parents. As the child gets older, the plan is reviewed and revised. The aim is to provide maximum possible independence to the child.	Unfortunately, cerebral palsy cannot be completely prevented during pregnancy or delivery. However, expecting mothers should try to deliver a healthy baby through regular visits to their gynecologist. Identifying potential Rh incompatibility between mother and child can also help prevent cerebral palsy in the unborn child.

This note on one of the most vital systems of the human body will help you in your static GK preparation. However, it is important for the candidate to be prepared with the other human body processes as all work hand-in-hand.