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The nervous system is the organ system in the human body that is responsible for bodily functions such as muscle mechanisms, reception of stimuli and nerve impulse transmission. Its main components are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).


I.                   Introduction

II.                The Central Nervous System

a.       The Brain

b.      The Spinal Cord

III.             The Peripheral Nervous System

a.       The Autonomic and the Sensory-Somatic Nervous Systems

b.      The Motor and Sensory Nerves

IV.             Ailments and Injuries of the Nervous System

a.       Head Injuries

b.      Stroke

c.       Epilepsy

V.                Conclusion

The Nervous System

            The nervous system is often described as a “biological information highway” (Biology Online, 2000). This portrayal most likely stemmed from the fact that the nervous system is responsible for directing all biological processes in the human body, including movement. It has also the capacity to receive and interpret information through electrical signals. The nervous system is made up of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) (Biology Online, 2000).

The Central Nervous System

            The Central Nervous System (CNS) is made up of the brain and the spinal cord. The brain is tasked with processing and initiating responses from nerves throughout the entire body. The spinal cord, meanwhile, facilitates the passage of sensory information to and from the brain. From the CNS, information will then proceed to the peripheral nervous system (Answers, 2008).

The Brain

            The brain is regarded as the center of the CNS. Although it weighs only less than 3 pounds, it is composed of almost 100 billion nerve cells. The brain regulates both voluntary and involuntary bodily procedures such as breathing and movement, respectively. This organ is likewise known as the seat of thought, creativity and consciousness (Discovery Communications, 2000).

            The brain is made up of the following regions: the forebrain, the midbrain and the hindbrain. The forebrain controls intelligence, memory, personality, emotion and the ability to speak, feel and move. The midbrain coordinates the transfer of sensory information from the brain to the spinal cord. The hindbrain is responsible for bodily functions such as heart rate, breathing, swallowing, blood pressure, blinking and digestion (Nemours Foundation, 2008).

The Spinal Cord

            The spinal cord is made up of nerves that facilitate the exchange of nerve impulses between the brain and the rest of the body. Upper motor neurons (UMNs) refer to nerves that lie within the spinal cord. UMNs are responsible for the transmission of messages between the brain and the spinal nerves that are located along the spinal tract. Lower motor neurons (LMNs), meanwhile, are spinal nerves that branch out to the rest of the body from the spinal cord. LMNs transmit messages to and from the brain in order for the body to be able to come up with actions including muscle movement and sensation (Spinal Cord Injury Resource Center, n.d.).

The Peripheral Nervous System

            The peripheral nervous system is composed of neurons or nerves that do not constitute the spinal cord or the brain. Although the nerves that belong to the PNS have their length outside the CNS, their ganglia (cell bodies) are inside the latter. PNS neurons both have myelinated and unmylinated axons. The second cranial nerve or the optic nerve is regarded as part of the brain, but all the cranial nerves are parts of the PNS (Multiple Sclerosis Encyclopedia, 2008).

The Autonomic and the Sensory-Somatic Nervous Systems

            PNS is divided into two parts – the autonomic nervous system (ANS) and the sensory-somatic nervous system (SNS). ANS, made up of both motor and sensory nerves running to and from the CNS, is responsible for the body’s involuntary functions such as heart activity and the production of hormones. The sympathetic nervous system and the parasympathetic nervous system further constitute ANS. SNS, meanwhile, consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves which allows movement and the reception of conscious information from the senses (Multiple Sclerosis Encyclopedia, 2008).

The Motor and Sensory Nerves

            The types of neurons that are present in the PNS are the motor and the sensory nerves. The motor nerves are attached to the muscles of the face, torso, internal organs and limbs. They facilitate the movement of body parts by carrying nerve signals to the CNS. Sensory nerves, on the other hand, are found in the sensory organs and sensors in the muscles, internal organs and the skin. They convey sensory information such as heat, touch and sound from the various organs of the body (Multiple Sclerosis Encyclopedia, 2008).

Ailments and Injuries of the Nervous System

            Akin to all other systems in the human body, the nervous system has its share of illnesses and injuries. Below are some examples:

Head Injuries

            The most common head injuries are concussion and contusion. A concussion is a brain injury that is a result of a blow to the head. Its symptoms include headache, vision disturbance, dizziness, nausea and loss of balance. Treatment for concussion usually consists of rest and painkillers (AAFP, 2007).

            A contusion is a more serious form of head injury. It occurs when, after a blow to the head, the brain bangs against the skull. This results in nerve damage, bruising of the brain and the tearing of the blood vessels. Some of the symptoms of a contusion are dizziness, nausea and memory loss, as well as difficulty in thinking or concentration and blurred vision. A contusion is treated often through rest, painkillers and adjustments to the patient’s lifestyle when still recovering (MedicineNet, 2008).


            The brain derives oxygen and nutrients from the blood. When blood flow to the brain is interrupted, its parts that are deprived of blood die. The most common effect of a stroke is permanent brain damage, which, in turn, leads to the permanent disability of the patient. Stroke survivors, therefore, experience difficulties in speech and in everyday activities such as walking and eating (MSN Encarta, 2008).


            Epilepsy is a chronic brain disorder that is characterized by disturbances in the normal electrical activity of the brain. It may be brought about by genetic conditions, stroke, a head injury, lead poisoning or a brain tumor. The symptoms of epilepsy include nausea, sudden sweating or flushing, seizures and uncontrollable jerky motions of a body part. Although it has no cure, its symptoms can be treated through drugs, surgery or a special diet (MSN Encarta, 2008).


            The nervous system has a very important role in the human body. It is like a computer program which allows all the other organ systems in the body to function harmoniously. Thus, it should be properly taken cared of by eating a balanced diet, wearing protective gear while playing sports and seeing a doctor as soon as signs of disorders appear. No amount of money can take the place of a healthy body.


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Multiple Sclerosis Encyclopedia. (2008, January 22). Peripheral Nervous System. Retrieved

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Nemours Foundation. (2008). Brain and Nervous System. Retrieved August 14, 2008, from


Spinal Cord Injury Resource Center. (n.d.). Spinal Cord 101. Retrieved August 14, 2008,


Photo Credits (2008). Nervous System Diagram.png. Retrieved August 13, 2008, from


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Appendix A

The Human Nervous System

Appendix B

The Central Nervous System (CNS)

Appendix C

The Peripheral Nervous System (PNS)

Appendix D

The Autonomic Nervous System (ANS)

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