The Nervous System

By Khamal Iwuanyanwu

Nervous System

• The Nervous System is the part of the body which controls its voluntary and involuntary actions and transmits signals between different parts of the body.

• The nervous system is usually broken down into two categories: the Peripheral Nervous System (PNS) and the Central Nervous System (CNS)

Central Nervous System• The Central Nervous System, or CNS

for short, is the center for the processing of information gathered by your Peripheral Nervous System. The two main organs of the CNS are the Brain, which controls thinking, motor skills, balance, coordination, breathing, heart rate, the processing of sensory information, etc.; and the Spinal Cord, which acts as a center for transmission of stimuli and information to and from the brain and other body organs. Both are protected by three layers of connective tissue called meninges.

Peripheral Nervous System

The Peripheral Nervous system, or PNS, is made up of two different cells; Cells that carry information to the CNS (sensory nervous cells) and cells that carry information from the CNS (motor nervous cells). Motor nervous cells are broken up into two sub-categories; the somatic and autonomic nervous systems. The somatic control voluntary muscles such as skeletal muscles and the autonomic controls the involuntary muscles such as the smooth and cardiac muscles.

Neurons

The cells that make up the nervous system are called neurons. They are specialized to carry information through electrochemical processes. Neurons have specialize cell parts called dendrites and axons. Dendrites bring electrical signals to the cell body and axons take information away from the cell. Neurons can also communicate with each other.

There are 3 different types of Neurons:• Sensory neurons: send information

from sensory receptors (in skin, eyes, nose, tongue, ears) TOWARD the central nervous system.

• Motor neurons: send information AWAY from the central nervous system to muscles or glands.

• Interneurons: send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

Reflexes

• A reflex is a simple, but vital, way to relay information that never reaches conscious awareness. If your neurons don’t have enough time to send and receive a message from the brain, it will send a message to another neuron to form a reaction instead.

HOW EXTERNAL STIMULI GETS TO THE BRAIN

EAR

EXAMPLE:

Diseases and Disorders• Alzheimer's disease: is a

neurodegenerative disease. That means that nerve cells in the brain start to die. This will impair memory, thinking, behavior, ability to understand, ability to talk, etc. because you won’t have as many areas in the brain where the external stimuli from the world can be processed and you can’t send information from dead brain cells.

• Acute Spinal Cord Injury: occurs when traumatic injury that results in a bruise, partial tear, or complete tear in the spinal cord. This can cause severe and permanent disability and possibly death. These severe outcomes are due to the fact that the spinal cord connects different nerve from different body parts to the brain. If they are severed, they will not function. If it were the heart that was not getting the brains signal to beat, you would die almost instantaneously.

Bibliography• The Nervous System. University of Miami Health system. http://

uhealthsystem.com/health-library/neuro/disorder/acute• Bio Text book :D• Vsauce. “How does the brain work..” YouTube. Web. \• Neurology. Peter Pressman, M.D. http://

neurology.about.com/od/NervousSystem/a/What-Is-A-Reflex.htm