Nervous System The basics
Can we truly understand all there is about the central nervous system? Some say that it crosses over into the religious aspects of our lives. Science still discovers new and interesting things about the human body or chemical machine of human anatomy all the time. But, just like all my articles I am going to focus on what the massage practitioner needs to know in order to pass the national exam or simply review what should already be known.
Nervous system - The nervous system is a communications system for the body. Unlike the endocrine system its much faster because its signals can more at the speed of light. The central nervous system is made up of the brain and spinal cord also known as the dorsal section of the body in general terms and the Peripheral Nervous System which have nerves which extend to outlying parts of the body. Oh, and don’t forget the Autonomic Nervous System the one that our body relies on the most which regulates the body’s involuntary functions. These three systems dubbed CNS, PNS, and ANS for short make up the nervous system. Now lets look a little deeper into the brain cells. There are two types of brain cells called neurons and Glia. They are divided into function you have sensory neurons and motor neurons. Sensory neurons are also known as afferent neurons. These neurons transmit to the brain and spinal cord information that the sensory neurons are providing about the surrounding environment. Motor neurons also known as efferent neurons transmit information from the brain and spinal cord to muscular and glandular epithelial tissues in the body and instruct these cells to preform a function.
Interneurons are also known as central or connecting neurons they conduct impulses from the sensory to the motor neurons within the gray mater of the brain or spinal cord. Within the cellular structure of the nerve cell myelin a white fatty substance is a segmented wrapping around the axon. Some peripheral nervous system axons have this fatty substance around the axon which is called schwann cells.
Glia cells with threadlike extensions of the cell separate the nerve and blood tissue of the body forming the blood brain barrier (BBB) which protects the brain from chemicals in the blood is called astrocytes. Microglia are smaller than astrocytes and are usually stationary, but inflammed or degenerating brain tissue activates the microglia and the microglia enlarge and move to eat the microbes within the brain. Oligodendrocytes help to hold nerve fibers together and produce myelin sheath covering nerve fibers in the brain and spinal cord. The nodes of ranvier are indentations between adjacent schwann cells they look like ridges that connect the schwann cells together.
Neurilemma are in the outer cell membrane of a schwann cell they are important for regeneration of cut or injured axons. Axons in the brain and spinal cord have no neurilemma and therefore cannot repair themselves once the damage has been done its permanent.
So what is the definition of a nerve, its a group of peripheral nerve fibers or axons bundled together like strands of a cable which is also known as white matter of the peripheral nervous system (PNS) because the myelin is white and not gray. The bundles of axons in the Central Nervous system(CNS) are called tracts.
