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The definition of Brain as given in the Taber's Cyclopaedia Medical Dictionary is "Brain- a large soft mass of nerve tissue contained within the cranium; the carnal portion of the central nervous system. The anatomy of the brain is composed of neurons (nerve cells) and neuroglia or supporting cells. The brain consists of gray and white matter. Gray matter is composed mainly of neuron cell bodies and is concentrated in the cerebral cortex and the nuclei and basal ganglia. White matter is composed of neuron processes, which form tracts connecting parts of the brain with each other and with the spinal cord.
The brain consists of three major parts: the cerebrum, cerebellum, and brainstem (medulla, pons, and midbrain). " (257) The brain is the heaviest organ in our bodies and the most important organ besides your heart. In this discussion you will be able to understand the brain a little better and will be more educated about the brain when you finish. Nerve, as defined in Taber's, is "a bundle of nerve fibers outside the central nervous system (CNS) that connect the brain and spinal cord with various parts of the body. " (1280) Nerves are bundles of nerve fibers. Neuralgia were once thought only to fill spaces and surround or support neurons. Nerves are essential in our everyday functions, they can effect everything we do. The neuralgia cells provide assistance, support, nutrition and protection to neurons in the central nervous system.
There are four types of neuralgia cells which are oligodendroglia, astrocytes, micro glia and ependymal. Neurons as defined in Taber's is " a nerve cell, the structural and functional unit of the nerves system. A neuron consists of a cell body (perikaryon) and it's processes, an axon and one or more dendrites. " (1292) Neurons function in initiation and conduction of impulses. " They transmit impulses to other neurons or cells by releasing neurotransmitters at synapses. Alternatively, " a neuron may release neuro hormones into the bloodstream. " (Monahan 712) In a resting stage, the neuron has a negative membrane potential. Because of this large negative difference, the membrane is said to be polarized. "Membrane depolarization, which can be initiated by chemical, mechanical, electrical, or thermal means, extends from one neuron to another, resulting in impulse transmission. " (Monahan 713) The central nervous system consist of the brain and the spinal cord. " The organs of the nervous system can be divided into two groups. The other group connect the central nervous system to other body parts is called the peripheral nervous system. " (Shier 352).
Together these systems provide three general functions- sensory, integrative, and motor. The definition of peripheral nervous system as defined in Taber's is "the portion of the nervous system outside the nervous system. The 12 pairs of cranial nerves and 31 pairs of spinal nerves. These nerves contain sensory and somatic motor fibers and the motor fibers of the autonomic nervous system. " (1446) Structures called sensory receptors at the ends of peripheral neurons provide the sensory functions of the nervous system.
These receptors gather information by detecting changes inside and outside the body. " Sensory receptors convert their information into nerve impulses, which are then transmitted over peripheral nerves to the central nerves system. " (Shier 353) Thus, the nervous system can defect changes in the body, make decisions on the basis of the information received, and stimulate muscles or glands to respond. The meaning of the spinal cord as defined in Taber's is " An ovoid column of nerve tissue averaging about 44 cm in length, flattened anteroposteriorly, extending from the medulla to the second lumber vertebra in spinal canal. Most nerves to the trunk and limbs emerge from the spinal cord, a reflex center for spinal cord reflexes that conducts impulses to and fro m the brain. " (1803) The internal structure of the spinal cord consist of gray matter and white matter. The gray matter has an H- shaped configuration. "The gray color is due to the neuronal cell bodies and synapses found there. The white matter contains ascending and descending pathways, which are mostly made up of myelin ated axons. " (Monahan 721). Motor and sensory pathways are configured in tracts and are named after the tract in which they travel, the location of the origin of the impulse, and the impulse, and the location o impulse termination. "Neurons transmit impulses through the propagation of action potential along conductive fibers. " (Monahan 728) Membrane depolarization, which can be initiated by chemical, mechanical, electrical, or thermal means, extends from one neuron to another, resulting in impulse transmission.
The synapse is where nerve impulses are transmitted from neuron to neuron. "Nerve transmission at the synapse involves a chemical process. " (Perry 1201) The brain consists of two dividing parts which are the cerebrum and the cerebellum. "The cerebral hemispheres have a convoluted surface with many peak, known as girl and valleys or indentations known as sulci. " (Perry 625) "The cerebellum is located in the posterior fossa, posterior to the pons and below the tentorium cerebellum. " (Monahan 720) It's functions include the coordination of movement five motor activities, equilibrium, and orientation in space (proprioception). " (Perry 532). Also, don't forget about the brain stem which has become known as the "life center of a person. " It's divided into the midbrain, pons, and medulla oblong ata. The midbrain is the upper most portion of the brain stem. "Cranial nerves three and four are located here. The midbrain functions as a relay station for impulses among the cerebral hemispheres, cerebellum, and spinal cord. " (Shier 612) There are also four lobes to the brain which divide the brain even more and makes it even more complicated to explain. First, is the frontal lobe. The frontal lobe forms the "anterior portion of each cerebral hemisphere.
It is bordered posterior by a central sales which passes out from the long itudinal fissure at the right angle, and inferior by a lateral sales which exits the undersurface of the brain aloud its sides. " (Shier 347) Third is the temporal lobe which "lies below and is separated from them by the lateral sulcus. " (Shier 398) And the forth is the occipital lobe which "forms the posterior portion of each cerebral hemisphere and is separated from the cerebellum by a shelf like cortex of dura matter called the tentorium cerebellum. The occipital lobe and parietal and temporal lobes have no distinct boundary. " (Shier 399) This book also hoes a little further and list a fifth part which is the Insula. Th insula is located "deep within the lateral sulcus and is covered by parts of the frontal, parietal and temporal lobes. A circular sulcus separates it from them. " (Shier 401) The forebrain is the anterior portion of the brain of the embryo. The forebrain also has another name, which is the pros encephalon. "It gives rise to the telencephalon and diencephalon. " (Shier 342) And there is also a Hindbrain which is the most "caudal of the three divisions of the embryonic brain. It differentiates into the met encephalon, which gives rise to the cerebellum and post and the myelencephalon, which develop into medulla oblong ata. " (Shier 343) the hindbrain also has another name which is called the rhombencephalon.
As you can see the brain is a very complicated organ. I have attempted to get you, the reader, acquainted with the brain by discovering some of the main parts of the brain and how they function and work together. First I started out by talking about the role of neuron and nerves. Then, I continued on by discussing the central and peripheral nervous system and it's relationship to the spinal cord and transmission of impulses.
I made mention of the hemispheres of the brain and how the hemispheres were broken into four lobes. Lastly I discussed the forebrain and hindbrain. Work Cited Monahan, Frances: Medical- Surgical Nursing 2 nd Edition; Philadelphia, PA. 1998 Perry, Potter: Fundamentals of Nursing; St. Louis, Missouri. 1997 Shier, David: Human Anatomy And Physiology; New York, New York. 1996 Thomas, M. D. , Clayton: Taber's Cyclopedia Medical Dictionary; Philadelphia, PA. 1997
Free research essays on topics related to: central nervous system, peripheral nervous system, spinal cord, frontal lobe, cerebral hemispheres
Research essay sample on Central Nervous System Peripheral Nervous System
