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The Nervous System AN UNDERSTANDING OF THE NERVOUS SYSTEM A Description of the Nervous System Student ID 80001023 Southern Cross International College Path Education Group (Malaysia) The Nervous System 2 An Understanding of the Nervous System The nervous system can be divided into several connected systems that function together. It monitors and controls almost every organ system through a series of positive and negative feedback loops. The nervous system is divided into the Central Nervous System (CNS) includes the brain and spinal cord and the Peripheral Nervous System (PNS) that connects the CNS to other parts of the body, and is composed of nerves (bundles of neurons). At the centre of the nervous system is the brain. The brain sends and receives messages through a network of nerves. The central nervous system is divided into two parts: the brain and the spinal cord. The average adult human brain weighs 1.3 to 1.4 kg (approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillons of "support cells" called glia. The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column. The peripheral nervous system is divided into two major parts: the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system and motor nerve fibers that project to skeletal muscle. The autonomic nervous system is divided into three parts: the sympathetic nervous system, the parasympathetic nervous system and the enteric nervous system. The autonomic nervous system controls smooth muscle of the viscera (internal organs) and glands. The nerve system interacts with other body systems. ...read more.


The others are termed the protoplasmic processes or dendrons; they begin to divide and subdivide soon after they emerge from the cell, and finally end in minute twigs and become lost among the other elements of the nervous tissue. To understanding the nerve message, there is the plasma membrane of neurons, like all other cells, has an unequal distribution of ions and electrical charges between the two sides of the membrane. The outside of the membrane has a positive charge, inside has a negative charge. The charge difference is a resting potential and is measured in millivolts. Passage of ions across the cell membrane passes the electrical charge along the cell. The voltage potential is -65mV (millivolts) of a cell at rest (resting potential). Resting potential results from differences between sodium and potassium positively charged ions and negatively charged ions in the cytoplasm. Sodium ions are more concentrated outside the membrane, while potassium ions are more concentrated inside the membrane. This imbalance is maintained by the active transport of ions to reset the membrane known as the sodium potassium pump. The sodium-potassium pump maintains this unequal concentration by actively transporting ions against their concentration gradients. Action potential is a reversal of the electrical potential in the plasma membrane of a neuron that occurs when a nerve cell is stimulated; caused by rapid changes in membrane permeability to sodium and potassium. Changed polarity of the membrane is the action potential, results in propagation of the nerve impulse along the membrane. An action potential is a temporary reversal of the electrical potential along the membrane for a few milliseconds. Sodium gates and The Nervous System 8 potassium gates open in the membrane to allow their respective ions to cross. Sodium and potassium ions reverse positions by passing through membrane protein channel gates that can be opened or closed to control ion passage. Sodium crosses first. At the height of the membrane potential reversal, potassium channels open to allow potassium ions to pass to the outside of the membrane. ...read more.


Also, a left-brain stroke might cause problems with speech while a right-brain stroke is more likely to cause abnormal/inappropriate emotional responses. Nerves carry messages back and forth between the brain and other parts of the body. All of our nerves together make up the nervous system. Some nerves tell the brain what is happening in the body. For example, when we step on a tack, the nerve in our foot tells the brain about the pain. Other nerves tell the body what to do. For example, nerves from the brain tell our stomach when it is time to move food into your intestines. Every minute of every day, our nervous system is sending and receiving countless messages about what happens both inside and around our body. Right now, our nervous system is receiving sensory input from our eyes about the words on the screen, from our ears about the sound of the computer, from our skin about the feel of our clothes, etc. At the same time, our brain is receiving information from sensors that monitor our heart rate, blood pressure, levels of oxygen and the contents of our stomach and intestines. Our brain then interprets all of these The Nervous System 13 signals, which allows for an understanding of the words on the screen, the recognition of the noise as computer noise, and the development of motor responses such as moving our eyeballs, changing positions in our chair, and decreasing or increasing our heart rate and digestion. In short, our nervous system coordinates all the activities of our body. In general, the nervous system as a whole is a system capable of so many sophisticated and complicated functions that can be extremely complex. This essay cannot possibly present all the information about the nervous system and it will probably take a few trips through the nervous system before the pieces fall into place. To sum it up, the nervous system is in charge of directing and overlooking all bodily functions - keeping us alive and healthy, fighting off diseases and infections, and healing us after we have sustained injury. ...read more.

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