Anatomy Of Human Nervous System

Anatomy of Human Nervous system: an explanation of the Nervous system in the human body and how it is the master controller.

Your nervous system keeps you informed of changes in the environment. It also allows you to respond to these changes. For instance, suppose a car is approaching as you step off the curb. Sensory cells in your eyes respond, impulses are then carried along sensory nerves to the brain. The brain interprets the impulses and responds, sending impulses along motor nerves to the muscles in your legs and feet. This allows you to step back from the curb.

The nervous system harmonizes all bodily activities: directs the work of all other tissues toward a common particular function. Because of the nervous system there is a line of communication between the receptors: the ears, eyes, nose, skin, and the effectors: the muscles and glands. The receptors enable you to be aware of your surroundings, and the effectors carry out the reactions necessary to survive in these surroundings. The nervous system is the center of all psychic activity. All feeling and thought, all mental faculties such as judgment and reason originate here. It is the basis of all instincts and reflexes.

The complex group of organs and nerves (they control all your actions and thoughts) is the nervous system. The brain is the control center of the nervous system. Nerve cells in the brain receive messages from every part of the body. The brain processes these messages and sends a response back to other parts of the body through other nerve cells. The brain is the master control unit for the body. The central nervous system includes the brain and the spinal cord. The central nervous system receives and processes information and sends out instructions. Most of the messages travel through the spinal cord.

Your nervous system allows you to respond to changes in your environment and stores information to be used days, months, or even years later. It also is in charge of your body's voluntary and involuntary muscle movements. It makes your muscles contract and relax. Your nervous system can do all this because of billions of nerve cells throughout your body. The nerve cells send signals to each other and to muscles.

The neuron is the basic unit of the nervous system and is commonly called a nerve cell. These neurons will carry messages from one part of your body to another. The name of these messages of sensation and information are called impulses. The neurons form the communication system that controls the body's many functions and stores information. There are different types of neurons, but they all have certain features that are similar. All the organs and parts of the nervous system are composed of neurons and their accessory or protective tissues. The neuron consists of the nerve-cell body and its parts. Dendrites are a number of short, branch-like processes, which conduct impulses toward the cell body. The axon is one process of the cell that is much longer than any of the dendrites and carries the impulses away from the cell.

Nerve impulses travel along a neuron and are similar to a tiny electrical charge. These nerve impulses may travel as fast as 360 feet per second along an axon.

A space called the synapse is between the end of the axon of one neuron and the dendrite of another. When the impulse reaches the end of an axon, it is passed to a dendrite of the next neuron by neurotransmitters. These are chemicals that pass across a synapse from an axon to a dendrite. Neurotransmitters trigger an impulse, which travels down the dendrite to the cell body and out along the axon.

There are three basic types of nerve cells. Sensory nerve cells perform one of two functions. Specialized sensory nerve cells respond to particular stimuli in the environment, such as light or heat. They pass impulses to other sensory nerve cells that carry the information to the brain and spinal cord. In the brain and spinal cord, decisions can be made. Motor nerve cells carry instructions from the brain and spinal cord to muscles and glands. Connecting nerve cells join sensory and motor nerve cells in the brain and spinal cord. Nerve cells are grouped together in large bundles called nerves.

A nerve fiber is either an axon of a motor neuron or the dendrite of a sensory neuron. of the nervous system to collect information and send instructions throughout the body. Some nerves contain only sensory and some only motor fibers, while some, like the great sciatic nerve of the thigh, contain both. The central core of a nerve fiber is usually covered with a fatty substance known as the myelin sheath. It is white, so the fibers will appear white also. The nerve-cell bodies and their parts are gray. Portions of the brain and cord in which the cell bodies congregate are called gray matter, while the portions made up mostly of the fibers are known as white matter. Three parts of the nervous system work together to accomplish this task. The central nervous system includes the brain and the spinal cord. The central nervous system receives and processes information and sends out instructions.



The nervous system has two closely associated divisions. The cerebrospinal system, made up of the brain and spinal cord and their attached nerves, controls all voluntary functions, and some usually involuntary, like breathing. The autonomic system, consisting chiefly of a connected series of ganglia lying alongside the vertebral column, controls such vital processes as circulation, digestion, swallowing, respiration, and is subject to influence from the emotions, but not from the will.

The brain is a soft, grayish mass containing billions of nerve cells. The hard, platelike bones of the skull protect it. The brain can be divided into three parts, the cerebrum, the cerebellum, and the brain stem. The cerebrum is responsible for the highly developed intelligence of human beings. Some regions receive messages about what you see, hear, and smell, or how you move. Other parts control your ability to think, write, talk, and express emotions. The part of the brain that coordinates the muscles that you use for auction, such as running or walking, is the cerebellum. It is under and behind the cerebrum and coordinates a constant flow of nerve impulses from the body and cerebrum. The cerebellum puts this information together to help your muscles perform the way you walk. It helps control your balance and maintain posture. The brainstem is the structure that connects the cerebrum with the spinal cord. There are three divisions that form this stem: the midbrain, pons, and the medulla.

The medulla is the center that controls some of the most important functions of life, such as breathing, blood pressure, heart rate, and swallowing. The pons is a bundle of nerve fibers that link the cerebrum with the cerebellum and the right side of the brain with the left side of the brain. The midbrain is a group of nerves that control certain involuntary actions such as pupil size and eye movements.

The spinal cord is within the vertebral column and is the main trunk of the body. It extends from the medulla to just below the ribs. The nerve fibers in the spinal cord reach out to all parts of the body, connecting all of the nerves in your body to the central nervous system. If the spinal cord is damaged, the body may be unable to feel or move from the point of injury downward. The spinal cord is actually a continuation of the medulla and is about l8 inches long. The spinal cord is contained within the cavity formed by the interlocked vertebrae of the backbone. There are thirty-one pairs of spinal nerves emerging from the cord, each nerve bringing in impulses to the back side of the cord, and carrying away impulses from the front side. Within the cord these impulses are distributed to higher or lower centers.

Three protective membranes, known collectively as the meninges, surround both the brain and spinal cord. The space between these membranes is bathed with a spinal fluid much like lymph, which serves as a protective cushion for the delicate nerve tissue, and allows some expansion space for the brain when its blood supply is increased.

The system that carries messages between the body and the central nervous system is the peripheral nervous system. Impulses constantly travel between the two nervous systems. This happens through 31 pairs of large nerves branching from the spinal cord and 12 pairs of nerves branching from the brain. These nerves contain thousands of sensory and motor nerve fibers that reach to all parts of the body. Part of the peripheral nervous system carries sensory information. Part of the peripheral nervous system carries motor impulses that control voluntary action.

The autonomic nervous system is the part of the peripheral nervous system that controls involuntary responses. It is made up largely of motor nerves. It affects many organs including the heart, lungs, stomach, intestines, liver, kidneys, sweat glands, salivary glands, and pupils of the eye. This autonomic nervous system consists of two parts. The parasympathetic nervous system generally slows down the body's functions, such as heartbeat and rate of breathing, when you are resting. The sympathetic nervous system is that part that works when you are active or under emotional stress. If you were to get excited blood flow would travel to the active muscles, making your heart rate and your breathing rate increase. This interplay between the two parts of the autonomic nervous system keeps your body working properly in all situations. It is done without your conscious control.

The above information defines the various parts of the nervous system to hopefully give you a better understanding of this complex system in the body. The nervous system is likened to a communication system, as it is able to communicate with all other body systems. It directs all activities of all the systems and receives information about the conditions in all other systems. There is a massive power to the brain, the master organ of the body and the seat of the thinking mind. It controls almost every physical body function, every thought, and every emotion. The brain obtains information about events and conditions around the body with the help of the spinal cord that consists of nerves that connect the brain to all the body parts. These two main parts of the nervous system keep your body working properly in all situations and this is done without your conscious control.

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