The Nervous System
Overview of Lesson 9 The Nervous System
The nervous system consists of the brain, the spinal cord, and the network of nerves throughout the rest of the body. It is sometimes called the master system, since it regulates and coordinates every other body system. The nervous system provides a rapid means for the various parts of the body to communicate with each other. It allows us to adjust to the world around us and cope with the challenges of life. It influences how we act or react to stress. The fight or flight response is a good example. This is a hormonally stimulated state to prepare the body for an upcoming threat or challenge.
- Introduction
- The Central and Peripheral Nervous Systems
- The Autonomic Nervous Systems
- The Sympathetic Nervous System
- The Parasympathetic Nervous System
- The Nerve Cell
- The Myelin Sheath
- The Propagation of a Nerve Impulse
- The Nerve Synapse and Neurotransmitters
- Axoplasmic Flow and the Neurotrophic Function of the Nerve Cells
- Common Diseases of the Nervous System
- Herbal and Nutritional Support for the Nervous System
- Conclusion
- Nervous System Flow Chart
- Nervous System Product List
- Word Review List
- Self Evaluation
The nervous system is composed of two major parts; the central nervous system (CNS) and the peripheral nervous system (PNS). The central system is the brain and spinal cord, and is where most information is processed. The peripheral system is the network of nerves throughout the rest of the body. The peripheral nervous system allows signals to travel between the central nervous system and the body's sensory receptors and motor effectors, such as the muscles.
The Central Nervous System (CNS) consists of the brain and spinal cord. The CNS and PNS are anatomical divisions of the nervous system. The nervous system is also divided into two physiological (or functional) divisions -- a voluntary system, which as the name implies is concerned with voluntary actions such as muscle movement; and an involuntary or automatic system referred to as the autonomic nervous system.
The Autonomic Nervous System
An automatic, or autonomic, nervous system controls basic functions of the body that we do not normally have conscious control over, such as the heart beat, digestion, breathing and blood flow. These involuntary actions are controlled by the opposite and antagonistic actions of the two divisions of the autonomic nervous system - the sympathetic and the parasympathetic divisions. Most organs receive impulses from both divisions and under normal circumstances they work together for proper organ function and adaptation to the demands of life.
The sympathetic system tends to stimulate a particular function while the parasympathetic tends to calm. Normally the two nerve supplies create a balance. However, if the body is stressed, such as in the fight or flight response, the sympathetic nervous system dominates causing an increase in heart rate, breathing, blood pressure and blood sugar levels. This prepares the body for quick and strenuous action. When the emergency situation has passed the parasympathetic system takes over and decreases the heart and breathing rates and diverts blood supply back to activities such as digestion and food absorption.
Problems may occur when the autonomic nervous system is out of balance. For example, over-stimulation of the sympathetic nervous system can lead to such problems as anxiety, hypertension, and digestive disturbances. Over-stimulation of the parasympathetic nervous system can result in low blood pressure and fatigue. Both imbalances lead to poor adaptation to stress.
Which division of the autonomic nervous system is called upon to stimulate and prepare the body for emergency action, such as in the "fight or flight" response?
Sympathetic
Parasympathetic
Central
Peripheral(Select the best answer and click on the "Continue" button.)
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