2)CNS(Central Nervous System) PNS(Peripheral Nervous System) ANS(Autonomic Nervous System

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Author: Kevin Baker @ 08/24/08 - 01:42 am

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This entry is exerps from Wikipedia for a basic understanding of the interacting nervous systems.




The human nervous system can be grouped into both with gross anatomy, (which describes the parts that are large enough to be seen with the naked eye,) and microanatomy, (which describes the system at a cellular level.) At gross anatomy, the nervous system can be grouped in distinct organs, these being actually stations which the neural pathways cross through. Thus, with a didactical purpose, these organs, according to their ubication, can be divided in two parts: the central nervous system (CNS) and the peripheral nervous system (PNS).


1)
The central nervous system (CNS) is the part of the vertebrate nervous system which is enclosed in the meninges. It contains the majority of the nervous system and consists of the brain (in vertebrates which have them), and the spinal cord. Together with the peripheral nervous system it has a fundamental role in the control of behavior. The CNS is contained within the dorsal cavity, with the brain in the cranial cavity and the spinal cord in the spinal cavity. The brain is protected by the skull, while the spinal cord is protected by the vertebrae.


2)
The peripheral nervous system (PNS) resides or extends outside the central nervous system (CNS), which consists of the brain and spinal cord, to serve the limbs and organs. Unlike the central nervous system, however, the PNS is not protected by bone, leaving it exposed to toxins and mechanical injuries. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system
2a)
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles, and with reception of external stimuli, which helps keep the body in touch with its surroundings (e.g., touch, hearing, and sight).

The system includes all the neurons connected with muscles, skin and sense organs. The somatic nervous system consists of efferent nerves responsible for sending brain signals for muscle contraction.
2b)
The autonomic nervous system (ANS) (or visceral nervous system) is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These activities are generally performed without conscious control or sensation. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind. Its main components are its sensory system, motor system (comprised of the parasympathetic nervous system and sympathetic nervous system), and the enteric nervous system.

3)
The autonomic nervous system (ANS) (or visceral nervous system) is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body. These activities are generally performed without conscious control or sensation. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind. Its main components are its sensory system, motor system (comprised of the parasympathetic nervous system and sympathetic nervous system), and the enteric nervous system.

The ANS is a classical term, widely used throughout the scientific and medical community. Its most useful definition could be: the sensory and motor neurons that innervate the viscera. These neurons form reflex arcs that pass through the lower brainstem or medulla oblongata. If the central nervous system (CNS) is damaged above that level, life is still possible, because cardiovascular, digestive, and respiratory functions will continue to be adequately regulated.

3a)
The parasympathetic nervous system (PSNS) is a division of the autonomic nervous system (ANS), along with the sympathetic nervous system (SNS) and enteric nervous system (ENS or "bowels NS"). The ANS is a subdivision of the peripheral nervous system (PNS). ANS sends fibers to three tissues: cardiac muscle, smooth muscle, or glandular tissue. This stimulation, sympathetic or parasympathetic, is to control smooth muscle contraction, regulate cardiac muscle, or stimulate or inhibit glandular secretion.
3b)
The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system. It is always active at a basal level (called sympathetic tone) and becomes more active during times of stress. Its actions during the stress response comprise the fight-or-flight response.
3c)
The enteric nervous system (ENS) is a subdivision of the Peripheral Nervous System, that directly controls the gastrointestinal system. It is capable of autonomous functions such as the coordination of reflexes, although it receives considerable innervation from the autonomic nervous system and thus is often considered a part of it. Its study is the focus of neurogastroenterology. It has as many as one billion neurons, one hundredth of the number of neurons in the brain, and considerably more than the number of neurons in the spinal cord. The enteric nervous system is embedded in the lining of the gastrointestinal system.





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