Page 55 - 84 human physiolofy part-1

The Nervous System

Overview of the entire nervous system

The nervous system has three main functions, sensory input, integration of data and motor output.
Sensory input is when the body gathers information or data, by way of neurons, glia and synapses. The
nervous system is composed of excitable nerve cells and synapses connecting the cells to one another,
to centers throughout the body or to other neurons. These neurons operate on excitation or inhibition
and although nerve cells can vary in size and location their communication with one another
determines their function. These nerves conduct impulses from sensory receptors to the brain and
spinal cord. The data is then processed by way of integration of data, which occurs only in the brain.
After the brain has processed the information, impulses are then conducted from the brain and spinal
cord to muscles and glands, which is called motor output. Glia cells are found within tissues and are not
excitable but help with myelination, ionic regulation and extracellular fluid.

The nervous system is comprised of two major parts, or subdivisions, the central nervous
system(CNS) and the peripheral nervous system(PNS). The CNS includes the brain and spinal cord.
The brain is the body's "control center". The CNS has various centers located within it that carry out
the sensory, motor and intergration of data. These centers can be subdivided to Lower Centers
(including the spinal cord and brain stem) and Higher centers communicating with the brain via
effectors. The PNS is a vast network of spinal and cranial nerves that are linked to the brain and the
spinal cord. It contains sensory receptors which help in processing changes in the internal and external
environment. This information is sent to the CNS via afferent sensory nerves. The PNS is then
subdivided into the autonomic nervous system and the somatic nervous system. The autonomic has
involuntary control of internal organs, blood vessels, smooth and cardiac muscles. The somatic has
voluntary control of skin, bones, joints, and skeletal muscle. The two systems function together, by way
of nerves from the PNS entering and becoming part of the CNS, and vice versa.

General functions of the CNS

The central nervous system (CNS) represents the largest CNS:
part of the nervous system, including the brain and the spinal The "Central Nervous System",
cord. Together, with the peripheral nervous system (PNS), it has comprised of brain, brainstem, and
a fundamental role in the control of behavior. spinal cord.

The CNS is conceived as a system devoted to information processing, where an appropriate motor
output is computed as a response to a sensory input. Many threads of research suggest that motor
activity exists well before the maturation of the sensory systems, and senses only influence behavior
without dictating it. This has brought the conception of the CNS as an autonomous system.

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