The
part of the nervous system that regulates the involuntary activity of the
heart, intestines, and glands, including digestion, respiration, perspiration,
metabolism, and blood-pressure modulation.
The autonomic nervous
system regulates involuntary and unconscious actions, such as internal-organ
function, breathing, digestion, and heartbeat. This system consists of two
complementary parts: the sympathetic and parasympathetic systems. Both
divisions work without conscious effort and have similar nerve pathways, but
they generally have opposite effects on target tissues.
The
part of the peripheral nervous system that transmits signals from the central
nervous system to skeletal muscle and from receptors of external stimuli to the
central nervous system, thereby mediating sight, hearing, and touch.
The somatic nervous system
keeps the body adept and coordinated, both through reflexes and voluntary
action. The somatic nervous system controls systems in areas as diverse as the
skin, bones, joints, and skeletal muscles. Afferent fibers, or nerves that receive
information from external stimuli, carry sensory information through pathways
that connect the skin and skeletal muscles to the CNS for processing. The
information is then sent back via efferent nerves, or nerves that carry
instructions from the CNS, back through the somatic system. These instructions
go to neuromuscular junctions—the interfaces between neurons and muscles—for
motor output.
What
is an example of a reflex action?
A reflex action occurs when the body responds to a stimulus without the involvement of the brain. Batting of eyelids and rapid withdrawal of hands from a hot surface are examples of reflex actions. The contraction of the pupils of the eyes when exposed to bright light is a perfect example of a reflex action.
Normally, the brain coordinates a
response to any stimulus via the spinal cord and the central nervous system. In
certain circumstances, the brain is bypassed for a very quick response. A
response takes longer when the brain, the nerves and the spinal cord are
involved.
All reflex actions occur very quickly
without any thinking. The action is not premeditated, and this makes it
instantaneous. The pathways that cause a reflex action are called reflex arcs.
These arcs consist of a sensory nerve, neurons or nerve cells and a motor
nerve. Neurons are like sensory pathways. Millions of neurons are
interconnected to make a nerve. Neural pathways make it possible for a reflect
action to take place. Various muscle groups are involved in a reflex action.
The first reflex actions start in the
womb even before birth. Reflexes related to touching, sucking and swallowing
are ready by the time birth takes place.
Nervous System Diseases
Multiple Sclerosis – Literally, “many hardenings,” MS is
a disease of unknown cause that manifests as multiple hard plaques of degeneration
of the insulating layer of nerve fibers in the central nervous system. The loss
of insulation allows “short circuiting” of nerve impulses. Depending upon where
the degeneration occurs, patients may suffer paralysis, sensory disturbances or
blindness.
Cerebrovascular accident (CVA) – the fancy name for a “stroke”. A
blood vessel in the brain may burst causing internal bleeding. Or, a clot may
arise in a brain blood vessel (a thrombus), or arise elsewhere (embolus) and
travel to get stuck in a brain vessel which then deprives brain tissue of
oxygen. Depending upon the area of the brain involved, the patient may suffer
paralysis, loss of speech or loss of vision.
Transient Ischemic Attack (TIA) – “Ischemia” was introduced previously
in the circulatory diseases module referring to the heart. It literally means
“not quite enough blood”. A short period of insufficient blood supply to the
brain can have the same signs and symptoms as a stroke such as weakness in an
arm, a partial loss of vision, but the problem lasts less than 24 hours. People
who get TIA’s are at increased risk of having a stroke in the future.
Epilepsy – a Greek word for “seizure.”
Convulsions is another term used. Seizures may have many causes and not all
seizures are epilepsy. High fevers in young children may trigger seizures which
are short in duration, easily controlled and, typically, have no permanent
aftereffects. Epilepsy is a specific condition which may occur at any age,
seizures are more intense, longer lasting in duration, and recur with some
frequency. The condition may be controlled with medication, or if unresponsive
to drugs, may require surgery.
Aphasia – loss of speech. The speech centers
are located on the left side of the brain in a majority of people. If someone
suffers a “stroke” (cerebrovascular accident-CVA), or traumatic brain injury,
and it involves the left side of the brain, they may suffer speech impediments
that vary over a spectrum of problems from difficulty in finding the right
word, speaking slowly and with difficulty, or complete loss of speech.
Actually, there are two speech centers. Injury described above involves the
motor speech area, the area of the brain that produces language by integrating
thoughts of speech with the movements of the larynx, lips and tongue. There is
a second speech area, the receptive or sensory area, that enables us to
understand speech. Injury to the latter results in still fluent speech, but the
individual does not understand what they are hearing.
Reference:
https://www.boundless.com/definition/autonomic-nervous-system/
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