Download The autonomic nervous system

Stellek Bálint Sándor
2016.10.27.
The autonomic nervous system
The autonomic nervous system (ANS) is a division of the peripheral nervous system (other division is somatic nervous
system) It influences the function of internal organs. It acts largely unconsciously and regulates bodily functions such
as heart rate, digestion, urination, respiratory rate etc.
Within the brain, the ANS regulated by the hypothalamus. It acts as an integrator for autonomic functions, receiving
ANS regulatory input from the limbic system to do so.
The hypothalamus most important role is to link the nervous system to the endocrine system. It responsible for
certain several activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones.
The autonomic nervous system is divided into two part:
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Sympathetic nervous system
o Emerges from the spinal cord in the thoracic and lumbar areas ("thoracolumbar outflow”)
Parasympathetic nervous system
o It has “craniosacral outflow”, meaning that the neurons begin at the cranial nerves and sacral spinal
cord.
Sympathetic nervous system
It’s primary process is to stimulate the body's fight-or-flight response. And it constantly active at a basic level to
maintain homeostasis. Fight-or-flight response means that when somebody is in danger under the command of the
hypothalamus the neural activity and the hormones together unleash the flight-or-flight response. It causes tunnel
vision, the liberation of metabolic energy and the acceleration of heart and lung action.
Two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and
post-ganglionic. Ganglion is a nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous
system. (Ganglia house the cell bodies of afferent nerves.) The shorter preganglionic neurons originate from the
thoracolumbar region of the spinal cord specifically at T1 to L2~L3, and travel to a ganglion, often one of the
paravertebral ganglia, where they synapse with a postganglionic neuron.
Parasympathetic nervous system
The parasympathetic nervous system (PSNS) is the other divisions of the autonomic nervous system. The
parasympathetic system is responsible for stimulation of "rest-and-digest" or "feed and breed” activities that occur
when the body is at rest. These occur when the body is at rest, especially after eating, including sexual arousal,
salivation, lacrimation (tears), urination, digestion and defecation.
As in the sympathetic nervous system, efferent parasympathetic nerve signals are carried from the central nervous
system to their target organs by a system of two neurons (pre- and postganglionic).
The axons of preganglionic parasympathetic neurons are usually long, extending from the CNS into a ganglion that is
either very close to or embedded in their target organ, while sympathetic is the opposite.
Parasympathetic nerve supply arises through three primary areas:
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Cranial nerves are the nerves that emerge directly from the brain (including the brainstem). Cranial nerves
relay information between the brain and parts of the body, primarily to and from regions of the head and
neck. They provide motor and sensory innervation mainly to the structures within the head and neck. The
sensory innervation includes both "general" sensation such as temperature and touch, and "special"
innervation such as taste, vision, smell, balance and hearing.
The vagus nerve is the tenth cranial nerve or CN X, and interfaces with parasympathetic control of the heart,
lungs and digestive tract. The vagus nerves are paired; however, they are normally referred to in the
singular. It is the longest nerve of the autonomic nervous system in the human body.
The pelvic splanchnic nerves arise from the anterior rami of the sacral spinal nerves S2-S4 and enter the
sacral plexus. They travel to their side's corresponding inferior hypogastric plexus, located bilaterally on the
walls of the rectum.From there, they contribute to the innervation of the pelvic and genital organs. The
nerves regulate the emptying of the urinary bladder, control opening and closing of the internal urethral
sphincter, influence motility in the rectum as well as sexual functions like erection.
en.wikipedia.org/wiki/Autonomic_nervous_system
en.wikipedia.org/wiki/Cranial_nerves
en.wikipedia.org/wiki/Sympathetic_nervous_system
en.wikipedia.org/wiki/Parasympathetic_nervous_system