Autonomic Nervous System. Functions

The autonomic nervous system, consisting of the sympathetic and parasympathetic activity regulates smooth muscle, cardiac and certain glands. The somatic nervous system, regulated or voluntary striated muscle.

To maintain homeostasis the SNA depends on a continuous flow of sensory input from visceral organs and blood vessels to the CNS (central nervous system). From the functional point often operate without conscious control. It is regulated by centers located in the brain: hypothalamus and medulla mainly that receive input from the limbic system and other regions of the brain.

Similarities between the sympathetic and parasympathetic systems

1. Both systems consist of sets of 2 motor neurons (efferent) in series, one after the other. The body of the first neuron is in the CNS and its axon extends to reach a node. In the SNA there ganglia localized areas (places where there are bodies of neurons outside the CNS: brain and spinal cord. Besides these nodes are different from the posterior roots of the horns of the spinal cord). In these nodes are placed second neurons in this chain. There occurs synapses and the axon of the second neuron will go to the effector organ.

2. The first neuron is called preganglionic and postganglionic leaving the ganglion. This second neuron has an axon without myelin.

3. Autonomic motor neurons release acetylcholine or noradrenaline as neurotransmitters. Preganglionic neurons always acetyl choline release.

4. Many organs receive motor fibers from sympathetic and parasympathetic. When a board receives input from both, is said to have dual innervation. When you act the other is inhibited.

Differences between the sympathetic and parasympathetic systems
1. In the case of sympathetic system, the preganglionic and postganglionic is short is long. In the case of PS is reversed (as explained in paragraphs 4 and 5, below).

2. In the sympathetic system, the cell bodies of preganglionic neurons are located in the lateral horns of gray matter of the 12 thoracic segments and the 2 or 3 lumbar spinal cord. Therefore, this system is also called "back injury".

3. In the case of the parasympathetic system, the preganglionic are located in the nuclei of the oculomotor nerve (III), facial (VII), glossopharyngeal (IX), vagus (X) in the brainstem and the lateral horns the gray matter of the second to fourth sacral segments of the spinal cord. Therefore also called "craniosacral".

4. The sympathetic chain ganglia are well-defined structures (each preganglionic fiber may synapse with postganglionic fibers 20 or more) and find: the paravertebral (chain of nodes), parallel to both sides of the vertebrae, the prevertebral and also collateral located above the spine and near the large abdominal arteries (cervical, celiac, mesenteric).

5. The parasympathetic cranial according to their location are: ciliary, pterygopalatine, submandibular, otic and vagal (X), which travel through the heart, liver, gallbladder, stomach, pancreas, kidney, small intestine and part thickness. In the sacral pelvic splanchnic nerves are: supplying colon, ureters, bladder and reproductive organs.

6. Parasympathetic ganglia are not defined structures, as it synapses with few neurons (about 4 or 5) and are placed intramural, at the end of the road autonomous driving very close or inside the wall of a viscus.

7. Sympathetic responses tend to spread throughout the body. Blood vessels, erector muscles of hairs, sweat glands (these 3 are specific to the sympathetic system) and specific target organs.

8. Parasympathetic responses tend to be located. Effector organ in which they arrive. As exclusive where we get their endings lacrimal glands (mourn activation is characteristic of PS).

9. In the case of the sympathetic, there communicating rami of spinal nerves emerging from the spinal cord, and through which the fibers are distributed around the body and into the chain of nodes. Communicating rami are white and gray. The color difference is because neurons are preganglionic (myelinated) or postganglionic (unmyelinated).

10. The sympathetic system controls how the university and the posterior lateral hypothalamus.

11. The parasympathetic system is controlled by both the anterior and medial hypothalamus.

Parasympathetic system:

It is a system of conservation and energy recovery. Mainly regulates the activities that conserve and restore body energy during times of rest or recovery. He used the acronym "SLUD" to remember the parasympathetic response: salivation, lacrimation (this is also one of the parasympathetic system), Urinary (urination), defecation. The parasympathetic system also decreases heart rate, respiratory closes not necessary in the rest, and so on.

It is related to digestion and absorption of food and elimination of waste products. The fear that can arise in certain situations makes it activates the parasympathetic system, and loss of control of defecation and urination.

Sympathetic system:
It prepares the body against emergencies. Energy expenditure processes. During the physical and emotional stress, the sympathetic system dominates the parasympathetic system processes. The sympathetic system is stimulated by exercise and situations of fear, shame, anger. The set of physiological responses of the sympathetic system are called "fight or flight response."

* Dilated pupils.
* Increases the heart rate, contractile force and blood pressure.
* Constriction of blood vessels of nonessential organs such as skin and viscera.
* Dilation of blood vessels of organs involved in exercise or in combating a threat: skeletal muscle, heart muscle, liver, adipose tissue. Thus rising temperatures also.
* Rapid breathing deep and bronchiolar dilatation to permit a flow of air into and from the lungs faster.
* Rise in blood glucose levels as the liver converts glycogen into glucose.
* Stimulation of the adrenal medulla to release adrenaline and noradrenaline. In this case it is needed the second neuron, but there is a direct connection by the time of the adrenal glands.
* Inhibition of the processes that are not essential to remedy the stress, for example, muscular movements of the gastrointestinal tract and digestive secretions are teething or interrupt.

The control of SNA by the cerebral cortex occurs mainly during emotional stress. In situations of extreme anxiety, which may result from conscious or subconscious stimulation of the cerebral cortex, it can stimulate the hypothalamus as part of the limbic system. This, in turn, stimulates the cardiac and vasomotor centers of the bulb, which increase the frequency and strength of heart contraction and blood pressure rise. The cortex stimulation on hearing bad news or experience an extremely unpleasant may cause vascular vasodilation, reduced blood pressure and fainting. Although most of the responses of the ANS are involuntary, in practice it may be possible to get some voluntary control.

Although it has to mimic the sympathetic and parasympathetic system with the Yin and Yang, if I like that comment is more a duality of our being.

We depend on the balance of these two parties. When one of the two systems do not work by default as well as excess, unbalance the other. We moved away from homeostasis, and the more chronic, more difficult to return to stability.

Although the innervation of the autonomic system is governed by institutions not aware, the relationship is so close to the conscious part of university, which often stimulates both positively or negatively its operation. Thus, emotions can wreak havoc on our being and our health. May become unbalanced to the point of causing illness somaticized from our unconscious. We will try our mental health care and social support to encourage all our equilibrium.

Also comment as a curiosity, that there are substances called anthraquinones in plants such as cassia angusitfolia laxatives, which makes extensive use blood to pass and then deposited in the smooth muscle of various organs. Involuntary contractions in this muscle without pathological origin or known, so will all diagnostic tests negative. It takes time to cleanse the body of these substances.

Related Topic
Central nervous system
The nerve impulse. Afector tissue. Neural circuits

*Automatic Translation