Sympathetic nervous system

The sympathetic nervous system ( sympathetic ) or the sympathetic nervous system is in addition to the parasympathetic nervous system and the enteric nervous system ( enteric nervous system ) a portion of the autonomic nervous system. Most organs are controlled by the first two systems, which act as antagonists ( antagonistic ), thus enabling a very fine regulation of organ activity. The sympathetic nervous system has a ergotropic effect, that is, it increases the outward readiness to act ( " fight or flight" ) in this system.

Anatomy

The cell bodies of the so-called first neurons of the peripheral sympathetic nervous system (sympathetic root cells ) are localized in the thoracic and lumbar cord ( thoraco - lumbar system ). Parent centers of the sympathetic nervous system are the hypothalamus, brain stem and reticular formation, which send impulses to the sympathetic root cells in the spinal cord.

This root cells are located in the lateral horn of the spinal cord and form the nucleus intermediolateralis. They send their fibers to nerve cell assemblies next to the spine, the Paravertebralganglien that are connected to each other and in their entirety by the sympathetic trunk ( sympathetic trunk ) represent. This extends into the area of the cervical spine and the sacrum. In humans, there are three cervical ganglia: the upper ( superior cervical ganglion ), the median ( middle cervical ganglion ) which is not constant and the lower cervical ganglion ( inferior cervical ganglion ). In the paravertebral ganglia, most fibers of the sympathetic nervous system can be switched to a second neuron. The neurotransmitter is (as in the parasympathetic nervous system ) acetylcholine. The second ( post-ganglionic ) neuron transmits its pulses to the target organ by norepinephrine. An exception is the transmission of impulses to the sweat glands and the adrenal medulla, this is also done by acetylcholine.

Some axons leave the sympathetic trunk without switching and drag to the prevertebral ganglia in the aorta ( celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion ) or ganglia in the wall of the supplied organs ( intramural ganglia).

Word origin

The term was coined by the Danish (but working in Paris ) anatomist Jacob Winslow ( 1686-1760 ) invented and used in his textbook exposition anatomique de la structure du corps humain. It is derived from the ancient Greek words συμπαθεῖν sympatheín " sympathize " and συμπάθεια sympátheia " Mitempfindung " now and has been used in this way, also already by the ancient Greek physician Hippocrates ( 460-370 BC to ). This points to an early misunderstanding of the function of the sympathetic nervous system: The ancient Greek physician Galen ( 129-216 to AD), who had described the sympathetic nervous system for the first time, assumed that the sympathetic communication (a kind of compassion ) between different institutions enable, see also the historic medicinal concept of sympathy.

Paraganglia

The largest sympathetic Paraganglion is the adrenal medulla. Here the second neuron is a neuroendocrine cell that emits its transmitter to the blood, thus releasing the hormone.

Functional Aspects

Target tissue of the sympathetic are mainly the smooth muscles of the blood vessels and glands. Like the other units of the autonomic nervous system controls the sympathetic vital processes. This regulation is carried out largely without conscious awareness and can hardly be influenced at will.

The sympathetic nervous system causes an overall increase in performance of the organism ( Ergotropie ). He puts the body in high motivation, preparing him to fight or flight, or other extraordinary efforts (→ stress reaction).

It increases:

• Cardiac activity
• Blood pressure
• Circulation and tone of the heart and skeletal muscles
• Glycolysis
• Metabolism.

He prevents that of others, for the immediate activity is not necessarily required operations, such as the intestinal activity.

He also has an impact on:

• Lung function ( bronchodilator )
• Bladder function ( continence causes )
• Reproductive organs ( including the causes ejaculation in men and orgasm in women)
• Internal eye muscles (dilated pupils, mydriasis )
• Secretion of the glands ( sweat glands and increase the adrenaline in the adrenal medulla, reduction of salivary and pancreatic secretion ).