Анатомия домашних животных неврология = Anatomy of domestic animals Neurology. Учебно-методическое пособие

3. AUTONOMOUS (VEGETATIVE) NERVOUS

SYSTEM

Autonomous (vegetative) nervous system innervates internal organs (heart, lungs, stomach, intestines etc.), glands, vessels, and regulates metabolic processes and maintains homeostasis of the internal environment of an organism.

Anatomically autonomous nervous system of superior vertebrates is presented by vegetative centers in the brain and spinal cord, vegetative ganglions and nervous fibers. Versus somatic nervous system autonomous system has several features:

1.Vegetative centers or nuclei, are local, i.e. in particular areas of mesencephalon, medulla oblongata and spinal cord.

2.The path to the innervated organ goes obligatory through ganglion, thus nervous paths of vegetative nervous system are formed by two neurons. First neuron is in vegetative centers, its fibers end on the ganglion and are called preganglionic. Second neuron is in ganglion, continuing fibers are called postganglionic. They go to innervated organ. (center – preganglionic fibers – ganglion – postganglionic fibers – organ).

3.Along the nervous fibers vegetative plexuses are formed – plexus autonomici – around blood vessels, in organic portal or inside its wall.

4.Maintenance of promotive features of the structure – it is lesser caliber of nervous fibers, absence of myelinic coat in most fibers. Thus, vegetative fibers are commonly amyelinic and consist of several nervous fibers (3-20), covered by common coat of connective tissue.

5.Absence of strict segmental structure, that is a feature of somatic nervous system.

6.Presence of its own sensitive (afferent) neurons and due to it formation of simple local reflex arches.

21

3.1Sympathetic nervous system

Sympathetic part of autonomous nervous system (pars sympathica) is trophic by its main functions. It stimulates metabolic processes, cardiac and respiratory acceleration, rise of arterial pressure, oxygenation of muscles, and decrease secretory and motional functional of gastrointestinal tract.

Centers are in lateral horns of thoracolumbar part of the spinal cord (nuclei intermediolateralis). Preganglionic fibers branch from it and along with spinal nerves go to sympathetic ganglions. Mostly ganglions are along vertebral column and along big blood vessels. From it postganglionic fibers branch as part of spinal and cerebral nerves for innervation.

22

3.2Parasympathetic nervous system

Parasympathetic part (pars parasympathica) provides mostlyprotectivefunction.Itsexcitationprovidesnarrowingofthe pupil in bright light, inhibition of cardiac activity in sleep and rest, decrease of blood pressure, bronchial narrowing and stimulation of gastrointestinal functions. Main structure of parasympathetic system is like sympathetic. It comprises central and peripheral structures.

Centers of parasympathetic nervous system are in mesencephalon and medulla oblongata, and in sacral part of spinal cord. Peripheral part is presented by ganglions, that set near or inside innervated organs (extra and intramural), trunks and plexuses.

23

3.3 Metasympathetic nervous system

Most of internal organs have individual autonomous mechanism beside sympathetic and parasympathetic innervation, it helps rhythmical contraction with particular periodicity without

24

external influence. This autonomous mechanism provides rhythmical contraction the heart, gastrointestinal tract, uterus etc., is performed by metasympathetic part of nervous system.

Centers (“pacemakers”) are in walls of the organ. It has preganglionic fibers going to microganglions in organ walls. From this microganglions postganglionic fibers go out and provide rhythmic contractions of innervated organs.

4. ANALYZERS

Analyzer is a unite functional system of neurons, that sense irritation, produce nervous impulse, transfer it and analyze in central nervous system. Each analyzer has three parts: sensitive (receptors, sense organs – organum sensuum), conductive (cerebral and spinal nerves) and central (brain and spinal cord).

1.Olfactory analyzer provides ability to recognize smells. It comprises sensitive (olfactory epitheliumofnasal cavity), conductive (olfactory nerves) and central (rhinencephalon, hippocamp, thalamus, subcortex, cortex) parts.

2.Visual analyzer senses size, shape, color of things in external environment, their position, movements etc. It comprises sensitive (visual organ), conductive (optic nerve) and central (thalamus, optic thalamus, subcortex, cortex) parts.

Table 18

25

3.Taste analyzer provides analyze of feed and water. It comprises sensitive (taste buds on tongue), conductive (facial and glossopharyngeal nerve) and central (thalamus, medulla oblongata, subcortex, cortex) parts.

4.Statoacusticus analyzer is for audition and sensation of body position in space. It comprises sensitive (vestibulocochlear organ), conductive (vestibulocochlear nerve) and central (thalamus, auditory thalamus, cerebellum, medulla oblongata, subcortex, cortex) parts.

Table 19

Vestibulocochlear organ - organum vestibulocochleare

26

5.Tactile analyzer senses different irritations from environment (cold, warmth, touches, pressure, pain etc.). It comprises sensitive (exteroceptors of skin), conductive (nerves) and central (brain and spinal cord) parts.

6.Visceral analyzer senses irritation, produced by different organs and tissues of an organism, signals CNS about internal environmental condition. It comprises sensitive (interceptors), conductive (nerves) and central (brain and spinal cord) parts.

27

Bibliography

1.Akaevskii A.I., Udichev U.F., Seleznev S.B. The anatomy of the domestic animals. – Moscow: Akvarium, 2009.

2.Hrustaleva I.V. et.al. The anatomy of the domestic animals. - Moscow: Koloss, 2000.

3.König H.E., Liebich H. G. Veterinary anatomy of domestic mammals. -Schattaeur, 2007.

4.Sisson S. The anatomy of the domestic animals. – Philadelphia: Saunders Company, 2014.

5.Dyce K.M., Sack W.O., Wensing C.J.G. Textbook of Veterinary anatomy 4th ed. – Saunders, 2010.

28