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The Reticular formation, its role in the organism

The reticular formation is a complex of structures situated in the central parts of brain stem and distinguished by the following morphological feautures:1) The neurons of R.f. differ from the their neurons in structure. 2) The nerve fibers extend in different directions and resemble on microscopy a network, on grounds of which Dieters (a hundred years ago) called it the R.f. 3) the R.F. consists of cells differing in size(giant, large, moderate-sized and small) and shape(polygonal, spherical, spine-shaped oval). 4) The cells of R.F. are at places from nuclei the discernment of which was initiated by Bechterew when he described the reticular nucleus of the tegmentum of the pons (nucleus reticularis tegmenti pontis). Location: 1)in general it is placed in the deep and dorsal parts of the neural axis. 2) It is very diffuse in its distribution and has ill-defined boundaries. 3) It is better define physiologically than anatomically. Connections: The R.F. connected to all the principal parts of the nervous system, including motor, sensory and autonomic pathways with their centers. The connections are reciprocal with feed-back mech. Functions:. It is demonstrate inhibiting effect. Now believed that the R.F. is “generator of energy” and regulates processes in other parts of the CNS including cerebral cortex. 1) Inhibitory and facilitatory influences: Through its connections with the motor areas of the N.S., certain areas of the R.F. inhibit voluntary and reflex activity of the body, whereas certain other areas can facilitate them.2 ) State of arousal, general awareness and alertness: The ascending R. activating system is responsible for maintaining the state of wakefulness and alertness, by its connections with a great number of collaterals from sensory tracts. Sleep is a normal, periodic inhibition of the R.F. Hypnotics and general anesthetics produce their effects by acting on this system. 3) Autonomic infl. Through this connection, R.F. influences respiratory and vasomotor activities. They are stimulated or depressed according to the needs. Also it is participates in emotional, behavioral and visceral activities, in neuroendocrine regulation and development of cond.reflexes.

15. Functional anatomy of cranial nerves: deep and superficial origin, functional components, classification. There are 12 pairs of cranial nerves. Each nerve has a number and name as follows: 1-Olfactory, 2-Optic, 3-Oculomotor, 4-Trochlear, 5-Trigeminal, 6-Abducent, 7-Fascial, 8-Vestibulocochlear, 9-Glossopharingeal, 10-Vagus, 11-Accessory, 12-Hypoglossal. Out of these 1-st and 2-nd nerves are attached to the forebrain, the 3-4-th to the midbrain, 5-8 to the pons, 9-12 to medulla. Nerves arising from the brain: Olfactory - contain visceral-sensory fibers which run from the organs of perception of chemical stimuli.They have no ganglion and they are accumulation of 12-15 thin nerve filaments(fila olphactoria)wich are central processes of olph cells located in the olphactory region in the mucous membrane of nose.Fila olph pass through the openings of the lamina cribrosa in the sup. wall of nasal cavity and terminate in the olph.bulb. which continues in olph.tract and olph.pyramid. Optic- formed from diencephalon and connect with mesenc.which originates in association with the receptor of light. It contains somatic-sensory fibers also hasn’t ganglion.Multipolar n.c. of retina-post.periphery of eyeball-optic nerve(through optic canal)-optic chiasma(optic groove of sphenoid bone)

16. General morphology of the vegetative nervous system. Anatomical and functional characteristic. Peculiarities of the structure of the vegetative reflex arch. Differences of the VNS from somatic one. General plan of the structure of respiratory organs. Peculiarities of struc. and development.

The vegetative nervous system controls activity of all organs concerned with the vegetative functions of the body (nutrition, respiration, excretion, reproduction, and fluid circulation) and accomplishes trophic function. The VNS is separated into 2 systems: sympathetic and parasympathetic.

The sympathetic part is mainly concerned with trophic functions. It is responsible for intensification of oxidation processes, nutrient consumption, respiration, increases the rate of cardiac activity and the supply of oxygen to the muscles. The sympathetic division has thoracolumbar “outflow”, meaning that the neurons begin at the thoracic and lumbar(T1-L2/3) portions of the spinal cord.

The parasympathetic system carries a protective role: constriction of the pupil in bright light, inhibition of cardiac activity, evacuation of cavitary organs. The parasympathetic division has craniosacral “outflow”, meaning that the neurons begin at the cranial nerves (Cranial nerves III, VII, IX, and X) and sacral (S2-S4) spinal cord.

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