The topic studied actuality. Neurologists examine vegetative nervous system functions by vascular tone, cardiac activity, endocrine glands secretory activity

Neurologists examine vegetative nervous system functions by vascular tone, cardiac activity, endocrine glands secretory activity, thermoregulation, metabolism regulation, eye smooth muscles investigation.

Vegetative-vascular dystony is met in every second-third person.  

Dentists can get in touch with such vegetative innervation disorders expressions as changing the salivary glands secretion, swallowing, food gustatory features assessment as well as oral cavity noceoceptive, tactile and temperature sensitivity.

2. Study aims:

To know: autonomic nervous system physiological role; vegetative reflexes arcs structure peculiarities; excitement conductance mechanisms in excitable synapses and their blockade principles; sympathetic and parasympathetic nervous systems influencings on inner organs functions; different CNS floors role in organism vegetative functions regulation.

To be able to: draw vegetative reflexes arcs; investigate vegetative reflexes; analyze organism functions chanings at parasympathetic and sympathetic part activation and inhibiting.

1. Pre-auditory self-work materials.

3.1.Basic knowledge, skills, experiences, necessary for study the topic:

Histology	Vegetative nervous system (fibers, ganglia) histological peculiarities	Recognize vegetative ganglion preparation
Anatomy	Morphology of autonomic nervous system; vegetative reflexes arc	Draw autonomic nervous system elements location
Biochemistry	Vegetative mediators biochemical action mechanism to human body
Neurology	Autonomic nervous system morphology, physiology, influence on different organism systems and organs, representation about vegetative center tone	Analyze vegetative nervous system pathology signs while its action at different organs (for example, vegetative-vascular dystony)
Dentistry	Vegetative nervous system influence on oral cavity organs

Topic content.

Autonomic (ANS) or vegetative nervous system (VNS)

ANS is a complex of central and peripheral cellular structures regulating organism internal life functional level necessary for all systems adequate reaction.

ANS together with the endocrine (hormone), controls the body’s internal organs. It:

· innervates smooth muscle;

· cardiac muscle;

· glands;

· controlling blood circulation;

· gastro-intestinal tract activity;

· body temperature etc.

Most of this control is not conscious.

ANS is divided into 3 main parts:

– sympathetic nervous system (SNS);

– parasympathetic nervous system (PNS);

– metasympathetic nervous system (MNS).

 

Vegetative and somatic nervous system comparative characteristics

 

Features	Vegetative	Somatic
Target organs	Smooth muscles, myocardium, glands, fatty tissue, immunity organs	Skeletal muscles
Ganglii	Paravertebral, prevertebral and organic	Located in CNS
Efferent neurons number	Two	One
Effect of stimulation	Exciting or inhibiting	Exciting
Nervous fibers types	Thin myelinized or non-myelinized, slow	Myelinized fast

 

ANS mediator mechanisms

 

Mediator	Receptor	Effect mechanism
Acetylcholine	Nicotinic n-cholinoreceptor	Na^+-K^+-channels activation
Acetylcholine	Muscarine M1-M4-cholinoreceptors	Effect on inositol-3-phosphate, cAMP, cGMP as well as G-protein-mediated effect on K^+-channels
Noradrenaline	α1α2β1β2-adrenoreceptors	Effect is based on cAMP, inositoltriphosphate, phospholipase C, G-protein-mediated effect on K^+ and Ca^++ - channels

 

Organs with monosympathetic innervation:

1) blood vessels;

2) spleen capsule;

3) hair bulbs smooth myocytes;

4) pancreatic insulas cells.

Organs with monoparasympathetic innervation:

1) arteries of penis, clitoris, small sexual lips;

2) lacrimal glands;

3) pupil’s sphincter;

4) hypophysis;

5) suprarenal medulla.

Vegetative ganglii features:

1) connective tissue absence;

2) insignificant extracellular spaces;

3) many glial elements;

4) excitement wave one-sided conductance;

5) excitement convergency and divergency;

6) temporary and space summation;

7) occlusion;

8) nervous impulses rhythm transformation;

9) long-termed synaptic delay (1,5-30 msec);

10) EPSP;

11) prolonged trace hyperpolarization;

12) impulses rate is equal to 10-15 impulses per second;

13) autonomic regimen.

ANS mediators:

1) acetylcholine;

2) noradrenaline;

3) ATP;

4) histamine;

5) substance P;

6) angiotensine;

7) prostaglandine E;

8) serotonine.

ANS parts:

1) cranial-bulbar – nuclei of III, VII, IX and X pairs;

2) sacral – pelvic nerve;

3) thoracical-lumbal – spine lateral corns nuclei.

ANS floors

1) intramural plexuses – metasympathetic nervous system;

2) paravertebral and prevertebral ganglii;

3) SNS and PNS central structures – preganglionary neurons accumulation in brain stem and spine;

4) the highest vegetative centers:

· hypothalamus;

· cerebellum;

· reticular formation;

· basal ganglii;

· big hemispheres cortex.

ANS total structural plan

Central (preganglionar) neurons:

A. parasympathetic nervous system –

· in a brain stem (nuclei of III, VII, IX, X th pairs of cranial-cerebral nerves;

· in S_II-S_IV of spine;

B) sympathetic nervous system –spine lateral corns C₈-L_2-4 or thoraco-lumbal center of Yacobson.

Their processes – preganglionary neurons – come to corresponding vegetative ganglii:

a) sympathetic – to:

· paravertebral;

· prevertebral;

b) parasympathetic – to:

· intramural.

Here, in ganglii, they are finished with synapses on postganglionary neurons.

Postganglionary fibers – axons of postganglionary neurons – come directly to the organ.