2. 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.