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.

Effects of autonomic nervous system of selected organs

 

Organ	Effect of sympathetic stimulation	Effect of parasympathetic stimulation
Eye – pupil; – ciliary muscle – ocular fissures – eyes brilliance – exophthalm	Dilated Slight relaxation (far vision) Dilated Enforced Characteristic	Constricted Constricted (near vision) Normal, constricted Normal, dim Absent
Heart: – muscle     - coronaries	Increased rate Increased force of contraction   Dilated (β), constricted (α)	Slowed rate Decreased force of contraction (especially of atrium) Dilated
Systemic arterioles: - abdominal; - muscle;   - skin	Constricted Constricted (adrenergic α) Dilated (adrenergic β) Constricted	None None   None
Blood pressure	Normal or increased	Decreased or normal
Pulse	Tachycardia or norm	Bradycardia or norm
Dizziness	Absent	Present (characteristic)
Lungs: – bronchus; – blood vessels	Dilated Mildly constricted	Constricted Dilated
Respiration	Tachypnoe or norm	Retarded, deep, difficult (tendency to bronchospasm)
Arteries medullary secretion	Increased	None
Liver	Glucose releasing	Slight glycogen synthesis
Sweat glands	Copious sweating	None
Lard glands function	Decreased (skin dryness)	Increased (lard excessive secretion)
Tears secretion and releasing	Normal	Increased
Salivation, saliva content	Decreased, viscous	Enforced, liquid
Dermographism	Rose, white	Bright-red, spotted, rising
Pilo-motoric reflex	Enforced	Normal
Body temperature	Normal, subfebrile	Normal, hypothermia
Skin temperature	Decreased	Increased
Suffering from cold	Absent	Increased
Warmth endurability	Bad	Satisfactory
Shivering hyperkinesis	Distinguishing feature	Absent
Glands: nasal, lacrimal, salivary, gastric	Vasoconstriction and slight secretion	Stimulation of copious secretion (except pancreas)
Gut: – lumen; – sphincter	Decreased peristalsis and tone Increased tone	Increased peristalsis and tone Relaxed (most times)
Alimentary tract	Atonic constipation	Diarrhoea, meteorism, dyskinesia, spastic constipation
Nausea	Absent	Characteristic
Stomach juice acidity	Decreased, normal	Increased
Gallbladder and bile ducts	Relaxed	Contracted
Kidney	Decreased output and renin secretion	None
Bladder: – detrusor; – trigone	Relaxed (slight) Excited	Excited Relaxed
Penis	Ejaculation	Erection
Libido	Increased	Norm
Basal metabolism	Increased	Decreased
Fat accumulation	Weight loosing	Obesity
Skin colour	Pale	Tendency to hyperemia
Vascular figure	Is not expressed	Enforced
Allergy reactions (oedemas, itch)	Absent	Tendency
Sleeping	Short, bad	Sleepiness (somnolence)
Temperamentum	Excitability, enforced emotional tone, choleric, sanguinic	Low motility, phlegmatic, melancholic
White blood state	Leucocytosis, eosinopenia	Lymphocytosis, eosinophylia
Erythrocytes sedimentation rate, blood viscosity and coagulation	Increased	Decreased
Acid-alkaline equillibrium	Tendency to acidosis	Tendency to alkalosis
Cholesterol level in blood	Decreased, norm	Increased
K/Ca coefficient	Decreased	Increased
Copper level in blood	Increased	Decreased
Creatine level	Increased	Decreased
Blood sugar level	Increased, norm	Decreased
Fasting endurance	Usual	Bad (hypoglycaemia)
ECG	Sinus tachycardia	Sinus bradycardia, high dense T
Reaction to ultra-violet irradiation	Normal, decreased	Enforced
Orthosthatic probe	Pulse is relatively accelerated	Pulse is relatively retarded
Clinosthatic probe	Pulse is relatively retarded	Pulse is relatively accelerated
Ashner’s probe (eye-heart reflex)	Norm, paradox pulse acceleration	Significant pulse retardation
Electrical skin resistance	Norm, decreased	Increased

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