THE AUTONOMIC NERVOUS SYSTEM

D. C. MIKULECKY

PROFESSOR OF PHYSIOLOGY

ORGANIZATION OF THE NERVOUS SYSTEM

BRAINSPINAL CORD

CENTRALNERVOUSSYSTEM (CNS)

PERIPHERALNERVOUS SYSTEM

AFFERENT

NERVES

EFFERENT

NERVES

EXTERO-RECEPTORS

INTERO-RECEPTORS

SOMATIC AUTONOMIC

EFFECTORORGANS

SKELETALMUSCLES

SMOOTH AND CARDIAC MUSCLES AND GLANDS

THE AUTONOMIC NERVOUS SYSTEM

• TWO NEURON CHAINS

• SYMPATHETIC

• PARASYMATHETIC

ORGANIZATION OF THE AUTONOMIC NERVOUS SYSTEM

SYMPATHETIC

GANGLIA

TARGET

ORGANS

BRAIN

SPINAL CORD

PARASYMPATHETIC

GANGLIA

TWO NEURON CHAINS

SPINEEFFECTOR

ORGAN

PRESYNAPTICNEURON

POSTSYNAPTICNEURON

SYMPATHETIC

SPINEEFFECTOR

ORGAN

SYMPATHETICGANGLIA (NEAR SPINE)

PARASYMPATHETIC

SPINEEFFECTOR

ORGAN

PARASYMPATHETICGANGLIA (NEAR EFFECTOR ORGAN)

AUTONOMIC CONTROL IS IN BRAIN STEM

• HYPOTHALAMUS

• PITUITARY

• PONS

• MEDULLA

PARASYMPATHETIC

• GANGLION NEAR EFFECTOR ORGAN• LONG PREGANGLIONIC NEURONS• SHORT POSTGANGLIONIC NEURONS• “COUCH POTATO”• POSTGANGLIONIC NEURONS ARE

CHOLINERGIC• CRANIAL AND SPINAL NERVES

SYMPATHETIC

• GANGLION NEAR SPINE

• SHORT PREGANGLIONIC NEURONS

• LONG POSTGANGLIONIC NEURONS

• FLIGHT OR FIGHT

• POSTGANGLIONIC NEURONS ARE ADRENERGIC

• THORACIC AND LUMBAR NERVES

EFFECTS OF ANSORGAN S PHEART + -BLOODVESSELS

CONSTRICT(MOSTORGANS)

DILATE (HEART

AND SKELETAL)

DILATE (PENISAND CLITORIS)

BRONCHIOLES DILATE CONSTRICT

PUPIL DILATE CONSTRICT

DIGESTION INHIBIT ENHANCE

DUAL INNERVATION OF MOST VISCERAL ORGANS

• MOST INNERVATED BY BOTH SYSTEMS

• EFFECTS ARE OPPOSITE IN MOST CASES

• TONIC ACTIVITY

• DOMINANCE

EFFECTS OF PRE AND POSTGANGLIONIC NEUROTRANSMITTERS: PHYSIOLOGY AND

PHARMACOLOGY

• NOREPINEPHRINE (ADRENERGIC):FLIGHT OR FIGHT REACTION (SYMPATHETIC POSTGANGLIONIC)

• ACETYLCHOLINE (CHOLINERGIC): “COUCH POTATO” RESPONSE (PARASYMPATHETIC POSTGANGLIONIC AND ALL PREGANGLIONIC).

ACETYLCHOLINE (CHOLINERGIC): “COUCH POTATO” RESPONSE (PARASYMPATHETIC

POSTGANGLIONIC AND ALL PREGANGLIONIC).

• NICOTINIC RECEPTORS (PREGANGLIONIC)

• MUSCARINIC RECEPTORS (POSTGANGLIONIC)

NICOTINIC RECEPTORS (PREGANGLIONIC)

• ACTIVATED BY ACETYL CHOLINE ENDOGENOUSLY AND NICOTINE EXOGENOUSLY

• BLOCKED BY CURARE AND HEXAMETHONIUM

MUSCARINIC RECEPTORS (POSTGANGLIONIC)

• ACTIVATED BY ACETYL CHOLINE ENDOGENOUSLY AND MUSCARINE EXOGENOUSLY

• BLOCKED BY ATROPINE

THE ADRENAL MEDULLA SECRETES EPINEPHRINE

• ANALOG TO A LARGE POST GANGLIONIC SYMPATHETIC NERVE TERMINAL

• IS AN ENDOCRINE GLAND: SECRETES THE HORMONE INTO THE BLOOD

TYPES OF RECEPTORS

• ALPHA: MORE SENSITIVE TO NOREPINEPHRINE

• BETA: MORE SENSITIVE TO EPINEPHRINE

ALPHA RECEPTORS

• ALPHA-1: POSTSYNAPTIC TARGET CELLS OF SYMPATHETICALLY INNERVATED ORGANS

• ALPHA-2: PRESYNAPTIC TERMINALS OF CHOLINERGIC NERVE FIBERS

BETA RECEPTORS

• BETA-1: EPINEPHRINE AND NE EQUALLY POTENT

• BETA-2: RESPOND BETTER TO EPINEPHRINE THAN TO NE (PROBABLY TO CIRCULATING HORMONE THAN TO NEUROTRANSMITTER)

FACTORS AFFECTING THE CONCENTRATION OF NE IN THE

JUNCTIONAL CLEFT

• NEURONAL UPTAKE

• DIFFUSION INTO CAPILARIES

• UPTAKE INTO EFFECTOR CELLS

AUTONOMIC REFLEXES

• REFLEX ARCS MIMIC SOMATIC SPINAL REFLEXES

• DEFICATION AND URINATION AMONG OTHERS

REFERRED PAIN

• PAIN PATHWAYS FROM VISCERA SHARE SECONDARY NEURONS WITH SOMATIC PAIN NEURONS

• HYPERALGESIC ZONES