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
