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8/11/2019 Autonomics I
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Autonomics IDr. Gloria Roque
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The Autonomic Nervous System Organization of Nervous System
in Man
Central Nervous SystemBrainSpinal
Peripheral Nervous SystemSomatic nervous system Autonomic nervous system
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The Autonomic Nervous System Differences Between Somatic and Autonomic Nervous System Somatic Nervous System
Fibers do not synapse once they have left the centralnervous systemInnervates skeletal muscle Always leads to excitation of the muscle
Autonomic Nervous SystemFibers synapse once in ganglia after they have left thecentral nervous systemInnervates smooth or cardiac muscle or gland cellsCan lead to excitation or inhibition of the effector cells
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Summary of Differences Between
SNS and ANSParts of Differences SNS ANS
1. Efferent pathway 1 neuron pathway 2 neuron pathway
2. Effector/s Skeletal muscle Smooth MuscleCardiac Muscle
Glands/Organs3. Effect of effective stimulation Always excitation of skeletal
muscleExcitation or inhibition ofeffector
4. Sites of Inhibition of impulse - CNS- neuroeffector junction
- CNS- Ganglion- Neuroeffector junction
5. Function For locomotion Regulates visceral functions
CNS CNS
.
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The Autonomic Nervous System
Subdivisions of ANS: Sympathetic NS Parasympathetic NS
Differences between SYMP. &PARA. NS Anatomical Biochemical Physiological Pharmacological
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Anatomical Differences BetweenSympathetic and ParasympatheticDivisions of the ANS
SYMPATHETICDIVISION
PARASYMPATHETICDIVISION
(a) Origin of preganglionicfibers
Spinal nerves T1-L2(thoracolumbar division)
Cranial nerves III, VII, IX, X;spinal nerves S2-S4 (cranio-sacral division)
(b) Location of Ganglia In sympathetic chain(paravertebral ganglia orabdominal prevertebral or
collateral ganglion,preganglionic fibers usually;shorter than post-ganglionicfibers (except adrenal medulla)
In or near effector organs thuspreganglionic fibers usuallylonger than post-ganglionic
fibers
(c) Branching of Preganglionicfibers
Extensive branching ave. ratiopreganglionic to postganglionicfibers = 1:20
Limited branching; ave. ratio ofpreganglionic to post-ganglionic fibers 1.1 (except the
vagus)
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Biochemical Differences Between
Sympathetic & Parasympathetic Divisions The transmission of an impulse along a nerve fiber is an electricalphenomenon. In contrast, transmission, across synapses and neuroeffector junctions is mediated by chemical substances called neurohumors orneurotransmitter agents (NTA)
2 Main NTAs of the ANS Acetylcholine (Ach) Norepinephrine (NE)
Nerves secreting Ach are CHOLINERGIC NervesNerves secreting NE are ADRENERGIC Nerves
Biochemical subdivision of ANS - Cholinergic Division- Adrenergic Division
CNS
.
Preganglionic fiber
ganglion (synapse)
Postganglionic fiber
Neuroeffector junction
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Summary of Neurohumoral
Transmission AUTONOMICCHOLINERGICSympatheticCholinergic
Sympathetic Adrenergic
Parasympathetic
SOMATIC
CNS
ACH
CNS CNS CNS
ACH
ACH
effectorcell
effectorcell
effectorcell
effectorcell *
ACh ACh AChNE
Pregang. Pregang. Pregang.
SomaticFibers
Postgang. Postgang. Postgang.
Transmitter
Transmitter
Sweat Glands blood vessels of skeletal
musclespiloerector muscles
SkeletalMuscle
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4 Steps in Chemical Transmission
Process Synthesis and / storage of NTA inthe prejunctional fiber
Release of NTA from the storage vesicles (exocytosis) Interaction of NTA with receptors
and initiation of post junctionalactivity Destruction or dissipation
(deactivation) of NTA
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NTA: Acetylcholine (ACH) Synthesized and stored in vesicles at the terminal of
prejunctional fibers Released by the terminals ofnerve fiber upon arrival of nerve
impulse- Influx of Ca ++ precedes therelease
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NTA: Acetylcholine (ACH) Interaction with receptors to produce the response:
Ach on Cholinergic Receptors:NicotinicMuscarinic
Cholinergic transmission occurs at the following 4 locations:1. All parasympathetic
neuroeffector junctions2. Sympathetic cholinergic
neuroeffector junctions3. All peripheral ganglia
4. All somatic neuromuscular junctions
Response excitatory or inhibitory in ANS
Deactivation: by enzymatic hydrolysis byacetycholinesterase (Ach E)
muscarinicreceptors
nicotinicreceptors
cholinergicreceptors
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Summary of adrenergic
receptor subdivision Alpha ( ) receptorsstimulation excitatory responses
examples: vasoconstriction in skin and mucosa;contraction of gastrointestinal
sphincters; piloerectionexception: decreased gastrointestinal motility and tone
Beta ( ) stimulation inhibitory responsesexamples: vasodilation in skeletal muscles
relaxation of bronchial muscleexception: increased heart rate, contractility,conduction velocity
B1 Receptors - found in the heartB2 Receptors - elsewhere in the body
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Summary of Receptors AUTONOMIC
SympatheticCholinergic
Sympathetic Parasympathetic
SOMATIC
CNS CNS CNS CNS
effectorcell **
effectorcell *
effectorcell
effectorcell **
muscarinic nicotinicmuscarinic Adrenegic receptors
Nicotinic Nicotinic Nicotinic
** (skeletal muscle)
Adrenergic Cholinergic
*** (receptor type) B1 B2
depends on effector
organ
** sweat glands(most individuals);
blood vessels of
skeletal muscles
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Relationship of Adrenal Medulla
and SympatheticSympathetic preganglionic fiber innervatesthe adrenal medullary cells.
Stimulation of sympathetics also stimulateadrenal medullary cells secretion and
release of norepinephrine & epinephrine
into circulation B1 B2 receptors.+
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2 Sources of NE Sympathetic Adrenergic
Postganglionic Fibers
Adrenal Medulla
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Source of E: Adrenal MedullaNE strongly and B1 receptors
weakly B2 receptors
E strongly B1 B2 receptors.
- Adrenal medulla reinforcessympathetic effects
+
+
+