Nervous System

Autonomic Nervous System

Lawrence M. Witmer, PhD I.Kevin Johnson, AS,BS, NREMTI. www.castonline.ilstu.edu

Nervous SystemCentral Nervous Systembrain & spinal cordbrain cordPeripheral Nervous SystemCranial and peripheral nervesSomatic nervous systemvoluntary movementAutonomic

Central nervous SystemPeripheral Nervous System

Somatic NervousAutonomic Nervous System System

ParasympatheticSympatheticAlfa reseptorBeta reseptor

Autonomic Nervous System

Responsible for control of involuntary or visceral bodily functionscardiovascularrespiratoryDigestiveUrinaryreproductive functionsKey role in the bodies response to stress

Autonomic Nervous SystemSympathetic nervous systemallow body to function under stressAlarm reaction : fight or flight response - dilation of pupilsincrease of heart rate, force of contraction & BPdecrease in blood flow to nonessential organsincrease in blood flow to skeletal & cardiac muscleairways dilate & respiratory rate increasesblood glucose level increaseParasympathetic nervous systemcontrols vegatative funtionsEnhance rest-and-digest activities (Mechanisms that help conserve and restore body energy during times of rest)constant opposition to sympathetic system

Major componentsNeuronSensory - AfferentMotoneurons- EfferentNeurotransmitterchemical substance which travels across a synaptic junction to act on a target cell.Effector Organsspecific tissues stimulated by the autonomic nervous system

Neuron

Autonomic Nervous systemactivated by reflex centers located in the brain and spinal cordReflex arccomplete circuit of nerves involved in an involuntary movementFrom the stimuli to the effector organ

NeurotransmitterNorepinephrinePost-ganglionic Neurotransmitter for the sympathetic nervous systemAcetylcholinepre-ganglionic neurotransmitter for both systemsPost-ganglionic neurotransmitter for the parasympathetic nervous system

SynapseJunction of Pre and Post synaptic neuronsNeurotransmitter produced in presynaptic membraneMoves across synaptic spacebinds with receptor on postsynaptic membranecauses impulse potential

Synapse

DopamineCycle

Neurologic ConductionInitiationSensory bodies initiate impulsedepolarizationAfferent impulseConductionimpulse is conducted along neuron to Synaptic JunctionNeurotransmitter is released

Synaptic Activityneurotransmitter is releasecrosses synaptic cleftStimulates receptors on next neuronImmediately, neurotransmitter is inactivated by enzyme (cholinesterase)Action Potential is intiated along 2nd neuronimpulse travels down efferent neuron to Effector Gland or muscle

SympatheticThoracolumbar T1 L2/L3 levels of the spinal cord

ParasympatheticCraniosacral Brain: CN III, VII, IX, X Spinal cord: S2 S4

Sympathetic Gangliatrunk (chain) ganglia near vertebral bodiesprevertebral ganglia near large blood vessel in gutceliac superior mesentericinferior mesenteric

Parasympathetic Gangliaterminal ganglia in wall of organ

Autonomic PlexusCardiac plexusPulmonary plexusCeliac (solar) plexusSuperior mesentericInferior mesentericHypogastric

Sympathetic Stimulation

Edivisionexerciseexcitementemergencyembarrassment

stimulate sweat glandsconstrict peripheral vesselsincrease blood to skeletal musclesincrease chronotropic and inotropic effects bronchodilationstimulation of NRG productionreduce blood flow to abdomendecrease digestive activityrelax smooth muscle in wall of bladderrelease glucose stores from liver

Symphatetic reseptors

As norepinephrine is released, it travels is across the synaptic cleft and interacts with adreneric receptorsEpinephrine will also stimulate these receptorsTwo Types of Sympathetic Receptorsadrenergicdopaminergic

Adrenergic ReseptorsAlpha 1Peripheral VasoconstrictionPositive inotropic effectNegative chronotropic effectAlpha 2Peripheral vasodilationlimits release of norepinephrinestimulated by excessive amounts of Norepinephrine synaptic in cleft

Beta 1positive inotropic effect on heartincreased contractilitypositive chronotropic effect on heart increased heart ratepositive dromotropic effect on heart automaticity

Beta 2Peripheral vasodilation Bronchodilation Uterine smooth muscle relaxationGI smooth muscle relaxation

Cholinergic

Cholinergic neurons release acetylcholine from preganglionic neurons & from parasympathetic postganglionic neurons

Excites or inhibits depending upon receptor type and organ involvedNicotinic receptors are found on dendrites & cell bodies of autonomic NS cells and at NMJMuscarinic receptors are found on plasma membranes of all parasympathetic effectors

Sympathomimeticsmeds that stimulate the sympathetic nervous systemSympatholyticsinhibit the sympathetic systemAlpha or Beta agoniststimulate Alpha sitesAlpha or Beta antagonistsblock effects of Beta stimulation

EpinephrineAlpha & Beta stimulatorAlpha Effectsarterioles in Bronchioles constrictReducing edemaPeripheral vasoconstrictionincreased BPBeta EffectBeta 1 - increases heart rate & COBeta 2 - bronchiole smooth muscle relaxesincreases lung capacity

Parasympathetic Nervous SystemDdivisiondigestiondefecationdiuresis (urination)

Pupillary constrictionSecretion by digestive glandsIncreased smooth muscle activity along GI tractBronchoconstrictionReduce HR & negative inotropic effects

Parasympathomimeticsstimulate parasympathetic nervousPhysostigmineAnticholinesterase inhibitorOD of Atropine, Tricyclic Antideressantss, CO poisoningSome research on improving Alzheimer'sParsympatholyticsblock action of parasympathetic systemAtropine Sulfateparasympathetic blocker

Cholinesterase breaks down excess Acetylcholine shutting down the parasympathetic system. Exposure to some organophosphates (fertilizers) or biochemical weapons such Sarin, Soman, Tabunbind up cholinesterase, preventing the system from shutting down and causing the signs belowSalivationLacrimation (teary eyes)UrinationDefecationGastric disturbanceEmesis

Antidote would be a parasympathetic blocking drug such as Atropine Sulphate

Physiological Effects of ANSMost body organs receive dual innervationinnervation by both sympathetic & parasympatheticHypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels Some organs have only sympathetic innervationsweat glands, adrenal medulla, arrector pili mm & many blood vesselscontrolled by regulation of the tone of the sympathetic system

Controlling Factors1. Autonomic reflexesExample: baroreceptorslocated in arteries sensitive to pressure changesresults in changes in heart rateThese reflexes control most of the activity of visceral organs, glands, and blood vessels.

2. Cerebrum3.Hipotalamus