Autonomic Nervous SystemThe Autonomic Nervous SystemAutonomic versus Somatic NSSlide 4Basic Anatomy of ANSDivisions of the ANSSlide 7Sources of Dual InnervationANS NeurotransmittersParasympatheticSympatheticSlide 22Physiological Effects of the ANSSympathetic ResponsesParasympathetic ResponsesComparison1Autonomic Nervous SystemI. OverviewII. AnatomyIII. Physiology2The Autonomic Nervous SystemRegulate activity of smooth muscle, cardiac muscle & certain glandsStructures involved1. general visceral afferent neurons2. general visceral efferent neurons3. integration center within the brainReceives input from limbic system and other regions of the cerebrum3Autonomic versus Somatic NSSomatic nervous systemconsciously perceived sensationsexcitation of skeletal muscleone neuron connects CNS to organAutonomic nervous systemunconsciously perceived visceral sensations involuntary inhibition or excitation of smooth muscle, cardiac muscle or glandular secretiontwo neurons needed to connect CNS to organpreganglionic and postganglionic neurons4Autonomic versus Somatic NSAutonomic NS pathway is a 2 neuron pathway Somatic NS pathway only contains one neuron.5Basic Anatomy of ANSPreganglionic neuroncell body in brain or spinal cord axon is myelinated type B fiber that extends to autonomic ganglionPostganglionic neuroncell body lies outside the CNS in an autonomic ganglionaxon is unmyelinated type C fiber that terminates in a visceral effector6Divisions of the ANS2 major divisions1. parasympathetic2. sympatheticDual innervationone speeds up organone slows down organSympathetic NS increases heart rateParasympathetic NS decreases heart rate7Autonomic Nervous SystemI. OverviewII. AnatomyA. NeurotransmitterIII. Physiology8Sources of Dual Innervation1. Sympathetic (thoracolumbar) divisionpreganglionic cell bodies in thoracic and first 2 lumbar segments of spinal cord2. Parasympathetic (craniosacral) divisionpreganglionic cell bodies in nuclei of 4 cranial nerves and the sacral spinal cord19ANS NeurotransmittersClassified as either cholinergic or adrenergic neurons based upon the neurotransmitter releasedAdrenergicCholinergic20ParasympatheticCholinergic neurons release acetylcholine from preganglionic neurons & from parasympathetic postganglionic neuronsAction: Excites or inhibits depending upon receptor type and organ involvedReceptor:Nicotinic receptors are found on dendrites & cell bodies of autonomic NS cells and at NMJMuscarinic receptors are found on plasma membranes of all parasympathetic effectors21SympatheticAdrenergic neurons release norepinephrine (NE) from postganglionic sympathetic neurons onlyAction: Excites or inhibits organs depending on receptorsReceptor:Alpha1 and Beta1 receptors produce excitationAlpha2 and Beta2 receptors cause inhibitionBeta3 receptors (brown fat) increase thermogenesisNE lingers at the synapse until enzymatically inactivated by monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT)22Autonomic Nervous SystemI. OverviewII. AnatomyIII. PhysiologyA. HypothalamusB. SympatheticC. Parasympathetic23Physiological Effects of the ANSHypothalamusSome organs have only sympathetic innervationsweat glands, adrenal medulla, arrector pili mm & many blood vessels controlled by regulation of the “tone” of the sympathetic systemMost body organs receive dual innervationinnervation by both sympathetic & parasympatheticHypothalamus regulates balance (tone) between sympathetic and parasympathetic activity levels24Sympathetic ResponsesDominance by the sympathetic system is caused by physical or emotional stress -- “E situations”emergency, embarrassment, excitement, exercise Alarm reaction = flight or fight responsedilation of pupilsincrease of heart rate, force of contraction & BPdecrease in blood flow to nonessential organsincrease in blood flow to skeletal & cardiac muscleairways dilate & respiratory rate increasesblood glucose level increaseLong lasting due to lingering of NE in synaptic gap and release of norepinephrine by the adrenal gland25Parasympathetic ResponsesEnhance “rest-and-digest” activitiesMechanisms that help conserve and restore body energy during times of restNormally dominate over sympathetic impulsesSLUDD type responses = salivation, lacrimation, urination, digestion & defecation 3 “decreases”--- decreased HR, diameter of airways and diameter of pupilParadoxical fear when there is no escape route or no way to wincauses massive activation of parasympathetic divisionloss of control over urination and defecation26ComparisonCVS: HeartCVS: VeinsResp: BronchiolesGIT: Stomach and IntestinesGIT: LiverGIT: Gall BladderUT: KidneyUT: Urinary BladderRepro: Sex OrgansSympatheticIncrease HRConstrictionDilationEjaculationParasympatheticIncrease motilityGlycogenesisContractionDiuresisContraction/ urinationErectionRepro: Sex