Chapter 15: The Autonomic Nervous SystemChapter ObjectivesCOMPARISON OF SOMATIC AND AUTONOMIC NERVOUS SYSTEMS1. List the structural and functional characteristics of the autonomic nervous system.2. Distinguish between the pre- and postganglionic neurons, in terms of location.3. Specify the different origins and destination ganglia for the sympathetic (thoracolumbar) and parasympathetic (craniosacral) preganglionic neurons.4. Describe the differing locations of the ganglia of the sympathetic and parasympathetic systems.PHYSIOLOGICAL EFFECTS OF THE ANS5. Discuss the primary purpose of the sympathetic division and the general body functions itdirects.6. Describe specific responses of effectors due to increased sympathetic stimulation.7. Discuss the primary purpose of the parasympathetic division and the general body functions it directs.8. Describe specific responses of effectors due to increased parasympathetic stimulation.ANS NEUROTRANSMITTERS AND RECEPTORS9. Identify the cholinergic neurons, receptors, and neurotransmitters.10. Identify the adrenergic neurons, receptors, and neurotransmitters.Chapter Lecture NotesCharacteristics of the autonomic nervous system (Table 15.1)Involuntary control Sensory input mostly from interoceptorsMotor pathways divided into sympathetic and parasympathetic divisionsTwo-neuron pathway (Fig 15.1)PreganglionicPostganglionicNeurotransmittersPreganglionic – acetylcholinePostganglionic – acetylcholine (parasympathetic and sympathetic to sweat glands (except on palms and soles), blood vessels in skeletal muscle and arrector pili muscles) or norepinephrine (remainder of sympathetic)Effects smooth muscle, cardiac muscle and glands Physiological effects of the autonomic nervous system (Table 15.4)Sympathetic – “E” situations (exercise, emergency, excitement and embarrassment) - fight or flight responsePupils dilateHeart rate, force of contraction and blood pressure increaseAirways dilateBlood vessels to kidneys and gastrointestinal tract constrictBlood vessels to skeletal muscles, cardiac muscle, liver and adipose tissue dilateLiver cells perform glycogenolysis and lipid cell perform lipolysisRelease of glucose by the liverParasympathetic – rest and digest responseIncreased salivation, lacrimation, urination, digestion and defecationDecreased heart rate, diameter of airways and diameter of pupils (constriction)Anatomical Differences between the Parasympathetic and Sympathetic Divisions (Table 15.3)Characteristics Parasympathetic SympatheticOrigin (Fig 15.2 & 15.3) Craniosacral outflow: brainstem nuclei of cranial nerves III, VII, IX and X; spinal cord segments S2-S4 Thoracolumnar outflow: lateral horn of gray matter of spinal cord segments T1-L2Location of ganglia Ganglia in (intramural= terminal) or close to visceral organ servedGanglia within a few cm of CNS: alongside vertebral column (paravertebral ganglia=chain) and anterior to vertebral column (prevertebralganglia)Relative length of pre- and postganglionic fibersLong preganglionic; short postganglionicShort preganglionic; long postganglionic Sympathetic ganglia (Fig 15.5)Paravertebral ganglia = chain gangliaInnervate organs above the diaphragm like the heart and lungsPrevertebral ganglia = collateral gangliaPrevertebral ganglia surround the following arteries that branch from the aortaCeliac artery (celiac ganglia forms the solar plexus)Superior mesenteric arteryInferior mesenteric artery Neurotransmitters and receptors (Table 15.2 & Fig 15.7)Cholinergic neurons – release acetylcholine (all preganglionic neurons, select sympathetic postganglionic neurons and all parasympathetic postganglionic neurons)Cholinergic receptors – receptors on the postsynaptic membrane that bind acetylcholineNicotinic receptorFound in the dendrites and cell bodies of sympathetic and parasympathetic postganglionic neurons, the motor end plate in the neuromuscular junction and adrenal medullary cells (excitatory)Is mimicked by nicotineMuscarinic receptorFound in all parasympathetic target organs (excitatory in all but cardiac muscle where it is inhibitory), sweat glands (activation) and some blood vessels in skeletal muscle(inhibition; vasodilation) and arrector pili muscle (excitatory)Is mimicked by muscarine (a mushroom poison)Adrenergic neurons – release norepinephrine (most sympathetic postganglionic neurons) Adrenergic receptors – bind norepinephrine and epinephrine α1Smooth muscle of blood vessels (excitation; vasoconstriction)radial muscles of eye (dilation of pupil) sphincter muscles of stomach and urinary bladder (closing)salivary gland cells (decreased salivation) sweat glands on palms and soles (increased sweating)α2 Smooth muscle in some blood vessels (inhibition; vasodilation) beta cells in pancreatic islets (decrease insulin secretion)pancreatic acinar cells (inhibition of digestive enzyme secretion)blood platelets (aggregation)β1 Cardiac muscle (excitation; increased force and rate of contraction) posterior pituitary (secretion of antidiuretic hormones)adipose cells (breakdown of triglycerides)β2Smooth muscle in airways (relaxation; bronchodilation) blood vessels (relaxation; vasodilation) walls of internal organs (relaxation) cillary muscles (inhibition; relaxation) hepatocytes (glycogenolysis)β3 – Brown adipose tissue (thermogenesis)Sympathetic ResponsesTarget Organ Ganglia LocationEffectBlood vessels of skeletal and cardiac muscleParavertebral DilationBlood vessels of skin, gut and kidneys Paravertebral ConstrictionArrector pili muscle Paravertebral ContractionSweat Glands Paravertebral Sweat productionEyes Paravertebral Dilates pupils and relaxes ciliary muscles for far visionLungs Paravertebral Dilates bronchiHeart Paravertebral Increased rate and force of contractionLiver Prevertebral Breakdown of glycogen to glucose and triglyceridesto fatty acidsSmall and Large Intestines Paravertebral Slows digestion, stops secretions and contracts sphinctersUrinary Bladder Paravertebral Contracts sphincterAdrenal Medulla Stimulates release of norepinephrine and epinephrineParasympathetic ResponsesTarget Organ Origin EffectEyes Cranial Nerve III Constricts pupils and ciliary muscles for near vision and stimulates tearsSalivary Glands Cranial Nerve VII&IX Stimulate salivationLungs Cranial Nerve X Constricts bronchi and stimulates secretionHeart Cranial Nerve X Decreased rate and force of contractionGall Bladder Cranial Nerve X ConstrictionPancreas Cranial Nerve X Stimulation of exocrine