Lecture 18 Lecture Outline:I Autonomic Nervous System:a. Sympathetic ganglia and pathwaysb. Parasympathetic ganglia and pathwaysc. Neurotransmitters of the ANSAutonomic Nervous System: - Efferent/motor pathway: CNS  (myelinated) Preganglionic fiber  autonomic ganglion  (non-myelinated) post ganglionic fiber  effector organs- Parasympathetic and sympathetic divisions can be differentiated anatomically:o Location of preganglionic nerve cell body (brain stem or spinal cord)o Point and means of exit of preganglionic axon from CNS (which cranial or which spinal nerve)o Location of ganglia- Sympathetic nervous system: o Location of preganglionic nerve cell bodies: Unipolar sensory neuron synapses in dorsal horn, then again in the lateral horn, then goes out to effectoro Types of ANS ganglia Paravertebral ganglia: most numerous, 2 sympathetic chains running down length of vertebral column. - Sympathetic trunks connect paravertebral ganglia Prevertebral or collateral ganglia: in stomach Adrenal medullae: in adrenal glands near kidneyso Efferent pathway of sympathetic ANS Presympathetic ganglion are extensively branched and usually take all four pathways and travel throughout entire body, giving widespread sympathetic responses Pathway always begins with synapse of interneuron with cell bodies of sympathetic ANS in lateral horn of spinal cord, preganglionic nerve then leaves through ventral root of spinal cord andenters sympathetic chain ganglion through white ramus communicans and can then take one of four pathways:- Synapse at same level:o Preganglionic neuron immediately synapses with post ganglionic neuron in sympchain ganglion and leaves through grey ramus out to effector- Synapse at a higher or lower levelo Preganglionic neuron will travel up or down sympathetic chain and synapse in a ganglion above or below it, then leave through grey ramus out to effector- Synapse in a collateral gangliono Preganglionic neuron leaves symp chain ganglion through splanchnic nerve and synapse in collateral ganglion then out to receptor- Synapse on chromaffin cell in adrenal medulla:o Leaves symp chain ganglion and synapses with endocrine/chromaffin cells in adrenal medulla to produce epinephrine (80%) or norepinephrine (20%)- Parasympathetic Nervous System: much less divergence of parasympathetic preganglionic neuronsBio 312o Most preganglionic neurons originate in cranial nerves 3,7,9,10  Cranial nerves 3,7,9 innervate organs in head and neck Cranial nerve 10 (vagus) innervate organs in thoracic cavity (stomach, intestines, liver- Mixed nerve, 90% of all PNS preganglionic fibers contained in vagus nerves- Vagal stimulation = parasympathetic stimulationo Parasympathetic preganglionic neurons travel from origin all the way to, or very close to the effector before they synapse with postganglionic neuron- Sympathetic nervous system: relatively short preganglionic axons with long post ganglionic axons- Parasympathetic nervous system: relatively long preganglionic axons, very short post ganglionic axonso Synapse very close to or in the effector organ- Neurotransmitters of the ANS: has 2 synapses to regulate (autonomic ganglion, effector organ)o Somatic nervous system uses stimulatory acetylcholineo Sympathetic and parasympathetic preganglionic axons utilize acetylcholineo All parasympathetic post ganglionic axons use acetylcholine with effector (cholinergic neurons)o Vast majority of sympathetic nervous system utilize norepinephrine with effector (adrenergic neurons)o Axons of post ganglionic autonomic neurons branch and cover many cells of the effector Varicosities: nodes in web of neuron covering effector that secrete NT to activate effector- Longer distances than typical synaptic cleft means slower acting and longer duration relative to other synaptic clefts- NT receptors of the ANS: receptors on effectors/postganglionic neuron must be the same type as NT released- Review slide 17 in slide set 2- Focus on nicotinic, muscarinic, beta receptorso Cholinergic receptors: activated by acetylcholine Nicotinic (N1 & N2): also activated by drug nicotine (always excitatory)- Found in skeletal muscles N1- Found in all autonomic postganglion neurons- N2 Muscarinic: also activated by drug muscarine- All parasympathetic target organs (excitatory everywhere except heart)- Found in sweat glandso Adronergic receptors: Activate by Norepinephrine or epinephrine Alpha: 2 subtypes- Constrict blood vessels and visceral organ sphinctes, dilates pupils- Inhibits NE release from adrenergic terminals Beta: 3 subtypes- 1: increases heart rate and strength, stimulates renin release by kidneys- 2: inhibitory in most cases, dilates blood vessels and bronchioles, relaxes smooth muscle walls of digestive and urinary tract visceral organs- 3: stimulates lipolysis by fat cells/mobilization of fatty acids for energy use Both found throughout heart Different types of effector cells only have 1 type of receptor- Extrinsic muscles of the eye: innervated by somatic NS, ACH activated N1 nichotinic