Slide 1Autonomic Nervous SystemAutonomic Nervous SystemAutonomic NeuronsAutonomic NeuronsVisceral EffectorsComparing the EffectorsSympathetic DivisionSympathetic DivisionSympathetic DivisionCollateral GangliaAdrenal GlandsAdrenal GlandsAdrenal GlandsParasympathetic Division of ANSParasympathetic Division of ANSFunctions of the ANSCholinergic StimulationCholinergic StimulationReview on the ReceptorsAdrenergic StimulationAdrenergic StimulationAdrenergic StimulationAdrenergic StimulationAdrenergic StimulationAgonist and AntagonistBeta blockersNitric OxideOrgans with and without Dual InnervationControl of the ANSExam 2 Physiology- Chapter 9Autonomic Nervous System•“Law unto thyself”•The autonomic nervous system helps regulate the activities of cardiac muscle, smooth muscles, and glands. In this regulation, impulses are conducted from the CNS by an axon that synapses with a second autonomic neuron. It is the action of this second neuron in the pathway that innervates the involuntary effectors.Autonomic Nervous System•Autonomic motor nerves innervate organs whose functions are not usually under voluntary control. The effectors that respond to autonomic regulation include cardiac muscle, smooth muscles, and glands. These effectors are part of the visceral organs (organs within body cavities) and of blood vessels. The involuntary effects of autonomic innervation contrast with the voluntary control of skeletal muscles by way of somatic motor neurons.Autonomic Neurons•Neurons of the peripheral nervous system (PNS) that conduct impulses away from the central nervous system are known as motor, or efferent, neurons. There are 2 major categories of motor neurons: somatic and autonomic. •Somatic motor neurons have their cell bodies within the CNS and send axons to skeletal muscles, which are usually under voluntary control. Somatic motor neurons conduct impulses along a single axon from the spinal cord to the neuromuscular junction.Autonomic Neurons•Autonomic motor control involves two neurons in the efferent pathway. The first of these neurons (preganglionic neuron) has its cell body in the gray matter of the brain or spinal cord. The axon of this neuron does not directly innervate the effector organ but instead synapses with a second neuron (postganglionic neuron) within an autonomic ganglion. The post ganglionic neuron has an axon that extends from the autonomic ganglion to an effector organ, where it synapses with its target tissue.Visceral Effectors•Unlike skeletal muscles, which enter a state of flaccid paralysis and atrophy when their motor nerves are severed, the involuntary/visceral effectors are independent of their innervation. Cardiac muscle and visceral effectors can contract on own without any neural input.Comparing the EffectorsSomatic Effectors•Skeletal muscle•Somatic motor neurons generate action potentials or don’t.•Somatic motor neurons are cholinergic, receptors are nicotinic. •Always stimulates effector organ (EPSPs).Visceral Effectors•Cardiac muscle, smooth muscle, and glands (contract all my itself without innervation).•Autonomic innervation simply increases or decreases this intrinsic activity. Autonomic nerves maintain a resting tone that can either be increased or decreased (Parasympathetic). For example, a decrease in the excitatory input to the heart will slow its rate of beat.•Can stimulate or inhibit effector organs (EPSPs or IPSPs)(Sympathetic).Sympathetic Division •The autonomic system is divided into the sympathetic and parasympathetic divisions. •The sympathetic division is also called the thoracolumbar division of the autonomic system because the cell bodies of preganglionic neurons are located in the spinal nerves from the T1 (first thoracic)-L2 (second lumbar).•Most synaptic nerve fibers separate from the somatic motor fibers and synapse with postganglionic neurons within a double row of sympathetic ganglia called paravertebral ganglia. Ganglia within each row are interconnected, forming a sympathetic chain of ganglia that parallels the spinal cord on each lateral side.•Review: Every segment of spinal cord is a spinal nerve. Backbone composed of vertebrae (7 of them). Cervical vertebrae are in neck (7 of them). Thoracic vertebrae are in chest and have ribs attached to them. Lumbar vertebrae (trunk diaphragm) have absence of ribs. Sacrum is 5 vertebrae fused together to help support legs. The tail has smaller coccygeal vertebrae .Sympathetic Division•The myelinated preganglionic sympathetic axons exit the spinal cord in the ventral roots of spinal nerves, but they soon diverge from the spinal nerves within short pathways called white rami communicates. The axons within each ramus enter the sympathetic chain of ganglia, where they can travel to ganglia at different levels and synapse with post ganglionic sympathetic neurons. The axons of the postganglionic sympathetic neurons are unmyelinated and form the gray rami communicates as they return to the spinal nerves and travel as part of the spinal nerves to their effector organs.Sympathetic Division•Divergence occurs within the sympathetic chain of ganglia as preganglionic fibers branch to synapse with numerous postganglionic neurons located in ganglia at different levels in the chain•Convergence also occurs here when a postganglionic neuron receives synaptic input from a large number of preganglionic fibers. •The divergence of impulses from the spinal cord to the ganglia and the convergence of impulses within the ganglia can result in the mass activation of almost all of the post ganglionic sympathetic neurons. This mass activation allows the entire sympathetic division to be constantly active to a certain degree and to increase its activity in response to “fight or flight” situations. •However, mass activation does not always occur. In response to particular visceral stimuli (changes in blood pressure, blood volume, and plasma osmolality), the CNS can direct appropriate increases or decreases in the activity of postganglionic sympathetic axons to the heart and kidneys that allows these organs to compensate for the changes and maintain homeostasis.Collateral Ganglia•Many preganglionic fibers that exit the spinal cord below the level of the diaphragm pass through the sympathetic chain of ganglia without synapsing. Beyond the sympathetic chain, these preganglionic fibers form splanchnic nerves. Preganglionic fibers in the splanchnic nerves synapse in