The Autonomic Nervous System

The Autonomic Nervous System - The Autonomic Nervous System...

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Unformatted text preview: The Autonomic Nervous System 2 Autonomic Nervous System (ANS) The ANS consists of motor neurons that: l Innervate smooth and cardiac muscle and glands l Make adjustments to ensure optimal support for body activities l Operate via subconscious control l Have viscera as most of their effectors 3 Divisions of the ANS Sympathetic division (thoracolumbar, fight or flight) l Thoracic and lumbar segments Parasympathetic division (craniosacral, rest and repose) l Preganglionic fibers leaving the brain and sacral segments Enteric nervous system (ENS) l May work independently 4 ANS in the Nervous System 5 Sympathetic and Parasympathetic Often they have opposing effects May work independently May work together each one controlling one stage of the process 6 ANS Versus Somatic Nervous System (SNS) The ANS differs from the SNS in the following three areas l Effectors l Efferent pathways l Target organ responses 7 Effectors The effectors of the SNS are skeletal muscles The effectors of the ANS are cardiac muscle, smooth muscle, and glands 8 Efferent Pathways Heavily myelinated axons of the somatic motor neurons extend from the CNS to the effector Axons of the ANS are a two-neuron chain l The preganglionic (first) neuron has a lightly myelinated axon l The ganglionic (second) neuron extends to an effector organ 9 Neurotransmitters and Receptors 10 Neurotransmitter Effects All somatic motor neurons release Acetylcholine (ACh), which has an excitatory effect In the ANS: l Preganglionic fibers release ACh l Postganglionic fibers release norepinephrine or ACh and the effect is either stimulatory or inhibitory l ANS effect on the target organ is dependent upon the neurotransmitter released and the receptor type of the effector 11 Comparison of Somatic and Autonomic Systems 12 13 Preganglionic neurons between segments T1 and L2 lateral gray horn of spinal cord Preganglionic fibers l Short l Travel in the ventral root and spinal nerve Ganglionic neurons in ganglia near vertebral column l Specialized neurons in adrenal glands Postganglionic fibers l Long fibers Sympathetic division anatomy 14 Sympathetic chain ganglia (paravertebral ganglia) Collateral ganglia (prevertebral ganglia) Adrenal medulla Sympathetic ganglia 15 The Organization of the Sympathetic Division 16 Organization and anatomy of the sympathetic division Segments T1-L2, ventral roots give rise to myelinated white ramus Leads to sympathetic chain ganglia 17 Some fibers will return to the spinal nerve through a gray ramus and will innervate skin, blood vessels, sweat glands, adipose tissue, arrector pili muscle Some fibers will form...
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The Autonomic Nervous System - The Autonomic Nervous System...

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