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The Peripheral Nervous System: Efferent Division

The Peripheral Nervous System: Efferent Division. Chapter 7. Objectives. PNS: Efferent Division. System by which CNS communicates and controls muscles and glands Autonomic and somatic systems. Overview of Nervous System. octc.kctcs.edu. Autonomic Nervous System.

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The Peripheral Nervous System: Efferent Division

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  1. The Peripheral Nervous System:Efferent Division Chapter 7

  2. Objectives

  3. PNS: Efferent Division • System by which CNS communicates and controls muscles and glands • Autonomic and somatic systems

  4. Overview of Nervous System octc.kctcs.edu

  5. Autonomic Nervous System • System of motor neurons that innervates smooth and cardiac muscle and glands • Involuntary nervous system • General visceral motor system

  6. Characteristics • Effectors • Cardiac and smooth muscle • Glands • Efferent Pathway • Involves two neurons • Ganglia • Preganglionic neuron > preganglionic axon > ganglionic neuron > postganglionic axon > effector • Neurotransmitter • Norepinephrine, acetylcholine • Excitatory, inhibitory • All preganglionic neurons release acetylcholine

  7. Divisions of ANS • Sympathetic • Fight or flight • Norepinephrine • Cholinergic fibers • Parasympathetic • Rest and digest • Acetylcholine • Adrenergic fibers • Dual innervation • Counterbalance • Tonic activity • Ongoing activity of both divisions becomehealthynow.com

  8. Parasympathetic Division • Anatomically simpler • Craniosacral origin • Cranial nerves III, VII, IX, X • Oculomotor • Facial • Glossopharyngeal • vagus • Splanchnic nerves S2 - S4 anatomy.med.umich.edu

  9. Sympathetic Division • Anatomically more complex • Innervates more organs • Thoracolumbar origins • T1 – L2 • Sympathetic chain (A) • Paravertebral ganglia wps.aw.com

  10. Paravertebral Ganglia • Synapse within same chain ganglion • Ascend or descend then synapse in chain ganglion • Pass through chain ganglion without synapsing • Collateral ganglia anatomy.med.umich.edu

  11. Receptor Types • Initiate tissue specific response • Cholinergic receptors • Acetylcholine receptors • Nicotinic • Opens nonspecific ion channels in postganglionic cell • Action potential results • Excitatory • Muscarinic • Activate secondary messengers via G proteins • Cardiac and smooth muscles, exocrine and few endocrine glands • Excitatory of inhibitory

  12. Receptor Types • Adrenergic receptors • Norepinephrine and epinephrine receptors • Alpha1 • Most sympathetic tissues • Activates IP3/Ca2+ secondary messenger pathway • Excitatory • Alpha2 • Digestive organs • Inhibitory (inhibits cAMP) • Beta1 • Heart • Activates cAMP • Excitatory • Beta2 • Smooth muscle of small vessels • Activates cAMP • inhibitory

  13. Somatic Nervous System • Motor neurons supply skeletal muscle • Single neuron with cell bodies in ventral horn of spinal cord • Release acetylcholine • Only excitatory

  14. Neuromuscular Junction • Junction of motor axon with a muscle cell • Only one junction per muscle cell • Motor end plate • Specialized area on muscle cell for synapse • High concentration of cholinergic receptors • Open nonspecific ion channels • Na+ rushes in producing an end-plate potential • Action potential on muscle cell • EPP opens ion channels in adjacent membrane • Threshold is reached and an action potential propagates away from the motor end plate

  15. Acetylcholinesterase • Enzyme that inactivate Ach • Ensures that muscles only contract when needed • Please look at chemicals and disease associated with the neuromuscular junction

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