1. The Peripheral Nervous System: Efferent Division
Chapter 7
The Peripheral Nervous System: Efferent Division

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 Efferent Pathway Neurotransmitter
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 Parasympathetic Dual innervation
Fight or flight
Norepinephrine
Cholinergic fibers
Parasympathetic
Rest and digest
Acetylcholine
Adrenergic fibers
Dual innervation
Counterbalance
Tonic activity
Ongoing activity of both divisions
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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 Thoracolumbar origins
Innervates more organs
Thoracolumbar origins
T1 – L2
Sympathetic chain (A)
Paravertebral ganglia
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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
Beta2
Smooth muscle of small vessels
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