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Physiology - Efferent branch of the PNS

Efferent branch of the PNS


2 parts:

  1. Somatic (skeletal muscles)
  2. Autonomic (smooth and cardiac muscles, glands)

Somatic Muscles

    • Voluntary (you can control the movement)
    • Singe neurons between CNS and effectors (muscle)
    • Innervates only skeletal muscles
    • Causes muscle excitation only (cannot inhibit muscle function)
    • Acetylcholine (ACh) (neurotransmitter used by neurons of CNS and PNS) primary neurotransmitter

****  Diagram goes here


Broken down into:

  • Parasympathetic (rest and digest)
  • Sympathetic (physical activity and stress)
    • Involuntary
    • 2 neuron chain between CNS and effectors
    • synapse between these neurons is located in cell clusters (autonomic ganglia)


  • pre ganglionic: cells leading from CNS to ganglion
  • Postganlionic: cells leading from the ganglion to the effector


  • Innervates smooth and cardiac muscles, glands, GI tract
  • Can be either excitory or inhibitory (has a finer level of control than somatic)
  • Primary neurotransmitters:
  • Acetylcholine

1.       Nicotinic receptors - in autonomic system, always at autonomic ganglion. Lets Na and K pass. 

 i.      First part always nicotinic

ii.      At motor end plates of sympathetic and parasympathetic ganglia

2.       Muscunaric receptors - in parasympathetic autonomic system. Only at target tissue.

  • Norepinephrine (NE) - for sympathetic autonomic system

Sympathetic Pathway

****  Diagram goes here

Parasympathetic Pathway

**** Diagram goes here

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