PHIS 206 Lecture Notes - Lecture 8: Parasympathetic Nervous System, Sympathetic Nervous System, Sympathetic Ganglion
2 May 2018
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Professor
Lecture 8: PNS Efferent - ANS and NMJ
PNS Efferent Division
• Autonomic Nervous System
• Somatic Nervous System - control skeletal muscle
• The Neuromuscular Junction
Autonomic Organization
• Autonomic signals originate in the CNS and employ a two neuron system to reach target
• Ganglion (plural ganglia) → bundle of nerve tissue
• Skeletal muscles are not targets of the autonomic nervous system
ANS Overview
• Diagram
• Parasympathetic nervous system and sympathetic nervous system oppose each other
• They originate from different place, PSNS is from head and pelvic region, SNS more
from mid body
PSNS (Parasympathetic Nervous System) Fibers, Neurotransmitters, and Receptors
• Long preganglionic fibers
• Short postganglionic fibers
• PSNS preganglionic fibers release acetylcholine (ACh) that activates nicotinic (also
responds to nicotine) receptors on postganglionic fibers
• PSNS postganglionic fibers release ACh that activates muscarinic receptors (responds to
ACh) on target organ (do not have nicotinic receptors)
SNS Fibers, Neurotransmitters, and Receptors
• Short preganglionic fibers
• Long postganglionic fibers
• SNS preganglionic fibers release ACh that activates nicotinic receptors on postganglionic
fibers
• SNS postganglionic fibers release NE (norepinephrine, or noradrenaline) that activates
adrenergic receptors on target organ
• SNS also causes epinephrine release into bloodstream via the adrenal medulla→ acts on
adrenergic receptors
• Adrenergic receptor types → alpha-1, alpha-2, beta-1, beta-2
• Not everything that you want to control will have nerves attached to it, but will have
receptors (makes sense, kinda like hormone receptors i guess?)
SNS vs PSNS
• You should know this
• Parasympathetic system tries to make you rest
• Parasympathetic tries to slow heart, sympathetic tries to make it faster
• Both these systems are always on, never off
find more resources at oneclass.com
find more resources at oneclass.com
• If you want heart to slow, you don’t have to turn up parasympathetic nervous system, you
can just turn down sympathetic system (and vice versa)
Comparison of the Sympathetic and the Parasympathetic Nervous System
Feature
Sympathetic System
Parasympathetic
System
Origin of preganglionic
fiber
Thoracic and lumbar regions of the
spinal cord
Brain and sacral region
of the spinal cord
Origin of
postganglionic fiber
Sympathetic ganglion chain (near the
spinal cord) or collateral ganglia (about
halfway between spinal cord and
effector organs)
Terminal ganglia (in or
near effector organs)
Fiber length
Short preganglionic fibers, long
postganglionic fibers
Long preganglionic
fibers, short
postganglionic fibers
Neurotransmitter
Released
Preganglionic: ACh
Postganglionic: NE
Preganglionic: ACh
Postganglionic: ACh
Types of Receptors for
Neurotransmitters
For preganglionic neurotransmitter:
nicotinic
For postganglionic neurotransmitter:
alpha-1, alpha-2, beta-1, beta-2
For preganglionic
neurotransmitter:
nicotinic
For postganglionic
neurotransmitter:
muscarinic
Dominance
Dominates in “fight-or-flight” situations
Dominates in “rest-and-
digest” situations
ANS Overview 2
• Dual Innervation
o Many organs receive both PSNS and SNS inputs
o Receiving opposing input (hence DUAL)
• Atropine → blocks parasympathetic system
ANS Actions
• Sympathetic nervous system job is to save your life, bring you back from that is job of
parasympathetic nervous system
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 8: pns efferent - ans and nmj. Pns efferent division: autonomic nervous system, somatic nervous system - control skeletal muscle, the neuromuscular junction. Autonomic organization: autonomic signals originate in the cns and employ a two neuron system to reach target, ganglion (plural ganglia) bundle of nerve tissue, skeletal muscles are not targets of the autonomic nervous system. Ans overview: diagram, parasympathetic nervous system and sympathetic nervous system oppose each other, they originate from different place, psns is from head and pelvic region, sns more from mid body. Ach) on target organ (do not have nicotinic receptors) Sns vs psns: you should know this, parasympathetic system tries to make you rest, parasympathetic tries to slow heart, sympathetic tries to make it faster, both these systems are always on, never off. If you want heart to slow, you don"t have to turn up parasympathetic nervous system, you can just turn down sympathetic system (and vice versa)
