chapter 11 efferent division

8/7/2019 Chapter 11 Efferent Division

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Efferent Peripheral NS: The Autonomic &Efferent Peripheral NS: The Autonomic &

Somatic Motor DivisionsSomatic Motor Divisions

Running Problem: Smoking



Review (again)Review (again)



H omeostasis and theH omeostasis and the Autonomic DivisionAutonomic Division

BP, H R, Resp., H BP, H R, Resp., H 2 2 O balance, Temp. . .O balance, Temp. . .

Mostly dual reciprocal innervationMostly dual reciprocal innervation

i.e., agonist/antagonist or excitatory/inhibitory i.e., agonist/antagonist or excitatory/inhibitory

Sympathetic:Sympathetic:

AKA Thoracolumbar AKA Thoracolumbar

flight flight--or or--fight fight

Parasympathetic:Parasympathetic:

AKA Craniosacral AKA Craniosacral

rest and digest rest and digest



Autonomic TargetsAutonomic Targets Smooth MuscleSmooth Muscle

Cardiac MuscleCardiac Muscle

Exocrine GlandsExocrine Glands

Some Endocrine glandsSome Endocrine glands

Lymphoid TissueLymphoid Tissue AdiposeAdipose



Autonomic pathway:Autonomic pathway: Two Efferent Neurons inTwo Efferent Neurons in

SeriesSeriesPreganglionic neuron cell body in CNS Preganglionic neuron cell body in CNS

Synapse in autonomic ganglion outside CNS (oftenSynapse in autonomic ganglion outside CNS (often divergencedivergence!)!)

Postganglionic neuronsPostganglionic neurons

target cellstarget cells

N1 N 2



= Thoracolumbar

division (T1 to L2 )

Preganglionic neurons (N1)from

thoracolumbar region of spinal cord

Pre and paravertebral ganglia

Long postganglionic neurins (N 2 )

secrete NE onto adrenergic receptors



= Craniosacral Division

Long preganglionic axons from

brain & S 2 - S4

Intramural ganglia

Postganglionic (nonmyelinated)neurons secrete ACh onto

cholinergic muscarinic receptors



Most Common Autonomic NTs:Most Common Autonomic NTs:

Acetylcholine (ACh)Acetylcholine (ACh)ACh neurons & ACh receptors are called ACh neurons & ACh receptors are called cholinergic cholinergic

(nicotinic or muscarinic).(nicotinic or muscarinic). Located at autonomic Located at autonomic preganglionic & parapreganglionic & para--sympathetic postganglionic sympathetic postganglionic synapsessynapses

Norepinephrine (NE)Norepinephrine (NE)NE neurons & receptors are called (nor)NE neurons & receptors are called (nor) adrenergic ( adrenergic ( EE and and

FF).). Located at sympathetic postganglionic synapsesLocated at sympathetic postganglionic synapses

Fig 11-7



NTs of Autonomic NS NTs of Autonomic NS

Compare to Fig 11-7

E and

N1

N1

N 2

N 2



Neuroeffector JunctionNeuroeffector Junction= Synapse between postganglionic cell = Synapse between postganglionic cell

and target and target

Most are different from model Most are different from model

synapsesynapse (compare to Fig 8 (compare to Fig 8--20 , p.20 , p.2 7 0 )2 7 0 )

ANS synapse: axon hasANS synapse: axon has varicositiesvaricositiescontaining neurotransmitter containing neurotransmitter

May supply many cells, resulting inMay supply many cells, resulting in

less specific communicationless specific communication

Synthesis of NT is in the varicosity Synthesis of NT is in the varicosity

Fig 11-8



Summary:Summary: PrePre-- & Postganglionic Parasympathetic & Postganglionic Parasympathetic

Neurons Release AChNeurons Release ACh

muscarinic muscarinic nicotinic nicotinic

Receptors

N1

N 2



Two Types of Cholinergic Receptors:Two Types of Cholinergic Receptors:

Nicotinic and Muscarinic Nicotinic and Muscarinic

1.1.

Nicotine=

agonist Nicotine=

agonist 2 .2 . In autonomic ganglia & somatic NS In autonomic ganglia & somatic NS

3.3. Directly opens a NaDirectly opens a Na++ & K & K ++ channel:channel: ? ?

4.4. Curare = antagonist Curare = antagonist

1) Nicotinic

cholinergic

receptor



2 )2 ) Muscarinic cholinergic Muscarinic cholinergic

receptor receptor

Muscarine = agonist Muscarine = agonist

Found in neuroFound in neuro--effector junctions of effector junctions of parasympathetic branchparasympathetic branch

G G--protein coupled mechanismsprotein coupled mechanisms

Atropine = antagonist Atropine = antagonist

Amanita muscarina

N1

N 2



Muscarinic ACh are G Muscarinic ACh are G--protein Mediated protein Mediated Receptor Mechanism of Sweat GlandsReceptor Mechanism of Sweat Glands::

Also some 2 Also some 2 nd nd

messenger mechanismsmessenger mechanisms



Adrenergic Adrenergic

ReceptorsReceptors

Found in neuroeffector junctions of sympathetic branchFound in neuroeffector junctions of sympathetic branch

G protein linked, with various 2 G protein linked, with various 2 nd nd mess. Mechmess. Mech

NT is NE NT is NE

-- and and -- ReceptorsReceptors



NE Action



Sympathetic ReceptorsSympathetic Receptors

Receptors:Receptors:

��NT is NE NT is NE

��(most common)(most common) ExcitationExcitation [Ca2 +] In[Ca2 +] Inoo muscle

contraction or secretion by exocytosis.� Inhibition of GI tract and pancreas



FF ReceptorsReceptors Clinically more important Clinically more important

FF ExcitationExcitation heart heart ([ ([ E] = [NE])E] = [NE])

³ ³ FF -- blockers´ = Antagonistsblockers´ = Antagonists (e.g.: Propranolol)(e.g.: Propranolol)

FF usually usually inhibitory inhibitory : smooth muscle relaxation of some blood : smooth muscle relaxation of some blood vessels and vessels and bronchiolesbronchioles ([E] > [NE])([E] > [NE])

FF Adipose; [NE]>[E]Adipose; [NE]>[E]

³ ³ FF --blockers´ = Antagonistsblockers´ = Antagonists (e.g.: Propranolol)(e.g.: Propranolol)



Termination of NT Termination of NT

Activity Activity

ACh:ACh: ACh esteraseACh esterase

CatecholamineCatecholaminereuptakereuptake repackagingrepackaging

degradation (MAO )degradation (MAO )

Blocked by cocaineBlocked by cocaine

Fig 11-9

Fig 8-22



Somatic Motor DivisionSomatic Motor Division Pathway consists of single neuron fromPathway consists of single neuron from

CNS to target CNS to target

Neuromuscular junction:Neuromuscular junction: nicotinic nicotinic

cholinergic receptorscholinergic receptors

Similar to synapse; post Similar to synapse; post ±± synaptic synaptic

membrant called Motor End Platemembrant called Motor End Plate

Recall Motor Unit Recall Motor Unit

Always excitatory Always excitatory muscle contractsmuscle contracts

All Ach mediated All Ach mediated

Degraded by Ach esteraseDegraded by Ach esteraseFig 11-13



Myasthenia gravis

MG: Antibodies block, alter, or destroy the receptors for

acetylcholine at the neuromuscular junction



Direct (Ant)agonist = mimic or block the NT receptor Direct (Ant)agonist = mimic or block the NT receptor (Ant)agonist = mimic or block secretion, reuptake or (Ant)agonist = mimic or block secretion, reuptake or

degradation of NT degradation of NT



Strychnos Toxifera( Curare) from Koehler's

Medicinal-Plants 1887

Direct Direct AntagonistsAntagonists

AtropineAtropineppmuscarinic muscarinic

CurareCurarepp nicotinic nicotinic

Propranolol Propranolol pp

FF11 and and FF2 2

Metoprolol Metoprolol pp FF11



Indirect (Ant)agonistsIndirect (Ant)agonists Botulinum toxinBotulinum toxin

pp inhibits ACh releaseinhibits ACh release

Parathion, malathionParathion, malathion organophosphate insecticidesorganophosphate insecticides pp inhibit inhibit

AChE (anticholinesterases)AChE (anticholinesterases)

CocaineCocaine

pp prevents NE reuptakeprevents NE reuptake

AmphetaminesAmphetamines

pp stimulates NE releasestimulates NE release



Summary Summary of Efferent of Efferent NS NS

chapter 11 efferent division

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