AUTONOMIC NERVOUS SYSTEM

Preganglionic neuron

Postganglionic neuron

Two divisions:

Sympathetic

Parasympathetic

Anatomy of Autonomic Motor Pathways

Action Potential

Na+

aa

b

ACH

Acetylcholinesterase

Na+

Parasympathetic Ganglionic Synapse

Preganglionic neuron Postganglionic neuron

Nicotinic

Receptor

Action Potential

Na+

ACH

Acetylcholinesterase

Parasympathetic Organ Synapse

K+

G

Effector

Organ

Postganglionic neuron

Muscarinic

Receptor

Summary of parasympathetic neurons

and synapses

Preganglionic neurons Long

Synapse with postganglionic neurons at or near organ

Release acetylcholine (ACH) to activate nicotinic receptors

on postganglionic neurons

Postganglionic neurons Short

Synapse on the target organ

Release acetylcholine (ACH) to activate muscarinic

receptors on the target organ

Action Potential

Na+

aa

b

ACH

Acetylcholinesterase

Na+

Sympathetic Ganglionic Synapse

Preganglionic neuron Postganglionic neuron

Nicotinic

Receptor

Action Potential

Na+

NE

Sympathetic Organ Synapse

Effector

Organ

Postganglionic neuron

Adrenergic

Receptor

Summary of sympathetic neurons

and synapses

Preganglionic neurons

Short

Synapse with postganglionic neurons near spinal cord

Release acetylcholine (ACH) to activate nicotinic

receptors on postganglionic neurons

Postganglionic neurons

Long

Synapse on the target organ

Release norepinephrine to activate adrenergic

receptors on target organs

General principles of chemical

transmission

Dale’s principleIts unlikely that a single neuron can store and release different transmitters at different nerve terminals of the

same neuron.

Denervation super sensitivity• Proliferation of receptors

• Loss of mechanisms for transmitter removal

• Increased post junctional responsiveness

Pre-synaptic modulation• Heterotropic interaction

• Homotrotropic interaction

MODULATION OF NEUROTRANSMISSION

Modulation of

Neurotransmisson

Presynaptic

Modulation

Postsynaptic

Modulation

PresynapticInhibition

PresynapticFacilitation

Postsynaptic

InhibitionPostsynaptic

Facilitation

Mechanisms of Neuromodulation

Mechanisms of Neuromodulation

COTRANSMISSION

Release of More Than One

Neurotransmitter from the Same

Nerve Terminal

Cotransmitter A Cotransmitter B

Synergistic or Opposite Actions

Types of Postsynaptic Synergism

Many Examples of NANC Neurotransmitters

Sites of drug action