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Autonomic Nervous System 1 Dr
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In the GI tract and uterus
o All exocrine and some endocrine secretions
o Heat beat
o Some steps in intermediary metabolism
Preganglionic
Ganglion
Postganglionic

Acetylcholine Receptors
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Nicotinic:
o Binds Ach to initiate the end-plate potential in skeletal muscle or excitatory postsynaptic potential (EPSP) in nerve post-ganglionic neuron
o Nm (nicotinic muscle) is pharmacologically distinct from Nn (nicotinic muscle)
Muscarinic
o M1, 2, 3, 4 and 5 – also subtypes
o Distinct anatomical localisations and chemical specification’s
o M1 – autonomic ganglia
o M2 – heart
o M3 – smooth muscle and secretory glands
o All types found in CNS
o Muscarinic 2nd messenger systems
 M1, 3 and 5 action via Gq which activates Phospholipase C, which then
generates the 2nd messengers, IP3 and DAG
 M2 and 4 – action via Gi which inhibits Adenylate Cyclase, thus activating K+
channels and modulating Ca2+ channel activity

Adrenergic Receptors
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Alpha 1 and 2, beta1 and 2
Beta1 found mostly in the heart, whilst beta2 found elsewhere
All beta receptor sub-types activate Gs which stimulates Ad Cy, increasing cAMP production
and activation PKA
Alpha1 is post-junctional at neuroeffectors and activates Gq, stimulating PLC
Alpha2 occurs both pre and post-synaptically and inhibits Ad Cy
Adrenergic transmission occurs via exocytosis just like cholinergic transmission
Chromogranin stops NA from leaking out of vesicles

Examples of Co-transmission and neuromodulation
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Presynaptic inhibition – neurotransmission switches itself off

Autonomic Nervous System 1 Dr

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