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Flashcards in Cholinergic Physiology Deck (10):

Ach Funtcions

Somatic efferents at NMJ
Pre-synaptic neurons in parasympathetic and sympathetic ganglia
Post-ganglionic neurons in parasympathetic system to activate smooth muscle and glands


Nicotinic Receptors

Fast acting & Ionotropic
Located at NMJ and autonomic ganglia to cause muscle contraction and post-synaptic firing respectively
Three types: Muscular, Ganglionic, CNS


Muscarinic Receptors

Slow acting and metabotropic
Located on effector tissue
5 subtypes: M1-M5
Odd numbers act through Gq to activate Inositol Phosphate
Even numbers act through Gi to inhibit Adenylate Cyclase
All post-synaptic, evens are pre too


Muscarinic Subtypes

M1(Neural): Excitatory in CNS and glandular tissue
M2(Cardiac): Inhibitory in cardiac muscle
M3(Glandular and Smooth Muscle): Excitatory of these
M4(CNS): Inhibitory in CNS
M5(CNS): Excitatory in CNS


Ach Synthesis

Choline is taken into nerve terminal via Choline Transporter
Choline Acetyltransferase adds and Acetyl group from AcetylCoA to choline to form Ach


Ach Storage

Synthesised Ach is pumped into vesicles for storage by vesicular Ach transporter


Ach Release

Depolerisation of the nerve terminal causes Ca influx.
This causes fusion of storage vesicles to the membrane and release of Ach by exocytosis


Ach Degradation

Cholinesterase enzymes break Ach into Choline and Acetate


Ach Reuptake

Choline is recycled and taken into nerve terminal once again by Choline transporter where it is made into Ach again


Pre-Synaptic Modulation

Inhibitory M2: Ach release stimulates these receptors which inhibit Ach release
Adrenergic Receptors: Sometimes present on pre-synaptic terminals. They are inhibitory and dampen parasympathetic transmission during sympathetic input