Spray and Pray

Membrane and receptor           SPRAY AND PRAY

11 )   Neurotransmission that is involved in cholinergic responses
  1) Synthesis of acetylcholine
  a) Acetylcholine is synthesis from acetyl CoA and choline, catalyzed by choline acetyltransferase in the presynaptic terminal.
  b) Choline is taken up by carrier system that cotransports sodium from the extracellular fluid into the neuron terminal.
  c) Acetyl CoA is synthesized in the mitochondria that can be found in the nerve ending. In mitochondria, pyruvate undergoes decarboxylation to form acetyl CoA via pyruvate dehydrogenase.

                                                            Choline acetyltransferase
                Choline   +   Acetyl CoA                                                   acetylcholine                

  2) Storage of acetylcholine in vesicles
  a) Acetylcholine is packaged into the vesicles by an active transport process coupled to the efflux of protons.
  b) The mature vesicles contain acetylcholine, ATP and proteoglycans.

  3) release of acetylcholine
arrival of action potential at the nerve ending

Voltage sensitive Calcium channel in the presynaptic membrane open

Influx of Calcium

Concentration of intracellular Calcium increase

Promote the fusion of the vesicles to the cell membranes (increase of calcium concentration will interact with special proteins associated with the vesicular membrane and ‘destabilize’ it).

Release of acetylcholine into the synaptic cleft through exocytosis  

Acetylcholine diffuse across the synaptic space

Binds to the receptors (presynaptic [nicotinic] or postsynaptic [muscarinic] receptors)

Cause biological response (initiate nerve impulse or activation of specific enzyme)

Acetylcholine is degraded by acetylcholinesterase that cleaves acetylcholine to choline and acetate.

Choline is recaptured by a sodium-coupled, high affinity uptake system that transport the molecule back...