QS Study

Biosynthesis, Storage, and Release of Acetylcholine

Neurotransmitters are highly active chemical agents released at the nerve ending and transmit impulses from nerve to nerve or nerve to effector tissue. Acetylcholine is a part of Neurotransmitters. Acetylcholine is a chemical that is found between the nerve synapses, or gaps, between nerve cells. When activated, it causes the contraction of skeletal muscles and activates glandular functions in the endocrine system.

It is also found in sensory neurons and in the autonomic nervous system. It plays a significant function in the signal of muscle movement, the sensation of pain, learning, and memory formation, the guideline of the endocrine system and rapid eye movement sleep cycles.

Site of synthesis

Most synthesis occurs in the axoplasm of cholinergic nerve endings.

Required material:

  • Acetyl CoA – from TCA cycle
  • Choline.

Reaction of synthesis:

Acetyl-CoA + Choline → (choline acetyltransferase) → Acetylcholine.


After synthesis ach is transported to the interior of vesicles where it is stored in a highly concentrated form until it is released.


Impulse → entrance of Ca++ within the nerve ending → release of acetylcholine by exocytosis.


Acetylcholine → (acetylcholinesterase) → Choline + Acetate ion

After secretion acetylcholine persists in the tissue for a few seconds, then most of it is spilled into an acetate ion and choline catalyzed by the enzyme acetylcholinesterase. The choline that is formed is, in turn, transported back into the terminal nerve ending where it is used again and again for the synthesis of new acetylcholine.

The fate of neurotransmitter after release –

The fate of neurotransmitter –

  • Enzymatic destruction,
  • Diffusion into surrounding fluid,
  • Postsynaptic membrane-bound,
  • By active transport back into the presynaptic terminal.