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Acetylcholine Receptors

High Yield Facts ⭆ Acetylcholine released in postsynaptic cleft and binds to α-subunit of acetylcholine receptor. When acetylcholine bind a nicotinic AchR, a conformational change occurs in the receptor, resulting in the formation of an ion pore. The opening of a ion pore produces a rapid increase in the cellular permeability of sodium and calcium ions, resulting in the depolarisation and excitation of the muscle cell. It activate the sodium channel and depolarizes the nerve fibers. Direction of transmission of nerve impulse from postsynaptic junction to nerve fibers.

Question

Which of the following ion channel opens, when acetylcholine (ACh) binds to acetylcholine receptor (AChR) at postsynaptic junction?
  1. Potassium (K)
  2. Chloride (Cl)
  3. Calcium (Ca)
  4. Sodium (Na)

Acetylcholine Receptors

Two types of Acetylcholine Receptor:
  1. Muscarinic Type: G-Protein Coupled Receptor. Slow metabolic response through intracellular secondary messenger system involving an increase of intracellular calcium to transmit signals inside cells. Smooth muscle, Heart muscle.
  2. Nicotinic Type: Ligand-Gated Ion Channel. Fast synaptic transmission of the neurotransmitter. Neuromuscular Junctions, Brain.
Nicotinic Type Acetylcholine Receptors may be:
  1. Neuronal Type:
  2. Muscle Type: Neuromuscular Junctions

Reference:

  • Sargent, Peter B. "The diversity of neuronal nicotinic acetylcholine receptors." Annual review of neuroscience 16.1 (1993): 403-443.
  • Caulfield, Malcolm P., and Nigel JM Birdsall. "International Union of Pharmacology. XVII. Classification of muscarinic acetylcholine receptors." Pharmacological reviews 50.2 (1998): 279-290.

[Answer is D. Na channel]

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