Question

The correct sequence of sigl transmission at a chemical sypse:
A. Nerve impulse at syptic end bulb
B. Neurotransmitter molecules released
C. Binding of neurotransmitter molecules to their receptor
D. Postsyptic potential
E. Opens voltage gated Ca$^{2+}$ channels

• A. D, A, B, C, E
• B. D, E, A, B, C
• C. A, B, C, E, D
• D. A, E, B, C, D

Hint:

Syptic Transmission Sequence:
Action Potential (A) $\to \text{Ca}^{2+}$ channels open (E) $\to$ Exocytosis of Neurotransmitter (B) $\to$ Receptor binding (C) $\to$ Postsyptic potential (D).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question requires ordering the physiological steps of syptic transmission across a chemical sypse upon arrival of an action potential.

Step 2: Key Formula or Approach:
Chemical syptic transmission transfers nerve sigls across syptic clefts via neurotransmitters: Action Potential (A) $\rightarrow{}$ Ca^{2+} Channel Opening (E) $\rightarrow{}$ Exocytosis of NT (B) $\rightarrow{}$ Receptor Binding (C) $\rightarrow{}$ Postsyptic Potential (D)

Step 3: Detailed Explation:

• 1. Impulse Arrival (A): An action potential propagates along the presyptic axon and reaches the syptic end bulb.

• 2. Calcium Influx (E): Membrane depolarization triggers the opening of presyptic voltage-gated $\text{Ca}^{2+}$ channels, causing $\text{Ca}^{2+}$ ions to flow into the bulb.

• 3. Neurotransmitter Release (B): Increased intracellular $\text{Ca}^{2+}$ triggers syptotagmin/SRE-mediated exocytosis of syptic vesicles, releasing neurotransmitters into the syptic cleft.

• 4. Receptor Binding (C): Neurotransmitters diffuse across the cleft and bind to ligand-gated ionotropic or metabotropic receptors on the postsyptic membrane.

• 5. Postsyptic Potential (D): Ion channel opening alters postsyptic membrane permeability, producing excitatory (EPSP) or inhibitory (IPSP) postsyptic potentials.

Step 4: Fil Answer:
The correct sequential order of syptic transmission is A, E, B, C, D.