Q.27 A nerve impulse is transmitted from one neuron to another through junction called :

1. Dendrite
2. Synapse
3. Axon
4. Impulse

   Synapse is the Junction for Nerve Impulse Transmission Between Neurons

   A nerve impulse transmits from one neuron to another through the synapse, a specialized junction where neurotransmitters relay the signal across a synaptic cleft. This makes “Synapse” the correct answer.​

   Introduction

   The nerve impulse transmitted from one neuron to another occurs exclusively through the synapse junction. This electrochemical interface converts action potentials into neurotransmitter signals, enabling complex neural networks. This guide dissects each option for neurobiology exam precision.

   Option Analysis

   Neural communication pathway: Dendrites → Cell body → Axon → Synapse → Next neuron dendrites.

   • Dendrite: Incorrect. Receives incoming signals from presynaptic neuron synapses; integrates EPSPs/IPSPs at axon hillock. No transmission to other neurons.​

   • Synapse: Correct. Microscopic junction (~20-40 nm cleft) between axon terminal (presynaptic) and dendrite/soma (postsynaptic). Action potential → Ca²⁺ influx → vesicle fusion → neurotransmitter release → receptor activation.

   • Axon: Incorrect. Long fiber conducts action potentials away from cell body toward synapse (~1-2 m/s myelinated). Transmission ends at axon terminal.​

   • Impulse: Incorrect. Action potential itself (Na⁺/K⁺ depolarization wave); not anatomical junction. Cannot “transmit through impulse.”​

   Synapse Structure & Function

   Components:

   1. Presynaptic terminal: Synaptic vesicles (ACh, glutamate, GABA)

   2. Synaptic cleft: 20-50 nm gap; neurotransmitter diffusion

   3. Postsynaptic membrane: Receptors (ionotropic/metabotropic)​

   Transmission Process:

   text

   Action Potential → Voltage-gated Ca²⁺ channels → Vesicle exocytosis →
Neurotransmitter diffusion → Receptor binding → Postsynaptic potential


   Synapse Type	Speed	Example
   Chemical	0.3-5 ms	CNS (99%)
   Electrical	<0.1 ms	Cardiac muscle, some CNS ​

   Neurotransmitter Cycle

   1. Release (Ca²⁺-triggered)

   2. Binding → Na⁺/K⁺/Cl⁻ channel opening

   3. EPSP (depolarization) or IPSP (hyperpolarization)

   4. Reuptake/degradation/recycling​

   Exam Relevance

   GATE Life Sciences: Synapse = only inter-neuron junction. Mnemonic: “SYNapse = SYNaptic transmission SYNapse.” Visualize: Axon → SYNAPSE → Dendrite (not dendrite→dendrite).