What travels across the synapse to convey signal to the next neuron?

• A. Chemical message
• B. Electrical impulse
• C. Nerve impulse
• D. Nuclear signal

Answer: (A)

Chemical neurotransmitters released by the presynaptic neuron travel across the synaptic cleft to convey the signal to the next neuron. When an action potential reaches the synaptic terminal, calcium enters and triggers vesicles to fuse with the membrane, releasing neurotransmitters. These chemicals diffuse across the gap and bind to receptors on the postsynaptic membrane, opening ion channels or activating signaling cascades that change the postsynaptic cell’s membrane potential. This chemical step can be excitatory or inhibitory, shaping whether the next neuron fires. While electrical impulses move along neurons, they don’t directly cross the synapse in the common fast synapse type; that crossing is accomplished chemically. Nuclear signals are not involved in neurotransmission.