How are impulse transmitted across a synapse?
Impulse transmission through synapse is accomplished by electric current. When the impulse reaches the pre synaptic knob, the impulse itself act as stimulus for the post synaptic neuron causing depolarization. Now the action potential generate in second neuron.
What crosses the synapse between two neurons?
Neurotransmitter A chemical released from a neuron following an action potential. The neurotransmitter travels across the synapse to excite or inhibit the target neuron.