How does an electrical signal transmit across a synaptic cleft?

The correct choice highlights the pivotal role neurotransmitters play in synaptic transmission. When an electrical signal, or action potential, reaches the end of a neuron (the presynaptic terminal), it triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft, which is the small gap between two neurons.

Once released, neurotransmitters diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic neuron. This binding can generate a new electrical signal in the receiving neuron if the binding is sufficient to reach the threshold needed for depolarization. This process enables communication between neurons, allowing for the transfer of information throughout the nervous system.

Understanding the role of neurotransmitters in this context is fundamental in neurobiology, as it emphasizes the importance of chemical signaling in what might initially seem to be purely an electrical process. The ability of neurotransmitters to facilitate or inhibit signal transmission exemplifies the complexity of neural communication.