What causes a nerve signal to move from one end of a neuron along the length of the neuron to the other end? What is a nerve signal, exactly? Why can't it go backward? How is a nerve signal transmitted from one neuron to the next across a synapse? Write a short paragraph that answers these questions.

Verified step by step guidance

1. Understand that a nerve signal, or action potential, is an electrical impulse that travels along the membrane of a neuron. It is caused by the movement of ions across the neuron's membrane through ion channels.
2. Learn about the role of the resting membrane potential, which is the difference in electric charge across the membrane in a resting state. This potential is crucial for the initiation and propagation of the action potential.
3. Recognize that the action potential moves in one direction—from the axon hillock (near the cell body) to the axon terminals—due to the sequential opening and closing of ion channels and the refractory period that prevents immediate reactivation of the channels.
4. Explore how the nerve signal is transmitted across a synapse, the junction between two neurons. When the action potential reaches the axon terminal, it triggers the release of neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic neuron, initiating a new action potential.
5. Consider the importance of neurotransmitters and their specific receptors in ensuring the correct transmission of nerve signals across synapses, and how this process ensures that signals are sent to the correct target cells.