Question

When the local change in membrane potential generates a spreading signal across the membrane, how do neurons counteract the signal weakening over increasing distances? What is the traveling wave called? How far can an action potential carry an (unattenuated) signal across a neuron? What other channels/pumps primarily affect the action potential?

Answer 1

Neurons transmit electrical signals using action potentials, initiated by the opening of sodium channels followed by potassium channels, with the entire process preventing signal weakening over long distances. Myelinated axons conduct signals more rapidly due to saltatory conduction.

Step-by-step explanation:

Neurons propagate signals through the process of action potentials, which are waves of electrical activity that travel across the neuron's membrane. When a neuron receives a sufficient stimulus, voltage-gated sodium channels open, allowing Na+ ions to flow into the cell, causing a rapid depolarization. The neuron's interior becomes less negative, reaching a threshold that triggers the action potential. As the depolarization spreads, adjacent voltage-gated sodium channels further along the axon open in a wave-like fashion. After the peak of the action potential, potassium channels open, allowing K+ ions to flow out, which repolarizes the membrane. In the wake of the action potential, a refractory period ensures the impulse travels in one direction toward the synapse.

Propagation of the action potential is the key to signal transmission over long distances without weakening. Myelinated axons conduct signals even faster due to the insulation provided by myelin sheaths, with propagation speeds up to 100 m/s, allowing signals to move rapidly along the axon in a jumping fashion known as saltatory conduction. This efficient system ensures that neurotransmitters are released at the synapse to continue the communication process between neurons.