Biology – Control and coordination in mammals | e-Consult
Control and coordination in mammals (1 questions)
Non-myelinated neurons transmit impulses continuously down the entire length of the axon. The action potential is regenerated at every point along the axon membrane. This process requires a significant amount of energy to maintain the ion gradients and the depolarization/repolarization cycles. The speed of transmission is relatively slow, typically around 1 metre per second.
Myelinated neurons, as described previously, transmit impulses via saltatory conduction. The action potential 'jumps' between the nodes of Ranvier. Because the action potential is only regenerated at the nodes, the transmission is much faster, typically around 10-100 metres per second. This is a significant increase in speed.
Comparison Table:
| Feature | Non-myelinated Neuron | Myelinated Neuron |
| Transmission Mechanism | Continuous propagation | Saltatory conduction |
| Speed of Transmission | Slow (1 m/s) | Fast (10-100 m/s) |
| Energy Expenditure | High | Lower |
| Myelin Sheath | Absent | Present |
The energy expenditure is lower in myelinated neurons because the action potential is regenerated less frequently. The myelin sheath also reduces the metabolic demands of the neuron by minimizing ion leakage and maintaining the resting membrane potential. Therefore, the increased speed of transmission in myelinated neurons is a significant evolutionary advantage.