Final answer:
In saltatory conduction, the myelin sheaths are only 1 mm thick because the action potential 'jumps' from one node of Ranvier to the next. The myelin sheath acts as an insulator, preventing current leakage and allowing faster conduction. The nodes of Ranvier regenerate the action potential, saving energy for the neuron.
Step-by-step explanation:
In saltatory conduction, the myelin sheaths are only 1 mm thick because the action potential 'jumps' from one node of Ranvier to the next, instead of propagating continuously along the entire axon. The myelin sheath acts as an insulator, preventing the leakage of current. By having small unmyelinated gaps called nodes of Ranvier, the action potential is regenerated at these points, resulting in faster conduction and conservation of energy for the neuron.
There seems to be a misconception in your question. Myelin sheaths are not typically 1 mm thick. In fact, myelin sheaths are much thinner, usually in the range of micrometers (μm). The thickness of a myelin sheath varies depending on the type of nerve fiber and the species, but it is not on the scale of millimeters. Saltatory conduction is a process where nerve impulses jump from one node of Ranvier to another along a myelinated axon, which significantly speeds up the transmission of the nerve impulse. The nodes of Ranvier are small, unmyelinated gaps between the myelin sheaths where the axon membrane is exposed. The myelin sheath is thicker at certain regions (internodes) and thinner at the nodes.