Final answer:
Continuous conduction is the slowest neural propagation, occurring in unmyelinated axons with voltage-gated Na+ channels throughout, leading to a slower depolarization process compared to the faster saltatory conduction in myelinated axons.
Step-by-step explanation:
The slowest type of neural propagation is B. Continuous conduction.
Continuous conduction is the slow propagation of an action potential along an unmyelinated axon, where the voltage-gated Na+ channels are located along the entire length of the cell membrane. In contrast, saltatory conduction occurs along myelinated axons and is much faster because the action potential 'jumps' from node to node at the Nodes of Ranvier. Myelination and the axon's diameter influence propagation speed; larger diameters offer less resistance, similar to how a wider river allows water to flow faster compared to a narrow one, enhancing the rate at which Na+ depolarization spreads down the axon.
Saltatory conduction is the slowest type of neural propagation among the options given. In saltatory conduction, the action potential jumps from one node of Ranvier to the next in myelinated axons, renewing the depolarized membrane at each node. On the other hand, continuous conduction occurs in unmyelinated axons and is slower because voltage-gated sodium (Na+) channels are continuously opening, allowing more sodium to rush into the cell.