Final answer:
Graded potentials lose strength due to passive electrical current flow and spatial and temporal summation. Action potentials do not lose strength because they are regenerated at each segment of the axon.
Step-by-step explanation:
Graded potentials lose strength as they move through the cell due to two main reasons: passive electrical current flow and spatial and temporal summation. Passive electrical current flow occurs because ions naturally flow from areas of higher concentration to areas of lower concentration, causing the graded potential to become weaker as it spreads through the cell. Spatial and temporal summation refer to the adding up of multiple graded potentials at different locations or times, which can result in cancellation or weakening of the signal.
Action potentials, on the other hand, do not lose strength because they are regenerated at each segment of the axon. This occurs at the nodes of Ranvier in myelinated axons and at each segment of unmyelinated axons. The action potential is an all-or-nothing event, meaning it either happens fully or not at all, and it propagates down the axon without weakening.