Final answer:
The statement is false; graded potentials are local changes in membrane voltage that decrease in intensity as they travel away from their point of origin. They can summate to trigger an action potential, but unlike action potentials, they do not maintain their strength over the entire membrane.
Step-by-step explanation:
The statement 'Graded (local) potentials spread throughout the entire area of the membrane on which they are generated without decreasing in intensity or magnitude' is false. Graded potentials are changes in membrane voltage related to the strength of a stimulus. They can either be depolarizations, where the inside of the cell becomes less negative due to the influx of positively charged ions like Na+ or Ca2+, or hyperpolarizations, where the cell becomes more negative because of the exit of positive ions like K+ or the influx of negative ions like Cl-.
These potentials are usually initiated in the dendrites of neurons and can summate to trigger an action potential if they reach a specific threshold. However, graded potentials decrease in intensity as they travel through the neuron, meaning they are not able to spread throughout the entire membrane without a decrease in magnitude. This decremental nature of graded potentials is due to the leaky structure of the neuron's membrane and the resistance inside the cell, which dissipates the signal as it travels away from the point of origin.
Graded potentials contrast with action potentials, which do not degrade in strength as they propagate along the axon. When the sum of graded potentials is positive and reaches a certain threshold, typically around -55 mV from a resting potential of -70 mV, an action potential is generated, which is akin to flipping a light switch that activates the neuron to transmit a signal over long distances.