Final answer:
Graded potentials are variations in a neuron's membrane potential in response to stimuli, which can summate to initiate an action potential if they are strong enough.
Step-by-step explanation:
When electrical signals in neurons are described as graded, it means that they are changes in membrane potential that vary in size and are not all-or-nothing responses like action potentials.
These graded potentials are usually associated with the neuron's dendrites, and their magnitude is determined by the intensity of the stimulus.
This stimulus can cause the graded potential to be either depolarizing, leading to an excitatory postsynaptic potential (EPSP), or hyperpolarizing, leading to an inhibitory postsynaptic potential (IPSP).
Graded potentials can summate, meaning they can add up to bring the neuron to a threshold potential where an action potential can be triggered.
If the summation of these potentials is enough to depolarize the neuron from, for example, -70 mV to -55 mV (a positive 15 mV change), then an action potential may be generated.
This process makes the communication between neurons in the nervous system highly flexible and allows for a wide range of responses to different stimuli, such as during the testing of shower water temperature or receiving sensory input from the environment.