Final answer:
Graded potentials originate on dendrites and cell bodies, representing changes in the membrane potential that vary with the stimulus. Types include generator potential and receptor potential, which can trigger action potentials or neurotransmitter release, respectively. Postsynaptic potentials, excitatory or inhibitory, are also graded potentials.
Step-by-step explanation:
The potentials that originate on dendrites and cell bodies are known as graded potentials. These are local changes in the membrane potential of a neuron. These graded potentials can be categorized into various types, depending on where they occur and their role. For example, a generator potential is a type of graded potential that originates from the dendrites of unipolar cells and is capable of initiating an action potential in the axon of the same cell. Similarly, a receptor potential is the change in membrane potential in sensory receptor cells that leads to neurotransmitter release.
Local changes in membrane potential related to sensory stimuli can result in either a generator potential or a receptor potential. The former can initiate an action potential directly in the axon's initial segment, while the latter causes neurotransmitter release without necessarily reaching a threshold. Moreover, there are postsynaptic potentials (PSPs), which are graded potentials resulting from neuron-to-neuron interactions at synapses. They can be either excitatory (depolarizing) or inhibitory (hyperpolarizing).
To answer the student's question, graded potentials are the potentials that originate on dendrites and cell bodies, while action potentials are typically initiated by graded potentials when they reach the axon hillock or initial segment, where they can be generated due to the high concentration of voltage-gated Na+ channels.