Final answer:
Voltage-gated channels initiate action potentials, while ligand-gated channels are responsible for the creation of graded potentials such as EPSPs and IPSPs.
Step-by-step explanation:
Voltage-gated channels are responsible for initiating an action potential, while ligand-gated channels create graded potentials (EPSPs, IPSPs) in the dendrites or soma. Action potentials result from the sequential opening and closing of voltage-gated channels along the axon, which mediates the propagation of a nerve impulse. In contrast, ligand-gated channels open in response to the binding of neurotransmitters and generate localized changes in membrane potential, which are referred to as graded potentials.
Graded potentials, such as excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs), are triggered when neurotransmitters bind to ligand-gated ion channels, causing them to open and allow ions to flow into or out of the neuron. This disturbances in the resting membrane potential can either depolarize or hyperpolarize the neuron. If the summation of these graded potentials at the axon hillock reaches a certain threshold, it can initiate an action potential, characterized by the opening of voltage-gated Na+ channels.