How do sensitization and habituation change a reflex response?

Although reflex actions are often described as "stereotyped," they are not invariable and can be modified through nonassociative learning processes known as habituation and sensitization. These processes alter the strength of the behavioral response to a stimulus.12

Habituation

Habituation is the waning or decrease of a behavioral response following the repeated presentation of a stimulus, particularly when that stimulus lacks reinforcement. Physiologically, this is often correlated with a decline in the size of postsynaptic potentials, which may result from the closing of calcium channels, a decrease in neurotransmitter release, or a reduction in the number of activated neurons in the network. In long-term habituation, the number of active zones at nerve terminals may also be reduced.312

Sensitization

Sensitization is the opposite process, characterized by an increase in the probability or strength of a response to a stimulus. It often occurs during the initial presentations of a stimulus. At the cellular level, sensitization is correlated with an increase in the magnitude of postsynaptic potentials, often driven by presynaptic facilitation and an increase in the second messenger cAMP in sensory neuron terminals. Long-term sensitization can lead to an increase in the number of active zones at nerve terminals.412