How do neurotransmitter release and synaptic transmission mechanisms

Can you explain the physiological mechanisms underlying the generation and propagation of action potentials in neurons, including the roles of ion channels, membrane potential changes, and neurotransmitter release? How do graded potentials and summation events depolarize the neuronal membrane to reach the threshold for action potential initiation, leading to the opening of voltage-gated sodium channels and rapid sodium influx? Additionally, how does the subsequent repolarization phase involve the opening of voltage-gated potassium channels, potassium efflux, and restoration of the resting membrane potential? Furthermore, how do neurotransmitter release and synaptic transmission mechanisms contribute to neuronal communication, synaptic plasticity, and information processing in neural networks?