Within the ganglion the axons synapse onto the postganglionic parasympathetic neurons. BDNF enhances the growth and survival of cortical neurons and synapses. These transmit axons of upper motor neurons. EEG reflects correlated synaptic activity caused by post-synaptic potentials of cortical neurons. Muscarine binds with muscarinic acetylcholine receptors leading to the excitation of neurons bearing these receptors. Recent investigations discovered opioid receptors on peripheral sensory neurons. Methamphetamine is neurotoxic to human midbrain dopaminergic neurons at high doses. This progression leads to the neurons and glia that populate cortical layers. Nicotine can modulate the firing rate of the ventral tegmental area neurons. This makes multiple synaptic connections with other neurons possible. RyRs are especially important in neurons and muscle cells. An artificial neural network consists of a collection of simulated neurons. Research on these molecules helped improve understanding of the physiology of neurons and receptors. Endocannabinoids are molecules that can relieve pain by modulating nociceptive neurons. They are glutamatergic, exciting striatal neurons.