• What are three differences between small and large-molecule neurotransmitters?
◦ Small-molecule neurotransmitters are synthesized in the cytoplasm of the terminal button,
large-molecule neurotransmitters are synthesized in the cell body's cytoplasm on ribosomes
with the other proteins
◦ Small-molecule neurotransmitters are packaged in vesicles by the axon terminal's golgi
complex, large-molecule neurotransmitters are packaged in vesicles by the cell body's golgi
complex and then travel along microtubules to the terminal button
◦ Small-molecule neurotransmitters are of several types or varieties, large-molecule
neurotransmitters are all neuropeptides
◦ Small-molecule neurotransmitters often release multiple vesicles during exocytosis (Per
action potential), large-molecule neurotransmitters often release a single vesicle of
neurotransmitters during exocytosis (Per action potential)
◦ Function of small-molecule neurotransmitters seems to be to transmit fast messages in short
bursts in a specific area, function of large-molecule neurotransmitters seems to be to
transmit messages more diffusely and over a slower, longer period of time
• What is meant by coexistance?
◦ When two neurotransmitters are produced and released by the same neuron
◦ In every documented case of coexistance one neurotransmitter is a small-molecule
neurotransmitter and the other is a large-molecule neurotransmitter
• Explain the process of Exocytosis – is any part different for small and large molecule
neurotransmitters? (Hint: Explain how neurotransmitters are released)
◦ Synaptic vesicles have a tendency to congregate around button walls in areas rich in calcium
◦ When the action potential comes down the axon, calcium channels are opened, causing
calcium ions to rush in
◦ Calcium ions allow the synaptic vesicles to bind to the wall of the terminal button and
release its contents into the synapse
◦ Large-molecule neurotransmitters often release a single vesicle per action potential
◦ Small-molecule neurotransmitters often release many vesicles in a wave with each action
• What are the two types of receptors possible on the post-synaptic membrane?
◦ Ionic receptors open ion channels in response to the neurotransmitter binding to the
◦ Metabotropic receptors are serpentine proteins that wind their way through the button wall 7
times, can either trigger ion channel openning or can release a second messenger into the
• What are the two mechanisms of reuptake?
◦ Reuptake: Neurotransmitters are taken up by the presynaptic neuron via transporter
mechanisms to be repackaged into synaptic vesicles
◦ Enzyme Degradation: Enzymes break down the neurotransmitter into its components
• What are the three conventional classes of small-molecule neurotransmitters? The fourth class?
◦ Amino Acids
◦ Unconventional Small-Molecule Neurotransmitters • Describe the 4 most widely studied neurotransmitters within the AminoAcid class of
◦ Glutamate: Brain's most prevalent excitatory neurotransmitter
◦ GABA: Inhibitory neurotransmitter synthesized from glutamate. Brain