Name _________________________________________
Period ______
Date ___________
Synapse/Neurotransmitter Worksheet
Please label the diagram below: Note that this synaptic terminal is sending
neurotransmitter to a receptor protein on the postsynaptic cell, not a ligand gated channel.
It is likely that these receptors will initiate a signal transduction pathway within the target
cell.
Please define/explain how each plays a role in synaptic signaling:
Neurotransmitter: Chemical messengers that pass information from the transmitting neuron to
the receiving cell.
Vesicles: a fluid filled sack enclosed by a lipid bilayer (can contain many cellular products
including neurotransmitters)
Protein receptor: plays a role in modulated synaptic transmission. Neurotransmitter binds to
receptor on post synaptic cell and this binding starts a signal transduction pathway within the
target cell.
Axon Terminal (pre synaptic receptor): synaptic terminal/synaptic knob or button that receives
action potential from axon that precedes it and releases neurotransmitters.
Dendrite (post synaptic receptor): part of a post synaptic cell that receives the neurotransmitter
released from the neuron upstream.
Axon: portion of neuron that propagates an action potential located between the cell body and
the synaptic terminal.
Ligand-gated ion channels: binding of a neurotransmitter to these channels as a ligand opens the
channel and allows specific ions to flow across the post synaptic membrane.
Neurotransmitters:
1. Neurotransmitters are the chemical __messengers__________ that neurons use to
communicate with other cells____________.
2. Neurotransmitters can be :
• _Excitatory___________ (cause something to happen)
• _Inhibitory___________ (stopping a process)
3. When neurotransmitters are released into the synaptic gap, they bind to
__receptors__________ which cause the next neuron to create an action potential or signal
transduction pathway starting the whole process over again.
4. Neurotransmitters:
• Dopamine- present in feelings of __euphoria____ or feeling high. Also activates the
____________ ____________ in the brain.
• Serotonin- responsible for __sleep__________, __mood__________, ___attention_________.
• Endorphins- responsible for __block pain________ __feelings of pleasure__________.

Acetylcholine – responsible for ______excitatory transmitter that binds to ligand gated
channels on muscle cell receptor proteins.__ ________________________.

Epinephrine and norepinephrine – responsible for __fight or flight response act as
neurotransmitters and hormones.____ ______.
5. The Binding Process:
When the sending neuron releases Nt’s across the synaptic gap, the Nt’s fit into receptors like a
key fits in a lock.
6. Stopping the Process:
When the next neuron creates an action potential (after enough Nt’s have attached to receptors)
the Nt’s are stopped in one of three ways.
• Diffusion: simple diffusion causes neurotransmitters to be removed from the synaptic cleft
• Reuptake: neurotransmitters can be actively transported into the presynaptic neuron to be
repackaged into synaptic vesicles (from whence they came), or transported to glia to be
metabolized as fuel.
• Enzymes: through hydrolysis enzymes break down neurotransmitters and clear them from the
synapse