Video Transcript
Which two ion channels are involved in the transmission of information across a
synapse? (A) Nitrogen and hydrogen ion channels. (B) Calcium and sodium ion channels. (C) Calcium and potassium ion channels. (D) Carbon and sodium ion channels. (E) Hydrogen and potassium ion channels.
To answer this question, we need to recall the ion channels found at the synapse that
help to transmit the signal between neurons. The synapse is the connection between two neurons or between a neuron and an
effector. They are critically important for transmitting information between two neurons or
between a neuron and an effector. The transmission of information from one neuron to the next or an effector starts
with the arrival of the action potential at the end of the presynaptic neuron,
called the synaptic knob.
When an action potential arrives at the synaptic knob, it causes the synaptic knob to
depolarize. This depolarization causes the voltage-gated calcium ion channels to open and allows
for calcium ions to diffuse into the synaptic knob. The influx of calcium ions triggers the synaptic vesicles located in the synaptic
knob to fuse with the presynaptic membrane. These synaptic vesicles contain neurotransmitters, such as acetylcholine or ACh,
which will be released into the synaptic cleft via exocytosis.
Once acetylcholine is released into the synaptic cleft, the neurotransmitter moves
across the synaptic cleft via passive diffusion from an area of high concentration
to an area of low concentration. When acetylcholine reaches the postsynaptic membrane, it binds to the receptor sites
on the sodium ion channels causing them to open. When the sodium channels open, it allows for sodium to diffuse into the postsynaptic
neuron.
The influx of sodium ions into the postsynaptic neuron triggers an action potential
in the postsynaptic neuron. This action potential can then travel down the axon of the postsynaptic neuron to be
propagated to the next neuron.
From this review, we now recall that the ion channels found at the synapse, which
help propagate the action potential, are the voltage-gated calcium ion channels on
the presynaptic neuron and the sodium ion channels on the postsynaptic neuron.
With this information, we are now ready to answer the question. The two ion channels involved in the transmission of information across a synapse are
the calcium and sodium ion channels.
