Video Transcript
The flowchart provided shows the
stages of transmission of the information across a synapse, with each stage assigned
a number. State the correct order of
stages. (A) 1, 4, 3, 5, 6, 2; (B) 2, 1, 4,
6, 5, 3; (C) 6, 2, 1, 4, 3, 5; (D) 6, 2, 1, 3, 5, 4.
The following question asks us
about the transmission of information across the synapse. Let’s review this process to put
our flowchart into the correct order.
A synapse refers to the connection
between two neurons or a neuron and an effector. In a synapse between two neurons,
the neuron that comes before a synapse is called the presynaptic neuron, which ends
in the synaptic knob. The synaptic knob receives the
electrical signal that is the action potential which has traveled down the axon and
converts it into the chemical messengers called the neurotransmitters. So, box 6 must be the first part of
our response.
When the action potential reaches
the synaptic knob, it causes the synaptic knob to depolarize. Depolarization causes voltage-gated
calcium ion channels to open, allowing calcium ions to diffuse into the synaptic
knob, which corresponds to box 2. The influx of calcium ions into the
synaptic knob influences the synaptic vesicles containing neurotransmitters to fuse
with the membrane of the synaptic knob. In different types of synapses,
there are vesicles that contain different types of neurotransmitters, such as
acetylcholine, dopamine, or serotonin.
When the vesicles containing these
neurotransmitters fuse with the presynaptic membrane, they release their contents
into the synaptic cleft, which is the space between two neurons. This refers to box 1, which states
that the neuron releases the neurotransmitter acetylcholine. The released neurotransmitters, in
this case acetylcholine, will diffuse across the synaptic cleft and bind to the
receptors on the sodium ion channels located on the membrane of the postsynaptic
neuron. This corresponds to box number
4.
When the acetylcholine binds to the
sodium ion channels, it causes the sodium ion channels to open and allows for an
influx of sodium ions into the postsynaptic neuron. This is described by box number
3. The influx of sodium ions will
cause depolarization of the postsynaptic neuron, which initiates a new action
potential in the postsynaptic neuron. This is how the action potential
from one neuron is propagated to the next neuron, which corresponds to box number
5.
Now that we’ve reviewed the whole
process of information transmission across the synapse of a cell, we are able to
correctly respond to our question. The correct order of stages to
transmit a signal across the synapse is 6, 2, 1, 4, 3, 5.
