Video Transcript
What is the role of synaptic
vesicles in the presynaptic neuron? (A) To store neurotransmitters. (B) To store enzymes. (C) To attach to receptor sites on
the postsynaptic membrane. (D) To stimulate the influx of
sodium ions.
To answer this question, let’s
start by reviewing key components of the synapse, which comprises the presynaptic
neuron. The junction of two neurons in
communication is called the synapse. It is usually composed of three
parts: the axon terminals of the presynaptic neuron; the synaptic cleft; and the
postsynaptic cell, which can be the dendrites of a postsynaptic neuron, a gland, or
a muscle fiber. Our capacity to think, learn,
memorize, and move depends crucially on the strength and number of our synapses. This is because synapses play a
major role in the transmission of nerve impulses.
To transmit the nerve impulse from
one neuron to the next, the presynaptic neuron must release specialized chemical
messengers called neurotransmitters, which are shown here in green. These neurotransmitters are able to
cross the synaptic cleft and carry the message of the nerve impulse to the next
neuron. To make sure that neurotransmitters
are ready to transmit on demand, they’re stored in special packages called synaptic
vesicles, which are concentrated at the ends of presynaptic neurons.
As the nerve impulse reaches the
end of the presynaptic neuron, it stimulates an influx of calcium ions into the
presynaptic neuron. The influx of calcium ions causes
the synaptic vesicles to fuse with the membrane of the presynaptic neuron and
release neurotransmitters into the synaptic cleft. The neurotransmitters will travel
unidirectionally to the receptors on the postsynaptic membrane, which open sodium
ion channels and generate the next nerve impulse.
With these key facts in mind, let’s
take a look at our possible answer choices. The role of synaptic vesicles in
the presynaptic neurons is to store neurotransmitters.
