Final answer:
The statement about neurotransmitters being released into the synaptic cleft due to synaptic vesicle fusion with the presynaptic membrane is true. The depolarization of the presynaptic membrane results in Ca2+ channels opening, causing neurotransmitters to be released and to bind to receptors on the postsynaptic neuron.
Step-by-step explanation:
The statement that neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the presynaptic membrane is true. The process begins when the presynaptic membrane is depolarized, leading to the opening of voltage-gated Ca2+ channels. The influx of calcium ions triggers the synaptic vesicles to fuse with the presynaptic membrane.
As a result of this fusion, neurotransmitters are released into the synaptic cleft, which is the extracellular space between the presynaptic and postsynaptic membranes. Once in this space, neurotransmitters diffuse across and bind to receptor proteins on the postsynaptic membrane. The binding of neurotransmitters to these receptors, typically ligand-gated ion channels, induces a change in the postsynaptic cell, which can be a localized depolarization or hyperpolarization. This process allows for the transmission of signals across the synaptic gap, thereby facilitating communication between nerve cells or between neurons and other types of cells.