BioFlix Activity: How Synapses Work – Events at a Synapse Drag the labels to identify the sequence of events that occurs at a synapse. Calcium channels at the synaptic terminal open, allowing calcium ions to enter. Neurotransmitter molecules diffuse across the synaptic cleft. The rise in calcium levels causes vesicles containing eurotransmitter to fuse with the plasma membrane of the sending neuron. Neurotransmitter molecules bind to the receptors in the plasma membrane of the receiving neuron, causing ion channels there to open. An action potential arrives at the synaptic terminal.
The Correct Answer and Explanation is:
Here is the correct sequence of events at a synapse:
- An action potential arrives at the synaptic terminal
- Calcium channels at the synaptic terminal open, allowing calcium ions to enter
- The rise in calcium levels causes vesicles containing neurotransmitter to fuse with the plasma membrane of the sending neuron
- Neurotransmitter molecules diffuse across the synaptic cleft
- Neurotransmitter molecules bind to the receptors in the plasma membrane of the receiving neuron, causing ion channels there to open
The process of communication between two neurons takes place at the synapse and is essential for transmitting signals in the nervous system. It begins when an action potential, which is an electrical signal, travels along the axon of the sending neuron and reaches the synaptic terminal. This sudden change in voltage activates voltage-gated calcium channels located in the membrane of the synaptic terminal.
When these channels open, calcium ions from the extracellular fluid flow into the synaptic terminal. This influx of calcium creates a concentration spike that signals synaptic vesicles, which are small membrane-bound compartments containing neurotransmitter molecules, to move toward the presynaptic membrane. These vesicles then fuse with the plasma membrane and release their neurotransmitter content into the synaptic cleft, a narrow space between the sending and receiving neurons.
Once released, neurotransmitter molecules diffuse across this cleft through simple diffusion and bind to receptor proteins embedded in the membrane of the receiving neuron. These receptors are typically ligand-gated ion channels. When neurotransmitters bind to them, the channels open and allow specific ions, such as sodium or chloride, to pass through the membrane. This ionic movement changes the membrane potential of the receiving neuron, which may lead to the initiation of a new action potential. This precise and rapid sequence of events ensures that signals travel efficiently across the nervous system, enabling everything from muscle contraction to thought processing.
