Describe vesicles and terminal buttons in a presynaptic neuron. How are neurotransmitters released into the synaptic cleft, and what happens to them after they are released? What must happen at the postsynaptic neuron to ensure binding?

Describe vesicles and terminal buttons in a presynaptic neuron. How are neurotransmitters released into the synaptic cleft, and what happens to them after they are released? What must happen at the postsynaptic neuron to ensure binding?

The neuronal axon extends from the cell body and branches at its end. At the end of each branch is a presynaptic terminal that forms an end bulb, also referred to as terminal buttons. At the terminal buttons the axon releases neurotransmitters that cross the synaptic cleft to reach other cells (Kalat, 2015).

Inside terminal buttons are vesicles prepacked with neurotransmitters via active transport. The filled vesicles are then translocated to the active zone and attach to the intracellular presynaptic membrane, referred to as docking or priming pre-fusion. They are fused to facilitate rapid response to the influx of Ca+. The action potential reaches the terminal button, it activates voltage-gated Ca+ channels, and there is an influx of Ca+. Ca+ influx causes the complete attachment of the primed vesicles to the presynaptic membrane and releases the neurotransmitter into the synaptic cleft via exocytosis. The released neurotransmitter moves across the synaptic cleft and then binds the postsynaptic membrane. The synaptic vesicles may be recycled via endosomes, but it is not mandatory. The postsynaptic membrane has neurotransmitter-specific receptors, where the neurotransmitter binds to activate the postsynaptic target cell (Kalat, 2015).

Neurons are released into the synaptic cleft where the neurotransmitter diffuses throughout the space. What are the advantages and disadvantages of not having neurons connected to each other?

One of the advantages of having neurons connected by the synaptic cleft is signal amplification. The signal comes in as a single impulse, but neurotransmitters’ release allows activation of multiple cells. The other is signal computation, since a neuron may receive both excitatory and inhibitory and the presynaptic membrane does not respond to sub-threshold depolarization, preventing unnecessary release of neurotransmitters and activation postsynaptic cells (Huether & McCance, 2016)

Diseases or chemicals may affect the synaptic cleft. For instance, myasthenia gravis is an autoimmune disorder characterized by antibodies against postsynaptic acetylcholine receptors that impairs signal transmission (Huether & McCance, 2016).

What role do the supporting cells play in neurotransmission? Describe the role of at least two different types of supporting cells. Are the supporting cells as important as the neurons when it comes to neural communication?

Other cells play a part in facilitating neurons transmits signals without disturbances. For instance, astrocytes, type glial cells surround neurons and shield them from circulating chemicals. They also take up ions released by neurons and releases, enabling closely related neurons to synchronize activity and send signals in waves. Microglia is part of the immune system and removes bacteria, fungi, viruses, and damaged or dead neurons. They also contribute to learning by removing the weakest synapse. Yes, these cells are as important as neurons by playing a part in signal transmission (Kalat, 2015). For instance, if there are no astrocytes, neurons may be unnecessarily activated by surrounding ions or lack synchronization. Although there will be signals, they would not be meaningful.