Why is a chemical synaptic transmission unidirectional? Does calcium open up Ca+ channels in the bulb and Ca+ rushes in and allows for neurotransmitters to enter?

Answer 1

Synaptic transmission is undirectional because neurotransmitters cannot be exchanged otherwise.

A synapse is a link between two neurons in our bodies. The synapse is showed schematically below.

A synapse has a side which releases neurotransmitters and a side that can receive them. When a signal travels towards such a synapse, these neurotransmitters are released in the synaptic gap and can travel free around. If such a neurotransmitter is bonded to a receptor on the other site of the synaptic gap, this releases another signal which travels further and further in our body.

We see now, that these neurotransmitters cannot cause a signal to go backwards. The receptor site cannot release them and the synaptic knob cannot receive them.
For your interest, neurotransmitters are mostly broken down in the synaptic gap after they are released, so another signal can come through!

There are two types of effects caused by neurotransmitters: excitation and inhibition. Inhibition is when a molecule lowers the potential to create a new electrical signal and excitation is when a molecule raises the potential to create a new electrical signal output.

Why is it important to have a unidirectional unit in our nerve system?
This is because all the other neurons do not have a specific direction. Image what a chaos would be created if everything gets triggered and triggered because there is no way you can stop a signal!

What has calcium to do with this?
Calcium is part of the system that releases the neurotransmitters in the synaptic cleft. If an electric signal reaches the synapse, membrane ports are put open and calcium is transferred into the synapse, creating a high concentration inside (see image below). Specific proteins on the membrane of the neurotransmitter carrier (the bubbles) react on this higher concentration and fuse with the cell membrane, releasing the neurotransmitters in the synaptic cleft.

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Answer 2

Chemical synaptic transmission is unidirectional because neurotransmitter release occurs only from the presynaptic neuron and neurotransmitter receptors are located on the postsynaptic neuron. Calcium ions (Ca2+) do play a crucial role in this process by triggering neurotransmitter release. When an action potential reaches the presynaptic terminal, voltage-gated calcium channels open, allowing Ca2+ to enter the terminal. This influx of Ca2+ triggers the fusion of synaptic vesicles containing neurotransmitters with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron, initiating a response in the postsynaptic neuron.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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