Question

At what stage of Neural transmission does calcium enter the cell through voltage-gated calcium channels?

Answer 1

Calcium enters near the end of the cell to release neurotransmitters, chemicals that convey information to the next neuron.

Explanation:

Messages are transmitted through axa, the long tail-end of neurons, by ions flowing in and out of the cell. The electrical signal induces `Na^+` ions to be pumped into the relatively negative cytoplasm, which attracts the electronic nerve impulse. The sodium also stimulates potassium channels to pump potassium out of the cell, repolarising it, and stimulates sodium to be pumped into the cell further down. This has the effect of tying a note to a piece of string and pulling it down the street with a cartoon character chasing after it.

Calcium comes into play near the end of the cell in the axon terminal. When the impulse reaches the terminal, voltage-dependent ion channels open and allow `Ca^(2+)` to flow into the cell.

Calcium interacts with proteins inside the cell which cause vesicles (bubbles) of neurotransmitters to bind to the membrane and open, releasing the chemicals for the next cell to receive. The vesicles then split off from the membrane and are filled with new neurotransmitters in a process called recycling.