The ions that enter the skeletal muscle cell during the generation of an action potential are a. calcium ions, b. chloride ions, c. sodium ions, d. potassium ions.

Video transcript

Hi, everybody. Let's look at our next question. What is the role of calcium ions in the neuromuscular junction? A to terminate the neurotransmission B to generate the action potential C to initiate muscle contraction and D to open voltage gated calcium channels. Well, this question is a little bit tricky because calcium ions actually have multiple roles in muscle contraction. But it's important to note here that it's asking us specifically for their role in the neuromuscular junction. So I'm going to go ahead and eliminate choice C which is to initiate muscle contraction. Calcium does initiate muscle contraction. It binds to troponin which removes it from the Myerson binding site on the acting filament, making it available for my to bind in a cross bridge to generate the muscle contraction. But this is in the cytoplasm of the muscle cell and that's not what we're looking for. So even though that's a correct function of calcium, we're looking for what calcium does in the neuromuscular junction. So that's why choice C isn't correct. When we think about events at the neuromuscular junction, they start with the generation of an action potential, but this is not done by calcium ions, this is generated in the neuron. So that is not our answer choice as it's not done by calcium. Once that action potential reaches the axon terminal, the voltage gates are open the voltage gated calcium channels and calcium flows into the axon terminal. So the calcium is flowing through the channels, but they're also opened by calcium. So choice D is going to be our correct answer here to open the voltage gated calcium channels. This occurs when the action potential reaches the axon terminal. Would you have one final choice to look at choice A to terminate the neurotransmission? But calcium is not involved in that, that is done by the cole and aerate, that enzyme that breaks down the ach, thereby ending the you sort of mop up the last of the ach and thereby ending that particular sequence of events that led to muscle contraction. So choice A is not our answer. So again, the role of calcium ions specifically in a neuromuscular junction choice D to open voltage gated calcium channels. See you in the next video.