Contraction elicited by a single brief stimulus is called a. a twitch, b. temporal summation, c. multiple motor unit summation, d. fused tetanus.

Video transcript

Hi everyone. Let's take a look at this practice problem together. What is the small fluid filled gap between the neuron and muscle fiber membranes called the answer. Options are a synaptic cleft B. Neuromuscular junction, C motor unit and D acetylcholine. OK. So when you have an interaction where a signal is being sent from the neuron to a muscle fiber recall that neurotransmitters are released into the small fluid filled gap or the extracellular space that exists between them. Also recall that acetylcholine option D is a neurotransmitter and it can get released into that gap during signaling. It is not the term for the gap itself. So we can eliminate option D option C, the motor unit recall is a single motor neuron. So a single neuronal cell and all of the muscle cells that it interacts with. So we can go ahead and eliminate option C as well. For option B, what is the neuromuscular junction? It's the region or area where the neuron and the muscle cell are. Now remember that the two cells, the neuron and the muscle cell do not touch and you have that small fluid filled gap in between them and that space is called the synaptic cleft, that cleft is filled with interstitial fluid. So it's the synaptic cleft that can be found within the neuromuscular junction. That means option B is incorrect and the correct answer is option A synaptic cleft. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.