This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'Post-tetanic potentiation is due to \nSelect and explain. \nA. Hyper polarization of muscle fibres, B. Rapid K efflux, C. Increased availability of Ca, D. Rapid Na influx', 'role': 'user'}, {'content': "Answer: C \nExplanation: Post-tetanic potentiation one form of plastic change it is the production of enhanced postsynaptic potentials in response to stimulation. This enhancement lasts up to 60s and occurs after a brief tetanizing train of stimuli in the presynaptic neuron. The tetanizing stimulation causes Ca2+ to accumulate in the presynaptic neuron to such a degree that the intracellular binding sites that keep cytoplasmic Ca2+ low are overwhelmed. Ref: Ganong's Review of Medical Physiology 26th edition", 'role': 'assistant'}]