This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sensory System, Subject name: Physiology
[{'content': 'Which statement concerning sensory neurons or their functional propeies is true? \nSelect and explain. \nA. All sensory fibers are unmyelinated, B. In spatial summation, increasing signal strength is transmitted by using progressively greater numbers of sensory fibers, C. Increased stimulus intensity is signaled by a progressive decrease in the receptor potential, D. Continuous subthreshold stimulation of a pool of sensory neurons results in disfacilitation of those neurons', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The different gradations of intensity can be transmitted either by using increasing numbers of parallel fibers or by sending more action potentials along a single fiber. These two mechanisms are called, respectively, spatial summation and temporal summation. In spatial summation, increasing signal strength is transmitted by using greater numbers of sensory fibers. Other options: Most of the sensory nerve fibres are myelinated except ones carrying slow pain sensation which are unmyelinated. Increased stimulus intensity has no change in the receptor potential. Continuous subthreshold stimulation of sensory neurons results in facilitation of these neurons.', 'role': 'assistant'}]