A mechanoreceptor is a sensory receptor that responds to changes in pressure or movement. An example of a mechanoreceptor specialized for detecting muscle movement is shown in the diagram below. Which of the following best describes the nervous system change during muscle contraction?
A. A resting potential is disrupted at the spindle, which sends a wave of sodium and potassium ions along the axon, across the synapse to another neuron, and eventually to the brain.
B. A proton gradient forms in response to changes at the spindle, which triggers a wave of depolarization along the axon to the synapse, which transfers the signal to the brain.
C. An electrical signal begins at the spindle and is carried to the sensory neuron cell body, where it connects with interneurons that continue the signal to the brain.
D. An action potential is triggered, which moves down the axon, across the synapse to another neuron, and then to another, and so on until the signal reaches the brain.