What is a control mechanism that intensifies an earlier reaction

The correct answer is positive feedback.

The sensory receptors are nerve endings or specialized cells able to capture internal or external stimuli, and generate in response nerve impulses.

The answer is:  A sensory receptor.

answer; i believe the answer is hydraulic action;

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.