The top cover is a feat of engineering by itself. Within its walls are contained:

Main control wheel, shutter/aperture control wheel, live view lever, On/Off switch, "info" button, record button, shutter button, exposure compensation button, IR sensor, AF lamp, flash, flash control circuitry, flash actuator, and the microphone.

The flash is actuated by a linear solenoid that pushes on a lever to release the spring-loaded flash -- either automatically if the sensor detects a low-light situation, or when the flash button is depressed.