The auditory system has both afferent and efferent pathways. In the afferent auditory system, the vibration of incoming sound waves moves the tympanic membrane, and the ossicular chain in the middle ear mechanically focuses this movement into a piston-like action at the oval window, which generates fluid waves that propagate through the cochlea and stimulate type 1 cochlear hair cells in a frequency-specific fashion, triggering action potentials that eventually reach the auditory cortex and are perceived as specific tones. In short, the afferent pathway transduces kinetic energy from the vibration of sound waves into the electrochemical activity that constitutes a neural signal and functions as a frequency analyzer. In the efferent pathway, signals from the inferior colliculus synapse on type 2 cochlear hair cells which serve to modulate (amplify or dampen) the activity of type 1 cochlear hair cells; thus, the efferent auditory system functions as an equalizer. The efferent auditory pathway also controls the activity of the tensor tympani and the stapedius, mediating a protective reflex against overly loud acoustic stimuli. A range of neurotransmitters are found throughout the auditory system.