As a sound vibration enters the ear it travels through the external canal to the eardrum. The vibrations then moves past the mallet, anvil and stirrups to create a pressure wave in the fluid inside the cochlea. The vibrations are then transferred to an impulse as it travels through the organ of Corti and out the vestibulcochlear nerve traveling to the brain for interpretation.
The impulse is received in the primary auditory cortex located in the temporal lobe of the brain. Next the auditory cortex sends the impulse to Wernicke’s area where the impulse is interpreted and understood. Afterward it is sent to the Broca’s area where the interpreted sound is formed into ideas to form a response. Finally the understood and interpreted sound is transferred to the motor cortex where an impulse is sent to the oral muscles to form words.
Therefore when I am walking down the hall and bump into a kid I can interpret his polite apology of “Excuse me” and form my polite response of “That’s okay”. When the spoken word is received by the organ of corti and transferred to the Wernicke’s area to be understood, then to Broca’s area to form the reply. Since there are two different areas that work together to form the complete communication cycle, when one part of the brain is damaged in for instance a stroke, the other part continues to function. For example, when the Broca’s area is damaged the patient can still understand what they hear with the Wernick’e area, while not being able to respond.
Broca's Area was discovered by Paul Broca when he studied a man known only as "Tan," as he could only say that one word. It is a main area in tha cerebral cortex, responsible for producing speech. Patients with damage to this area can understand language, but can't produce more than short sentences.
Wernicke's Area was named after Carl Wernicke, who discovered an illness characterized by mental deficiency. Wernicke's area is responsible for interpreting language, and is in Temporal Lobe of the brain. Patients with damage to this area cannot understand what they are saying, but can produce words efficiently, while they are usually nonsensical.
References
Ewart. (2013). [Image gives a description of the anatomy of the inner ear]. Retrieved from http://www.hearing-aids-wizard.com/image-files/human-ear-diagram.jpg.
Institute on Deafness and Other Communication Disorders. (2008). [Diagram of language areas in the brain]. Aphasia National. Retrieved from http://www.nidcd.nih.gov/health/voice/pages/aphasia.aspx.
Novella, S. (2007). How the brain interprets language. Retrieved from http://theness.com/neurologicablog/index.php/how-the-brain-interprets-language.