Question

The brain receives messages in signals called nerve impulses. Which part of the ear first generates these nerve impulses?

Answer 1

That's the job of the tiny "hair cells", located in the inner ear.

If you're a sound wave, this is how you reach the hair cells:

-- go into the big funnel of skin on the outside of the head, that thing we call the "ear"

-- go about an inch or two, down through a skinny dark tunnel inside the skull

-- at the end of the tunnel, hit a dead end, made of a wall of thin skin like a drum, called the "ear drum";  sound waves hit the ear drum and make it vibrate

-- on the other side of the ear drum, inside, is the chamber called the "middle ear".  In there are the three smallest bones in the body; the ear drum touches the first one and makes it vibrate; the first one touches the second one and makes it vibrate; the second one touches the third one and makes it vibrate;  then the third one touches another dead end made of thin skin.

-- the region on the other side of this wall of thin skin is the "inner ear";  it's a long skinny chamber, called the "cochlea",  wound up in a spiral and filled with liquid; the walls of the cochlea are lined with millions of tiny hairs, sticking out into the liquid; the vibrations make waves in the liquid, and the waves make the tiny hairs wave back and forth; each tiny hair is the end of a nerve that goes into the brain; when that hair wiggles, it sends a nerve "message" into the brain.  

-- there are two complete copies of this whole structure ... one on each side of your head.

Answer 2

Answer:

B. cochlea                                                                  

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