View the animation below, then complete the quiz to test your knowledge of the concept.

1	Muscle contraction is caused by
	A)	actin filaments sliding past each other.
	B)	myelin filaments sliding past each other.
	C)	myosin filaments sliding past each other.
	D)	actin filaments sliding past myelin filaments.
	E)	actin filaments sliding past myosin filaments.
2	Which of the following statements about H zones and I bands is TRUE?
	A)	the H zones contain only myosin, while the I bands contain only actin
	B)	the H zones contain only actin, while the I bands contain only myosin
	C)	the H zones contain only myosin, while the I bands contain both actin and myosin
	D)	the H zones contain both actin and myosin, while the I bands contain only actin
	E)	the H zones and the I bands each contain both actin and myosin
3	During muscle contraction
	A)	the A band remains the same and the I band narrows.
	B)	the I band remains the same and the A band narrows.
	C)	both the A band and I band remain the same.
	D)	both the A band and I band narrow.
	E)	both the A band and I band become wider.
4	In a contracting muscle the Z lines come closer together.
	A)	True
	B)	False
5	In a relaxed muscle, the H zone is at its narrowest width.
	A)	True
	B)	False