3. What role do valves play in the heart?
4. Which structure in the heart functions as the natural pacemaker? What does this term mean?
5. How does the movement of the electrical impulse relate to the contraction of the chambers of
the heart?
O AME

idk im sorry.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.

b is the answer and if you need further with anything message me