Beginning with all chambers of the heart in the "relaxed" phase, describe the cardiac cycle in mammals, with systole and diastole of the atria and ventricles. For each time point in the cycle you select, state the following:. A) Whether the atria and ventricles are contracting or relaxing
B) Whether the AV valves and semilunar valves are closed or open
C) Whether the pressure in the atria and ventricles is high or low.

Answer and Explanation:

The cardiac cycle throughout mammals consists of four main different steps of activity:

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giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.