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The SAN (pacemaker) sends a wave of excitation across both atria. This triggers atrial systole, where both atria contract simultaneously. There is a time delay at the AV Node which al...
Respiration (breathing) is the way your body gets oxygen into the lungs from the air outside.Cellular respiration describes how your cells make ATP - a molecule used to provide energy for chemical reactio...
A-Level Biology has probably the most content of any of the A-Level sciences! Its tempting to memorise all the content in the textbook but in reality some textbooks will have extra information that is no...
they don't have a nucleus, the DNA is present in cytoplasm. prokaryotic cell has a cell membrane that controls movement of molecules in and out of the cell. prokaryotic cells also have cell walls that pro...
Blood flows through human bodies via a double circulatory system, the systematic system and the respiratory system, which are connected by the heart. Blood enters the right atrium of the heart from the ve...
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