Answer:
SA node
Explanation:
The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump.
Explanation:
It's superior vena cava and vena cava
Answer/Explanation:
All cells are not the same because not all cells contain membrane-bound organelles.
Prokaryotic cells lack membrane-bound organelles. In contrast, eukaryotic cells contain membrane-bound organelles like an endoplasmic reticulum, lysosomes, and importantly, a nucleus.
The nucleus is where genetic information (DNA) is stored. However, it is only present in eukaryotic cells. Prokaryotic cells do not possess a nucleus, the DNA is found in the cytoplasm.
<span>i think it is a.Molecules move against their concentration gradient. hope it helps
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