Answer: Option D) there are no holes for blood to enter or leave the system
The human cardiovascular system is considered closed because there are no holes for blood to enter or leave the system
Explanation:
The closed circulatory system are made up of blood vessels called arteries from the heart that branch into small units called capillaries but eventually join up with other blood vessels called veins that are connected to the heart. So, blood is always confined to circulate within the blood vessels and the heart as there are no holes for blood to enter or leave the system
Thus, the human cardiovascular system is considered closed
They help in that, many recently discovered fossils form series that trace the evolution of modern species from extinct ancestors. Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors. Evolutionary theory explains the existence of homologous structures adapted to different purposes as a result of descent with modification from a common ancestor.
I want to say it was erotion from water
Answer:
Cross-bridges would form in the absence of an action potential from a motor neuron.
Explanation:
The injected calcium ions would bind to troponin. Troponin would make tropomyosin move away from the myosin-binding sites on actin. The presence of free binding sites on the actin would be followed by the contraction cycle. This would include hydrolysis of ATP to energize myosin heads and binding of these heads to actin to form cross-bridges. Therefore, cross-bridge formation would occur without any action potential if calcium ions are injected directly into the muscle.
ANSWER:
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