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10. The diagram below shows how action potentials move through the heart to control the contraction of cardiac muscle cells. For each step of the four steps in the diagram, briefly explain what is happening in terms of action potential transmission and muscle contraction. On the diagram also indicate the point at which the atria contract and the point at which the ventricles contract. You may find it helpful to refer to Figure 37.24 in your textbook. SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers 11. The diagram below shows an electrocardiogram (EKG) for one cardiac cycle. Try to relate this EKG to the heart diagram in the previous question. On the EKG below, indicate when you would observe the atria in a contracted state and in a relaxed state. Indicate when you would observe ventricles in a contracted and in a relaxed state. You may find it helpful to refer to Figure 37.24 in your textbook. R مد Recorded potential Р T -Qs Time