Explain the mechanics of muscle contraction during a heartbeat, including the stimulus for the contraction
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Beating of the heart involves contraction of cardiac muscle, and most muscles require nervous stimulation to contract. The heart does not require outside stimulation to beat; the tendency is intrinsic, that is, within the heart muscle itself. The tempo of the heartbeat is set at the sinoatrial node, which is located in the right atrium; it functions as the pacemaker. About 100 milliseconds after the pacemaker fires, impulses stimulate an area between the two atria, the atrioventricular node. Once the AV node is stimulated, special fibers called the atrioventricular bundle carry the impulse to Purkinje fibers, which penetrate the walls of the ventricles, causing them to contract.
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The distribution of cytoplasm to daughter cells is
accomplished during a. prokaryotic fission. b. mitosis. c. meiosis. d. cytokinesis. e. karyokinesis.
Assume that a Chi-square test provided a probability value of 0.02. Should the null hypothesis be accepted?
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Excavates lack ________
Fill in the blank(s) with correct word
The relationship between plants and their pollinators is a good example of parasitism.
Answer the following statement true (T) or false (F)