Explain the mechanics of muscle contraction during a heartbeat, including the stimulus for the contraction
What will be an ideal response?
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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Which of the following reactions prevails in red blood cells traveling through alveolar capillaries? (Hb = hemoglobin)
A) Hb + 4 O2 ? Hb(O2)4 B) Hb(O2)4 ? Hb + 4 O2 C) CO2 + H2O ? H2CO3 D) H2CO3 ? H+ + HCO3- E) Hb + 4 CO2 ? Hb(CO2)4
A scientist is working with fungi in his lab, and in doing so he chemically modifies the cellular environment of the fungi so plasmogamy can occur, but karyogamy cannot occur. Explain what would happen with the fungi in this new circumstance.
A. Cells would not produce hyphae. B. Cells would not produce gametes. C. Cells would not produce cytoplasm. D. Cells would fuse but maintain separate nuclei. E. Hyphae would fuse but cytoplasm would not fuse.
Which class contains all mollusks that live on land?
a. Solenogastres b. Scaphopoda c. Gastropoda d. Bivalvia
Lipid A causes which of the following symptoms?
A. hemorrhaging B. fever C. disseminated intravascular coagulation (DIC) D. fever and disseminated intravascular coagulation (DIC) E. fever and hemorrhaging