Which of the following statements about the coordination of the heartbeat is false?
A. Each heartbeat is generated by signals
from the nervous system that stimulate the
heart's pacemaker cells.
B. Cardiac muscles are in electrical
continuity, which allows for synchronous
contraction of the two atria followed by
synchronous contraction of the two ventricles.
C. Under normal conditions, the electrical
separation between the atria and ventricles
prevents all four chambers from contracting
synchronously.
D. Following activation of the AV node, the
action potential is transmitted to the base of
the ventricles by a modified set of cardiac
muscle fibers.
E. None of the answer options is false.
A
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Protection of the embryo is a major requirement for land plants given there is no aquatic environment in which to keep it safe from desiccation and other environmental hazards. Which structure, in both seed and seedless plants, provides the protection and nutrients needed by the embryo as it develops?
a. sporangium b. gametangia c. female gametophyte d. archegonium
A(n) ________ is an instrument used to separate subcellular structures and macromolecules on the basis of size, shape, and density. ________ developed this instrument in Sweden during the period 1925–1930
Fill in the blank with correct word.
The vaccine to prevent cervical cancer is a(n) (attenuated/recombinant/toxoid) vaccine
What will be an ideal response?
The reason water is polar is because
A. hydrophilic molecules interact with water. B. in polar molecules atoms share electrons evenly. C. there is a transfer of electrons from the hydrogen to the oxygen. D. the electrons spend more time circling the oxygen atom than the hydrogens. E. hydrophobic molecules do not interact with water.