If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid, ________.
A) threshold is reached more quickly and heart rate would increase
B) potassium channels compensate and no change in heart rate would occur
C) heart rate would decrease, but blood pressure would rise due to the excess sodium present
D) tetanic contraction would occur due to the short absolute refractory period of cardiac muscle
A) threshold is reached more quickly and heart rate would increase
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The lub-dup heart sounds heard during auscultation of the heart are associated with:
A. the SA node firing. B. the heart valves opening. C. the heart valves closing. D. blood flowing from the atria to the ventricles.
Describe the events that must occur in order for sperm to penetrate an egg. What prevents more than one sperm from entering? In the case of twins, how many sperm entered the egg? Why must a man have millions of sperm in a semen sample to be considered fertile? If only one sperm were present in the semen and that sperm managed to find its way to the egg, could it fertilize the egg? Explain.
What will be an ideal response?
A single, whip-like structure called a _____ occurs in only one human cell type, called _____
Fill in the blank(s) with the appropriate word(s).
Besides the supinator, which other muscle is a powerful supinator of the forearm?
A. Pronator teres B. Pronator quadratus C. Triceps brachii D. Brachialis E. Biceps brachii