What is responsible for initiating contraction of smooth muscle?
a. Stimulation by motor neurons
b. Inhibition of acetylcholinesterase
c. Membrane potential drifting to threshold as a result of automatic changes in ion movement across the membrane
d. Excitation of the gap junctions by a transmitter substance
e. Stimulation by the autonomic nervous system
C
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The body is made up of many different cell types, from small circular red blood cells to the elongated smooth muscle cells 20X its size. Why is there such variation in size and shape?
A. Variations in cell shape and size are due to chromosomal differences between cells. B. Cell size and shape does not vary among cell types. C. Different variations in size and shape allow differentiated cell types to perform unique functions. D. Different cell sizes are due to nutritional differences.
The ____________________ is the longest, heaviest, and strongest bone in the human body.
Fill in the blank(s) with the appropriate word(s).
Which of the following proteins is found only at the basolateral side of thyroid epithelium?
A. Na+-I– symporter B. pendrin C. megalin D. iodotyrosine deiodinase E. thyroid peroxidase
The portions of an antigen's exposed surfaces to which its specific antibody binds are regions called
A) opsonins. B) the constant segments of the light and heavy chains. C) antigenic-determinant sites. D) complement-binding sites. E) antigen-binding sites.