Where are the heart cells with the fastest rate of action potential initiation localized?
a. apex of the heart
b. Purkinje fibers
c. Bundle of His
d. AV node
e. SA node
e
You might also like to view...
With emphysema, the muscles that contract with normal exhalation include which of the following?
A. external intercostals and abdominal muscles B. internal intercostals C. internal intercostals and abdominal muscles D. abdominal muscles E. external intercostals
Which structure prevents food or water from entering the trachea?
a) Arytenoid cartilage b) Epiglottis c) Nasopharynx d) Thyroid cartilage e) Paranasal sinus
The two hormones released from the posterior pituitary are
A. oxytocin and antidiuretic hormone. B. prolactin and vasopressin. C. follicle-stimulating hormone and luteinizing hormone. D. thyrotropin-releasing hormone and corticotropin-releasing hormone. E. prolactin and growth hormone.
Which is NOT true about a binding site on a protein?
A. It is an area of the protein with a shape complementary to that of a ligand. B. It is determined by the amino acid sequence of the protein. C. There can only be one binding site on a given protein. D. Binding of a ligand to the binding site typically activates or inactivates a protein's specific function. E. The binding of a ligand to a binding site typically changes the conformation of the protein.