Briefly discuss the role of the myosin heads in the sliding filament mechanism of muscle contraction
What will be an ideal response?
The interaction of thin filaments sliding past thick filaments generates tension throughout the sarcomere during muscle contraction. This is known as the sliding filament mechanism. Myosin heads of the thick filaments grab active sites on thin filaments and pull the thin filaments toward the M line as the myosin heads rotate. The pulling action brings the Z discs closer together and shortens the sarcomere. Neither the thin nor the thick filaments actually shorten; instead the thin filaments are pulled and slide toward the M line.
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________ is characterized by a thickened alveolar membrane, slowing respiratory gas exchange.
Fill in the blank(s) with the appropriate word(s).
What prevents the dramatic increase in venous return that occurs during exercise from damaging the cardiac myocytes?
A. The exercise demand on the heart causes it to stiffen, preventing overstretch. B. The pericardium acts as a limit on the amount of stretch. C. The increased heart rate limits filling time. D. Venous return is not sufficient to stretch the heart very much.
On-center ganglion cells _____________ their spike frequency when the center of their receptive field is stimulated by light
a. increase b. decrease c. do not change
Which of the following is NOT true of the masseter muscle?
A. It inserts on the lateral portion of the mandible. B. It is innervated by the facial nerve. C. It closes the jaw by elevating the mandible. D. It originates on the zygomatic arch. E. All of these are true of the masseter muscle.