The action potential is conducted into a skeletal muscle fiber by
A) motor end plates.
B) neuromuscular junctions.
C) transverse tubules.
D) triads.
E) sarcoplasmic reticulum.
(
Question 2) Active sites on the actin become available for binding after
A) actin binds to troponin.
B) troponin binds to tropomyosin.
C) calcium binds to troponin.
D) calcium binds to tropomyosin.
E) myosin binds to troponin.
(
Question 3) Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber
A) lengthens.
B) shortens.
C) strengthens.
D) weakens.
E) pulls from the middle.
(
Question 4) When a skeletal muscle fiber contracts, the
A) H bands and I bands get larger.
B) zones of overlap get larger.
C) Z lines move further apart.
D) width of the A band increases.
E) All of the answers are correct.
(
Question 5) All of the following proteins are part of the thin filaments except
A) actin.
B) tropomyosin.
C) troponin.
D) titin.
E) None of the answers is correct; there are no exceptions.
(
Question 6) The series of membranous channels that surround each myofibril is the
A) sarcoplasmic reticulum.
B) sarcoplasm.
C) sarcomere.
D) sarcolemma.
E) endomysium.
(
Question 7) At rest, active sites on the actin are blocked by
A) myosin molecules.
B) troponin molecules.
C) tropomyosin molecules.
D) calcium ions.
E) ATP molecules.
(
Question 8) The region of the sarcomere that always contains thin filaments is the
A) Z line.
B) M line.
C) H band.
D) A band.
E) I band.
(
Question 9) Each thin filament consists of
A) two actin protein strands coiled helically around each other.
B) chains of myosin molecules.
C) six molecules coiled into a helical structure.
D) a rod-shaped structure with heads projecting from each end.
E) a double strand of myosin molecules.
(
Question 10) At rest, the tropomyosin molecule is held in place by
A) actin molecules.
B) myosin molecules.
C) troponin molecules.
D) ATP molecules.
E) calcium ions.
Quick Reply
