During concentric contractions of skeletal muscle, the I band and H zone shorten but the A band stays the same.
Indicate whether the statement is true or false.
(
Question 2) The force-generating sites in a myofibril are the Z lines.
Indicate whether the statement is true or false.
(
Question 3) During skeletal muscle contraction, the distance between the Z lines of a sarcomere decreases because of shortening of the thick and thin filaments.
Indicate whether the statement is true or false.
(
Question 4) Skeletal muscles are made up of bundles of muscle fibers attached to bone by connective tissue called tendons.
Indicate whether the statement is true or false.
(
Question 5) The name given to the repeating functional units that cause striations in a skeletal muscle myofibril is sarcomere.
Indicate whether the statement is true or false.
(
Question 6) Myasthenia gravis is a collection of muscle disorders that cause muscle fatigue and weakness. What is the major mechanism?
A. overproduction of acetylcholinesterase
B. autoimmune destruction of nicotinic acetylcholine receptors
C. demyelination of axons in motor pathways
D. autoimmune destruction of L-type Ca2+ channels.
E. a tumor that overproduces acetylcholine
(
Question 7) Which dietary supplement is most likely to contribute to greater skeletal muscle ATP availability in the first few seconds of skeletal muscle contraction?
A. fatty acids
B. sports drinks with electrolytes and mineral spirits
C. sugar
D. protein
E. creatine
(
Question 8) Which best describes a role of L-type Ca2+ channels in cardiac muscle cells?
A. They function exactly the same in cardiac muscle cells as they do in skeletal muscle.
B. They are directly responsible for making cardiac muscle fatigue-resistant.
C. They are responsible for preventing tetanic contractions.
D. They cause the absolute refractory period to be very brief.
E. They act as non-conducting voltage sensors that mediate excitation-contraction coupling.
(
Question 9) Which membrane protein transport process plays an important role in terminating the contraction of cardiac muscle?
A. Ca 2+-ATPase pumps move Ca2+ from the T-tubule back into the sarcoplasmic reticulum.
B. Na+/K+-ATPase pumps move Na+ back into the cytosol and K+ back into the T-tubule lumen.
C. Ca2+-ATPase pumps move Ca2+ from the cytosol back into the sarcoplasmic reticulum.
D. Na+/Ca2+-exchangers move Na+ out of the cytosol in exchange for Ca2+ movement into the sarcoplasmic reticulum.
E. Na+/K+-ATPase pumps move Na+ and K+ back out of the cell.
(
Question 10) The prolonged electrical depolarization of cardiac muscle cells that occurs during contraction is due primarily to the persistent influx of what ion?
A. sodium
B. calcium
C. nitrate
D. chloride
E. potassium
Quick Reply
