Vander's Physiology Ch.9 Exam Questions
Correctly Solved to Score A+
Which is FALSE statement about skeletal muscle structure?
a) A myofibril is composed of multiple muscle fibers.
b) Most skeletal muscles attach to bones by connective-tissue tendons.
c)Each end of a thick filament is surrounded by six thin filaments.
d) A cross- bridge is a portion of the myosin molecule.
e) thin filaments contain actin, tropomyosin and troponin. - Answer A
A single skeletal muscle fiber or cell is composed of many myofibrils.
Which is correct regarding a skeletal muscle sarcomere?
a) M Lines are found in the center of the I band.
b) The I band is the space between one Z line and the next.
c) The H zone is the region where thick and thin filaments overlap.
d) Z Lines are found in the center of the A band.
e) The width of the A band is equal to the length of a thick filament. - Answer E
The dark stripe in a striated muscle that constitues the A band results from the aligned thick filaments
within myofibrils, so thick filament length is equal to A-band width
When a skeletal muscle fiber undergoes a concentric isotonic contraction,
a) M Lines remain the same distance apart.
b)Z Lines move closer to the ends of the A bands
c) A bands become shorter
, d) I bands become wider
e) M Lines move closer to the end of the A band. - Answer B
As filaments slide during shortening contaction, the I band becomes narrower so the distance between
the Z line and the thick filaments ( at the end of the A band) must decrease
During excitation-contraction coupling in a skeletal muscle fiber:
a) the Ca2+ ATPase pumps Ca2+ into the T-Tubule.
b) action potentials propagate along the membrane of the sarcoplasmic reticulum
c) Ca2+ floods the cystol through the dihydropyridine ( DHP) receptors.
d) DHP receptors trigger the opening of terminal cisterane ryanodine receptor Ca2+ channels.
e) acetylcholine opens the DHP receptor channel - Answer D
DHP receptors act as voltage sensors in the T-tubule membrane and are physically linked to ryanodine
receptors in the sarcroplasmic reticulum membrane. When action potential depolarizes the T-Tubule
membrane, DHP receptors change conformation and trigger the opening of the ryanodine receptors.
This allows Ca2+ to diffuse from the interior of the sarcoplasmic reticulum into the cytosol.
Why is the latent period longer during an isotonic twitch of a skeletal muscle fiber than it is during an
isometric twitch?
a) Excitation- contraction coupling is slower during an isotonic twitch.
b) Action potentials propagate more slowly when the fiber is shortening, so extra time is required to
activate entire fiber
c) In addition to the time for excitation-- contraction coupling it takes extra time for enough cross-brides
to attach to make the tension in the muscle fiber greater than the load.
d) Fatigue sets in much more quickly during isotonic contractions and when muscles are fatigued the
cross- bridges move much more slowly.
e) The latent period is longer because isotonic twitches only occur in slow ( Type 1) muscle fibers. -
Answer C
Correctly Solved to Score A+
Which is FALSE statement about skeletal muscle structure?
a) A myofibril is composed of multiple muscle fibers.
b) Most skeletal muscles attach to bones by connective-tissue tendons.
c)Each end of a thick filament is surrounded by six thin filaments.
d) A cross- bridge is a portion of the myosin molecule.
e) thin filaments contain actin, tropomyosin and troponin. - Answer A
A single skeletal muscle fiber or cell is composed of many myofibrils.
Which is correct regarding a skeletal muscle sarcomere?
a) M Lines are found in the center of the I band.
b) The I band is the space between one Z line and the next.
c) The H zone is the region where thick and thin filaments overlap.
d) Z Lines are found in the center of the A band.
e) The width of the A band is equal to the length of a thick filament. - Answer E
The dark stripe in a striated muscle that constitues the A band results from the aligned thick filaments
within myofibrils, so thick filament length is equal to A-band width
When a skeletal muscle fiber undergoes a concentric isotonic contraction,
a) M Lines remain the same distance apart.
b)Z Lines move closer to the ends of the A bands
c) A bands become shorter
, d) I bands become wider
e) M Lines move closer to the end of the A band. - Answer B
As filaments slide during shortening contaction, the I band becomes narrower so the distance between
the Z line and the thick filaments ( at the end of the A band) must decrease
During excitation-contraction coupling in a skeletal muscle fiber:
a) the Ca2+ ATPase pumps Ca2+ into the T-Tubule.
b) action potentials propagate along the membrane of the sarcoplasmic reticulum
c) Ca2+ floods the cystol through the dihydropyridine ( DHP) receptors.
d) DHP receptors trigger the opening of terminal cisterane ryanodine receptor Ca2+ channels.
e) acetylcholine opens the DHP receptor channel - Answer D
DHP receptors act as voltage sensors in the T-tubule membrane and are physically linked to ryanodine
receptors in the sarcroplasmic reticulum membrane. When action potential depolarizes the T-Tubule
membrane, DHP receptors change conformation and trigger the opening of the ryanodine receptors.
This allows Ca2+ to diffuse from the interior of the sarcoplasmic reticulum into the cytosol.
Why is the latent period longer during an isotonic twitch of a skeletal muscle fiber than it is during an
isometric twitch?
a) Excitation- contraction coupling is slower during an isotonic twitch.
b) Action potentials propagate more slowly when the fiber is shortening, so extra time is required to
activate entire fiber
c) In addition to the time for excitation-- contraction coupling it takes extra time for enough cross-brides
to attach to make the tension in the muscle fiber greater than the load.
d) Fatigue sets in much more quickly during isotonic contractions and when muscles are fatigued the
cross- bridges move much more slowly.
e) The latent period is longer because isotonic twitches only occur in slow ( Type 1) muscle fibers. -
Answer C
