ESS 345 MIDTERM EXAM QUESTIONS AND
ANSWERS GRADED A++
A motor unit refers to ____________.
a single motor neuron plus all of the muscle fibers it innervates
Thick filaments are often named for which protein?
myosin
Why is it necessary to have an action potential (electrical signal) in the muscle for
contraction?
The SR will release Ca2+ only if it has been electrically stimulated.
According to the size principle, which motor unit will be recruited first for a task?
the motor unit with the smallest motor neuron
What is twitch summation?
A means by which gradation of muscle contraction may be accomplished
Increasing the frequency at which motor units are firing within a muscle
If you wanted to pick up something heavier than your pencil (such as your book),
you would need to have a stronger muscle contraction. In what way might you
accomplish this?
Stimulate more motor units.
If you want to hold a very heavy dumbbell to show your friends how strong you
are, you want to select the best joint angle ____________.
Where muscle length is optimal
Where leverage is maximal
,During concentric contractions, increasing the speed of contraction will
Decrease the force produced
The (1) is the basic unit of contraction in skeletal muscle.
sarcomere
Myofibril is (2) of muscle fiber.
a major component
At rest, (3) is stored in the sarcoplasmic reticulum (SR) and released by action
potential to bind to (4) for muscle contraction.
(3) Ca (2+)
(4) troponin
At the end of contraction phase, myosin bound (5) which (6) the cross-bridges.
(5) actin
(6) maintains
At rest, cross-bridge interaction between actin and myosin in skeletal muscle is
directly blocked by (7).
tropomyosin
When the myosin head pulls the thin filament toward the center of the sarcomere,
the tilting action of the head is called (8).
powerstroke
Type (9) fibers are typically engaged during short, higher-intensity exercise that
involves some degree of endurance.
IIa
, Type (10) fibers are not very easily stimulated by the nervous system, meaning
that they typically are not engaged until all other fiber types have been stimulated
first.
IIx
When maximal force is produced, type (11) fibers are used.
I, IIa, IIx (all fibers)
(12) is the oxygen-binding molecule associated with skeletal muscle.
myoglobin
To form cross-bridge, actin binding site to myosin must be (13) and myosin head
must be energized by (14).
(13) exposed
(14) ATP breaking into ADP and Pi
If, for some reasons, less calcium (Ca2+) is released from sarcoplasmic reticulum
(SR), what would happen to force production and why?
If less calcium is released from the SR, then the force production would decrease. This
is because force production is dependent on the amount of calcium (size of SR) in that
a greater amount of calcium allows more cross-bridges to be formed. When released,
calcium attaches to troponin which shifts, causing tropomyosin to aslo shift to expose
actin's mysoin-binding site. This allows myosin to bind to the myosin-binding site on
action to form a cross-bridge. This sets the stage for a powerstroke in which the
muscles contract to generate force. Without the formation of cross-bridges, a
powerstroke could not occur, preventing the movement of actin filaments inward,
ANSWERS GRADED A++
A motor unit refers to ____________.
a single motor neuron plus all of the muscle fibers it innervates
Thick filaments are often named for which protein?
myosin
Why is it necessary to have an action potential (electrical signal) in the muscle for
contraction?
The SR will release Ca2+ only if it has been electrically stimulated.
According to the size principle, which motor unit will be recruited first for a task?
the motor unit with the smallest motor neuron
What is twitch summation?
A means by which gradation of muscle contraction may be accomplished
Increasing the frequency at which motor units are firing within a muscle
If you wanted to pick up something heavier than your pencil (such as your book),
you would need to have a stronger muscle contraction. In what way might you
accomplish this?
Stimulate more motor units.
If you want to hold a very heavy dumbbell to show your friends how strong you
are, you want to select the best joint angle ____________.
Where muscle length is optimal
Where leverage is maximal
,During concentric contractions, increasing the speed of contraction will
Decrease the force produced
The (1) is the basic unit of contraction in skeletal muscle.
sarcomere
Myofibril is (2) of muscle fiber.
a major component
At rest, (3) is stored in the sarcoplasmic reticulum (SR) and released by action
potential to bind to (4) for muscle contraction.
(3) Ca (2+)
(4) troponin
At the end of contraction phase, myosin bound (5) which (6) the cross-bridges.
(5) actin
(6) maintains
At rest, cross-bridge interaction between actin and myosin in skeletal muscle is
directly blocked by (7).
tropomyosin
When the myosin head pulls the thin filament toward the center of the sarcomere,
the tilting action of the head is called (8).
powerstroke
Type (9) fibers are typically engaged during short, higher-intensity exercise that
involves some degree of endurance.
IIa
, Type (10) fibers are not very easily stimulated by the nervous system, meaning
that they typically are not engaged until all other fiber types have been stimulated
first.
IIx
When maximal force is produced, type (11) fibers are used.
I, IIa, IIx (all fibers)
(12) is the oxygen-binding molecule associated with skeletal muscle.
myoglobin
To form cross-bridge, actin binding site to myosin must be (13) and myosin head
must be energized by (14).
(13) exposed
(14) ATP breaking into ADP and Pi
If, for some reasons, less calcium (Ca2+) is released from sarcoplasmic reticulum
(SR), what would happen to force production and why?
If less calcium is released from the SR, then the force production would decrease. This
is because force production is dependent on the amount of calcium (size of SR) in that
a greater amount of calcium allows more cross-bridges to be formed. When released,
calcium attaches to troponin which shifts, causing tropomyosin to aslo shift to expose
actin's mysoin-binding site. This allows myosin to bind to the myosin-binding site on
action to form a cross-bridge. This sets the stage for a powerstroke in which the
muscles contract to generate force. Without the formation of cross-bridges, a
powerstroke could not occur, preventing the movement of actin filaments inward,
