UAFS Cornell Physiology Exam 2
UPDATED Exam Questions and
CORRECT Answers
Match from the following list.
A. A band
B. I band
C. Z disk
D. H zone
E. M line
The structures that serve as the attachment site for the thin filaments and mark the boundaries
for one sarcomere. - CORRECT ANSWER-...
The structures that serve as the attachment site for the thin filaments and mark the boundaries
for one sarcomere. - CORRECT ANSWER- C. Z disk
Which ion signals the beginning of skeletal muscle contraction? - CORRECT ANSWER-
Ca2+
________ is composed of multiple globular molecules polymerized to form long chains or
filaments. - CORRECT ANSWER- Actin
Match the structures with the accurate description.
A. muscle fiber
B. fascicle
C. sarcolemma
D. myofibril
E. t-tubules
,a single muscle cell - CORRECT ANSWER- A. muscle fiber
The function of the titin protein is to - CORRECT ANSWER- stabilize the position of the
contractile filaments.
After death, when metabolism stops, in which step of the contractile cycle must skeletal
muscles remain? - CORRECT ANSWER- the rigor state
A motor unit consists of - CORRECT ANSWER- one neuron and all the skeletal muscle
fibers it controls.
Excitation-contraction coupling is a series of events that occur after the events of the
neuromuscular junction have transpired. The term excitation refers to which step in the
process? - CORRECT ANSWER- Excitation, in this case, refers to the propagation of action
potentials along the sarcolemma.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle
fiber. What specific event initiates the contraction? - CORRECT ANSWER- Calcium release
from the sarcoplasmic reticulum initiates the contraction
A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic
reticulum. How are these components connected? - CORRECT ANSWER- A series of
proteins that control calcium release.
What is name given to the regularly spaced infoldings of the sarcolemma? - CORRECT
ANSWER- transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to
contraction of skeletal muscle fibers? - CORRECT ANSWER- Calcium ions.
What is the relationship between the number of motor neurons recruited and the number of
skeletal muscle fibers innervated? - CORRECT ANSWER- Typically, hundreds of skeletal
muscle fibers are innervated by a single motor neuron
,The cross bridge cycle is a series of molecular events that occur after excitation of the
sarcolemma. What is a cross bridge? - CORRECT ANSWER- A myosin head bound to actin
What structure is the functional unit of contraction in a skeletal muscle fiber? - CORRECT
ANSWER- The sarcomere
Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where
are calcium ions stored within the fiber? - CORRECT ANSWER- Calcium ions are stored in
the sarcoplasmic reticulum.
After a power stroke, the myosin head must detach from actin before another power stroke
can occur. What causes cross bridge detachment? - CORRECT ANSWER- ATP binds to the
myosin head.
How does the myosin head obtain the energy required for activation? - CORRECT
ANSWER- The energy comes from the hydrolysis of ATP.
What specific event triggers the uncovering of the myosin binding site on actin? - CORRECT
ANSWER- Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end? - CORRECT ANSWER- Cross bridge cycling ends
when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to
allow calcium to unbind from troponin.
________ is the backup energy molecule that can be rapidly converted to ATP in active
skeletal muscle. - CORRECT ANSWER- Phosphocreatine
What is it called when myosin crossbridges attach to actin filaments and pull them toward the
middle of the sarcomere? - CORRECT ANSWER- Power stroke
The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening
of a - CORRECT ANSWER- channel for both Na+ and K+.
Smooth muscle cells lack which protein(s)?
A. myosin only
, B tropomyosin only
C. troponin and tropomyosin
D. troponin only
E. actin only - CORRECT ANSWER- D. troponin only
The I band contains - CORRECT ANSWER- thin filaments only.
Which of the following would cause muscle relaxation to occur? - CORRECT ANSWER-
Calcium ions pumped into the SR
Calcium, released by the sarcoplasmic reticulum, binds to ________ to move the ________,
which allows actin to form a high-force crossbridge with myosin. - CORRECT ANSWER-
troponin C, tropomyosin
Which of the following best summarizes the events of excitation-contraction coupling?
Choose the best answer.
A. An acetylcholine signal from the motor neuron is converted into an electrical signal in the
muscle fiber.
B. Muscle action potentials initiate calcium signals that activate a contraction-relaxation
cycle.
C. The actin filament slides towards the sarcomere and the muscle contracts.
D. Cross-bridges release and the muscle relaxes. - CORRECT ANSWER- B. Muscle action
potentials initiate calcium signals that activate a contraction-relaxation cycle.
Which of the following statements best describes the neuromuscular junction?
Choose the best answer.
A. the point of synapse between a motor neuron and the muscle fiber that it innervates
B. the release of calcium from the sarcoplasmic reticulum as a result of the action potential
traveling down the t-tubule
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