UAFS Cornell Physiology Exam 2 ACTUAL
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 ANSWERS C. Z disk
Which ion signals the beginning of skeletal muscle contraction? - CORRECT
ANSWERS Ca2+
________ is composed of multiple globular molecules polymerized to form long chains or
filaments. - CORRECT ANSWERS 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 ANSWERS A. muscle fiber
The function of the titin protein is to - CORRECT ANSWERS stabilize the position of the
contractile filaments.
After death, when metabolism stops, in which step of the contractile cycle must skeletal muscles
remain? - CORRECT ANSWERS the rigor state
A motor unit consists of - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS A series of
proteins that control calcium release.
,What is name given to the regularly spaced infoldings of the sarcolemma? - CORRECT
ANSWERS transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction
of skeletal muscle fibers? - CORRECT ANSWERS Calcium ions.
What is the relationship between the number of motor neurons recruited and the number of
skeletal muscle fibers innervated? - CORRECT ANSWERS 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 ANSWERS A myosin head bound to
actin
What structure is the functional unit of contraction in a skeletal muscle fiber? - CORRECT
ANSWERS 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 ANSWERS 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 ANSWERS ATP binds to the
myosin head.
How does the myosin head obtain the energy required for activation? - CORRECT
ANSWERS The energy comes from the hydrolysis of ATP.
, What specific event triggers the uncovering of the myosin binding site on actin? - CORRECT
ANSWERS Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end? - CORRECT ANSWERS 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 ANSWERS Phosphocreatine
What is it called when myosin crossbridges attach to actin filaments and pull them toward the
middle of the sarcomere? - CORRECT ANSWERS Power stroke
The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening of
a - CORRECT ANSWERS 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 ANSWERS D. troponin only
The I band contains - CORRECT ANSWERS thin filaments only.
Which of the following would cause muscle relaxation to occur? - CORRECT
ANSWERS Calcium ions pumped into the SR
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 ANSWERS C. Z disk
Which ion signals the beginning of skeletal muscle contraction? - CORRECT
ANSWERS Ca2+
________ is composed of multiple globular molecules polymerized to form long chains or
filaments. - CORRECT ANSWERS 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 ANSWERS A. muscle fiber
The function of the titin protein is to - CORRECT ANSWERS stabilize the position of the
contractile filaments.
After death, when metabolism stops, in which step of the contractile cycle must skeletal muscles
remain? - CORRECT ANSWERS the rigor state
A motor unit consists of - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS A series of
proteins that control calcium release.
,What is name given to the regularly spaced infoldings of the sarcolemma? - CORRECT
ANSWERS transverse or T tubules
Which of the following is most directly responsible for the coupling of excitation to contraction
of skeletal muscle fibers? - CORRECT ANSWERS Calcium ions.
What is the relationship between the number of motor neurons recruited and the number of
skeletal muscle fibers innervated? - CORRECT ANSWERS 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 ANSWERS A myosin head bound to
actin
What structure is the functional unit of contraction in a skeletal muscle fiber? - CORRECT
ANSWERS 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 ANSWERS 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 ANSWERS ATP binds to the
myosin head.
How does the myosin head obtain the energy required for activation? - CORRECT
ANSWERS The energy comes from the hydrolysis of ATP.
, What specific event triggers the uncovering of the myosin binding site on actin? - CORRECT
ANSWERS Calcium ions bind to troponin and change its shape.
When does cross bridge cycling end? - CORRECT ANSWERS 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 ANSWERS Phosphocreatine
What is it called when myosin crossbridges attach to actin filaments and pull them toward the
middle of the sarcomere? - CORRECT ANSWERS Power stroke
The binding of acetylcholine to its receptor at the neuromuscular junction causes the opening of
a - CORRECT ANSWERS 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 ANSWERS D. troponin only
The I band contains - CORRECT ANSWERS thin filaments only.
Which of the following would cause muscle relaxation to occur? - CORRECT
ANSWERS Calcium ions pumped into the SR
