PSIO 201 EXAM 3 ACTUAL EXAM PAPER
2026 COMPLETE QUESTIONS AND
CORRECT ANSWERS
◉ Dystrophin
Answer: - cytoskeleton protein that links the thin filaments to the
sarcolemma
- attached to the extracellular proteins in the connective tissues
surrounding the muscle fibers
- helps transmit tension from the sarcomeres to tendons
- found at the end of the myofibrils
◉ What are the other structural muscle proteins?
Answer: 1. Nebulin
2. alpha-actinin
3. myomesin
◉ Nebulin
Answer: - spans across the length of the thin filament
- anchors thin filaments to Z disc
,◉ Alpha-actinin
Answer: - found in the Z disc
- binds to actin molecules of the thin filaments and to titin
◉ Myomesin
Answer: - found in the M line
- binds to titin and thick filaments to connect them together at the M
line
◉ Explain the order of the sliding filament model of muscle
contractions
Answer: 1. myosin 'heads' bind to actin to form a 'crossbridge'
2. conformational change, energized by ATP hydrolysis, causes thin
filaments to slide along thick filaments
3. myosin head groups release, form new crossbridges, and the
sliding cycle repeats
RESULT: shortening of the sarcomere= Z disc toward one another,
myofirbils shorten, muscle fibers shorten
◉ Crossbridge
Answer: force production in the muscle
◉ As thick/thin filaments overlap increases...
,Answer: - I band length decreases
- A band length stays the same
- H zone length decreases
- Zone of overlap increases
◉ Which of the following statements is true?
A. Endomysium covers a group of muscles
B. Epimysium covers a muscle fiber
C. perimysium covers a muscle fascicle
Answer: C. perimysium covers a muscle fascicle
◉ Muscles get larger in diameter because ______, a process
called______
Answer: each cell get larger in diameter; hypertrophy
◉ The muscle cell membrane is called the _____ and is specialized in
condition of electrical signals
Answer: sarcolemma
◉ Which of the following is a contractile protein of muscle?
A. myosin
B. myomesin
, C. tropomyosin
D. all of the above
Answer: myosin
◉ When does the crossbridge cycle begin?
Answer: when calcium is present and the binding site is exposed
◉ What happens at the end of the last muscle contraction of a
crossbridge cycle?
Answer: 1. ATP binds to the myosin head
2. This ATP is hydrolyzed by the unbound head, and the released
energy results in a conformational 'cocking' of the head group
(the ADP and Pi remain bound to the cocked head)
◉ What gets the myosin ready?
Answer: ATP
◉ Where does crossbridge cycling occur?
Answer: within the sarcomeres and myofibrils between the thick
and thin filaments
◉ When does the contraction cycle begin?
2026 COMPLETE QUESTIONS AND
CORRECT ANSWERS
◉ Dystrophin
Answer: - cytoskeleton protein that links the thin filaments to the
sarcolemma
- attached to the extracellular proteins in the connective tissues
surrounding the muscle fibers
- helps transmit tension from the sarcomeres to tendons
- found at the end of the myofibrils
◉ What are the other structural muscle proteins?
Answer: 1. Nebulin
2. alpha-actinin
3. myomesin
◉ Nebulin
Answer: - spans across the length of the thin filament
- anchors thin filaments to Z disc
,◉ Alpha-actinin
Answer: - found in the Z disc
- binds to actin molecules of the thin filaments and to titin
◉ Myomesin
Answer: - found in the M line
- binds to titin and thick filaments to connect them together at the M
line
◉ Explain the order of the sliding filament model of muscle
contractions
Answer: 1. myosin 'heads' bind to actin to form a 'crossbridge'
2. conformational change, energized by ATP hydrolysis, causes thin
filaments to slide along thick filaments
3. myosin head groups release, form new crossbridges, and the
sliding cycle repeats
RESULT: shortening of the sarcomere= Z disc toward one another,
myofirbils shorten, muscle fibers shorten
◉ Crossbridge
Answer: force production in the muscle
◉ As thick/thin filaments overlap increases...
,Answer: - I band length decreases
- A band length stays the same
- H zone length decreases
- Zone of overlap increases
◉ Which of the following statements is true?
A. Endomysium covers a group of muscles
B. Epimysium covers a muscle fiber
C. perimysium covers a muscle fascicle
Answer: C. perimysium covers a muscle fascicle
◉ Muscles get larger in diameter because ______, a process
called______
Answer: each cell get larger in diameter; hypertrophy
◉ The muscle cell membrane is called the _____ and is specialized in
condition of electrical signals
Answer: sarcolemma
◉ Which of the following is a contractile protein of muscle?
A. myosin
B. myomesin
, C. tropomyosin
D. all of the above
Answer: myosin
◉ When does the crossbridge cycle begin?
Answer: when calcium is present and the binding site is exposed
◉ What happens at the end of the last muscle contraction of a
crossbridge cycle?
Answer: 1. ATP binds to the myosin head
2. This ATP is hydrolyzed by the unbound head, and the released
energy results in a conformational 'cocking' of the head group
(the ADP and Pi remain bound to the cocked head)
◉ What gets the myosin ready?
Answer: ATP
◉ Where does crossbridge cycling occur?
Answer: within the sarcomeres and myofibrils between the thick
and thin filaments
◉ When does the contraction cycle begin?
