Muscle Fiber Quiz
Questions: 16 · 10 minutes
1. Under a microscope, a student sees repeating contractile units extending from one Z disc to the next. What are these units?
Fascicles
Sarcomeres
Terminal cisternae
Motor units
2. An action potential must travel quickly from the sarcolemma into the interior of a muscle fiber. Which structure provides that route?
Myofibril
Terminal cisterna
Endomysium
Transverse tubule
3. A student must label the central part of the A band where thick filaments are present but thin filaments do not overlap them. Which label is correct?
Z disc
H zone
M line
I band
4. A label covers the full length of the thick filaments in a sarcomere, including areas where thick and thin filaments overlap. Which band is labeled?
A band
I band
H zone
Z disc
5. A motor neuron branches and controls several skeletal muscle fibers. What is the neuron together with all the fibers it controls called?
A motor unit
A neuromuscular junction
A muscle fascicle
A muscle spindle
6. When a sarcomere shortens normally, which pattern of changes should be observed?
The thick and thin filaments both become shorter
The A band narrows while the I band stays the same length
The I band and H zone narrow while the A band stays the same length
The Z discs move farther apart while the H zone narrows
7. During cross-bridge formation, which structure directly attaches to an exposed binding site on actin?
A myosin head
A troponin molecule
A calcium ion
A tropomyosin strand
8. Which term refers to the cytoplasm inside a muscle fiber?
Myoplasm
Sarcoplasm
Endomysium
Sarcolemma
9. Which sarcomere region contains thin filaments but no thick filaments and is crossed by a Z disc?
A band
H zone
M line
I band
10. A model shows one T tubule positioned between two enlarged sacs of the sarcoplasmic reticulum. What complete structure is being modeled?
A sarcomere
A dyad
A triad
A neuromuscular junction
11. Which structure forms a membranous network around myofibrils and stores calcium needed for contraction?
Golgi apparatus
Sarcolemma
Sarcoplasmic reticulum
Mitochondrion
12. Which protein in the sarcoplasm binds oxygen and helps make it available within muscle fibers?
Hemoglobin
Dystrophin
Tropomyosin
Myoglobin
13. Which description correctly identifies a typical mature skeletal muscle fiber?
A spindle-shaped cell with one central nucleus and no striations
A long striated cell with multiple nuclei near the sarcolemma
A short cuboidal cell with a single peripheral nucleus
A branched cell with one or two central nuclei and intercalated discs
14. Which sequence correctly orders skeletal muscle structures from smallest to largest?
Sarcomere → myofilament → fascicle → myofibril
Myofibril → myofilament → fascicle → muscle fiber
Myofilament → muscle fiber → myofibril → fascicle
Myofilament → myofibril → muscle fiber → fascicle
15. A diagram label points to the plasma membrane surrounding a skeletal muscle fiber. Which term belongs on the label?
Sarcoplasm
Endomysium
Sarcolemma
Sarcoplasmic reticulum
16. A connective-tissue layer wraps each individual skeletal muscle fiber. What is it called?
Endomysium
Perimysium
Deep fascia
Epimysium