Structural Hierarchy: Muscle to Fiber

Which statement best explains the relationship among epimysium, perimysium, and endomysium in a skeletal muscle?

• They each line the sarcolemma internally

• They form layers around muscle fiber bundles

• They only attach to bone via tendons

• They all surround each fascicle individually

Match each structural level with its correct description.

• Elongated, multinucleated cylindrical cell

• Epimysium

• Bundle of muscle fibers within perimysium

• Muscle

• Delicate connective layer around each fiber

• Fascicle

• Dense connective covering of entire muscle

• Endomysium

• Organ containing multiple fascicles and vessels

• Muscle fiber

A biopsy shows intact perimysium but damage to the delicate connective tissue directly surrounding individual cells. Which layer is primarily affected?

• Fascia surrounding bone surface

• Endomysium around each fiber

• Epimysium around the whole muscle

• Perimysium around each fascicle

Which scenario would most reduce force transmission from muscle to bone despite normal myofibrils?

• Disrupted tendon continuity at the insertion

• Slightly smaller muscle fiber mitochondria

• Fewer nuclei at fiber periphery

• Shortened sarcoplasmic reticulum terminals

You must microdissect from whole muscle down to a single cell. Which correct sequence of structures would you remove?

• Endomysium, perimysium, epimysium, tendon

• Epimysium, perimysium, endomysium, sarcolemma

• Perimysium, endomysium, epimysium, sarcolemma

• Sarcolemma, epimysium, endomysium, perimysium

Tags

NGSS.HS-LS1-2

In the sarcomere diagram, which change best explains why the H zone narrows during contraction?

• Myosin thick filaments slide past Z lines

• Z lines move apart as tension increases

• Actin filaments shorten toward the Z lines

• Myosin heads pull actin toward the M line

A micrograph shows alternating light and dark bands along a myofibril. Which structures define one sarcomere along that myofibril?

• M line to the nearest Z line

• Two A bands with an H zone

• Alternating I bands and A bands

• Adjacent Z lines at each band edge

Match each sarcomere region to the primary filament arrangement shown in the diagram.

• Midline proteins of thick

• A band

• Thin filaments only

• H zone

• Overlap of thick and thin

• M line

• Thick filaments only

• I band

Tags

NGSS.HS-LS1-1

You isolate a protein that binds ATP and forms cross-bridges in striated muscle. In the labeled filament diagram, where is this protein most concentrated?

• Regulatory troponin-tropomyosin complex

• Globular subunits of actin filament

• Heads on the thick myosin filament

• Z line anchoring thin filaments

A mutation prevents tropomyosin from shifting position when Ca2+ binds troponin. Based on the filament model, which immediate effect is most likely?

• Z lines drift apart at rest length

• A band disappears during contraction

• Actin hydrolyzes ATP more rapidly

• Myosin cannot access actin binding sites