Type the term that completes each statement, using the word bank. Pull it from memory first.
Word bank
A bandMuscle fiber (cell)Z-lineT-tubulesWhole muscleH zoneSarcomereM lineMyofibrilFascicleSarcoplasmic reticulumI band
Wrapped in epimysium (dense irregular CT).
Bundle of muscle fibers wrapped in perimysium.
Single multinucleate cell wrapped in endomysium. · Plasma membrane = sarcolemma. Cytoplasm = sarcoplasm.
Rod-shaped contractile organelle inside the fiber. Hundreds per fiber.
Functional unit. Z-line to Z-line. Hundreds end-to-end down each myofibril.
Sarcomere boundary. Thin filaments anchor here.
Thin filaments only (light under microscopy). Shortens during contraction.
Full length of thick filament (dark band). Width never changes during contraction.
Thick filaments only, no overlap. Shortens during contraction.
Center of sarcomere. Thick filaments anchor here.
Invaginations of sarcolemma. Carry the action potential deep into the fiber.
Smooth ER specialized for Ca2+ storage. Releases Ca2+ when the T-tubule signal arrives.
Define it: high-yield vocabulary
Write a clear definition in your own words for each term.
Fascicle
Muscle fiber
Myofibril
Sarcomere
Z-line
I band
A band
H zone
M line
T-tubule
Sarcoplasmic reticulum
Part 2 of 4 · Anatomy lab
Draw and label
Box A. Hierarchy (whole muscle to myofibril)
Directions
Draw a long oval representing a whole muscle (cross-section). Wrap it in a thin line. Label that line Epimysium.
Inside the oval, draw three or four smaller circles. Each is a fascicle. Wrap one of them with a thin line. Label that line Perimysium.
Inside one fascicle, draw several smaller circles. Each is a muscle fiber (cell). Wrap one with a thin line. Label that line Endomysium.
Inside one muscle fiber, draw a stack of long rods. Each rod is a myofibril. Label one Myofibril.
Above your hierarchy, write the order of wrappings from outside to inside in one short sentence.
ColorSizeTool
Box B. Sarcomere close-up
Directions
Draw a long rectangle. Mark the left and right ends with vertical lines. Label both lines Z line.
In the center, draw a vertical line. Label it M line.
Between the two Z lines, draw thick filaments (myosin) in the middle and thin filaments (actin) extending from each Z line.
Bracket and label the A band (the full length of the thick filaments).
Bracket and label the I band (the region with only thin filaments).
Bracket and label the H zone (the central thick-only region).
Draw a T-tubule entering from above and a sarcoplasmic reticulum wrapping the myofibril. Label both.
ColorSizeTool
Structures to label
Label each on your drawing.
Epimysium
Perimysium
Endomysium
Muscle fiber (cell)
Myofibril
Sarcomere
Z line
M line
A band
I band
H zone
Thick filament (myosin)
Thin filament (actin)
T-tubule
Sarcoplasmic reticulum
Part 3 of 4 · Physiology lab
Reason it through
A. Mechanism trace: from action potential to power stroke
Explain the main structure-function relationship for this topic.
B. Synthesis
1. The I band shortens dramatically during contraction, but the A band barely changes length. Explain why, in terms of which filaments make up each band.
2. A toxin disrupts the triad junctions specifically (the points where T-tubules meet the SR). Predict the effect on contraction and explain at which step the cycle fails.
3. A muscle is stretched so far that thick and thin filaments no longer overlap. Predict the tension the muscle can generate at this length, and justify your answer using the cross-bridge mechanism.
Submit
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