Muscle Cell Physiology

By what name is the plasma membrane of a muscle cell known?

• sarcoplasm

• sarcomere

• sarcoplasmic reticulum

• sarcolemma

During muscle cell contraction, what happens because of Ca ++ binding to

troponin?

• The binding site on actin is uncovered.

• Acetylcholine (ACh) is released.

• The cross-bridge disengages from the thin filament.

• ATP hydrolyses to ADP.

Which of the following is the smallest structure within a muscle fibre?

• myosin

• myofilament

• myofibril

• sarcomere

Which of the events below is the FIRST to occur prior to a muscle cell contracting?

• ATP binds to myosin.

• ADP detaches from myosin.

• the active site on actin is exposed.

• Ca++ is released from the sarcoplasmic reticulum.

What is a “sarcomere”?

• a layer of connective tissue

• the cytoplasm of a muscle cell

•  a section of a myofibril.

• the plasma membrane of a muscle cell.

Which protein(s) are found in thin myofilaments?

• actin

•  actin and tropomyosin

• actin, tropomyosin, and troponin

• actin, myosin, tropomyosin and troponin

What causes the myosin binding site of an actin molecule to be exposed?

• ATP attaching to the myosin cross-bridge

• a nerve impulse reaching the motor end plate of a motor nerve.

• calcium ions attaching to troponin

• acetylcholine crossing the neuromuscular junction

Skeletal muscle cells have all of the following characteristics EXCEPT one.

Which one?

•  a neuromuscular junction crossed by ACh (acetylcholine)

• invaginations of sarcolemma called “T tubules”.

• they are branched

• they are striated

What is the role of acetylcholine in muscle cell contraction?

•  it is a neurotransmitter

• it binds to troponin causing it to change shape

•  it supplies the energy for contraction

• it engages with the binding site on actin

Skeletal muscle cells can be characterised as:

• unstriated, involuntary, multinucleate

• unstriated, voluntary, multinucleate

• striated, voluntary, uninucleate

• striated, voluntary, multinucleate