IB SEHS Topic 4 Exam 2025 Questions
and Answers
Myofibril - ANSWER✔✔-One of the slender threads of a muscle fiber, composed of
numerous myofilaments
Myofilament - ANSWER✔✔-Myofibrils are made up of even smaller threadlike
structures
Actin Filament and Myosin Filament - ANSWER✔✔-Two protein sites responsible for
movement
Sarcomere - ANSWER✔✔-Is the basic unit of a muscle and is the part of the muscle that
contracts
H Zone - ANSWER✔✔-The region of the sarcomere that contains only thick
myofilaments
I Band - ANSWER✔✔-From the end of the Myosin to the Z Line
A Band - ANSWER✔✔-The band of the sarcomere that extends the full length of the
thick filament
, Z Line - ANSWER✔✔-Separates one sarcomere from the next and is where actin
filaments attach
Tropomyosin - ANSWER✔✔-An actin-binding protein which regulates muscle
contraction. Active sites of actin are blocked by this
Troponin - ANSWER✔✔-The protein that acts as a calcium receptor in skeletal muscle
Sarcoplasmic Reticulum - ANSWER✔✔-Organelle of the muscle fiber that stores
calcium. (Ca+)
Calcium Ions - ANSWER✔✔-Serves as the actual "trigger" for muscle contraction by
removing the inhibition of the troponin molecules
ATP (Adenosine Triphosphate) - ANSWER✔✔-The main energy source that cells use
for most of their work
Movement types - ANSWER✔✔-Flexion, Extension, Adduction, Abduction, Rotation,
Circumduction, Plantar, Dorsi, Supination, Pronation, Inversion, Eversion, Depression,
Elevation
Muscle contraction - ANSWER✔✔-Shortening/lengthening of sarcomere. Z Lines move
closer, I Band, H Zone decrease
Straited (striped) Muscle - ANSWER✔✔-Another name for skeletal muscle
Motor Unit - ANSWER✔✔-A motor neuron and all the muscle cells it stimulates
and Answers
Myofibril - ANSWER✔✔-One of the slender threads of a muscle fiber, composed of
numerous myofilaments
Myofilament - ANSWER✔✔-Myofibrils are made up of even smaller threadlike
structures
Actin Filament and Myosin Filament - ANSWER✔✔-Two protein sites responsible for
movement
Sarcomere - ANSWER✔✔-Is the basic unit of a muscle and is the part of the muscle that
contracts
H Zone - ANSWER✔✔-The region of the sarcomere that contains only thick
myofilaments
I Band - ANSWER✔✔-From the end of the Myosin to the Z Line
A Band - ANSWER✔✔-The band of the sarcomere that extends the full length of the
thick filament
, Z Line - ANSWER✔✔-Separates one sarcomere from the next and is where actin
filaments attach
Tropomyosin - ANSWER✔✔-An actin-binding protein which regulates muscle
contraction. Active sites of actin are blocked by this
Troponin - ANSWER✔✔-The protein that acts as a calcium receptor in skeletal muscle
Sarcoplasmic Reticulum - ANSWER✔✔-Organelle of the muscle fiber that stores
calcium. (Ca+)
Calcium Ions - ANSWER✔✔-Serves as the actual "trigger" for muscle contraction by
removing the inhibition of the troponin molecules
ATP (Adenosine Triphosphate) - ANSWER✔✔-The main energy source that cells use
for most of their work
Movement types - ANSWER✔✔-Flexion, Extension, Adduction, Abduction, Rotation,
Circumduction, Plantar, Dorsi, Supination, Pronation, Inversion, Eversion, Depression,
Elevation
Muscle contraction - ANSWER✔✔-Shortening/lengthening of sarcomere. Z Lines move
closer, I Band, H Zone decrease
Straited (striped) Muscle - ANSWER✔✔-Another name for skeletal muscle
Motor Unit - ANSWER✔✔-A motor neuron and all the muscle cells it stimulates
