6.3.1 Structure of Skeletal Muscle

• What is the primary function of skeletal muscle tissue?

  Voluntary movement
• Smooth muscle is attached to bones.

  False
• What is the structural difference between skeletal and smooth muscle fibers?

  Striated vs. non-striated
• What is a skeletal muscle fiber?

  A single muscle cell
• Skeletal muscle is attached to bones
• Match the muscle type with its attachment location:

  Skeletal muscle ↔️ Bones

  Smooth muscle ↔️ Internal organs

  Cardiac muscle ↔️ Heart
• Skeletal muscle is controlled by the conscious control system.
• Match the anatomical component of a skeletal muscle fiber with its description:

  Sarcolemma ↔️ Plasma membrane

  Sarcoplasm ↔️ Cytoplasm of the fiber

  Myofibrils ↔️ Contractile elements

  Sarcoplasmic Reticulum ↔️ Stores calcium ions

  T-tubules ↔️ Transmit action potentials
• Myofibrils are composed of repeating units called sarcomeres
• What distinguishes skeletal muscle from smooth and cardiac muscle?

  Voluntary movement
• What is the function of the sarcoplasm in a skeletal muscle fiber?

  Medium for metabolic reactions
• Why is the sarcoplasmic reticulum important in muscle contraction?

  Stores and releases calcium ions
• What are the repeating units of myofibrils called?

  Sarcomeres
• Actin filaments contain actin, troponin, and tropomyosin.
• Steps of the sliding filament theory

  1️⃣ Calcium ions bind to troponin

  2️⃣ Tropomyosin moves to expose binding sites on actin

  3️⃣ Myosin heads attach to actin

  4️⃣ Myosin pulls actin filaments, shortening the sarcomere
• Actin filaments are composed of actin, troponin, and tropomyosin
• What is the role of myosin filaments in muscle contraction?

  Pull on actin filaments
• Steps of the sliding filament theory during muscle contraction

  1️⃣ Calcium ions bind to troponin

  2️⃣ Tropomyosin moves to expose binding sites on actin

  3️⃣ Myosin heads attach to binding sites, forming cross-bridges

  4️⃣ Myosin heads swivel, pulling actin filaments

  5️⃣ ATP binds to myosin heads, releasing them from actin
• As sarcomeres contract, the actin and myosin filaments slide past each other, causing the muscle fiber to shorten.

  True
• Skeletal muscle is attached to bones, while smooth muscle is attached to internal organs.
• The sarcolemma is the plasma membrane of a skeletal muscle fiber.


  True
• Actin filaments bind to myosin heads to enable muscle contraction.
• Steps of the sliding filament theory during muscle contraction

  1️⃣ Calcium ions bind to troponin

  2️⃣ Tropomyosin moves to expose binding sites on actin

  3️⃣ Myosin heads attach to binding sites, forming cross-bridges

  4️⃣ Myosin heads swivel, pulling actin filaments

  5️⃣ ATP binds to myosin heads, releasing them from actin
• Myosin heads pull on actin filaments, shortening the sarcomere
• Steps of the sliding filament theory during muscle contraction

  1️⃣ Calcium ions bind to troponin

  2️⃣ Tropomyosin moves to expose binding sites on actin

  3️⃣ Myosin heads attach to binding sites on actin

  4️⃣ Myosin heads swivel, pulling actin filaments

  5️⃣ ATP binds to myosin heads, releasing them from actin
• A sarcomere is the basic contractile unit within a skeletal muscle fiber
• Match the sarcomere component with its description:

  Actin Filaments ↔️ Thin filaments composed of actin

  Myosin Filaments ↔️ Thick filaments with myosin heads

  Z-lines ↔️ Anchor actin filaments at sarcomere ends

  H-zone ↔️ Region with only myosin filaments

  A-band ↔️ Region containing both actin and myosin

  I-band ↔️ Region with only actin filaments
• The H-zone is the central region of the sarcomere where only myosin filaments are present.
• What are actin filaments composed of?

  Actin, troponin, tropomyosin
• Steps of muscle contraction according to the sliding filament theory

  1️⃣ Calcium ions bind to troponin

  2️⃣ Binding sites on actin are exposed

  3️⃣ Myosin heads attach to actin

  4️⃣ Myosin heads pull actin filaments

  5️⃣ ATP releases myosin heads
• What is the function of tendons?

  Transmit force to bone
• Tendons and ligaments work together to facilitate voluntary movement.


  True
• Which two structures are key to muscle contraction in a skeletal muscle fiber?

  Myofibrils and Sarcoplasmic Reticulum
• The sarcolemma conducts action potentials throughout the muscle fiber.


  True
• Skeletal muscle fibers are striated and multinucleated.
• Myofibrils contain the key protein filaments actin and myosin.
• The T-tubules transmit action potentials to the sarcoplasmic reticulum.


  True
• Myosin heads bind to actin to enable muscle contraction.


  True
• What are the repeating units of myofibrils called?

  Sarcomeres
• Actin filaments bind to myosin heads to enable muscle contraction.


  True