Skeletal muscle physio

• What percentage of body mass is muscle?

  40-50%
• What are the homeostatic actions that muscles are involved in?

  • Chewing and swallowing food
  • Breathing
  • Generating heat
  • Regulating blood supply
• Why do muscles have high energy demands?

  Because they contain lots of mitochondria

  
• What do muscles require for proper function?

  Nutrients and oxygen, with a good blood supply essential
• What is the most abundant type of muscle in the body?

  Skeletal muscle
• What are the functions of skeletal muscle?

  • Facilitates movement
  • Maintains balance
  • Supports posture
• Where is smooth muscle found?

  Throughout the body, lining organs such as blood vessels, stomach, and intestines
• What is the primary function of cardiac muscle?

  To pump blood around the body
• What are the two classification systems for muscle types?

  1. Appearance: Striated and unstriated
  2. Innervation: Voluntary and involuntary

  
• What is an isometric contraction?

  A contraction where the muscle develops tension but does not shorten
• What is an isotonic contraction?

  A contraction where the muscle shortens under constant load
• What are the components of skeletal muscle composition?

  • Connective tissue
  • Contractile tissue

  
• What connects muscles to bones?

  Tendons
• What is fascia?

  Connective tissue surrounding the whole muscle
• What are the three layers of connective tissue in muscles?

  1. Epimysium: Underneath fascia
  2. Perimysium: Surrounding fascicles
  3. Endomysium: Surrounding muscle fibers

  
• What is the sarcolemma?

  A specialized muscle membrane
• What is the function of the sarcoplasmic reticulum?

  Calcium storage
• What is a muscle fiber?

  One single muscle cell
• How large can a muscle fiber be?

  10-100 µm in diameter and can be up to 75 cm long
• How are muscle fibers formed?

  During embryogenesis via fusion of multiple myoblasts
• What is a myofibril?

  • A specialized intracellular structure
  • 1 µm in diameter
  • Composed of hundreds to thousands of sarcomeres
  • Makes up 80% of muscle fiber

  
• What is a sarcomere?

  The contractile unit of skeletal muscle
• How long is a sarcomere?

  Approximately 2 µm in length

  
• What are Z-lines in a sarcomere?

  Cytoskeletal discs that anchor the thin filaments

  
• What is the I band in a sarcomere?

  The light band containing thin filaments

  
• What is the A band in a sarcomere?

  The dark band where thick and thin filaments overlap

  
• What is the H Zone in a sarcomere?

  The area within the A band that only has thick filaments

  
• What is the M-line in a sarcomere?

  Structural proteins that anchor the thick filaments within the H-zone

  
• What is titin?

  An extremely large protein that gives structural support to the sarcomere
• What are cross bridges in muscle contraction?

  Points of contact between thick and thin filaments

  
• How many thin filaments surround each thick filament?

  Six thin filaments
• How many thick filaments surround each thin filament?

  Three thick filaments
• What is myosin?

  The thick filament in muscle contraction

  
• What is the structure of a myosin molecule?

  Contains two identical subunits with intertwined tails and two hinge regions for flexibility

  
• What is the function of the head region of myosin?

  Forms cross bridges with actin and has an ATPase site

  
• What is actin?

  Spherical molecules that form an intertwined string with a myosin binding site