Bio212 Worksheet 9

• A muscle fiber is equivalent to one muscle cell

  • The fiber is made up of filaments
  • Thin filaments are made of actin and troponin
  • Thick filaments are made of myosin
• Skeletal muscle looks striated due to the arrangement of the filaments within the muscle fibers
• According to the sliding filament model, when muscles contract:

  • Myosin filaments pull actin filaments towards the center of the sarcomere
  • The sarcomere shortens, causing muscle contraction
• Ca++ plays a role in muscle contractions by binding to troponin, allowing myosin to bind to actin

  • Ca++ is stored in the sarcoplasmic reticulum between muscle contractions
• Muscle twitch is an all or nothing event due to motor units

  • The strength of contraction varies based on the recruitment of motor units, summation, and tetanus
  • When picking up a pen, fewer motor units are recruited compared to picking up a biology book
• Oxidative fibers rely on aerobic metabolism for energy production

  • Glycolytic fibers rely on anaerobic metabolism for energy production
• Fast twitch fibers contract quickly and are used for rapid, powerful movements

  • Slow twitch fibers contract slowly and are used for endurance activities
• Cardiac muscle uses actin and myosin for contractions

  • Smooth muscle also uses actin and myosin for contractions
• An example of an antagonistic pair of muscles is the biceps and triceps in the arm
• Hydrostatic skeleton: fluid-filled cavity providing support, found in jellyfish

  • Exoskeleton: hard external covering, found in insects
  • Endoskeleton: internal skeleton, found in humans
• Forces opposing locomotion: friction and gravity

  • Energy used differs based on the medium: land requires the most energy, water less, and air the least
• Muscle tissue is made up of muscle fibers, which are muscle cells
• Muscle tissue is made up of muscle fibers, which are muscle cells
• There are three types of muscle tissue: Cardiac Muscle tissue, Smooth Muscle tissue, and Skeletal muscle tissue
• Cardiac Muscle tissue is found in the heart, has branched and striated muscle fibers with one nucleus, and contains intercalated discs
• Smooth Muscle tissue doesn't have striations, has spindle-shaped fibers with one nucleus, and is found in various organs like the digestive system and bladder
• Skeletal muscle tissue attaches to bone or skin, is involved in voluntary control, and has long, multinucleated striped fibers
• All muscle tissue can stretch (extensibility), retract back to its starting length (elasticity), be stimulated (excitability), and contract (contractility)
• Skeletal muscles are often named by their location or shape, with many having Latin or Greek root words
• Muscles have an insertion (attaches to the bone that will be moved) and an origin (attaches to a fixed part of the bone)
• The main muscle doing the work is called the agonist, while antagonists are muscles that can do the opposite action
• Skeletal muscle contraction involves the sliding-filament model
• Sarcomeres are the repeating sections in myofibrils that contribute to the muscle's striated look
• Actin makes up thin filaments, myosin makes up thick filaments
• During muscle contraction, thin filaments are pulled by thick filaments towards the center, causing overlap and movement of Z lines closer together
• Myosin heads bind to actin forming cross bridges, undergo a power stroke, and detach with the help of ATP
• Regulation of muscle contraction involves tropomyosin and troponin blocking and unblocking myosin bonding sites on actin, triggered by the release of calcium ions