Muscles Wk 2

Structural arrangement of skeletal muscles (REFER TO PPT EXPLANATION AND DIAGRAM)

• Skeletal muscles consist of lightly packaged muscular bundles (fascicles) surround by connective tissue (perimysium)

• Each bundle contains multiple muscle fibres, which contain myofibrils --> responsible for muscular contraction

• Structure of skeletal muscles:

  • Tendons --> muscle to bone

  • Epimysium --> connective tissue that wraps around the muscle (protects against friction from other muscles and bones)/ protective barrier!!

  • Perimysium --> Connective tissue surrounding muscle bundles (provides structural support to muscles)

  • Muscle fibre --> single muscle cell can be classified as type 1 or type 2a/b

    • Classification of muscles

      • Type one: slow twitch muscle fibre --> aerobic exercise, long running, cycling, rowing (long continuous activities but with lower intensity)

        • Large amount of myoglobin (chemical in blood) --> high amount of mitochondria + oxygen

        • Very resistant to fatigue and good at aerobic metabolism --> produces repeated low-level contractions by producing large amounts of ATP

        • Often postural muscles (neck and spine e.g.)

        • Can be obtained partly through training and partly through genetics

• Type two A: moderate fast twitch muscle fibre --> compound exercise (gym activities --> squats, push ups, curls e.g.); medium intensity

  • Fast oxidative fibres

  • Hybrid of type 1 and 2 fibres

  • Large amount of myoglobin --> high amount of mitochondria + oxygen

  • Manufacture + split ATP at fast rate

  • Uses BOTH aerobic and anaerobic metabolism

  • Produce fast, strong muscle contractions --> more prone to fatigue than type 1 muscles

• Type two B: fast twitch muscle fibre --> sprints, plyometrics (jumping, bounding, power in legs e.g.); high intensity but cannot do for a long time

  • Can be turned into type two 1 from resistance training, increases muscles ability in oxidative cycle

  • Fast glycolytic fibres

  • Low level of myoglobin --> contain few mitochondria

  • Produces ATP at slow rate by anaerobic metabolism and break it down very quickly

  • Results in short, rapid bursts of power + rapid fatigue

  • Found in large quantities in muscles of arms

• Fascicle --> bundle of muscle fibres

• Myofibril --> long filaments that form muscle fibres

• Sarcomere (refer to ppt diagram!!) --> basic contractile unit of a muscle fibre (composed of two filaments --> actin and myosin (active structures responsible for muscular contraction/creates contraction)

• Stronger muscles = more muscle fibres in each bundle (vice versa)

• Neuromuscular junction:

  • Specialised synapse where a motor neuron connects with a muscle fiber, enabling transmission of signals that cause muscle contraction

• Muscle glycogen:

  • Serves as readily available fuel source for muscle cells

  • Stored form of glucose within muscle tissue --> quick energy reserve during exercise (particularly during high intensity/prolonged activity)