Biology

Skeletal muscles:

• make up nearly half the body weight of an adult
• contraction: need E + O2 -> rich blood supply
• functions: active movement, heat generation, stores glycogen

Structure:

• cells = muscle fibres:
  • long, have many nuclei
  • contain myofibrils – contractile elements
    • actin – thin
    • myosin – thick

      

  • gives a striped appearance à striated muscle
  • we can move them at will à voluntary muscle
• muscle fibres form bundles of fibres
  • surrounded by connective tissue
  • blood supply, oxygen -> biological oxidation
  • lack of oxygen -> fermentation (lactic acid) – pain in muscles (muscle soreness)
  • nerves: trigger stimuli for contraction

Shape:

• spindle: on limbs
• flat: on the trunk
• circular: around openings (eyes, mouth, anus) -> closing

Operation:

• to operate skeletal muscle needs to have both ends connected to the skeleton – tendons
  • origin: end of muscle that remains fixed (closer to the trunk)
  • insertion: end of muscle that moves the bone (farther from the trunk)
• antagonistic pairs of muscles act in opposition to each other
  • one contracts - the other relaxes
    • flexor: flexes limbs (biceps)
    • extensor: extends a limb (triceps)
  • g. when biceps muscle of the upper arm contracts, the opposing triceps muscle relaxes -> the elbow is bent
• central nervous system -> signals -> contraction

• muscle tone

  is the continuous and passive partial contraction of the muscles 
  helps maintain posture, and it declines during sleep.
  Unconscious nerve impulses maintain the muscles in a partially contracted state.
  If a sudden pull or stretch occurs, the body responds by automatically increasing the muscle's tension.

Examples for muscles:

• mimics muscles:
  • origin and insertion on the skin – on the head
• sterocleidomastoid muscle (SCM)
  • on the neck -> moves the head
• diaphragm
  • at the bottom of the rib cage,
  • separates the abdominal and thoracic cavities
  • -> breathing
• intercostal muscles
  • between the ribs -> breathing
• pelvic floor muscles (perineum)
  • supports organs,
  • helps continence
• chest muscles
  • lift the arms and move them forward,
  • help breathing
• abdominal muscles
  • protect internal organs,
  • stabilise, twist and bend the trunk
  • maintain internal abdominal pressure.
  • Abdominal press - exhalation, elimination of wastes, birth

Importance of regular exercise

• stronger muscular system,
• more stable skeletal system,
• better circulation,
• respiration,
• has a positive effect on our nervous system,
• reduces stress,
• helps weight loss

Types of training

• Fitness
• Skill
• Endurance / strength

Warm-up: important before training, stimulates circulation of muscles, prevents injuries

Muscle soreness -> treat with exercise -> blood can take away lactic acid to the liver

 14 fun facts about your muscular system.

 Learningapps labeling task