muscles

• Muscle tissue


  • Excitable and can receive and respond to stimulus
  • Contractile (can shorten)
  • Extensible (can be stretched)
  • Elastic (can recoil to original length)

  
• Functions of muscle


  • Movement: muscle action moves bones
  • Posture: muscle actions maintain posture
  • Stabilises joints: muscles maintain joints
  • Heat (muscle is 40% of body mass)
• Types of muscle tissue

  • Skeletal (voluntary control)
  • Smooth (involuntary control)
  • Cardiac (involuntary control)

  
• Muscle


  An organ; mainly muscle fibres but also lots connective tissue, blood vessels, nerves etc

  
• Muscle contraction


  1. Insertion (more movable bone) moves TOWARD the Origin (less movable bone)

  2. Muscles are connected directly to bone via connective tissue ligaments and tendons

  
• Skeletal muscle fibre


  • Banded (can actually see the dark and light bands under the microscope)
  • Muscle fibre (cell) is made of myofibrils which are in turn made of myofilaments (= actin & myosin)
  • Myofibrils all aligned within each muscle cell
  • Myofibrils are made of proteins Actin and myosin
  • Muscle bands are due to the actin and myosin proteins overlapping each other (harder for light to penetrate) thus DARK band
  • No overlap, just thin filaments = actin = light band

  
• Muscle contraction


  1. When muscle contracts, myosin pulls the actin past itself

  2. The sliding of the filaments past each other means muscle fibre contracts but the actin and myosin filaments don't change their length

  
• Sliding filament theory of muscle action

  Actin and myosin proteins connect to each other to form muscle contraction

  
• Muscle contraction


  1. Transmission of an electrical impulse (excitation) from the nerve to the muscle fibre (at neuromuscular junction) which then stimulates calcium release which then binds to troponin to expose actin binding site

  2. Myosin binds, pulls the actin filaments TOWARD THE CENTRE OF THE sarcomere

  3. The filaments slide past each other

  
• Skeletal muscle contraction cycle

  1. Ca exposes binding site

  2. Myosin cross bridge attaches to Actin

  3. Powerstroke, slide past

  4. Myosin cross bridge detaches due to ATP

  5. Myosin head "cocked" by ATP

  
• Muscle naming


  • Shape, size, location, action, relative position, origin or insertion
  • Rectus= straight, transversus, oblique
  • Relative position: superficial or deep
  • Orbicularis oris "kissing muscle"

  
• Muscle actions


  • Agonists: muscles that cause the AGONY ie perform the action
  • Prime mover: the agonist mainly responsible for the movement
  • Antagonists: muscles whose action OPPOSES the agonist action
  • Synergists: muscles working together to perform the same task
• Muscles in same compartment (location) generally perform same action = agonists for the movement
• Muscles in opposite compartment perform antagonist or opposite function
• Fixation: where both compartments stabilise joint, fixing it in one position
• Anterior muscles from the hip superiorly are flexors, thus anterior muscles from the hip inferiorly are extensors

  
• Posterior muscles from the hip cranially are extensors and below the hip (ie Femoral region and inferior) posterior = flexors

  
• Thorax muscles


  • Muscles to stabilise/extend vertebral column
  • Muscles to stabilise/move scapula
  • Muscles to move arm (at shoulder joint)
  • Muscles to assist respiration
• Abdominal muscles


  • Muscles to stabilise/flex vertebral column
  • Muscles to move lower limb (at hip)

  
• Erector spinae


  • Prime movers of EXTENSION
  • Antagonist to abdominal muscles
• Muscles of the anterior abdominal wall

  • Prime mover (agonist) for flexion of vertebral column
  • Antagonist to erector spinae

  
• Pectoralis major


  Prime mover for shoulder flexion
• Latissimus dorsi


  Prime mover for shoulder extension
• Rotator cuff muscles


  • Subscapularis
  • Infraspinatus
  • Supraspinatus
  • Teres minor
• Anterior muscles of pelvis

  Flex femur

  
• Posterior muscles of pelvis

  Extend hip

  
• Anterior compartment of thigh

  Extensor (not flexor)

  
• Quadriceps femoris


  • Rectus femoris (acts over hip as well)
  • Vastus lateralis, medialis & intermedius

  
• Posterior compartment of thigh

  Flex leg, extend thigh

  
• Medial compartment of thigh

  Adductor, flex thigh

  
• Muscles of respiration


  • Inhale: diaphragm & external intercostals
  • Exhale: elasticity of lung, diaphragm & rib recoil
  • Forced inhale: scalenes, sternocleidomastoid, pectoralis minor
  • Forced exhale: oblique & transversus abdominis, internal intercostals
• Any exercise better than none!!
• Aerobic exercise


  Improve oxygen delivery and utilisation (more capillaries, more efficient fibres due to more mitochondria, myoglobin and oxidative enzymes)
• Resistance (high intensity) exercise

  • Individual muscle fibre size increases (fast, glycolytic)
  • Not number of muscle fibres = hypertrophy
  • Not hyperplasia (more splitting, myofilaments & myofibrils/cell, more connective tissue)
• Don't USE it, you LOSE it! Atrophy
• Benefits of exercise


  • Bone deposition
  • Cardiovascular system is more efficient
  • Diabetes Type II risk reduced (more insulin receptors better glucose regulation)
  • Reduced risk obesity (flow on effect to cancer reduction)
  • Reduced risk of chronic back pain
  • Improved chance pregnancy
  • Psychological benefits: "control", relaxation, social connection
  • Neurochemistry: Endorphin release alleviates depression
  • Improved study, reduced "stress"