musclesss

• striated muscles?


   makes up the muscles in the body that are attached to the skeleton.

   made up of muscle fibres
• what are muscle fibres?

  highly specialised cell-like unit
• what do muscle fibres contain?

  • Each muscle fibre contains an organised arrangement of contractile proteins in the cytoplasm
  • Each muscle fibre is surrounded by a cell surface membrane
  • Each muscle fibre contains many nuclei – this is why muscle fibres are not usually referred to as cells
• name of the cell surface membrane

  sarcolemma
• name of cytoplasm

  sarcoplasm
• name of endoplasmic reticulum

  sarcoplasmic reticulum
• where are myofibrils located?

  in the sarcoplasm
• what two types of protein filaments are myofibrils made up of?

  • Thick filaments made of myosin
  • Thin filaments made of actin
• sarcoplasm contains...

  • mitochondria and myofibrils
• the mitochondria...

  • Carries our aerobic respiration and produces ATP which is needed for muscle contraction
• myofibrils...

  bundles of actin and myosin filaments, which slide past each other during muscle contraction
• Sarcoplasmic reticulum...

  The membranes of the SR contain protein pumps that transport calcium ions into the lumen of the SR
• sarcolemma...

  has many deep tube-like projections that fold in from its outer surface:

  • These are known as transverse system tubules or T-tubules
  • These run close to the SR
• H band consists of...

  Only thick myosin filaments
• I band consists of...

  Only thin actin filaments
• A band consists of...

  Only myosin thick filaments and areas where myosin n actin filaments overlap
• M line...


  attachment for myosin filaments
• Z line...


  attachement for actin filaments
• sarcomere...


  the section of myofibril between two Z lines
• role of glycogen in skeletal muscle?

  1. As a store of glucose OR To be hydrolysed to glucose;
  2. For respiration/to provide ATP
• Describe the role of Ca ions in muscle contraction

  1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;
  2. (Calcium ions) cause movement of tropomyosin (on actin);
  3. (This movement causes) exposure of the binding sites on the actin;
  4. Myosin heads attach to binding sites on actin
• Describe the role of ATP in muscle contraction

  1. Hydrolysis of ATP (on myosin heads) causes myosin heads to bend;
  2. (Bending) pulling actin molecules;
  3. Attachment of a new ATP molecule to each myosin head causes myosin heads to detach (from actin sites);
• phosphocreatine...


   is a molecule stored by muscles that can be used for the rapid production of ATP

  • A phosphate ion from phosphocreatine is transferred to ADP
  • ADP + phosphocreatine → ATP + creatine
• Suggest and explain one advantage of the movement of mitochondria towards the presynaptic membrane when nerve impulses arrive at the synapse.

  1.(Mitochondria) supply (additional) ATP / energy;

  
  

  2. To move vesicles / for active transport of ions / for myosin to move past actin