CHP2 Support and movement

• Joints Define A place where 2 or more bones meet allowing different parts of a skeleton to move Bones are joined together by ligaments Extensor Muscle that contracts to cause straightening such as triceps and front limb muscles Flexor Muscle that contracts to cause bending such as biceps and back limb muscle
• How does leg bend ?

  Flexor muscle contracts and shortens Extensor muscle relaxes and flattens As they work in an antagonistic pair (one contracts the other relaxes) Leg bends as the bone is moved due to transfer of pull action by tendons from muscles
• How does leg straighten ?

  Flexor muscle relaxes and flattens Extensor muscle contracts and shortens As they work in an antagonistic pair (one contracts the other relaxes) Leg straightens as the bone is moved due to transfer of pull action by tendons from muscles
• How does forearm move upwards ?

  Biceps ( flexor muscle ) contract and shorten Triceps ( extensor muscle ) will relax and flatten Working antagonistic to each other. So tendons ( attaching muscles to bones ) transfer the force ( pull action of biceps) and cause the arm to bend at the joint ...raise the forearm
• How does forearm move downwards ?

  Biceps ( flexor muscle ) relax and flatten Triceps ( extensor muscle ) will contract and shorten Working antagonistic to each other. So tendons ( attaching muscles to bones ) transfer the force (pull action of biceps) and cause the arm to straighten at the joint ... lower the forearm
• Athletes use drugs to improve their muscle performance. Why are those drugs banned

  Unfair advantage Unethical These drugs have health risks such as reducing swelling and inflammation, causing weight loss / tremors / mild high blood pressure (hypertension) / hallucinations / stroke / heart attack and other circulatory problems. Athlete becomes not a good role model
• Describe the structure of a muscle fibre and a myocyte

  Muscle fibre has many myofibrils Which lie parallel to each other And are made from sarcomeres consisting of actin and myosin Myocytes consist of: Sarcomeres that have actin and myosin Sarcoplasm (cytoplasm) Sarcolemma (cell surface membrane) (Many) Mitochondria Sarcoplasmic reticulum (stores and releases calcium ions
• What is the importance of myoglobin in muscle fibres?

  It is a pigment with high affinity to oxygen so readily accepts oxygen from the blood and stores it in muscle
• Slow twitch fibers

  • Mainly rely on Aerobic respiration
  • Delayed contraction
  • Delayed fatigue
  • More Capillaries
  • More Mitochondria
  • More Myoglobin
  • Less Sarcoplasmic Reticulum
  • Less Glycogen
• Fast twitch fibers

  • Mainly rely on Anaerobic respiration
  • Rapid contraction
  • Rapid fatigue
  • Less Capillaries
  • Less Mitochondria
  • Less Myoglobin
  • More Sarcoplasmic Reticulum
  • More Glycogen
• Phosphocreatine is used for substrate level phosphorylation during glycolysis so allowing more anaerobic respiration
• Calcium ions


  In muscle contraction (sliding filament theory), calcium ions are released from sarcoplasmic reticulum and bind to troponin
• Muscle contraction (sliding filament theory)

  1. Calcium ions are released from sarcoplasmic reticulum and bind to troponin

  2. Troponin changes its shape causing the movement of tropomyosin

  3. This exposes myosin head binding sites on the actin filament

  4. Myosin head attaches to the actin filament at the binding sites forming actin myosin bridge (actomyosin / cross bridge)

  5. The myosin head then tilts due to release of ADP pulling the actin filament towards the centre of the sarcomere

  6. A molecule of ATP attaches to the myosin head causing the detachment of myosin head from the actin filament due to ATPase in myosin head (activated by calcium ions from SR) breaking down (hydrolysing) ATP to return the myosin head back to its normal position

  7. The process results in actin being pulled past myosin so sarcomeres shorten. As the filament slide past one another, it causes the sarcomere to shorten
• muscle contraction

  The Myosin molecule has a protruding bulbous head and the Actin filament above it has a series of complementary binding sites. - When the head binds to one site, the Actin filament is pushed to slide over Myosin due to tilting of the head. - Then the head straightens, detaches from this binding site and attaches to the next binding site to tilt again. - This movement of Actin over Myosin is described as Rowing movement. - The detachment and reattachment of the bulbous head needs energy released from the breakdown of ATP into ADP & Pi
• role of calcium ions


  During relaxation, the myosin binding sites on Actin are blocked by a protein called Tropomyosin. - When a nerve impulse arrives at the Neuromuscular Junction Ca++ ions are released from the Sarcoplasmic Reticulum. - Ca++ activates Troponin protein. Active Troponin removes Tropomyosin exposing the binding sites, so that the Myosin bulbous head can bind. - For the muscle to relax, Ca++ are actively pumped back into the Sarcoplasmic Reticulum. This proess needs energy from the hydrolysis of ATP. Troponin is now inactive and Tropomyosin blocks the binding sites again
• A torn ligament is replaced by autogenous tendon graft, Evaluate this surgery


  Advantages: - it’s possible to remove part of a tendon, but not part of a ligament -Autogenous, so there is NO foreign antigens and NO risk of tissue rejection. Disadvantages: - The tendon is inelastic, so it takes a long period of physiotherapy to slightly stretch the tendon. - Relatively slow healing, as different types of tissues are used.
• 2 types of growth

  • Hyperplasia: Increase in number of cells • Hypertrophy: Increase in size of cells
• Regular exercise leads to hypertrophy of muscle fibers. Muscle fibers increase in thickness due to increase in number of Actin & Myosin filaments inside each cell. BUT, the number of cells remains the same
• 1. Aerobic system:-
  2. ■ Advantages: - Large amount of ATP (38) - Doesn’t produce Lactic acid (↓ / No fatigue)
  3. ■ Disadvantages: - Long multiphasic process, so delayed supply of Energy - Consumes O2 (O2 is a limiting factor)
• 2. Anaerobic systems:- (A) Glycolysis Lactate pathway

  ■ Advantages: - Rapid supply of Energy - Doesn’t need O2

  ■ Disadvantages: - Produces Lactic acid, so rapid fatigue - Less ATP (only 2 ATPs)
• (B) Phosphocreatine pathway (minimal ATP contribution) equation

  A) PCr

  B) ADP

  C) Creatine Kinase

  D) Cr

  E) ATP

  
• (B) Phosphocreatine pathway (minimal ATP contribution)In this pathway, an enzyme called Creatine Kinase removes Phosphate from Phosphocreatine and adds this Phosphate to ADP forming ATP. ■ Advantages: - Very rapid supply of Energy - Doesn’t need O2 - Doesn’t produce Lactic acid

  ■ Disadvantages: - Minimal supply of ATP
• Explain how skeletal muscles get energy when there is limited supply of Oxygen

  The sources of ATP for muscles in this case would include: stored ATP, Phosphocreatine pathway (very limited supply) as well as minimal aerobic respiration if possible. - However, muscles in this case would mainly rely on Glycolysis Lactate pathway. In this pathway, Glucose is broken down in the cytoplasm producing Pyruvate, with a net gain of 2 ATPs by Substrate Level Phosphorylation. - Pyruvate then acts as the final Hydrogen & electron acceptor restoring oxidized NAD & FAD and producing Lactic acid
• • Fast twitch fibers are also adapted to anaerobic respiration by being less sensitive to lactic acid than slow twitch fibers. - Trials proved that fast twitch fibers are more responsive to stimulation than slow twitch fibers at low pH
• Muscle Fatigue - Anaerobic Respiration produces lactic acid - Lactic acid lowers pH - This decreases level of anaerobic respiration, so less ATP available - Therefore muscle contraction stops (Anaerobic Respiration is a self-inhibitory process)
• Suggest an explanation for the change in core temperatures of both runners in the first 30 minutes of the race.

  1. more {muscle contraction / respiration} / eq;

  2. idea that heat energy released;

  3. idea that more heat produced than lost;

  
• Explain the function of tendons and ligament

  Tendons attach muscle to bone Where they have no elastic fibres so being inelastic So they can transfer all of the force (pull action) of muscle to the bones so the bone moves They are mostly made of white fibrous tissue Ligaments attach bone to bone They have elastic fibres to allow bone movement at the joint without dislocation They have collagen to provide strength

• why a muscle work in antagonistic pairs

  A muscle can shorten only during contraction, but it cannot straighten itself. - A muscle is only straightened by contraction of its antagonistic muscle pair. - This allows for controlled movement.

• Why do fast twitch muscle fibres fatigue rapidly ?

  ATP supply is limited More anaerobic respiration occurred due to few mitochondria So there is a lot of lactate causing the pH to be lower Which affects enzyme activity and prevents muscle contraction