Muscles, skeleton and movementEdexcel A-Level Biology A: Mind map

Exam questions on Muscles, skeleton and movement

1. A physiotherapist is assessing a patient who is recovering from an elbow injury. She asks the patient to bend the arm at the elbow and then straighten it again, and observes which muscles of the upper arm are working. She is also checking the tissues that hold the joint stable.
   Explain why skeletal muscles are arranged in antagonistic pairs.2 marks
2. A sports scientist takes small samples of thigh muscle from a marathon runner and a sprinter. Sample X has many mitochondria, a high concentration of myoglobin and a dense network of capillaries. Sample Y has fewer mitochondria, thicker myosin filaments, large stores of phosphocreatine and glycogen, and a high activity of glycolytic enzymes.
   Explain why the fibres in sample Y can contract rapidly but fatigue quickly.2 marks
3. Skeletal muscle fibres are long cells formed by the fusion of many cells, so each fibre contains many nuclei. The fibre is surrounded by a cell surface membrane called the sarcolemma and is packed with myofibrils. The sarcolemma folds inwards at intervals to form T-tubules, and a network of membrane called the sarcoplasmic reticulum lies around the myofibrils.
   Describe how a myofibril is organised into sarcomeres.3 marks