What does a ligament do?

It joins bone to bone, stabilising the joint and limiting movement.

Why are muscles arranged in antagonistic pairs?

Muscles can only pull, so a second muscle is needed to pull the bone back the other way.

Which muscle is the flexor and which the extensor at the elbow?

The biceps is the flexor and the triceps is the extensor.

Which muscles act at the knee?

Quadriceps (extensor) and hamstring (flexor).

What happens in an antagonistic pair when the arm is straightened?

The triceps contracts and the biceps relaxes.

Inward folds of the sarcolemma that carry action potentials deep into the muscle fibre.

What is the function of the sarcoplasmic reticulum?

To store calcium ions and release them to trigger contraction.

Why are muscle fibres multinucleate?

They form by fusion of many cells, and the nuclei make mRNA for the large amount of protein in the many myofibrils.

Which parts of a sarcomere contain only actin, and only myosin?

I band contains only actin; H zone contains only myosin.

Give three features of slow twitch fibres.

Many mitochondria, much myoglobin, rich capillary supply (aerobic, fatigue resistant).

Give three features of fast twitch fibres.

Thicker myosin, high glycolytic enzyme activity, large phosphocreatine and glycogen stores (few mitochondria).

Why do fast twitch fibres fatigue quickly?

They rely on anaerobic respiration, so lactate builds up and fuel stores run out.

Muscles, skeleton and movementEdexcel A-Level Biology A: Flashcards

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What does a tendon do?: It attaches muscle to bone and transmits the force of contraction.
What does a ligament do?: It joins bone to bone, stabilising the joint and limiting movement.
Why are muscles arranged in antagonistic pairs?: Muscles can only pull, so a second muscle is needed to pull the bone back the other way.
Which muscle is the flexor and which the extensor at the elbow?: The biceps is the flexor and the triceps is the extensor.
Which muscles act at the knee?: Quadriceps (extensor) and hamstring (flexor).
What happens in an antagonistic pair when the arm is straightened?: The triceps contracts and the biceps relaxes.
What are T-tubules?: Inward folds of the sarcolemma that carry action potentials deep into the muscle fibre.
What is the function of the sarcoplasmic reticulum?: To store calcium ions and release them to trigger contraction.
Why are muscle fibres multinucleate?: They form by fusion of many cells, and the nuclei make mRNA for the large amount of protein in the many myofibrils.
Which parts of a sarcomere contain only actin, and only myosin?: I band contains only actin; H zone contains only myosin.
Give three features of slow twitch fibres.: Many mitochondria, much myoglobin, rich capillary supply (aerobic, fatigue resistant).
Give three features of fast twitch fibres.: Thicker myosin, high glycolytic enzyme activity, large phosphocreatine and glycogen stores (few mitochondria).
Why do fast twitch fibres fatigue quickly?: They rely on anaerobic respiration, so lactate builds up and fuel stores run out.

Exam questions on Muscles, skeleton and movement

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
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
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

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).