Discoving the muscle

• 1. +Understanding the muscle Pairings, microscopic structure and function

2. +Understanding the muscle Muscles never work on their own, and always work in teams.A muscle belly will have tendons at either end to attach them to boneA muscle is always attached to 2 or more bones (by tendons) to allow a stable and strong surface to pull against. These connections are called the origin and insertion. 3. + Muscle connections to bones Origin Is the place where the muscle is attached to the most stable surface which is usually a flat bone such as the scapula or pelvic girdle.This provides the muscle with a strong surface to pull againstInsertion Is at the other end of the muscle at attached to the bone where the movement occurs. 4. +Origin and insertion exampleBicepIts origin is at the scapula and insertion is the radiusSo when the bicep shortens, the lower arm (including the radius) will move towards its origin 5. +Reciprocal inhibitionWhen muscles on one side of a bone or joint relax to accommodate contraction on the other side of the bone or jointBiceps and tricepsQuads and HamstringsGastrocnemius and tibialis anterior 6. +Agonist Antagonist relationship Muscles always work in pairsThe agonist is the muscle primarily responsible for producing a movementThe antagonist is the muscle which relaxes while the movement takes place to prevent injuryWhen a muscle contracts, it is critical for the muscle which performs the opposite movement to relax to prevent an injury occurring (muscle tear) 7. +Stabilisers Provide stability to the origin so maximal contraction force can be applied.EXAMPLE: During elbow flexion the trapezius contracts to stabilise the scapula and provide a strong, rigid base for the bicep to pull on. 8. +Inside the Muscle BellyMicroscopic structure of a muscle 9. +The structures The muscle belly consists of thousands of muscle fibres known as fascicles which run side by side along the length of the muscleEach of these fibres is encased in and surrounded by connective tissue known as perimysium, which assists in keeping the fascicles together. 10. +Muscle FibresEach fascicle is made up of several muscle fibres, which are made up of even smaller fibres called myofibrils, which are similar to the many wires within a telephone cable. These have many units, known as sarcomeres, which are arranged end to end for their entire length of the myofibril 11. +The SarcomereIs a contractile unit, and each end is designated by a line called a Zline.Each sarcomere consists of two proteins myofilaments called actin and myosin.Actin is a thin filament which is attached to the Z-lineMyosin is a thick filament which is situated between each of the actin filaments 12. The Lines and Zones of a Sarcomere + 13. +The Lines and Zones of a Sarcomere The Z-line: Marks the two ends of a sarcomereThe I-band: Where only actin is foundThe A-band: Where both actin and myosin are found and equates to the length of the myosin filamentsThe H-zone: Where only myosin is found and is the gap between the ends of the actin 14. +A muscle contraction The myosin filaments have cross bridges (oar-like structures) that are attracted to the actin filamentsAt rest, there is little contact between the actin and the myosinHowever, when the sarcomere contracts, the cross bridges attach to the actin filaments and pull them into the centre of the sarcomere in a rowing action The cross bridges continue to detach and reattach themselves from the actin filaments, shortening the sarcomere.Every sarcomere along the muscle fibre shortens, leading the whole muscle to contract. The muscle will relax when the actin and myosin filaments lose contact with each other that is, when the cross bridges detach from the actin. 15. +Muscle ToneNot all the myosin filaments detatch themselves from the acti. Some may stay in contact, so the muscle is never completely relaxed.If this is the case, the muscle is said to have toneThe advantage of muscle tone is that the actin and myosin filaments are always ready to contract