PREPARATION: MUSCULOSKELETAL SYSTEM AHL Topic 11.2 IB Biology Miss Werba

11.2.1 HUMAN MOVEMENT Locomotion requires the combined effect of three parts of the body: Nerves Muscles Bones J WERBA – IB BIOLOGY 2

HUMAN MOVEMENT NERVES MUSCLES BONES Stimulate muscular contraction 11.2.1 HUMAN MOVEMENT NERVES MUSCLES BONES Stimulate muscular contraction Provide force for movement Anchor muscles Produce coordinated movements Tendons attach muscles to bones Ligaments connect bones & stabilise the skeleton Work in antagonistic pairs to carry out opposite movements Meet at junctions called joints J WERBA – IB BIOLOGY 3

11.2.2 HUMAN ELBOW JOINT J WERBA – IB BIOLOGY 4

11.2.2 HUMAN ELBOW JOINT J WERBA – IB BIOLOGY 5

HUMAN ELBOW JOINT 11.2.2 J WERBA – IB BIOLOGY 6 Ref: Advanced Biology, Kent 6

JOINT MOVEMENT HIP JOINT KNEE JOINT Bones at joint Pelvis / Femur 11.2.4 JOINT MOVEMENT HIP JOINT KNEE JOINT Bones at joint Pelvis / Femur Tibia / Femur Lever Femur Tibia Flexion / effort Quadriceps Hamstring Extension / effort J WERBA – IB BIOLOGY 7

JOINT MOVEMENT HIP JOINT KNEE JOINT Planes of movement Many One 11.2.4 J WERBA – IB BIOLOGY 8

SKELETAL MUSCLE Muscle are composed of fibres. 11.2.5 11.2.8 SKELETAL MUSCLE Muscle are composed of fibres. Each fibre is a bundle of myofibrils. Each myofibril is made up of thick and thin filaments: Thick myosin filaments Thin actin filaments The filaments are aligned in sarcomeres. J WERBA – IB BIOLOGY 9

11.2.5 11.2.6 11.2.8 THE SARCOMERE J WERBA – IB BIOLOGY 10

11.2.5 11.2.6 11.2.8 THE SARCOMERE J WERBA – IB BIOLOGY 11

11.2.7 MUSCULAR CONTRACTION Action potential arrives at motor end plate of a motor nerve Results in calcium ion release from the sarcoplasmic reticulum Calcium ions bound by troponin on actin filament ATP is required Troponin causes tropomyosin to move, shifting it from the myosin binding sites Actin-myosin crossbridges form Repeated formation & breaking of crossbridges resulting in sliding of filaments and sarcomere shortening J WERBA – IB BIOLOGY 12

11.2.7 MUSCULAR CONTRACTION J WERBA – IB BIOLOGY 13