Topic 11.2: Movement Flashcards
Movement Systems
1) Skeletal system
2) Muscular system
3) Nervous system
Skeletal system
Consists of bones that:
1) Act as levers
2) Provide a structure for the muscles to pull
Muscular system
Muscles deliver the force required to move one bone in relation to another
Nervous system
Delivers signals to the muscles which cause them to contract and create movement
Skeletons
Endoskeletons - Consist of numerous bones
Exoskeletons - Comprised of connected segments
Ligaments | Tendons
Tendon (BoTtom) - Bone to muscle
Ligament (BLob) - Bone to bone
Synovial joints
Capsules surrounding articulating bone surfaces that allow for certain movements but not others
Synovial joint components
1) Joint capsule
2) Cartilage
3) Synovial fluid
Joint capsule
Seals the joint space
Provides stability by restricting the range of possible movements
Cartilage
Lines the bone surface
1) Facilitate smoother movement
2) Absorbing shock and distributing load
Synovial fluid
Provides lubrication, oxygen, and nutrition to the cartilage
Hinge joint
1) It is capable of angular movement in one direction (i.e. flexion and extension)
2) A small amount of rotation may be possible
Elbow Joint Structures
1) Humerus - Anchors muscle (Muscle origin)
2) Radius - Acts as a forearm lever for biceps
3) Ulna - Acts as a forearm lever for triceps
4) Biceps - Bends the forearm (Flexor)
5) Triceps - Straightens the forearm (Extensor)
6) Joint capsule - Seals joint space and limits range of movements
7) Synovial fluid - Provides food, O2, and lubrication
8) Cartilage - Allows smooth movement, absorbs shock, and distributes load.
Human elbow
Example of a hinge joint
• It is capable of angular movement (flexion / extension)
Antagonistic pairs of skeletal muscles
When one contracts, the other relaxes to enable opposing movements (Flexion / Extension)
Antagonistic pairs of muscles in an insect leg
1) When the flexor muscle contracts, the extensor muscle relaxes and the tibia and femur are brought closer together
2) When the extensor muscle contracts, the flexor muscle relaxes and the tibia is pushed away from the femur
Organisation of Skeletal Muscles
1) Muscles -> Muscular bundles (surrounded perimysium)
2) Muscular bundle -> Muscle fibres (Muscle cells)
3) Muscle fibres -> myofibrils (Muscular contraction)
4) Myofibrils -> Sarcomeres (Single contractile unit)
Muscle Fibre Structure
1) Multinucleate (Fusion of individual muscle)
2) Large number of mitochondria (muscle contraction requires ATP hydrolysis)
3) Sarcoplasmic reticulum (Stores calcium ions)
4) Tubular myofibrils made up of actin and myosin
5) Continuous membrane surrounding the muscle fibre sarcolemma (contains invaginations called T tubule)
Sarcomeres
Repeating contractile units of myofibrils
1) Made up of myofilaments (actin + myosin)
2) Myosin has protruding heads that bind to actin
Appearance of sarcomere in electron micrographs
1) A band - The centre = darker (Actin/Myosin)
2) I band - The peripheries of the sarcomere = lighter (Actin)
3) H zone - Lighter central region of the dark A band (Myosin)
Muscle contraction electron micrographs
Actin filaments slide along the myosin, reducing the length of the lighter I bands
Diagram of a Sarcomere
1) Myosin (Thick myofilament)
2) Actin (Thin myofilament)
3) Z disc (Hold the myofilaments in place)
Process of muscular contraction
1) Depolarisation and calcium ion release
2) Actin and myosin cross-bridge formation
3) Sliding mechanism of actin and myosin filaments
4) Sarcomere shortening (muscle contraction)
Depolarisation and calcium ion release
1) Motor neurons release acetylcholine (neurotransmitter)
2) This triggers sarcolemma depolarisation, causing Ca+2 to be released from the sarcoplasmic reticulum
Actin and myosin cross-bridge formation
1) Ca+2 bind to a complex (troponin/tropomyosin) that blocks actin from binding with the myosin heads
2) Ca+2 displace this complex, allowing the actin and myosin heads to form a cross-bridge
Sliding Mechanism of Actin and Myosin
1) ATP binds to myosin heads and breaks the cross-bridge
2) ATP hydrolysis causes myosin heads to swivel and slide along the actin fibre – this shortens the sarcomere length
3) Via repeated ATP hydrolysis, skeletal muscles contract
Sarcomere shortening
1) The repeated reorientation of the myosin heads drags the actin filaments along the length of the myosin
2) As the individual sarcomeres become shorter in length, the muscle fibres as a whole contracts
