11.2 Muscles and Movement

Topic 11 Human health & physiology

11.2.1 State the roles of bones, ligaments, muscles, tendons and nerves in human movement.

11.2.2 Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps).

11.2.3 Outline the functions of the structures in the human elbow joint named in 11.2.2.

11.2.4 Compare the movements of the hip joint and the knee joint.

11.2.5 Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcoplasmic reticulum, nuclei and the sarcolemma.

11.2.6 Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands.

No other terms for parts of the sarcomere are expected.

11.2.7 Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads.

Details of the roles of troponin and tropomyosin are not expected.

Aim 7: Data logging could be carried out using a grip sensor to study muscle fatigue and muscle strength.

11.2.8 Analyse electron micrographs to find the state of contraction of muscle fibres.

Muscle fibres can be fully relaxed, slightly contracted, moderately contracted and fully contracted.

Locomotion Most animals can move from one place to another. This is

called Locomotion. Animals show a wide variety of types of locomotion. Locomotion is produced by the combined effect of three

parts of the body: Nerves Muscles Bones

Nerves, Bones & Muscles Nerves:

These carry impulses from the CNS to stimulate muscles to contract.

They stimulate each of the different used in locomotion to contract at the correct time, so the movement is coordinated.

Bones: Bones provide a firm anchorage for muscles in many animals. They also act as levers, changing the size or direction of forces

caused by muscles. Junctions between bones are called joints.

Nerves, Bones & Muscles Ligaments:

These binds bone to bone. Are slightly elastic. Preventing dislocation.

Tendons: Bind muscle to bone . Non-elastic, transferring full force of muscle contraction to

bone.

Nerves, Bones & Muscles Muscles:

When muscles contract they provide the force needed for locomotion.

Muscles only do work when they contract, so pairs of muscles are needed to carry out opposite movements.

These pairs of muscles are called antagonistic pairs.

Ref: Advanced Biology, Roberts

The Elbow Joint

Ref: IB Biology, Oxford Study Courses

The Elbow Joint The elbow joint is a good example of how nerves, muscles and bones

work together to make motion. The main parts of a synovial joint are:

Ligaments: binds bone to bone and slightly elastic, preventing dislocation.

Tendon: binds muscle to bone and non-elastic, transferring full force of muscle contraction to

bone. Joint capsule: encloses the joint cavity preventing leakage of

the synovial fluid. Synovial fluid: acts as a lubricant, reducing friction & shock absorber Cartilage: provides a smooth surface for joint movement,

reducing friction where bone surfaces meet. Extra point: Reduces friction is important to prevent damage/wear

to end of bones in the joint.

The Elbow Joint

Ref: Biology for the IB Diploma, Allott

Antagonistic Muscles in the Elbow Joint

Ref: Advanced Biology, Kent

Hip and Knee joints

Comparison: hip and knee jointsFeature Hip Knee

Type Synovial – ball & socket Synovial – hinge

Articulating bones Pelvis & Femur Femur & Tibia

Additional bones None Patella

Articulating surfaces Acetabulum & head of femur Femur & tibiaFemur & patella

Permitted movement Circumduction i.e. circular(three planes)

Flexion & extension(one plane)

Structure of Skeletal Muscle A muscle consists of bundles of multinucleated muscle

fibres (cells), each of which 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 contractile units called Sarcomeres.

The arrangement of thick and thin filaments appears as alternating light and dark bands when viewed in an electron micrograph.

Structure of Skeletal Muscle

Structure of a Sarcomere

Muscle Contraction The contraction of muscle is due to the sarcomeres in the

myofibrils becoming shorter. This is achieved by the sliding of actin and myosin

filaments over each others. This uses ATP.

Ref: Biology for the IB Diploma, Allott.

Controlling Muscle Contraction When a muscle fibre is relaxed, a protein called

tropomyosin blocks the myosin binding sites on actin. If a motor neurone stimulates the muscle fibre, calcium

ions are released from the sarcoplasmic reticulum. These calcium ions bind to another protein called

troponin.. Troponin then causes tropomyosin to move, which

exposes the myosin binding sites and allows contraction to begin.

Ref: Advanced Biology, Roberts etal.