The document discusses human movement and muscle structure and function. It describes how bones, ligaments, muscles and tendons work together at joints like the elbow, facilitated by nerves. Muscle contraction occurs when actin and myosin filaments slide past each other within sarcomeres in response to calcium ion release. The elbow joint contains cartilage, synovial fluid and antagonistic biceps and triceps muscles that work with the ulna and radius bones to enable flexion and extension.

1. 11.2 Muscles and Movement
Topic 11 Human health & physiology

2.  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.

3.  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.

4.  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.

5. 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

6. 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.

7. 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.

8. 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

9. The Elbow Joint
Ref: IB Biology, Oxford Study Courses

10. 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

11. The Elbow Joint
Ref: Biology for the IB Diploma, Allott

12. Antagonistic Muscles in the
Elbow Joint
Ref: Advanced Biology, Kent

13. Hip and Knee joints

14. Comparison: hip and knee joints
Feature 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 & tibia
Femur & patella
Permitted movement Circumduction i.e. circular
(three planes)
Flexion & extension
(one plane)

15. 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.

18. Structure of Skeletal Muscle

19. Structure of a Sarcomere

20. 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.

21. Ref: Biology for the IB Diploma, Allott.

22. 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.

23. Ref: Advanced Biology, Roberts etal.