1. Section 11.2 Muscles and Movement
Chapter 25 in Book
Mrs. Ragsdale
IB Biology

2. The Physics of Movement
Human movement can easily be compared to a lever using physics terminology
A lever minimizes the amount of effort or work that goes into moving objects.

3. Physics of Movement Lever = Bone Work Done (Effort) = Muscle
Fulcrum = Joint
Heavy Rock = Body weight (or an object you are lifting)

4. Muscle and Movement Equipment
Bones provide the rigid framework for muscles to attach to. They also provide leverage for our muscles to move our body or other objects.
Ligaments are what connect bone to bone. They reinforce our joints by restricting movement, preventing dislocation.
Tendons connect muscle to bone.
Nerve impulses are what drive muscle movement. They use a communication network that sends out messages and signals muscle movement allowing coordinated movement.

5. Radius and Ulna Synovial Membrane Synovial Fluid Humerus
Label a diagram of the human elbow joint including cartilage, synovial fluid, joint capsule, named bones and named antagonistic muscles (biceps and triceps).
Radius and Ulna
Synovial Membrane
Synovial Fluid
Humerus
Cartilage (red)
Ligaments

6. 11.2.3. Outline the functions of the structures of the human elbow joint named in 11.2.2.
cartilage: covers bones, prevents friction
synovial fluid: lubricates joint to reduce friction
joint capsule: seals the joint to hold in synovial fluid, prevent dislocation
humerus: upper arm bone: attachment of biceps & triceps
ulna & radius: forearm bones: attachment of biceps (radius) and triceps(ulna)
Triceps - extends joint
Biceps - flexes the joint

9. Antagonistic Pairs
To produce movement at a joint muscles work in pairs.
Muscles can only actively contract and shorten. They cannot actively lengthen.
One muscles bends the limb at the joint (flexor) which in the elbow is the biceps.
One muscles straightens the limb at the joint (extensor) which in the elbow is the triceps.

10. Exercise: Bend your arm in a flexion.
Point your elbow upwards vertically.
Raise your hand vertically above your head.
This is a true concentric contraction of the triceps
Pick up a heavy object in concentric biceps flexion.
Now lower and straighten your arm.
You should feel your biceps contracted but triceps relaxed.
That an eccentric contraction of the biceps.
This shows how complex movement can be!

11. Movement at the Hip Joint
Ball and socket joint – allows movement in 3 planes
Protraction / Retraction – forwards and backwards
Abduction / Adduction – sideways
Rotation - circular
The lever is the femur and the fulcrum is the hip joint
The effort is provided by the muscles of quadriceps, hamstring and gluteus.

12. Movement at the Knee Hinge joint – movement in one plane only
Pivot is the knee joint
Lever is the tibia and fibula of the leg
Knee extension – powered by quadriceps
Knee flexion – powered by hamstring

13. Comparison of the Hip and Knee Joint

14. Structure of Muscles

15. Basic Muscle Functions
Skeletal movement
Posture and body position
Support of soft tissues
Guarding of entrances & exits
Maintenance of body temperature

16. Skeletal Muscle Structure
Muscles are essentially tubular cells (or fibres)
Muscles cells are known as myocytes
Cells are multinucleated
Striated Muscle – meaning there are both light and dark bands
Basic unit of skeletal muscle tissue is the sarcomere

17. Structure of the Muscle Cell
Sarcolemma – the plasma membrane of a muscle cell
Contains tons of little holes called T Tubules that act like a sieve
Sarcoplasm – (cytoplasm)
Sarcoplasmic Reticulum – a special form of smooth E.R. that controls the storage and release of calcium ions (Ca2+)
Majority of cell volume comes from long filaments called myofibrils

19. Structure of Striated Muscle
Muscle fibres are multinucleated (more than one nucleus)
Whole muscle is made up of myofibrils that are bound together
Myofibrils are proteins that run parallel to one another
Contain combinations of two proteins
Actin
Myosin

20. Actin and Myosin
Actin and myosin proteins overlap. This causes the distinct banding pattern (something seen in electron microscopes).
Actin is considered the thin filament in a myofibril
Myosin is considered the thick filament in a myofibril
A = Actin only C = myosin attachment region
which adds stability
B = Myosin only D = Actin and myosin overlap

21. The Structure of a Sarcomere
The “sarcomere” is the functional unit of a muscle
Thousands of sarcomeres contract together
1 sarcomere = Z line to Z line
Z lines are so-named because they zig-zag
Actin filaments are attached to the Z lines
Z lines may have hundreds of actin myofilaments attached to them
Myosin filaments are attached to each other at the M line

22. 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

23. The H zone is the area only occupied by the thick filaments (myosin)
The I bands (light) are the regions occupied by only thin filaments (actin)
The A bands (dark) are the regions occupied by both filaments (overlap)
The Z lines represent the extremities of a single sarcomere

24. Muscle Contraction
Sarcoplasmic reticulum hordes Ca2+ ions by creating a concentration gradient
When the nerve impulse moves to the muscle via an action potential from a motor neuron, it triggers the release of the Ca2+ ions
The Ca2+ ions expose myosin heads by binding to blocking molecules (troponin and tropmyosin) which causes a structural change
Once their binding sites are removed, a cross bridge can form between the actin binding sites and myosin heads

25. Muscles Relaxing ATP is what causes the breaking of the cross-bridges
ATP attaches to the myosin heads, distracting them away from actin causing them to detach from the binding sites
The hydrolysis of ATP into ADP provides the energy for myosin heads to swivel away from the centre of the sarcomere
A new cross-bridge is formed where myosin heads attach to the actin at an adjacent binding site
Stored energy in the myosin head from the ATP causes the head to swivel inwards towards the centre of the sarcomere causing the movement of actin a short distance

26. Electron Micrographs
Muscle fibres can be fully relaxed, slightly contracted, moderately contracted and fully contracted
You can tell when a muscle is contracted because the sarcomere is shorter, however the A band is not