1. MOVEMENT AHL Topic 11.2 IB Biology Miss Werba
The roles of the musculoskeletal system are movement, support and protection.
AHL Topic 11.2
IB Biology
Miss Werba

2. TOPIC 11 – ANIMAL PHYSIOLOGY
11.1
ANTIBODY PRODUCTION & VACCINATION
11.2
MOVEMENT
11.3
THE KIDNEY & OSMO-REGULATION
11.4
SEXUAL REPRODUCTION
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3. THINGS TO COVER Statement Guidance U.1 U.2 U.3 U.4 U.5 U.6 U.7 U.8 U.9
Bones and exoskeletons provide anchorage for muscles and act as levers.
U.2
Synovial joints allow certain movements but not others.
U.3
Movement of the body requires muscles to work in antagonistic pairs.
U.4
Skeletal muscle fibres are multinucleate and contain specialized endoplasmic reticulum.
U.5
Muscle fibres contain many myofibrils.
U.6
Each myofibril is made up of contractile sarcomeres.
U.7
The contraction of the skeletal muscle is achieved by the sliding of actin and myosin filaments.
U.8
ATP hydrolysis and cross bridge formation are necessary for the filaments to slide.
U.9
Calcium ions and the proteins tropomyosin and troponin control muscle contractions.
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4. THINGS TO COVER Statement Guidance A.1 S.1 S.2 S.3 NOS 1.8
Antagonistic pairs of muscles in an insect leg.
S.1
Annotation of a diagram of the human elbow.
Elbow diagram should include cartilage, synovial fluid, joint capsule, named bones and named antagonistic muscles.
S.2
Drawing labelled diagrams of the structure of a sarcomere.
Drawing labelled diagrams of the structure of a sarcomere should include Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands.
S.3
Analysis of electron micrographs to find the state of contraction of muscle fibres.
Measurement of the length of sarcomeres will require calibration of the eyepiece scale of the microscope.
NOS 1.8
Developments in scientific research follow improvements in apparatus— fluorescent calcium ions have been used to study the cyclic interactions in muscle contraction.
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5. MOVEMENT Nerves: Joints: Muscles: Tendons: Bones: Ligaments:
coordinate and stimulate muscle contractions
Joints:
act as a pivot for movement
Muscles:
apply force for movement
Tendons:
connect muscle to bone
Bones:
act as levers for movement and structural support
Ligaments:
connect bone to bone
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6. HUMAN ELBOW JOINT The elbow joint is a hinge joint.
There are 3 bones associated with this joint:
humerus (upper arm)
radius, and
ulna (lower arm)
There are 2 muscles associated with flexion and extension at this joint:
Biceps brachii (anterior)
Triceps brachii (posterior)
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7. HUMAN ELBOW JOINT
U.3
Movement in the body requires muscles to work in antagonistic pairs.
This means that they work in opposite directions: ie. if one contracts, the other extends and vice versa
The triceps and biceps are examples of antagonistic muscles working to create movement at the elbow joint.
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8. HUMAN ELBOW JOINT
S.1
You need to be able to annotate a diagram of the human elbow.
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9. HUMAN ELBOW JOINT Biceps muscle Tendon: attaches muscle to bone
Humerus bone
Radius bone
Triceps muscle
Ulna bone
Cartilage: a layer of smooth and tough tissue that covers the ends of the bones where they meet to reduce friction
Capsule: seals the joint
Synovial fluid: lubricates the joint to reduce friction
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10. HUMAN ELBOW JOINT Biceps muscle Tendon: attaches muscle to bone
Humerus bone
Radius bone
Triceps muscle
Ulna bone
Cartilage: a layer of smooth and tough tissue that covers the ends of the bones where they meet to reduce friction
Capsule: seals the joint
Synovial fluid: lubricates the joint to reduce friction
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11. tough cords of tissue linking bone to bone, to prevent dislocation
HUMAN ELBOW JOINT
S.1
Capsule
Biceps tendon
Triceps tendon
Ligaments:
tough cords of tissue linking bone to bone, to prevent dislocation
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12. HUMAN ELBOW JOINT
S.1
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13. HUMAN ELBOW JOINT Biceps brachii: bends the arm (flexor)
Triceps brachii:  straightens the arm (extensor)
Humerus:  anchors muscle (muscle origin)
Radius / Ulna:  act as levers (muscle insertion)
biceps inserts into the radius
triceps inserts into the ulna
Cartilage:  allows smooth movement and absorbs shock
Synovial fluid:  provides food, oxygen and lubrication to the cartilage
Joint capsule:  seals the joint and provides stability by limiting range of movement
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14. ANTAGONISTIC MUSCLES eg. human elbow vs grasshopper legs A.1
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15. ANTAGONISTIC MUSCLES eg. human elbow vs grasshopper legs
The back leg of a grasshopper is much longer to aid jumping.
The two main muscles in a grasshopper leg are:
the extensor tibiae muscle
contracts  extends leg
the flexor tibiae muscle
contracts  flex the leg
These muscles are attached to the tibia, on either side of the hinge joint.
These muscles work antagonistically to enable movement in this joint.
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16. MOVEMENT OF JOINTS Both the knee and hip joints are synovial joints
U.2
Both the knee and hip joints are synovial joints
Both are involved in the movement of the leg.
Both are required for walking.
They allow certain movements but not others.
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17. MOVEMENT OF JOINTS Hip joint Knee joint Bones at joint Lever Flexion
U.2
Hip joint
Knee joint
Bones at joint
Pelvis / Femur
Tibia / Femur
Lever
Femur
Tibia
Flexion
Quadriceps
Hamstring
Extension
Planes of movement
many
one
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18. MOVEMENT OF JOINTS KNEE JOINT: A hinge joint. Can flex and extend;
U.2
KNEE JOINT:
A hinge joint.
Can flex and extend;
Also a small amount of rotation.
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19. MOVEMENT OF JOINTS HIP JOINT: A ball and socket joint.
U.2
HIP JOINT:
A ball and socket joint.
Can flex and extend;
Can abduct and adduct
Can rotate.
Head of femur
cartilage
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20. SKELETAL MUSCLE sarcolemma nuclei nuclei U.4 U.5 J WERBA – IB BIOLOGY20

21. SKELETAL MUSCLE
U.4
U.5
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22. SKELETAL MUSCLE
U.4
U.5
Skeletal muscle cells (fibres) are bundled together by the sarcolemma (a membrane).
Muscle cells are multinucleated – with the nuclei along the edges of the cell.
The muscle cells have many mitochondria to supply the large amount of ATP required.
The muscle cell is composed of myofibrils.
The myofibrils have striations - dark and light bands - and contracts longitudinally (ie. along its length).
The sarcoplasmic reticulum lies under the sarcolemma. This is a special type of smooth ER whose function is to store and release calcium ions.
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23. SARCOMERES
U.6
A sarcomere is a repeating, contractile unit of a skeletal muscle cell.
Each myofibril is made up of thick and thin filaments:
Thick myosin filaments
Thin actin filaments
The filaments appear as alternating light and dark bands when viewed in an electron micrograph.
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24. SARCOMERES
U.6
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25. SARCOMERES A sarcomere lies between two Z lines.
U.6
A sarcomere lies between two Z lines.
Z line = dark protein band to which actin filaments are attached
I band (LIGHT BANDS) = contains only thin actin filaments
M line = dark band to which myosin filaments are attached
H zone = contains only thick myosin filaments
A band (DARK BANDS) = contains both actin and myosin filaments overlapping
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26. SARCOMERES
S.2
You need to be able to draw a labelled diagram of the structure of a sarcomere.
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27. SARCOMERES
S.2
You need to be able to draw a labelled diagram of the structure of a sarcomere.
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28. SARCOMERES
S.2
You need to be able to draw a labelled diagram of the structure of a sarcomere.
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29. MUSCLE CONTRACTION
S.3
You need to be able to analyse electron micrographs to find the state of contraction of the muscle fibres.
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30. MUSCLE CONTRACTION
U.7
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31. MUSCLE CONTRACTION
U.6
U.7
There are a number of steps involved in the contraction of skeletal muscle, including:
Release of calcium ions from the sarcoplasmic reticulum
Formation of cross-bridges between filaments
Sliding of actin and myosin filaments along each other
Use of ATP to break cross-bridges and re-set myosin heads.
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32. MUSCLE CONTRACTION
U.6
U.7
An action potential arrives at a neuromuscular junction
Triggers release of Ca2+ ions from the sarcoplasmic reticulum.
The Ca2+ ions bind to troponin on actin filaments.
Troponin moves tropomyosin.
This exposes the myosin binding sites on the actin filament.
The heads of the myosin filaments form cross-bridges (bonds) with the exposed binding sites on actin filaments.
Action potential arrives at muscle
Calcium ions released
Bind to troponin
Moves tropomyosin
Exposes myosin binding sites on actin
Myosin heads form cross bridges with actin
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33. MUSCLE CONTRACTION U.6 U.7 Ref: Advanced Biology, Roberts etal.
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34. MUSCLE CONTRACTION ATP binds to the myosin heads.
Causes myosin heads to break the cross-bridges and detach from actin.
ATP hydrolysis changes the angle of mysoin heads – ie. cocked into new positions.
The myosin heads attach to binding sites on the actin further from the centre of the sarcomere.
The ADP and Pi are released.
Pushes actin inwards towards the centre of the sarcomere. This is called the power stroke.
ATP binds to myosin heads
Myosin heads break cross bridges
ATP hydrolysis
Myosin heads are angled
Attach to new positions
ADP and Pi are released
Power stroke moves actin inwards
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35. MUSCLE CONTRACTION This will be repeated as long as Ca2+ ions remain.
When muscle contraction needs to stop, the calcium is pumped back into the sarcoplasmic reticulum using a Ca2+ ATPase.
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36. MUSCLE CONTRACTION U.6 U.7 U.8
Ref: Biology for the IB Diploma, Allott.
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37. MUSCLE CONTRACTION
U.6
U.7
U.8
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38. MUSCLE CONTRACTION
U.6
U.7
U.8
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39. MUSCLE CONTRACTION
U.6
U.7
U.8
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40. Developments in scientific research follow improvements in apparatus
ASHLEY & RIDGEWAY
NOS 1.8
Developments in scientific research follow improvements in apparatus
Fluorescent calcium ions have been used to study the cyclic interactions in muscle contraction.
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41. ASHLEY & RIDGEWAY Experiments performed in 1968.
NOS 1.8
Experiments performed in 1968.
First to study the role of calcium ions at the neuromuscular junction.
Used aequorin – a bioluminescent protein that binds to calcium ions
Light is produced when calcium is released.
Linked the arrival of the action potential at the muscle fibre with the contraction of the muscle.
Consistent with the theory of the release of calcium ions from the sarcoplasmic reticulum.
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42. MOVEMENT Q1. Which is the sequence of events in muscle contraction?
Use of ATP
Formation of cross bridges
Release of calcium ions from the sarcoplasmic reticulum
Actin filament moves towards the centre of the sarcomere
I → II → III → IV
III → II → IV → I
IV → I → II → III
II → IV → I → III
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43. MOVEMENT Q1. What is indicated by the letters X, Y and Z?
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44. MOVEMENT Q3. Explain how skeletal muscle contracts. [8]
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45. MOVEMENT A1. B A2. D A3. (skeletal) muscle is composed of myofibrils;
operational unit is a sarcomere;
viewed as a series of light and dark bands;
thin actin fibres;
thick myosin fibres;
arrival of action potential;
release of Ca2+;
from sarcoplasmic reticulum;
exposes binding sites of myosin fibres;
ATP used to break cross bridges between myosin and actin fibres;
hydrolysis of ATP resets myosin head;
causing sliding of actin and myosin;
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