Topic 11.2

Question 1

Exoskeletons

Answer 1

• External skeletons that surround and protect most of the body surface of animals

Question 2

How do bones and exoskeletons facilitate movement

Answer 2

• Provide an anchorage for muscles
• Act as levers

Question 3

Give one example of an antagonistic pairs and explain

Answer 3

• Biceps and triceps
• When biceps contracts, tricepts relaxes
• the arm bends

Question 4

Name another animal that uses antagonistic pairs of muscles

Answer 4

• Grasshoppers use antagonistic pairs of muscles to produce a powerful jump

Question 5

Annotate the following diagram of the human elbow

Answer 5

Refer to picture

Question 6

Cartilage

Answer 6

• Tough, smooth tissue that covers the regions of bone in the joint
• Prevents contract between regions of bone that might otherwise rub together
• Prevents friction
• Absorbs shocks that might cause bones to fracture

Question 7

Synovial fluid

Answer 7

• Fills the cavity in the joint between the cartilages on the ends of the bones
• Lubricates the joint
• Prevent the friction

Question 8

Joint capsule

Answer 8

• Tough ligamentous covering to the joint
• Seals the joint and holds in the synovial fluid
• Prevent dislocation

Question 9

Tendon

Answer 9

Connects muscle to bones

Question 10

Ligaments

Answer 10

Connects bone to bone

Question 11

Hinge joint

Answer 11

• ie. knee joint
• only allows two movements (flexion/bending and extension/straightening)

Question 12

Ball and socket joint

Answer 12

• ie. the hip joint
• has greater range of movement
• can flex, extend, rotate and move sideways/back

Question 13

Label abduction and adduction in the following diagram

Answer 13

Refer to picture

Question 14

Label the following diagram of a muscle fibre

Answer 14

Refer to picture

Question 15

Skeletal muscle

Answer 15

• multinucleate
• contain specialized endoplasmic reticulum
• called skeletal muscle because are attached to bones
• called striated muscle because when their structure is viewed using a microscope, stripes are visible
• composed of bundles of muscle cells known as muscle fibres

Question 16

Muscle fibre

Answer 16

• makes up skeletal muscle
• although a single plasma membrane called the sarcolemma surrounds each muscle fibre, there are many nuclei present and muscle fibres are much longer than typical cells
• a modified version of the endoplasmic reticulum, called the sarcoplasmic reticulum, extends throughout the muscle fibre
• contains many myofibrils
• between myofibrils are large numbers of mitochondia which provide ATP for contraction

Question 17

Sarcoplasmic reticulum

Answer 17

• extends throughout the muscle fibre
• wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once
• stores calcium

Question 18

Myofibrils

Answer 18

• within each muscle fibre, there are many parallel, elongated structures called myofibrils
• have alternating light and dark bands, which give stiated muscle its stripes
• in the centre of each light band is a disc-shaped structure referred to as the Z-line
• made up of contractile sarcomeres

Question 19

Sarcomere

Answer 19

• many sarcomeres makes up a myofibril
• consists of a regular arrangement of two types of protein filaments: thin actin filaments and thick myosin filaments

Question 20

Draw a labelled draigram of the structure of a sarcomere

Answer 20

Refer to picture

Question 21

Draw the structure of a sarcomere in relaxed muscle and the structure after the muslce contracts

Answer 21

Refer to picture

Question 22

Identify the contracted and the relaxed sarcomere

Answer 22

Refer to picture

Question 23

Explain how skeletal muscle contracts

Answer 23

• muscles/fibres/myofibrils contain (repeating) units called sarcomeres;
• muscle/sarcomeres contain actin filaments and myosin filaments;
• actin fibres are thin AND myosin fibres are thick;
• arriving action potential causes release of calcium ions;
• from sarcoplasmic/endoplasmic reticulum;
• calcium ion binds to troponin;
• causing troponin and tropomyosin to move (on actin);
• ATP binds to myosin heads releasing them/breaking cross bridges;
• ATP hydrolysed/split into ADP + Pi;
• ATP/energy causes myosin heads to change shape/swivel/become cocked;
• myosin heads bind/form cross-bridges to (exposed) actin binding sites;
• myosin heads swivel/move actin (releasing ADP + Pi);
• myosin filaments move actin filaments towards centre of sarcomere;
• sliding of filaments/actin and myosin shortens the sarcomere