topic 11.2 - movement

Question 1

function of bones and exoskeletons

Answer 1

provide anchorage for muscles and act as levers

Question 2

define exoskeletons

Answer 2

external skeletons that surround and protect most of the body surface of animals such as crustaceans and insects

Question 3

describe a first class lever and give an example

Answer 3

E (down), F, R (up)

Example - when a person nods their head backwards

Question 4

describe a second class lever and give an example

Answer 4

F, R, E (down)

Example - someone walking, the moment where they stand on their tiptoes.

Question 5

describe a third class lever and give an example

Answer 5

F, E (up), R (down)

Example - flexing forearm down

Question 6

skeletal muscles are

Answer 6

antagonistic

Question 7

define antagonistic muscles

Answer 7

when one muscle contracts, the other relaxes - they thus produce opposite movements at a joint

Question 8

give a example of an antagonistic muscle pair

Answer 8

in the elbow, the triceps extends the forearm while the biceps flex the forearm

Question 9

give an example of antagonistic pairs of muscles in an insect

Answer 9

in the leg of a grasshopper, which is specialised for jumping.

1. when the grasshopper prepares to jump, the flexor muscles will contract
2. this will bring the tibia and tarsus into a position where they resemble the letter Z and the femur and tibia are brought closer together (flexing). extensor muscles relax during this phase
3. extensor muscles contract extending the tibia and producing a powerful propelling force.

Question 10

draw a diagram of insect legs and their antagonistic muscle pairs

Answer 10

478

Question 11

draw a diagram of a human flow as an example of a synovial joint

Question 12

define a synovial joint

Answer 12

a freely moveable joint that allows a wide range of movement (articulation)

Question 13

cartilage

Answer 13

• tough, smooth tissue that covers the regions of bone in the joint
• prevents contact between regions of bone that might otherwise rub together, helping prevent friction
• absorbs shocks that might cause bones to fracture

Question 14

synovial fluid

Answer 14

• fills a cavity in the joint between the cartilages on the ends of the bones
• lubricates the joint so helps to prevent the friction that would occur if the cartilages were dry and touching

Question 15

joint capsule

Answer 15

• tough ligamentous covering to the joint
• seals the joint and holds in the synovial fluid
• helps prevent dislocation

Question 16

radius bone

Answer 16

to which the biceps is attached

Question 17

biceps

Answer 17

flexes the joint

Question 18

humerus bone

Answer 18

to which the biceps and triceps are attached

Question 19

triceps

Answer 19

extends the joint

Question 20

ulna bone

Answer 20

to which the triceps is attached

Question 21

synovial joints allow

Answer 21

certain movements but not others

Question 22

what determines the movements that are possible in a body part?

Answer 22

the structure of a joint, including the joint capsule and the ligaments

Question 23

the knee joint can act as

Answer 23

a hinge joint, which allows only flexion (bending) and extension (straightening). It can also act as a pivot joint when flexed, which is when it has a greater range of movement

Question 24

the hip joint can act as

Answer 24

a ball and socket joint that can flex and extend, rotate, and move sideways (abduction) and back (adduction).

Question 25

state the three types of muscle

Answer 25

• striated (skeletal muscle)
• smooth muscle
• cardiac muscle

Question 26

function of striated/skeletal muscle

Answer 26

muscles attached to bones that are used to move the body

Question 27

what is striated muscle composed of?

Answer 27

bundles of muscle cells known as muscle fibres

Question 28

state the main features of muscle fibres

Answer 28

• sarcolemma
• many nuclei
• sarcoplasmic reticulum
• mitochondria
• myofibrils

Question 29

sarcolemma

Answer 29

single plasma membrane that surrounds each muscle fibre

Question 30

why are muscle fibres much longer than typical cells and contain many nuclei?

Answer 30

embryonic muscle cells fuse together to form muscle fibres

Question 31

what is the sarcoplasmic reticulum and what does it do?

Answer 31

it is a modified version of the endoplasmic reticulum and wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once. It also stores calcium.

Question 32

where are mitochondria stored?

Answer 32

between the myofibrils

Question 33

muscle fibres contain many…

Answer 33

myofibrils

Question 34

describe a myofibril

Answer 34

• alternating light and dark bands, which give striated muscle its stripes
• in the centre of each light band is a disc-shaped structure (Z-line)

Question 35

each myofibril is made up of…

Answer 35

contractile sarcomeres.

Question 36

define a sarcomere

Answer 36

the functional unit of a myofibril, located between one Z-line and the next.

Question 37

what is the pattern of light and dark bands in sarcomeres due to?

Answer 37

a precise and regular arrangement of two types of protein filament - thin actin filaments and thick myosin filaments

Question 38

location of actin filaments

Answer 38

attached to a Z line at one end

Question 39

location of myosin filaments

Answer 39

interdigitated with actin filaments at both ends and occupy the centre of the sarcomere

Question 40

describe the ratio of actin to myosin filaments and their function

Answer 40

each myosin filament is surrounded by six actin filaments and forms cross-bridges with them during muscle contraction.

Question 41

draw a labelled diagram of the structure of a sarcomere

Answer 41

p481

Question 42

how is the contraction the skeletal muscle achieved?

Answer 42

by the sliding of actin and myosin filaments; the myosin filaments pull the actin filaments inwards during the centre of the sarcomere. this shortens each sarcomere and therefore the overall length of the muscle fibre

Question 43

what causes the sliding motion of actin and myosin filaments?

Answer 43

myosin filaments: they have heads that can bind to special sites on actin filaments, creating cross-bridges, through which they can exert a force, using energy from ATP

Question 44

how is it that many cross-bridges can form at once?

Answer 44

the myosin heads are regularly spaced along the actin filaments

Question 45

what is the M-line?

Answer 45

another line in the centre of the sarcomere

Question 46

what is the visible difference between a relaxed and a contracted sarcomere?

Answer 46

in a relaxed sarcomere, there is a more visible light band on either side of the M-line

Question 47

what controls muscle contractions?

Answer 47

calcium ions and the proteins tropomyosin and troponin

Question 48

describe how calcium ions, tropomyosin and troponin work to control muscle contractions

Answer 48

• in a relaxed muscle, tropomyosin (a regulatory protein) blocks the binding sites on actin
• when a motor neuron sends a signal to a muscle fibre to make it contract, the sarcoplasmic reticulum releases calcium ions
• Ca ions bind to troponin which causes tropomyosin to move, exposing actin’s binding sites.

Question 49

describe the process of muscle contraction

Answer 49

1. myosin filaments have heads which form cross-bridges when they are attached to binding sites on actin filaments
2. ATP binds to the myosin heads and causes them to break the cross-bridges by detaching from the binding sites
3. ATP is hydrolysed to ADP and phosphate, causing the myosin heads to change their angle. The heads are said to be cocked in their new position as they are storing potential energy from ATP
4. the heads attach to binding sites on actin that are further from the centre of the sarcomere than the previous sites
5. the ADP and phosphate are released and the heads push the actin filament inwards towards the centre of the sarcomere (called the power stroke)