11.2– movement

Question 1

what is the general function of bones and exoskeletons?

Answer 1

• provide anchorage for muscles
• act as levers

Question 2

what are 3 specific functions of the skeletal system?

Answer 2

1. provide structural support
2. provide protection for organs
3. act as attachment points for muslces

Question 3

how are bones connected to other bones?

Answer 3

by ligaments

Question 4

ligaments are found in between…

Answer 4

bones

Question 5

tendons are found in between…

Answer 5

muscles and bones

Question 6

muscles work in _________ pairs

Answer 6

antagonistic

Question 7

what are the parts of an insect leg?

Answer 7

femur, tibia, tarsus

Question 8

what are the muscles involved in the jumping of an insect?

Answer 8

flexor muscle and extensor muscle

Question 9

how do antagonistic muscle pairs in an insect leg help the insect jump?

Answer 9

• when the flexor muscle contracts, the extensor muscle relaxes
  
  • tibia and femur are brought closer together
  • causes retraction of hind quarters -> prepares insect for pushing off the ground
• when the extensor muscle contracts, the flexor muscle relaxes
  
  • tibia is pushed away from femur
  • causes extension of the hind quarters -> jump

Question 10

label a diagram of the human elbow

Answer 10

-

Question 11

which part of the arm anchors the muscle?

Answer 11

the humerus

Question 12

what are the parts of the arm that act as a forearm level?

Answer 12

radius for biceps and ulna for triceps

Question 13

the biceps ______ the forearm

Answer 13

bends/flexes

Question 14

the triceps ______ the forearm

Answer 14

straightens/extends

Question 15

what does the joint capsule do?

Answer 15

it seals joint space and limits range of movement to provide stability

Question 16

the synovial fluid functions to…

Answer 16

provide food, O2 and lubrication to the cartilage

Question 17

what is the function of the cartilage?

Answer 17

• it reduces friction, allowing smooth movement
• it absorbs shock and distributes load

Question 18

why are skeletal muscle fibres multinucleated? (short)

Answer 18

• muscle cells fuse together to form a long fibre
• nuclei of the cells do not degenerate -> thus fused muscle fibre contains multiple nuclei

Question 19

what is the specialised feature of muscle fibres that provides energy?

Answer 19

muscle fibres have a large no. of mitochondria for ATP for contraction

Question 20

muscle cells have specialised endoplasmic reticulum called _______ which is adapted to store _____

Answer 20

sarcoplasmic reticulum, Ca ions

Question 21

muscle fibres contain ________

Answer 21

myofibrils

Question 22

what are the two types of myofilaments?

Answer 22

thin, actin
thick, myosin

Question 23

what is the continuous membrane surrounding the muscle fibre called?

Answer 23

sarcolemma

Question 24

sarcolemmas contain…

Answer 24

T tubules

Question 25

protein myofilaments myosin and actin make up a ______

Answer 25

sacromere

Question 26

what are the adaptations of a skeletal muscle fibre? (5) (mnemonic: FMSMT)

Answer 26

1. made up of **Fused skeletal muscle cells** - reduces the need for strong junctions between muscle cells to withstand forces of contraction 2. contains large no. of **Mitochondria** - to generate ATP for muscle contraction 3. contains **Sarcoplasmic reticulum** - to store and release Ca ions for muscle contraction 4. contains **Myofibrils** - w thin actin and thick myosin filaments for muscle contraction 5. contains **T-tubules** - runs deep into muscle fibre - allows for action potential to travel down the t-tubule to sarcoplasmic reticulum

Question 27

what do Z-discs do?

Answer 27

they hold the myofilaments in place

Question 28

draw a labelled diagram of a sacromere

Answer 28

-

Question 29

what does tropomyosin do when a muscle is at rest? (short)

Answer 29

- tropomyosin fibres wrap around actin filaments -> preventing myosin heads from binding to actin filaments - thus no contraction takes place

Question 30

what are the 4 key steps of muscular contraction?

Answer 30

1. depolarisation and Ca ion release 2. actin + myosin cross-bridge formation 3. sliding mechanism of actin and myosin filaments 4. sarcomere shortening = muscle contraction

Question 31

what triggers the release of acetylcholine into the motor end plate?

Answer 31

the action potential from a motor neuron

Question 32

how is depolarisation spread throughout muscle fibres?

Answer 32

by the T tubules on the sarcolemma

Question 33

which part of the sarcomere releases Ca ions?

Answer 33

sarcoplasmic reticulum

Question 34

what triggers the release of Ca ions by the sarcoplasmic reticulum?

Answer 34

depolarisation

Question 35

what happens during depolarisation and Ca ion release? (3)

Answer 35

- action potential from a motor neuron triggers the release of acetylcholine into the motor end plate - acetylcholine initiates depolarisation within the sarcolemma -> spreads through muscle fibre via T tubules - depolarisation triggers sarcoplasmic reticulum to release stores of Ca ions

Question 36

what are the binding sites on the myosin heads blocked by?

Answer 36

the troponin and tropomyosin complex

Question 37

how are the binding sites on myosin heads exposed?

Answer 37

Ca ions bind to troponin on actin, reconfiguring the troponin and tropomyosin complex

Question 38

the _______________ form a cross bridge with ____________________

Answer 38

myosin heads, actin filaments

Question 39

what happens during actin and myosin cross-bridge formation? (3)

Answer 39

1. on actin, the binding sites for the myosin heads are covered by a blocking complex comprised of troponin and tropomyosin 2. Ca ions bind to troponin on tropomyosin -> reconfiguring the complex -> this exposes the binding sites on actin for myosin heads 3. the myosin heads then form a cross-bridge with actin filaments

Question 40

what binds to myosin to break the cross bridge between actin and myosin

Answer 40

ATP

Question 41

ATP hydrolysis causes myosin heads to _______________ and _________

Answer 41

change balance, swivel

Question 42

what happens during the sliding mechanism of actin and myosin? (5)

Answer 42

- ATP binds to the myosin head, breaking the cross-bridge between actin and myosin - ATP hydrolysis causes myosin heads to change position and swivel -> pulls the actin filaments toward the center of the sarcomere -> releases ADP+Pi - new ATP molecule binds to the myosin head -> causes it to detach from actin filament - ATP is hydrolysed to ADP+Pi -> myosin head can re-cock back into high energy stage for next cycle

Question 43

which part is the 'sliding mechanism'?

Answer 43

the pulling of actin filaments toward the center of the sarcomere by the swivelling of myosin heads

Question 44

when do the myosin heads return to its original conformation?

Answer 44

when it swivels

Question 45

how do sarcomeres shorten? (short)

Answer 45

dragging of actin pulls the Z lines closer together, shortening the sarcomere

Question 46

how do individual sarcomeres lead to muscle contraction? (short)

Answer 46

- individual sarcomeres become shorter in length - contraction of muscle fibres as a whole

Question 47

what are the events in muscle contraction? (7)

Answer 47

1. action potential from a motor neuron triggers the release of acetylcholine into the motor end plate - acetylcholine initiates depolarisation within the sarcolemma -> spreads through muscle fibre via T tubules 2. depolarisation triggers sarcoplasmic reticulum to release stores of Ca ions 3. Ca ions bind to troponin on tropomyosin and cause tropomyosin to move - exposing binding sites on actin for myosin heads 4. Pi released from myosin heads - myosin heads bind to actin -> forms cross bridge 5. myosin heads, having hydrolysed ATP to ADP+Pi, have high energy state - chemical energy is used for the myosin heads to swivel, pulling the actin filaments toward the center of the sarcomere - releases ADP 6. new ATP molecule binds to the myosin head - causes it to detach from the actin filament 7. ATP is hydrolysed to ADP+Pi - re-cocks the myosin head into high energy state - another cycle can begin

Question 48

in electron micrographs, A bands are ______

Answer 48

darker

Question 49

the lighter part of electron micrographs are

Answer 49

- I bands - actin is present, myosin is not

Question 50

identify if the muscle in the electron micrograph is relaxed or contracted:

Answer 50

-