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biology paper 2 > topic 6 muscle contraction > Flashcards

topic 6 muscle contraction Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are the three types of muscle?

A

cardiac, skeletal and smooth

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2
Q

what is skeletal muscle used for?

A

movement

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3
Q

what do tendons do?

A

attach muscle to bone

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4
Q

what do ligaments do?

A

attach bones to bones

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5
Q

why do bones act as levers?

A

they are incompressible so a lever gives a muscle support to pull against

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6
Q

what is it called when muscles act in pairs?

A

antagonistic pairs

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7
Q

what is an agonist?

A

contracting muscle

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8
Q

what is an antagonist?

A

relaxing muscle

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9
Q

what is an example of an effector?

A

a muscle

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10
Q

how are muscles stimulated to contract?

A

by neurons/an action potential

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11
Q

what is skeletal muscle made from?

A

muscle fibres

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12
Q

what is the sarcolemma?

A

cell membrane of muscle fibres

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13
Q

what does the sarcolemma do?

A

folds inwards across muscle fibres and sticks to the sarcoplasm

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14
Q

what is the sarcoplasm?

A

muscle cell cytoplasm

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15
Q

what are folds of the sarcolemma called?

A

transverse (T) tubules

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16
Q

what do transverse tubules do?

A

spread electrical impulses throughout the sarcoplasm to reach all parts of the muscle fibre

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17
Q

what is the sarcoplasmic reticulum?

A

network of internal membranes that runs through the sarcoplasm, and releases calcium ions for muscle contraction

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18
Q

what organelles do muscle cells have many of?

A

mitochondria- provide ATP for muscle contraction

multinucleate

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19
Q

what are myofibrils?

A

long, cylindrical organelles
made up of proteins
bundles of thick/thin myofilaments that move past eachother to make muscles contract

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20
Q

what are thick myofilaments called?

A

myosin

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21
Q

what are thin myofilaments called?

A

actin

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22
Q

what can you see when looking at a myofibril under an electron microscope?

A

alternating light and dark bands

23
Q

what are the A bands?

A

thick myosin, some overlapping thin actin

appear dark

24
Q

what are the I bands?

A

thin actin, light bands

25
Q

what is a myofibril made from?

A

short units known as sarcomeres

26
Q

what is the end of a sarcomere called?

A

Z line

27
Q

what is the middle of a sarcomere called?

A

M line

28
Q

what is the H zone?

A

area either side of the M line

only myosin filaments

29
Q

what is the sliding filament theory?

A

myosin and actin filaments slide over eachother which makes sarcomeres contract
simultaneous contractions cause myofibrils and muscle fibres to contract
sarcomeres return to their original length as the muscle relaxes

30
Q

why do myosin filaments have hinged globular heads?

A

so they can move back and forth

31
Q

what do myosin filaments have a binding site for?

A

actin and ATP

32
Q

what do actin filaments have a binding site for?

A

myosin heads, known as the actin-myosin binding sites

33
Q

where is the protein tropomyosin found?

A

between actin filaments

helps myofilaments move past eachother

34
Q

what is the actin-myosin binding site blocked by in a resting muscle?

A

tropomyosin

35
Q

what happens because the actin-myosin binding site is blocked in a resting muscle?

A

myofilaments can’t slide past eachother because myosin heads can’t bind

36
Q

what are the stages of muscle contraction?

A

action potential from the motor neuron stimulates the muscle cell

this depolarises the sarcolemma

depolarisation spreads down the transverse tubules to the sarcoplasmic reticulum

so it releases stored calcium ions into the sarcoplasm

calcium ions bind to a protein attached to tropomyosin

so the protein changes shape and pulls attached tropomyosin out of the actin-myosin binding site on the actin filament

this exposes the binding site so the myosin head can bind, forming a bond called the actin myosin cross bridge

calcium ions activate ATP hydrolase which hydrolyses ATP to provide energy for muscle contraction

the energy released from ATP causes the myosin head to bind, and pull along another actin filament

another ATP provides energy to break the actin-myosin cross bridge

the myosin head detaches from the actin filament after it has moved

the myosin head reattaches to a different binding site further along the actin filament

so a new actin-myosin cross bridge is formed and the cycle is repeated

many crossbridges form and rapidly break, which pulls the actin filament along, shortening the sarcomere so the muscle contracts

the cycle continues if calcium ions are present

37
Q

what happens when excitation stops?

A

muscle stops being stimulated

calcium ions leave their binding site and move by active transport back to the sarcoplasmic reticulum

38
Q

what does calcium ions moving back to the sarcoplasmic reticulum do?

A

causes tropomyosin molecules to move back so they block the actin binding site
muscles aren’t contracted as no myosin heads are attached to actin filaments
no actin-myosin cross bridges formed
actin filaments slide back to their relaxed position which lengthens the sarcomere

39
Q

which are the three ways ATP can be regenerated for muscle cells?

A

aerobic respiration
anaerobic respiration
ATP phosphocreatine system

40
Q

how can ATP be regenerated by aerobic respiration?

A

regenerated by oxidative phosphorylation in the cell’s mitochondria
happens when oxygen is present
during long periods of low intensity exercise

41
Q

how can ATP be regenerated by anaerobic respiration?

A

rapidly made by glycolysis
end product is pyruvate which is converted to lactate by lactate fermentation
lactate quickly builds up resulting in muscle fatigue
during short periods of high intensity exercise

42
Q

how can ATP be regenerated by the ATP Phosphocreatine system?

A

phosphorylate ADP by adding a phosphate group from PCr (ATP-Phosphocreatine)
PCr is stored inside cells
the ATP-PCr system quickly regenerates ATP
runs out after a few seconds
used during short bursts of vigorous exercise
anaerobic and alactic system

43
Q

how do slow twitch muscle fibres contract?

A

slowly

44
Q

how do fast twitch muscle fibres contract?

A

rapidly

45
Q

what are slow twitch muscle fibres used for?

A

posture

endurance activities

46
Q

what are fast twitch muscle fibres used for?

A

fast movements

short bursts of speed/power

47
Q

do slow twitch muscles easily tire?

A

no

48
Q

do fast twitch muscles easily tire?

A

yes

49
Q

which type of respiration do slow twitch muscles perform?

A

aerobic

50
Q

which type of respiration do fast twitch muscles perform?

A

anaerobic

51
Q

which type of muscle fibres have many mitochondria and blood vessels?

A

slow twitch

52
Q

which type of muscle fibres have few mitochondria and blood vessels?

A

fast twitch

53
Q

why are slow twitch muscle fibres red?

A

rich in myoglobin

54
Q

why are fast twitch muscles fibres white?

A

little myoglobin

biology paper 2 (23 decks)

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