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BIO > MUSCLE CONTRACTION > Flashcards

MUSCLE CONTRACTION Flashcards

1
Q

what are the 2 types of muscle fibres

A

type 1

type 2

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2
Q

Describe the events of a muscle contraction

A

Action potential arrives at a neuromuscular junction
Neurotransmitter diffuses across gap and opens gated Na+ channel
Wave of depolarisation triggers calcium to be released from the sarcoplasmic reticulum by opening calcium ion channel and therefore diffuse out (low calcium in cytoplasm)
Calcium binds to tropomyosin causing it to change shape and expose myosin binding sites on actin
ADP attaches to myosin head = powerstroke
ATP attaches to myosin head = causing it to detach
Calcium activates ATPase which hydrolyses ATP–> ADP therefore providing energy for myosin to return to original position.
ADP reattaches and mason attaches further down actin filament

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3
Q

How are muscles attached to bones

A

tendons

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4
Q

What attaches bone to bone

A

ligaments

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5
Q

what is the agonist

A

the contracting muscle

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6
Q

what is the antagonist

A

the relaxing muscle

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7
Q

what are skeletal muscle fibres made up of

A

large bundles of long cells called muscle fibres

Look STRIATED due to alternating dark and light bands

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8
Q

what is the sarcolemma

A

the cell membrane of muscle fibres

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9
Q

What is the sarcoplasm

A

a muscle cells cytoplasm

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10
Q

what are the folds called that stick into the cytoplasm

A

T tubules

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11
Q

What is the function of a T tubule

A

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

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12
Q

what is the sarcoplasmic reticulum

A

a network of internal membranes that runs through the sarcoplasm

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13
Q

what is the function of the sarcoplasmic reticulum

A

stores and releases calcium ions that are needed for muscle contraction

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14
Q

wha organelle do muscles have lots of and why

A

mitochondria for aerobic respiration

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15
Q

a muscle fibre is multinucleate- what does that mean

A

it has many nuclei

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16
Q

what do muscle fibres have lots of

A

long cylindrical organelles called myofibrils

made up of proteins and highly specialised for contraction

17
Q

what 2 filaments do myofibrils contain

A

thick myosin filaments

thick actin filaments

18
Q

what does a myofibril look like under an electron microscope

A

alternating dark and light bands
dark bands - thick myosin filaments, and some overlapping thin actin filaments
light bands - thin actin filaments ONLY

19
Q

what are the dark bands called

A

A bands

20
Q

what are the light bands called

A

I bands

21
Q

what is each myofibril made up of

A

many short units called sarcomeres

22
Q

what is at the end of each sarcomere

A

a Z line

23
Q

what is in the middle of each sarcomere

A

an M line

The M line is the middle of the myosin filaments

24
Q

What is the H zone

A

The H zone is around the M line and only contains myosin filaments

25
Q

Explain the sliding filament theory

A

Myosin and actin filaments slide over one another to make the sarcomeres contract
The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract
Sarcomeres return to their original length as muscle relaxes

26
Q

what changes occur when the sarcomeres contract

A

A bands stay same length
I bands get shorter
H zones get shorter
Sarcomeres get shorter

27
Q

What do myosin filaments have

A

globular heads that are hinged so can move back and forth

binding sites - one for actin and one for ATP

28
Q

what do activists filaments have

A

a binding site for myosin heads called an actin-myosin binding site

29
Q

what protein is found between actin filaments and what does it do

A

tropomyosin

it helps filaments move past each other

30
Q

what happens to the binding sites in resting muscles

A

the binding sites in resting muscles are blocked by tropomyosin

31
Q

what happens to calcium when the muscle stops being stimulated

A

when muscle stops being stimulated
calcium ions leave their binding sites and are moved back to sarcoplasmic reticulum via active transport
This causes the tropomyosin to move back too
So they block the bonding sites
Actin filaments slide back to their relaxed position which lengthens the sarcomere

32
Q

what is it called when the myosin head is attached to the actin filaments

A

a cross bridge

33
Q

ATP-PC system, how long does PC last

A

a few seconds

34
Q

state some properties of slow twitch muscle fibres

A 
endurance activites
can work for a long time without fatigue
energy released slowly
aerobic respiration
lots of mitochondria 
red in colour as rich in myoglobin (red coloured protein that stores oxygen)
35
Q

state some properties of fast twitch muscle fibres

A 
used for fast movement
short bursts of energy - speed or power
get tired very quickly 
anaerobic respiration 
less mitochondria 
fatigue quickly due to lactic acid 
white in colour as less myoglobin (so can't store much oxygen)

BIO (10 decks)

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