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Biology Year 2 > contraction of a muscle > Flashcards

contraction of a muscle Flashcards

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1
Q

what cannot muscles do/ can do

A

they cannot push they can only pull

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2
Q

so what does this mean

A

muscles work in antagonistic pairs

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3
Q

what is the evidence for the sliding mechanism theory

A

the I band gets narrower and the h zone become narrower and the z lines move closer but a band remain same length

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4
Q

why does a band remain the same length

A

as this s determined by the length of the myosin filaments which hasn’t become smaller

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5
Q

what is myosing made out of

A

two protiens

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6
Q

what is the fibrous protein

A

arranged in a filament made up of several hundred molecules the tails

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7
Q

what is the globular protein

A

formed into two bulbous structures the heads

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8
Q

what is actin

A

a globular protein whose molecules are arranged into a long chain that twisted around to form a helical strand

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9
Q

what is tropomysin

A

form long thin sthreads that wrap around actin

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10
Q

what happens when an action potential reaches the neuromuscular junction

A

it reaches the junction simultaneously causing calcium ion channels to open and cause calcium ions to flow in and cause the synaptic vescicle to fuse with the pre synaptic membrane releasing the acetyl choline nto the synapse

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11
Q

what does acetyl choline do

A

diffuse and bind to the receptors found on the membrane of the muscle fibres causing it to depolarise

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12
Q

what happens to the action potential

A

travel deep into the fibre through a system of tubules

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13
Q

what are t tubules

A

extentions of the cell surface membrane and branch throughout the cytoplasm of the muscle

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14
Q

what are the tubules in contact with

A

the endoplasmic reticulum

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15
Q

what has the endoplasmic reticulum done

A

actively transported calcium ions from the cytoplasm into the er leading to very low concentration of ca + ions in the sarcoplasm

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16
Q

what does the action potential do next

A

open the calcium ion channel on the endoplasmic reticulum and calcium ion diffuse into the sacroplasm down a concentration gradient

17
Q

wha tdoes the calcium ions do

A

cause the tropomyosin that were blocking the binding site on the actin filament to pull away

18
Q

what happens when atp hydrolyses

A

the atp hydrolyses transferring energy and the adp ataches to the myosin head so they are in a state to bind to the actin filament and form cross bridges

19
Q

what happens once attached

A

the myosin head changes their angle pulling the actin filament along releasing a molecule of adp

20
Q

what does atp do

A

it attaches to the myosin head causing it to be detached from the actin filament

21
Q

what does the calcium ions

A

activate the enzyme atpase which hydrolyses atp to adp and provide energy for muscle contraction

22
Q

what does this provide energy for

A

atp is now adp attatched to the myosin head straightens the myosin head and return it to the original position

23
Q

what then happens to the myosin head

A

as it is attached with an adp molecule it attaches to an actin binding site further along

24
Q

how long is it repeated for

A

as long as the concentration of the calcium ions remain high

25
Q

what does it mean that the myosin heads are in opposite direction

A

the movement of one myosin head in the opposte direction of the other set so actin also moves in opposite direction

26
Q

why does z line shorten

A

the movement of actin in opposite direction shortens the distances between the z lines

27
Q

what happens when nervous stimulation ceases

A

the calcium ions are actively transported back into the endoplasmic reticulum using energy from hydrolysis of atp

28
Q

what happens as calcium ions are reabsorped

A

it allows tropomysin to block the binding site of the acitn again

29
Q

what does this mean for the myosin head

A

it is unable to bind to the actin filament and contraction ceases

30
Q

what happens following contraction

A

the muscle enters refractory period

31
Q

what does acetylcholinesterase do

A

break down the acetylcholine

Biology Year 2 (66 decks)

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