Muscle 4

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  • Created by: Hindleyc
  • Created on: 11-04-19 13:35
In animals what is more energy in the form of app used for
Muscle contraction than for any other process
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What does a muscle cell have
only enough ATP for about 3s of contraction
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So what does ATP supply have to be
constantly replenished
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What are the 3 systems muscle have for making ATP
The aerobic system, the anaerobic system and the creatine phosphate system
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Most of the time when muscles are resting or moderately active what do muscles use
aerobic respiration
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What of and where from
Glucose from glycogen stores in the liver to make ATP
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What does the aerobic system provide
An almost unlimited amount of energy but contraction is fairly slow
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why is contraction fairly slow
as it is limited by how quickly oxygen and glucose can be provided by the blood (why you can't run marathon at same speed as a sprint
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What is the aerobic system the only process to
respire fats (triglycerides) so aerobic exercise is the best way to lose body fat
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What happens if the rate of muscle contraction increases
ATP starts to be used faster that it can be made by aerobic respiration
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In this case what do muscles switch to
anaerobic respiration of local muscle glycogen
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What is it
quick
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why
nothing is provided by the blood
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what is produced
lactate
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what does this cause
muscle fatigue
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What does the glycogen store in the muscle provide
enough ATP to last for about 90s of muscle contraction
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What is the anaerobic system used for
short distance races like 400m and when running for a bys
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For the maximum speed of muscle contraction what isn't the anaerobic system
fast enough
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So what do muscles do
make ATP in a very fast one step reaction from creatine phosphate
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What is creatine phosphate
short term energy store in muscle cells
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How much CP vs ATP
10times more
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What is it made from
ATP while muscle is relaxed
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And how can it be used
Very quickly to make ATP when the muscle is contracting
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What does this allow
10s of fast muscle contraction enough for short burst of intense activity eg 100m sprint or running upstairs
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What does it do
Provide phosphate to make ATP (phosphorylates ADP)
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How is a neuromuscular junction set out
Pre s N with mitochondria, vesicles containing acetylcholine, then synaptic cleft, sarcolemma, T-tubules and muscle fibre
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What is ATP used for
AT Ca2+ out of synaptic ending so when action potential arrives Ca2+ floods in
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3 R's
Reabsorption, resynthesises, repackage
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In a relaxed muscle what blocks the binding sites and what does this mean
Tropomyosin and stops myosin head binding- prevents it so contraction is impossible
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Steps
Nervous impulse arrives at the NMJ which causes the release of Ca2+ ions from the sarcoplasmic reticulum which which diffuse through the sarcoplasm
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What does this initiate
movement of the protein filaments
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What does Ca2+ bind to
Troponin on the Actin filament
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What does this do
change its shape and move so the tropomyosin changes shape and moves from the AS of the actin exposing the myosin head binding sites on actin filaments so myosin filaments can now attach to actin forming cross bridges
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When myosin head binds to the actin what does it cause
ADP and Pi on the myosin head to be released
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Why
Breakdown of ATP releases energy which enables the myosin to pull the actin filaments inwards shortening the muscle
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When the myosin head changes shape causing myosin head to nod forwards what does the movement result in
relative movement of the filaments so the attached actin moves over the myosin
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WHERE does this occur
along entire length of every myofibril in the muscle cell
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Then what does the myosin do
detach from the actin and cross bridge is broken
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then
ATP molecule binds to MH
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When the ATP molecule is broken down what happens
the Mh can again attach to an actin binding site repeating the power stroke
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How
ATPase on MH hydrolyses ATP into ADP and Pi
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What is the ratchet mechanism
Repeating pulling of A over the Myosin
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What does this release of energy cause
change in the shape of the myosin head, returns to upright position enabling cycle to start again
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What does process of muscle contraction last for
as long as there is adequate ATP and Ca2+ stores
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Once impulse stops what happens
Ca2+ pumped back into SR and Actin returns to resting position causing muscle to lengthen and relax
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What does tropomyosin do
return to original shape when muscle is no longer stimulated by nerve
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what does 1 motor neurone synapse with
Many muscle fibres
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1 head to
6 actin
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So what is ATP used for
to detach MH
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If no AP
No release of Ca2+ return to original position no further contraction
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What is a motor unit
Motor neurone synapsing each with up to 150 muscle fibres -voluntary
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What do they do
Contract at same time (big region to bicep)
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What are the Z lines
pulled closer (many) and become more interlocked
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Upon binding what happens
Pulls actin closer to M line and increases overlap reducing M and A on own
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What is ATP used/broken down for
energy release to detach myosin head from actin and never back to original position
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then
enetire process repeats then realign causing sarcomere to contract fully decreasing H zone and I band
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then
muscle relaxes
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why
antagonistic muscle pulls sarcomere apart back to way they were- another muscle pulling
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What are myosin filaments formed from
number of myosin proteins wound together
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What does each end in
myosin head which contains ATPase
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What is Myofibril
Cylindrical organelle running the length of the muscle fibre containing actin and myosin filaments
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Sarcomere
functional units of myofibril divided into I A and H bands
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Actin
Thin contractile protein filaments containing active/binding sites
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Myosin
Thick contractile protein filaments with protrusions known as myosin heads
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Tropomyosin
Actin binding proteins which regulates muscle contraction
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Troponin
A complex of 3 proteins attached to tropomyosin
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What are the 2 types of muscle fibres
red and white
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together what do these 2 types of fibres allow
an organism to move about and maintain posture
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What are red fibres
contain more mitochondria and more of the pigment myoglobin which stores oxygen- they also have more blood capillaries associated with them
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What are Red or slow contracting slow twitch fibres used for
walking (long term endurance)
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fast contracting fast twitch fibres for
sprinting jumping escaping from danger
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Fast and sloe
anaerobic and aerobic !!???????
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What do most muscles contain
mixture of the 2 sorts of fibre but people diff in their red:white ratios
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What is proportion of red:white fibres in muscle is controlled by
genes and exercise has little effect so to this extent great athletes are born not made
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High jump
needs mainly white fibres (fast twitch) or rapid jumping actions
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Marathon runner needs
Mainly red muscle fibres (slow twitch ) for endurance
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What are fast twitch muscle fibres
2x diameter of slow Twitch and rely on stores of creatine phosphate and anaerobic respiration to supply ATP
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What do slow twitch fibres rely on
aerobic respiration to supply ATP
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Other cards in this set

Card 2

Front

What does a muscle cell have

Back

only enough ATP for about 3s of contraction

Card 3

Front

So what does ATP supply have to be

Back

Preview of the front of card 3

Card 4

Front

What are the 3 systems muscle have for making ATP

Back

Preview of the front of card 4

Card 5

Front

Most of the time when muscles are resting or moderately active what do muscles use

Back

Preview of the front of card 5
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