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A level Muscles
Terms in this set (32)
Where and how do muscles work?
Muscles act in opposite(antagonistic)pairs in an incompressible skeleton.
Muscles can only pull(they can't push)
To move a limb in both directions muscles need to work in antagonistic pairs
What do ligaments attach?
Attach bones to bones
What do tendons attach?
Attach bones to muscles
What does agonist mean?
What does antagonist mean?
Function and adaptations of a skeletal voluntary muscle
Skeletal voluntary muscles contain lot's of mitochondria
They are long and cylindrical cells called muscles fibres
Muscle fibres are multinucleate(have many nuclei)
contain long organelles called myofibrils
myofibrils contain myofilament e.g. actin and myosin
Sliding filament theory
what happens during a relaxed muscle?
The actin-myosin binding site is blocked by tropomyosin.
This prevents an actinomyosin bridge being formed
Sliding filament theory
what happens during a muscles contraction?
Ca2+ causes tropomyosin to move out of the binding site
This allows actinomyosin cross bridge to be formed.
Ca2+ ions also activate ATPase
ATP is used to change shape of myosin head(power stroke) this continues as long as the binding site is open(Ca2+=action potential) and then detaches the myosin head(like velcro)
Return myosin head to resting/ starting position(recovery stroke).
lastly- re-absorb Ca2+ into sarcoplasmic reticulum by active transport
What happens to the sarcomere, I band, H zone and A band whena a sarcomere contracts.
Sarcomere gets shorter
I band gets shorter
H zone gets smaller
A band stays the same
What is the equation for phosphocreatine and how does it produce energy?
PCr + ADP --> ATP + Cr
Phosphate group(PO43-)is added to ADP to make ATP
Cells store PCr
It is a short and simple reaction-fastest way to make ATP
PCr stores are used up quickly- they are used for
short duration e.g. powerlifting
It is an anaerobic process
it is Alactic- doesn't make lactic acid
ATP muscle contraction
Anaerobic respiration (glycolysis)
2 ATP made by glycolysis
Pyruvate--> lactate-causes muscle fatigue
Short duration, high intensity
ATP muscle contraction
Lot's of ATP by oxidative phosphorylation
slow- many reactions-->no harmful waste products
Slow twitch fibres
Low force of contraction
Resistant to fatigue
Lots of mitochondria -
Little anaerobic respiration
Fast twitch fibres
High forces of contraction
few blood vessels
little aerobic respiration
e.g. sprint long jump
Where is the sarcomere located
It is located between the 2 z-lines
Which structures are thinner when viewed in an electron micrograph?
What is the name given to the section of the A band which has no overlap from the I-band?
Describe the role of ATP and of calcium ions(Ca2+) in bringing about the contraction of a myofibril (4marks)
Breakdown of ATP provides energy
Energy is used for changing the shape of the myosin head and breakage of of actin-myosin cross bridges
Calcium ions activate ATPase
Calcium ions cause tropomyosin molecules to move out
People who have McArdele's disease produce less ATP than healthy people. As a result, they are not able to maintain strong muscle contraction during exercise. Use your knowledge of the sliding filament theory to suggest why.
ATP is needed for attachment for cross bridges between actin and myosin. for the movement of myosin heads
Describe the part played by tropomyosin in myofibril contraction.
Moves out of the when calcium ions bind.
Allowing myosin to bind
Describe the part played by myosin in myofibril contraction.
Head of myosin binds to actin and pulls actin past
Myosin detaches from actin and re-sets - moves further along (actin)
A sarcomere is made up of different molecules. Name the molecules that carry out each of the following function:
1. Breaks down ATP
2. Covers binding site on actin in relaxed myofibril
3. Attaches to z line at the end of the sarcomere
If myosin molecules are unable to bind to other myosin molecules, this prevents muscle contraction. Use your knowledge of how muscles contract to suggest why.
Can't form myosin/thick filaments
Can't pull/can't move actin
Myosin moves/ if attached doesn't move
Can't move actin towards each other
When a muscle fibre contracts the number of myosin heads....
stays the same
What is the role of phosphocreatine(PC
) in providing energy during muscle contraction?
Phosphocreatine provides phosphate
To make ATP
How is ATP regenerated from ADP in muscles other than from respiration?
Pi from creatine phosphate/phosphocreatine
Suggest and explain one advantage of the high glycogen content of fast muscle fibres
Glycogen broken down gives lots of glucose for glycolysis
Anaerobic respiration is not very efficient. Only 2 ATP per glucose
Suggest and explain one advantage of the number of capillaries supplying slow muscle fibres.
Many capillaries give high concentration of oxygen. Shorter diffusion pathway
Good glucose supply with little glycogen present
Allows high rate of aerobic respiration-prevents build of lactic acid
Examination of a muscle fibre found that there were only a few mitochondria present. Explain why you would expect this type of muscle fibre to fatigue quickly.
ATP supply is limited
Anaerobic respiration/lot's of lactate
pH is lower
affects enzymes/ prevents muscle contraction
The skeletal muscles of elite sprinters are likely to have many fast twitch muscle fibres.
Suggest why these muscles are less red in colour than muscles with many slow twitch muscle fibres.
Some have less myoglobin present
AS fewer capillaries present
Respiration is mainly anaerobic
slow twitch muscle fibres... have
have low glycogen content
slow twitch muscle fibres contain
more mitochondria than fast twitch fibres
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