Muscles Flashcards
How do muscles act?
In opposite (antagonistic) pairs in an incompressible skeleton
How can a limb move in both directions?
By using antagonistic pairs because muscles can only pull
What is the contracting muscle called?
Agonist
What is the relaxed muscle called?
Antagonist
What do ligaments do?
Attach bones to bones
What do tendons do?
Attach bones to muscles
When do skeletal muscles contact?
Contract voluntarily
What do skeletal muscles have lots of?
Mitochondria
What are skeletal muscles made up of?
Long cylindrical cells called muscle fibres (multinucleated)
What do muscle fibres contain?
Long organelles called myofibrils
What do myofibrils contain?
Myofilaments
What are 2 examples of myofilaments?
Actin and Myosin
How is myosin represented?
- Dark- Thick
How is actin represented?
- Light- Thin
What is the H-zone?
Overlapped myosin
What is the A-band?
- All myosin- Appears dark- Anchor
What is the I-band?
- Actin only- Doesn’t include overlap with myosin- Light in colour
What is the sarcomere?
Between z-lines
What does the sliding filament theory say about relaxed muscles?
- Actin-myosin binding site is blocked by trypomyosin- This prevents an actin-myosin cross bridge being formed
What does the sliding filament theory say about contracting muscles?
- Calcium ions cause trypomyosin to move out of the binding site allowing the actin-myosin cross bridge to form- Calcium ions activate ATPase (ATP -> ADP + Pi)- ATP is used to:Change the shape of the myosin head (power stroke) (continues as long as the binding site is openDetach the myosin headReturn the myosin head to rest (recovery stroke)Re-absorb calcium ions into the sarcoplasmic reticulum by active transport
What happens to the sarcomere during contraction?
Becomes shorter
What happens to the I-band during contraction?
Becomes shorter
What happens to the H-zone during contraction?
Becomes shorter
What happens to the A-band during contraction?
Remains the same
What is the fastest way to make ATP?
Phosphocreatine
How is phosphocreatine used to generate ATP?
PCr + ADP -> ATP + Cr
Where does PCr come from?
In cells
Why is phosphocreatine the fastest way to make ATP?
It is a short and simple reaction
When are PCr / Cr used?
During high intensity short duration activity because PCr/Cr stores are used up quickly
Is phosphocreatine aerobic or anaerobic?
Anaerobic
Does phosphocreatine produce lactic acid?
No, it is alactic
What are two slow ways of producing ATP?
- Anaerobic respiration- Aerobic respiration
What does anaerobic respiration produce?
- 2ATP (glycolysis)- Lactate (causes muscle fatigue)
What does aerobic respiration produce?
- Lots of ATP (mainly made by oxidative phosphorylation)- No harmful waste products
At what speed do slow twitch muscle fibres contract?
Slowly
At what speed do fast twitch muscle fibres contract?
Fast
At what speed do slow twitch muscle fibres relax?
Slow
At what speed do fast twitch muscle fibres relax?
Fast
What is the force of contraction of slow twitch muscle fibres?
Low
What is the force of contraction of fast twitch muscle fibres?
High
How quickly do slow twitch muscle fibres fatigue?
Slowly (they are resistant)
How quickly do fast twitch muscle fibres fatigue?
Very quickly
How do slow twitch muscle fibres respire?
Anaerobically (little aerobic respiration)
How do fast twitch muscle fibres respire?
Aerobically (little anaerobic respiration)
What do slow twitch muscle fibres have lots of?
- Mitochondria- Blood vessels- Myoglobin
What do fast twitch muscle fibres have few of?
- Mitochondria- Blood vessels- Myoglobin
What intensity of activity are slow twitch muscle fibres best for?
Low intensity and long duration e.g. marathon
What intensity of activity are fast twitch muscle fibres best for?
High intensity and short distance e.g. sprint/long jump
