5.1 Skeletal muscle Flashcards
what is each muscle composed of?
muscle fibres
what is the connective tissue called that bundles fibres together?
SARCOLEMMA
what are the smaller fibres in muscles called?
myofibrils
what do myofibrils contain?
2 types of protein
myosin and actin
muscles are made of…
fasicles
fascicles are made of…
muscle fibres
muscle fibres are made of…
myofibrils
myofibrils are broken down into…
sarcomeres
sarcomeres are made of…
thin & thick filaments (actin and myosin)
what are the I bands and why?
light - actin and myosin don’t overlap
only actin there
what is the A band and why?
dark bands
appear darkest where actin and myosin overlap
darkness due to presence of thick myosin filaments
where is the Z line found?
at the centre of each light band
what is the distance between the two z lines?
the sarcomere
what happens to the sarcomere when muscle contracts?
it shortens, z bands move closer and I bands nearly disappear
what is the H zone?
a lighter coloured region in the centre of the dark band
what is in the H zone?
only myosin filaments
what are the two different types of muscle fibres in skeletal muscle?
slow twitch and fast twitch
do slow twitch fibres contract slowly or quickly?
slowly
are slow twitch fibres more or less powerful over time?
less powerful
what are slow twitch fibres used for?
endurance activities
do slow twitch fibres tire easily?
no
where is slow twitch fibres energy gained from?
aerobic respiration
what are slow twitch fibres rich in?
myoglobin, blood vessels and mitochondria
Where are slow twitch fibres found in large proportion?
Muscles that maintain posture e.g. Back and calf muscles
Do fast twitch fibres contract quick or slow?
Quickly
Do fast twitch fibres give powerful contractions?
Yes for short periods
What are fast twitch fibres used for?
Short birds of speed and power
Do fast twitch fibres tire easily?
Yes
Where do fast twitch fibres gain energy from?
Anaerobic respiration
What colour are fast twitch fibres?
Pale
What are fast twitch fibres low in?
Levels of myoglobin and blood vessels
What do fast twitch fibres have more of?
More thick myosin filaments
What do fast twitch fibres store?
Creatine phosphate
What does creatine phosphate do?
Rapidly generates ATP from ADP in anaerobic conditions
Where are fast twitch fibres found in high proportions?
In muscles that need short bursts of energy such as biceps and eyes
What are myofibrils?
Long cylindrical organelles
Made of actin and myosin
Specialised for contraction
Lined up parallel to provide maximum force
What is actin?
Filament consisting of two strands twisted around each other
What is myosin?
The thick filament consisting of rod shaped fibres with bulbous heads that project to one side
How many actin to one myosin?
Six
