Muscles Flashcards
What are muscles
Cells arranged to form fibres -> when fibres contract, they become shorter, producing force
What are the 3 types of muscle
- Skeletal (/voluntary/striated)
- Smooth (involuntary)
- Cardiac
Features of skeletal muscle
Features of smooth muscle
Features of cardiac muscle
What are myofibrils
Actin (thin filament) structure details
Myosin (thick filament) structure
How is muscle contraction initiated?
- wave of depolarisation & action potential travels down the sarcolemma & transverse tubules into the muscle fibre
-> Ca2+ diffuse out of the sarcoplasmic reticulum & into the sacroplasm of the muscle fibre / into the muscle cell
Then, Ca2+ binds with troop in molecules -> this initiates muscle contraction
What happens to myosin & what happens to actin when muscles are released
Myosin = the myosin head has ADP attached to it
Actin = troponin holds tropomyosin in place to cover the actin-myosin binding site
Contraction is caused by the interaction of…?
Myosin & actin
Muscle fibre structure diagram
Myofibril structure diagram e.g. A band, I band, M line, z disc etc
What’s the A band
Contains actin & myosin
Remains same width (during contraction)
Whats the I band
Contains only actin
What’s the M line
Where all of the myosin joins together
What’s the H zone
- contains only myosin
- in centre of sac Romero
- no overlap of light & dark bands
What happens during contraction (explain using this image)
- Z lines move towards each other
- Sacromeres get shorter
- actin slides over myosin
- H zone & I band = shorter
- A bands stay same length
What’s a sacromere
Basic functional unit of a fibre, the distance between 2 Z lines
What’s the sarcoplasm & what does it contain
The shared cytoplasm within fibres
-> contains many mitochondria & extensive sarcoplasmic reticulum
What’s the sarcoplasmic reticulum / what does it have / what does it surround?
Specialised ER
Surrounds thick & thin filaments, stored Ca2+ ions, has protein pumps to transport Ca2+ into lumen of sarcoplasmic reticulum
What are the 3 processes in the sliding filament model
Stimulation
Attachment
Detachment
What happens in stimulation of the sliding filament model
What happens in attachment of the sliding filament model
What happens in detachment of the sliding filament model
What happens in the ‘power stroke of myosin’
Myosin head moves / tilts backwards
Actin filament slides past myosin filament
Releases ADP + Pi from myosin head
Contraction will continue if what is available + if what’s in the sarcoplasm
If ATP available
Lots of Ca2+ in the sarcoplasm
What happens to the muscle when Ca2+ is rapidly pumped back into the sarcoplasmic reticulum from the sarcoplasm
It relaxes
How is the ATP regenerated made available for continued muscle contraction
Aerobic respiration
Anaerobic respiration
Creatine phosphate
How does aerobic respiration regenerate ATP
- many mitochondria in muscle tissue
- Bohr shift releases more oxygen from haemoglobin in blood
- Intense activity = delivery of oxygen to muscle tissue limits rate of ATP production
How does anaerobic respiration make regenerated ATP available for continued muscle contraction
Anaerobic can occur in the sacroplasm of muscle tissue
Leads to production of toxic lactate
Build up of lactate causes fatigue
How does creatine phosphate release ATP rapidly
Acts as a store of inorganic phosphate groups
- uses these to phosphorylate ADP
- releases ATP very rapidly
