5. Muscle structure Flashcards
Myosin structure
6 subunits
2 large subunit heads
2 light chains on lever arm
2 tails twist
what happens once ATP has vanished from striated muscles
rigor mortis
how are myosins aligned in cardiac and skeletal muscle
antiparallel strands in thick filaments so actin pulled together
Sarcomere
contractile units of a protein
what does the amount of force depend on
starting length
at full stretch- weak (few myosin heads in contact with actin)
full contraction- max force until ends of actin get in eac others way
= length tension relationship
why is striated muscles a term used
they are adapted to be at maximal range of length- tension relationship (Skm)
sarcomeres are held in register by Z discs (cardiac)
where are T transverse tubules found
surrounding each myofibril at region of junction of A and I band
SR (stores calcium) membrane network between them
what are terminal cristernae
enlarged areas of SR surrounding T tubules
form a triad
what are Skm fibres
a syncytium
are cardiac fibres built of syncytium fibres
no
contains mono or dinucleated cells with limb like extensions
the role of extensions in cardiac muscle
connect neighbouring cells to form fibre like networks that produce force in the direction of cell’s axis
via intercalated discs
links Z disc and M line
are cardiac or skm muscle cells bigger
skm as cardiac are not syncytia
where are the nuclei in cardiac cells
centrally located
contraction in SM
further
thick filaments hit Z line
different myosin isoform
intermediate filaments of SM
prevent over stretching
