this is smooth muscle and this is skeletal muscle there's a lot of
similarities that both contractile that I have actin and myosin is their main
proteins they both have calcium as their trigger for contraction and ATP is their
powerful contraction but how are they different
let's have a look initially at the colors you can really see through smooth
muscle it's completely smooth as the name describes but it's a far pastier
compared to skeletal muscle which is much redder it's this stored myoglobin as it
comes in contact with the oxygen there's a far greater story of oxygen and blood
and nutrients in skeletal muscle because it uses them so much for all ravenously
then it is smooth muscle smooth muscle is this sort of a pasty white color
normally skeletal muscle a much darker color even when you get things like a
chicken breast to skeletal muscle it still it looks white after it's been
cooked but it's still that pinkish red colour far more richer than you find in
your average smooth muscle smooth muscle is a far slower process the
contractions about 10 times more energy efficient in smooth muscle than in
skeletal muscle but it happens far slower. Skeletal muscle has these
beautiful regular contractile elements it has striations it had lined up multi
nucleic fibres whereas smooth muscle tends to look more like a jumble of
cells
the main difference between skeletal muscle and smooth muscle is the gorgeous
way in which skeletal muscle is arranged to contract in one direction these
vesicles are full of muscle fibers the fibers are one of the longest cells in
the body, multi nucleic, and if you zoom in and look they're actually striated
this is just because they're so beautifully arranged they're lined up
perfectly as they develop in the body smooth muscle on the other hand tools
jumbled together in all different directions and when we build it up it
looks something like this smooth muscle are jumbles of cells which is in stark
contract to our skeletal muscle which are arranged in perfect parallel with
multiple nuclei the differences between these cells can be summed up from the
sole idea that skeletal muscle is designed to be in perfect parallel lined
up to perfectly contract in one direction whereas smooth muscle
contracts in all kinds of directions in the tissue it's not a line than it
doesn't need to be another difference the mechanism of activation skeletal
muscle uses calcium and smooth muscle also uses calcium
however skeletal muscle tends to come from inside the skeletal muscle in the
sarcoplasmic reticulum a very specialized calcium store in smooth
muscle most of the calcium comes from extracellular sources in the
interstitial fluid although there is a little bit of an SR in there as well the
calcium in smooth muscle activates calmodulin calmodulin is the mechanism
by which myosin light-chain kinase gets activated and that activates myosin and
starts crossbridge cycling in skeletal muscle the calcium activates troponin
and troponin moves tropomyosin, a long protein, away from the binding site and
that starts cross bridge cycling, shortening those sarcomeres. One last difference if
we look at how I've drawn the actin myosin filaments the you notice the
myosin filaments here have heads facing in two different directions whereas in
the skeletal muscle they only face in one direction in skeletal muscle the
myosin heads are aligned a perfect in the case they can only contract in
one direction the crossbridge cycling pools along it the actin shortens those
sarcomeres in one direction in smooth muscle. Resistant to fatigue. Far more
energy-efficient slower but another feature is the myosin heads face
different directions which means that you can contract in any direction you
can enlarge a hollow organ or contract a hollow organ. Active relaxation we call
that