Muscle Flashcards
tropomyosin
blocks binding sites on actin filaments which prevents myosin cross-bridge binding and prevents contraction in muscle as a result
troponin
blocks tropomyosin in place in the actin binding site
has a high affinity for Ca2+so when calcium levels rise they bind to troponin and move it and therefore move tropomyosin too unblocking the binding site
which topic do you remember the sarcolemma from?
autonomic physiology and Neuromuscular junction!!!
it’s the membrane on post synaptic terminal at NMJ
the sarcolemma has ___ that that penetrate into interior of muscle
it has transverse tubules that penetrate into the centre of skeletal and cardiac muscle
what do you have in cardiac and skeletal muscle
blood supply
mitochondria
sarcoplasmic reticulum
what is the function of the sarcoplasmic reticulum
calcium storage (easy access for the muscle)
characteristics of the transverse tubules
they protect depolarisation
are specific
release of Ca2+ from sarcoplasmic reticulum
depolarisation (caused by neurotransmitter binding on post-synaptic terminal receptors) flows down the transverse tubules
receptors on the S.R detect this depolarisation and it causes voltage gated Ca2+ channels (these aren’t on tubule side) to open allowing Ca2+ to pass through into the interior of muscle
as calcium levels rise it binds to troponin which pulls tropomysin away from actin binding site unblocking it. Myosin is now able to bind and MUSCLE CONTRACTION CAN NOW OCCUR
how and why is calcium taken back up
it’s taken back up into S.R by active transport- active calcium pumps keeps pumping it back into storage
re-blocking actin binding site. Ends contraction and muscle fibre relaxes
what happens when Ca2+ levels are high for too long?
muscle fatigue
and tension crashes once it’s at maximum
what do contraction and relaxation rely on
ATP
isotonic twitch
2 types contracting- shortening length, extending- lengthening
a constant tension but shortening or lengthening of muscle at same time
ie bicep curls
isometric twitch
holding a pose or fixed position
has same tension/ contraction is held
e.g like holding a glass of water in a position and someone filling it- you’re increasing the load but force exerted by muscle is the same
what is tetanus
when multiple twitches/small contractions that are from separate motor units but happen close together summate and feel like one big contraction
during vigorous muscle contraction what happens when maximum tension is reached
all the actin binding sites are exposed so myosin goes through cycle until it can’t increase muscle force anymore (no matter increasing calcium or A.Ps)
because there is a finite ATP supply you can’t maintain vigorous excersise- the cycle can’t be completed
Need ATP and O2 for muscle contraction and relaxation