Week 13: (D) Coupling and Skeletal Muscle Contraction Flashcards
What 2 Transporters can take Calcium out of the cytosol?
Na/Ca2+ exchanger
Ca2+ ion pump
Where does the majority of Ca2+ in cytosol go and by what pump?
back to the SR
by a serca Ca2+ ATPases pump
What inhibits re-uptake of Ca2+?
High conc of Ca2+ in the SR lumen
What delays Ca2+ inhibition into SR?
binding to proteins in SR lumen
What protein binds to Ca2+ to delay inhibition?
Casequestrin: cardiac and some smooth muscle
Calreticulin: high conc in skeletal muscle
What happens when the cell is in full excitation (AP) of T-tubules/SR system?
causes Ca2+release, increase calcium= muscle contraction, Ca2+ in excess
What happens after excitation?
SERCA Ca2+ pumps depletes Ca2+ again
Does the contractile response lag behind the AP?
YES
because excitation contraction coupling must occur before cross bridge activity begins.
What is the delay in contractions called?
latent period
What is contraction time?
onset to peak contractile response
when does contractile response end?
ends when lateral sacs have taken up all Ca2+ released in response to AP
What are lateral sacs?
extended regions of the SR located on either side of the thin T-tubule
How quick is re-uptake?
time consuming
What is quicker the AP or the contractile response?
AP
what is a twitch summation?
Muscle doesn’t have time to fully relax and second twitch is added on to the first