EX1; Smooth Muscle Flashcards
True or False
Smooth muscles are very large
False; they are very small (2-10µm in diameter)
Why are smooth muscle cells considered smooth
the striations are not present; have relatively little SR
True or False
The thick and thin filaments are similar, but not identical to those in skeletal and cardiac muscle
True
Smooth muscle cells have these; homologous to Z lines of started muscle
dense bodies
What is attached to the dense bodies
thin filaments
This is NOT expressed in smooth muscle
troponin
All the neural innervation of the smooth muscle is from what
the autonomic nervous system; therefore control is involuntary
Compared to cardiac and skeletal, there is a greater range of cell lengths over which what can occur
over which force can be generated; accommodates large changes in volume of organs that are designed to move fluids such as the bladder
The rate of ATP splitting by myosin in activated smooth muscle fibers is how many times lower than in skeletal muscle
10-100 times
Due to the extremely low rate of splitting of ATP, what is the virtually no of regarding smooth muscle
there is virtually no fatigue; the economy is much higher
The economy of muscle contraction equals what
force/ATP consumed
in smooth muscle, the force/cross sectional area is about the same as in skeletal muscle, but the ATP splitting is so much lower
In smooth muscle, a stimulus leads to what
increase in intracellular Ca concentration
The Ca is coupled with what in smooth muscle
Ca + calmodulin ⃗ Ca-calmodulin
The Ca-calmodulin is bound with what
myosin light chain kinase (MLCK) (inactive)
When the Ca calmoduin is bound with MLCK, what occurs
it becomes an active form
The Ca-calmodulin-MLCKacive then does what
it interacts with phosphatase and then either relaxes (Pi + myosin) or contracts (myosin + P)
This is continuously active, of which activation results when the MLCK activity is greater than its activity
phosphatase
This prevents the reattachment of myosin to actin
dephosphorylation
ATP causes this of myosin from actin, as with striated muscle
dissociation
Dephosphorylated myosin cannot bind actin, however, myosin bound to actin in smooth muscle can be dephosphorylated and what
remains attached in a rigor state with no movement of the cross bridges
This course of Ca is relatively sparse; there are no T tubules in smooth muscle
sarcoplasmic reticulum
There is some SR that is associated with what in the membrane can cause release of Ca from this DR
plasma membrane and SP
Ca ions enter from this through channels in the plasma membrane
extracellular fluid/extracellular space
APs in smooth muscle; the inward flow of positive charge is carried by what
Ca ions during the rising phase of AP
