Smooth Muscle Physiology Flashcards
What are the two types of smooth muscle and what are their characteristic differences
Multi-unit - 1 N to 1 M. Which allows for finer motor control
Unitary - 1N. To multiple muscles which allows for a group contraction through gap junctions
SM does not use what
Troponin
Define the characteristics of multi-unit SM
Fibers operate individually and are innervated by a single N.
Define the characteristics of unitary smooth muscle
Visceral muscle
Works together as a unit
Contains gap junctions
What type of Myosin heads are found in SM
Type II B
What binds actin (thin filaments) to the muscle cell walls
Dense bodies/adherens junctions
The myosin heads in unitary SM have what type of directionality
Bi-directionality
Cycling of myosin cross-bridges is faster or slower than in skeletal muscle
Slower
Define the latch mechanism
STP affinity is lower on myosin heads, which allows them to be attached for longer periods of time to the light chains and thus produce a more continuous, low force contraction
What allows Ca into the cell cytosol for use in contraction
IP3-Gated Ca release channels and ryanodine for SR
Ca(L) or Ca LGC (hormone activation) from extracellular fluid
What does Ca bind to in the cell to begin activation of the steps to contraction
Calmodulin
How does Ca exit the cell when it is done with it
SERCA - sarco/endoplasmic reticulum Ca-ATPase (pumps Ca back into SR)
Na/Ca antiporter
Sarcolemmal Ca-ATPase
What does CaM activate within the cell and what does this do
MLCK which phosphorylates MLC which allows for Myosin and actin binding
The contraction strength is proportional to what
The Ca level
What is the regulatory step of SM contraction and why
CaM because it uses ATP
What removes the phosphate group from MLC to allow for relaxation
MLCPhosphatase
Define varicosities
Neuroxmitter release sites for smooth muscle
Define NE/E effects for SM
Excitatory or inhibitory depending on the organ
Define Ah effect for SM
Contraction is direct effect
Relaxation is indirect effect
Define ANG II effect on SM
Contraction
Define adenosine effect on SM
Relaxation
Define NO effect on SM
Inhibitory and relaxation
What is thew RMP of SM
-50 to -60 mv
AP only occurs in what type of smooth muscle though what
Unitary through gap junctions
What are the spike potentials in SM AP caused by
Hormones, neuroxmitters, stretch receptors
What are the slow waves of SM caused by
Oscillating Ca influx Ca(L) and K efflux
What are the plateaus in SM caused by
Neuroxmitters and stretch receptors
