Vasuclar Smooth Muscle Flashcards
How are arterioles organized, explain their role in resistance
Organized in series
- in general have small radius so resistance is high
- site of resistance regulation- a change in its radius has large effects on R
capillaries have highest R but are in parallel so R isn’t variable
Composition of blood vessels: Aorta
High elastic fibers- allow high compliance
Highest internal radius
Composition of blood vessels: Arterioles
Larger wall thickness than internal radius
High smooth muscle b/c controls constriction of radius
Composition of blood vessels: Cappillaries
Smallest vessels
Only endothelial cell layer
Width of lumen of arteriole
10-30 micro m
What does VSM stand for
Vascular smooth muscle
What are the terms for constriction and dilation in smooth muscle
Vasoconstriction and vasodilation
What regulates smooth muscle contraction
Thick filament
What does SMC stand for
Smooth muscle cells
What is in the VSM thin filament
- Actin
- Calponin
- Caldesmon
* no nebulin, Tn complex*
What does calponin do
Inhibits actin- myosin interactions
What does caldesmon do
Inhibit actin-myosin interactions
What is the pattern and shape of vascular smooth muscle
Irregular pattern- no striations no Z lines
Spindle shaped
How do the thin filaments anchor
Dense bodies
- no Z lines in smooth muscle
How do gap junctions differ in different smooth muscle. Provide examples
Not all smooth muscle are connected for functional syncytium, but some are
ex. Aorta- multi unit, not coupled
ex. Arterioles- single unit, coupled
What creates mechanical coupling between smooth muscle cells
Adherens junctions (dense plaques)
What are the invaginations in smooth muscle called
Caveoli
lack t-tubules
How does the amount of mitochondria differ in smooth muscle vs cardiac muscle
Few mitochondria in vascular smooth muscle vs cardiac muscle
What cells can proliferate
Smooth muscle cells can proliferate (angiogenesis)
Striated muscle can not proliferate
What is the role of the myoendothelial junction
Allows communication between endothelium and smooth muscle in arteries
Where is smooth muscle located in relation to cardiac muscle
Smooth muscle is deep to cardiac muscle
Compare structures in vascular smooth muscle vs cardiac muscle
In smooth muscle:
1. SR less regular
2. Caveoli instead of t-tubules
3. Fewer mitochondria
How does the # of mitochondria differ in VSM vs cardiac and why
Fewer mitochondria in smooth muscle b/c glycolysis can support non-contractile ATP needs
What are caveoli and what is their function
-Caveoli are specialized lipid rafts, invaginations of the cell membrane
-contain Ca channels and ion channels
-can localize signaling molecules