Muscles And Vessels - Lowrie Lecture Flashcards
Locations of smooth muscle
Visceral structures (except the heart)
Blood vessels and arrector pili muscles
tunica media of blood vessels
In the visceral structures - forms an inner circular and outer longitudinal layer
Individual cells with smooth muscle characteristics include….?
Myoepithelial cells and myoid cells
Near the BM and have contractile function
Sometimes in mucus areas - squeeze juices into lumen
Smooth muscle cells also secrete extracellular matrix (collagen, elastin). They also divide
….
Smooth muscle cells are filled with what filaments?
Mostly thin filaments, some thick filaments, and desmin and vimentin (intermediate filaments)
What do dense bodies do for smooth muscle cells?
They anchor the thin filaments in smooth muscle cells!
Located mostly at the the PM
Gap Junctions electrically connect smooth muscle…. Sacroplasmic reticulum stores Ca2+ for SM…
….
What do both SM and endothelial cells have?
Pinocytotic vesicles!
SM is made of mostly thin filaments… actin!
…
Gap junctions have what type of appearance?
Curvy appearance
Basal lamina surrounds muscle cells
…
Thin filaments (actin) for SM are anchored to dense bodies by…
Alpha-actinin
Contraction of SM involves thick filaments (myosin) with pivoting heads.
Heads are oriented in opposite directions
….
SM contraction…
Intracellular Ca2+ increases due to neural stimulation or hormonal signals
Ca2+ via calmodulin activates myosin light chain kinase (MLCK)
Myosin light chain kinase phosphorylates the light chains on myosin, activating them
Myosin light chain phosphatase removes the phosphate from LC to inactivate it
…
In activate state of myosin light chains are coiled.. calcium activates them and uncoils them.
…
Voltage gated Ca2+ channel in membrane opens when SM is stimulated - this leads to an increase in intracellular Ca2+, which opens ligand gated Ca2+ channel in the sacroplasmic reticulum.
hormones (oxytocin) can bind to receptors, and through G-proteins and Ip3, cause ca2+ channel to open in the sacroplasmic reticulum
…
There are also mechanically gated ion channels that stimulate smooth muscle when stretched.
..
After SM stimulation ceases, ATPase pumps remove Ca2+ from the sacroplasm
…
Smooth muscle cells twist when contracted. Smooth muscle cells contract slowly, and use less energy (than skeletal and cardiac muscle).
Myosin heads can lock onto actin filaments, allowing muscle to maintain contracted state… this is called?
Latch-state!
Contraction tension for smooth muscle is not….
Length dependent!
So smooth muscle can contract even when stretched (actually, stretching stimulates reflex contraction) - this is important for the uterus that is very stretch when pregant
In multisubunit smooth muscle…
Each cell receives a synapse
This provides fine control (e.g. The iris)
In unitary (visceral) smooth muscle…
Only a few receive synapses and adjacent cells are excited through gap junctions or neurotransmitter baths smooth muscle cells.
This provides larger functional unit (bladder, intestine)
Two circulatory systems.. those are?
Vascular and lymphatic
Blood vessels have three components…
Tunica intima (TI) - which is endothelial cells and loose CT
Tunica media (TM) - mostly smooth muscle
Tunica Adventitia (TA) - dense irregular CT
Tunica media has smooth muscle and in between is elastic CT!
..
Look at EM of blood vessels
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Vasodilation occurs via relaxation of smooth muscles
..
Vasoconstriction occurs via contraction of smooth muscles
…
SM is blood vessels is always somewhat contracted….
Nitric oxide causes vasodilation
Clotting factors (thromboxane) causes contraction of blood vessels
..
Capillaries are everywhere, forming an _______ network
Anastomosing
Capillaries are composed of
Endothelial and basement membrane
Endothelial cells oriented longitudinally in capillaries - nucleus bulges - so it looks irregular
…
Continuous capillaries
Least permeable, endothelial cells have tight junctions with no fenestrae
Fenestrated capillaries
More permeable, endothelial cells have tight junctions but have fenestrae within the cells!!!
Find this in endocrine organs and intestinal tract
Capillaries have pinocytotic vesicles
…
Von Willebrand Factor is released from the endothelium and binds to platelet receptors causing adhesion of the platelets to exposed collagen fibers. As the platelets adhere to the collagen fibers on the damaged vessel wall, they become activated and release ADP and TXA2. The ADP and TXA2 attract additional platelets and lead to their aggregation
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Activated platelets have protrusions that enmesh them together
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What is the goal of the coagulation cascade?
Create fibrin glue to support plug until the endothelium and extracellular matrix remodel
