Smooth Muscle Flashcards
What does smooth muscle not have that skeletal and cardiac do have?
Striations
Power stroke
Movement of the myosin head pulling the actin filament
Microfilaments
beneath apical, form a newtwork inside the cell membrane
Microvilli
increase cell surface area
-supported by microfilaments
-Actin
Microfilaments are a modification of
cytoskeletal proteins found in all cells
-these functions interact with motors to produce movement
Type II Myosin
myosins that form bipolar filaments
-drive contraction in any kind of muscle
-found in all muscles
Cross Bridge Reaction
- ATP hydrolysis occurs on myosin head
- ADP and Pi bind to
- Myosin cross bridge attaches to actin myofilament
- Power stroke occurs
- ADP and Pi release.
- ATP binds with myosin head and causes the release of the myosin head from ATP
Multi-Unit smooth muscle
functions independent
-found in iris, erector pili
-long, tapered and SMALL (less than 2microns across)
-typically embedded in connective tissue
-single nucleus (similar to cardio muscles)
Unitary smooth muslce
-large and found in the gut, vessels
-ions can flow through unimpeded
-singular depolarization spreads RAPIDLY
-contract as one unit
“functional sinsitium (Spelled wrong check”
Dense bodies
anchor for thin filaments
-similar to Z disc in skeletal and cardio muscles
-only seen through electron microscope
Caveolae
“dimples” in the smooth muscle
increase surface area with ECF to allow calcium to enter
Sarcoplasmic Reticulum
Network for calcium
modification of smooth endoplasmic reticulum
-not very developed
Orientation of heads on thick filaments
smooth muscle has heads going in opposite orientation of opposite sides of the thick myosin filament
-Pulls the muscles very short
How much (%) can smooth muscles be shortened
About 80%
-due to myosin heads on both sides
Latch State
When the muscle is already contracted to a certain point, then it stays in the fixed position without expending too much energy.
Rate of contraction for smooth muscle
relatively slow compared to cardiac and skeletal muscle
-peak tension occurs around 2 seconds compared to less than .5seconds (skeletal and cardiac)
Rigor Mortis
caused because ATP is not being produced to cause the myosin head to release from the actin filament
Mechanism of smooth muscle contraction
- Calcium comes into the cell
- CaM binds to calcium to activate MLCK
- MLCK phosphorylates myosin
- Phosphorylated myosin contracts with actin
Mechanism of smooth muscle relaxation
- myosin phosphatase removes phosphate from myosin
- CaM and Calcium unbind
- calcium is sspumped out of the cell
second messenger of smooth muscle
ATP–ADP which phosphorylates proteins (phosphoprotein)
moves into protein phosphatase which removes the phosphate
Kinases
intracellular enzymes that phosphorylate
phosphatase
intracellular enzyme that removes phosphate
Control mechanisms sof Smooth muscle
-neural control
-hormonal control
-mechanical stimulation
-local factors
Neural control
ANS
-sympathetic (fight or flight)
-Parasympathetic (rest and digest)
Hormonal control
noerepinephrine, epinephrine, angiotensin II, vasopressin, oxytocin
mechanical stimulation
stretch
-contraction of GI tract, muscle tone in bladder
Local factors
pH, CO2, O2, NO
neural control of smooth muscle contraction (ANS)
visceral
-gap junction
-larger synapse
Multi-Unit
-autonomic neuron varicosity
varicosities
contain and release neurotransmitters
different patterns of contraction based on
electrical activity of the muscles
smooth muscles around bronchioles
aka bronchiolar smooth muscle
-connects to the aveoli
Bronchiolar smooth muscle receptors
B2: epi/NE (dilators)
mACHr: ACH (constrictors)
B2
agonist
dilators
sympathetic
epinepherine/Norepinephrine
mACHr
constrictor
antagonist
parasympathetic
bronchoconstriction
asthma
smooth muscle constriction
what do smooth muscles do in the cardiovascular sx?
regulate blood flow
moves blood where its needed
Smooth muscle in GI tract
move in gross ways
submucosa helps with movement
