Heart failure - Smooth muscle cells and vascular tone

13 important questions on Heart failure - Smooth muscle cells and vascular tone

What is the difference in contractile unit between skeletal and smooth muscles?

Bipolar vs side polar

How is contraction regulated in VSM cells?

1. Calcium enters the cell and is released from SR stores
2. Calcium binds to calmodulin
3. Ca-CaM activates myosin light chain kinase (MLCK)
4. MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity
5. Active myosin crossbridges slide along actin and create muscle tension

What is the difference between contractile and synthetic VSM cells?

Rhomboid shape vs spindle shape. Synthetic VSM cells play a role in atherosclerosis, pregnancy, arterial injury and restenosis (narrowing of bv).
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In which processes are synthetic VSM cells involved?

Embryogenesis, angiogenesis and atherogenesis

In which processes are contractile VSM cells involved?

Regulation of vascular tone and BP

What is the difference between electromechanical and pharmacomechanical coupling?

Electro = membrane depolarization
pharmaco = contraction initiated by receptor binding

What is the pathway of depolarization dependent contraction in VSM? And in which vessels?

Small arteries and arterioles (resistance vessels)
-> increase conductance L type calcium channels by binding of noradrenaline to adrenergic receptor -> PLCß activated > IP3 and DAG > calcium channels open > voltage gated calcium channels open > increased cytosolic calcium > MLCK activation > contraction

What is the pathway of depolarization-independent contraction in VSM? And in which vessels?

Large arteries (conductance vessels) = no (activation) of L type calcium channels

noradrenalin binds to adrenergic receptor > PLCß activation > IP3 and DAG > calcium influx and from SR > increased cytosolic calcium > MLCK activation > contraction
also PKC activation > calcium sensitization and activation rhoA kinase

Difference phasic vs tonic contraction in VSM cells?

Phasic = contraction remains for short time
Tonic = contraction remains due to calcium sensitization (force maintenance)

What is the Rho/ROCK signaling pathway?

Pathway that leads to ROCK formation, which phosphorylates MLCP (phosphatases). This makes MLCP inactive and thus light chains are not dephosphorylated and thus remain contracted

How is the VSM relaxed?

By ß2 adrenergic receptor that is activated by adrenaline. This receptor is Gs > adenylyl cyclase > cAMP > PKA activation > calcium expulsion and sequestration & inhibition of MLCK > decrease in calcium and calcium sensitivity > relaxation

How is penile flaccidity achieved

Binding to receptors that cause contraction of bv > no accumulation of blood

How is penile erection achieved?

Relaxatino of the bv which fills the sinuses (corpus cavenosum)

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