Regulation of the Cardiovascular System

Question 1

PKA mediated phosphorylation of phospholambam

Answer 1

relieves inhibition of SERCA, thus faster Ca2++ reuptake into SR.

Increases lusitropy, increases inotropy

Question 2

PLA mediated phosphorylation of ryanodine receptors

Answer 2

phosphorylation increases calcium sensitivity

increases inotropy by increasing Ca++ release from SR

Question 3

PKA-mediated phosphorylation of L-type calcium channels

Answer 3

slows inactivation, increases entry of trigger Ca++

Increased Ca++ induced Ca++ release increases inotropy

Question 4

PKA-mediated phosphorylation of Troponin I

Answer 4

phosphorylated Troponin I decreases calcium sensitivity of troponin C. Allows faster dissociation of Ca++ so faster filling, increased lusitropy

Question 5

The shit is lusitropy

Answer 5

myocardiac relaxation

Question 6

Sympathetic control of heart rate (HCN’s and L-type Calcium channels)

Answer 6

HCN’s - net inward current (funny current.) Promotes excitability and spontaneous action potential. Activity increased by cAMP binding.

L-type Ca++ channels - net inward current, promotes excitability and spontaneous action potentials. Increased trigger Ca++ from L-type Ca++ channels activates more calcium release from the SR with Ryr receptors -> Ca++ sensitivity of Ryr increased by PKA phophorylation

Question 7

Parasympathetic control of heart rate (GIRK channels)

Answer 7

GIRK channels - activation of the acetylcholine potassium current stabilizes Vm near K+ equilibrium potential. Increased outward K+ current decreases excitability. PRIMARY METHOD OF PARASYMPATHETIC CONTROL OF THE HEART.

Gi through muscarinic receptors, inhibits adenylate cyclase activity, less cAMP, less HCN channels, L-type Ca++ channels.