Cardiac output in acute stress Flashcards
Factors that influence Ca sensitivity in cardiac muscle
pH, temperature, sarcomere length, contractile protein phosphorylation, caffeine
Increased Ca in myocyte leads to what?
increase in force
Compare phosphorylation by PKC and PKA on TnI
PKC decreases velocity and PKA increases velocity
Mechanisms by which the heart moderates its performance throughout the day include:
Length dependent activation (Frank-Starling effects)
Enhanced contractility, chronotropy
What is a plausible cellular basis for Frank Starling relationship?
At longer lengths, the actin and myosin may actually be closer to each other and more cross bridges can form
What impact do positive inotropes have on cardiac muscle?
NE or catecholamines effect heart so that at the same length there is more force
On a cellular level, Beta adrenergic signaling ultiimately results in what?
Activation of PKA which phosphorylates Ca channel, TnI, RyR2 and/or PLB
Response to Phosphorylation of Ca channels
SAN cells
Increased HR and improved CO
Response to Phosphorylation of Ca channels (ventricular cells)
increased Ca entry, increased force of contraction thus improved ejection fraction
Response to phosphorylation of Na pump
increased Ca efflex vis Na/Ca exchanger which enhances relaxation and diastolic filling
Response to phosphorylation of phospholamban
Disinhibition of SR calcium pump (SERCA2) which increases SR calcium load and improves diastolic filling
Response to Phosphorylation of FKB
Enhances Ryr receptor mediated calcium release which enhances contractility
Response to Phosphorylation of troponin I
decreased Ca affinity for TnC and enhanced relaxation
What postural accomodations occur when standing up
Increased venous return from skeletal muscles increases EDV which increases stroke volume
What is isotonic workouts? Isometric?
isotonic= bike/jog/swim/ Isometric= lifting weights
Cardiac changes with isotonic workouts
Peripheral vascular resistance decreases and CO goes up, which increases venous return. Increased HR and increased inotropy
Cardiac changes with isometric workouts
Increased peripheral vascular resistance maintains blood flow to exercising muscle group. Increased HR. NO increase in CO
Cardiac changes during MI
•Loss of functional myocardium, Increased catecholamine surge
(Sweating, tachycardia, ± hypertension), Increased inotropy to maintain CO despite increase BP (afterload), Heterogeneous cellular environment,Local /regional changes in pH, membrane potential and secondary effect on cytosolic calcium
