CV Basics and Myocardium Flashcards
1
Q
Hypocalcemia
A
prolongues duration of contraction
lengthens QT interval
2
Q
Hypercalcemia
A
reduces duration of contraction
shortens QT interval
3
Q
Digoxin
A
cardiac glycoside (drug): positive inotropic effect
also, vagmimetic: slows SA and AV node condution; sensitives baroreceptors
inhibits Na+/K+ ATPase:
within cardiomyocytes, this results in increased intracellular Na+ –>
which impedes
4
Q
Axis Deviation
A
Average: 50-60 degrees
RAD: >100 degrees
LAD: (-30) to (-90) degrees
- Numerous causes*: increase in ventricular muscle mass and/or actual shift in anatomic oritentaiton of the heart
- More common causes*: ventricular hypertrophy; pregnancy
5
Q
Cardiac Cycle
(The normal cardiac cycle, showing pressure relationships between the left-sided heart chambers.)
A
- During diastole, the mitral valve (MV) is open, so that the left atrial (LA) and left ventricular (LV) pressures are equal.
- In late diastole, LA contraction causes a small rise in pressure in both the LAand LV(the a wave).
- During systolic contraction, the LVpressure rises; when it exceeds the LApressure, the MVcloses,contributingtothe rstheartsound (S1).
- As LVpressure rises above the aortic pressure, the aortic valve (AV) opens, which is a silent event.
- As the ventricle begins to relax and its pressure alls below that o the aorta, the AVcloses, contributing to the second heart sound (S2).
- As LVpressure alls urther, below that o the LA, the MV opens, which is silent in the normal heart.
- In addition to the a wave, the LApressure curve displays two other positive def ections: the c wave represents a small rise in LA pressure as the MVcloses and bulges into the atrium, and the v wave is the result o passive lling o the LA rom the pulmonary veins during systole, when the MVis closed.
6
Q
Murmur Ausculatation
A
7
Q
PKA Signaling in Cardia Myocytes
A
Overall effect:
- adrenergic activation of cAMP/PKA signaling cause an increase in the rate of cardiac pumping by causing changes in the intracellular Ca2+ –> contraction / relaxation respective to set threshold
- NB: cholinergic M2 receptor blocks the activation of adenylyl cyclase, impairing prod of cAMP
- ACh interrupts activation of L channels/slow cardiac muscle contracility
Triple Response
- type L channels are activated
- phospholamban is phosphorylated by PKA –> stimulates SERCA –>Rapid resequestering of Ca2+ into SR
- Troponin I phosphorylation: reduced affinity of troponin C for Ca2+
- Toponin C is activated in presense of elevated sarcoplamic [Ca2+], binds to Ca2+ –> conformational change in troponin-tropomyosin complex –>reveals myosin active binding site within actin
8
Q
Couple ECG and P-V plot
A
9
Q
Cardiac cycle and changes in LV V & LV P and ECG
A
