corrected powerpoint with practice questions is up on Sharepoint
p. 249. with increased preload (EDV) ejcection fraction will always increase. Lecturer mis-spoke when he said it may not change. Thanks to student for correcting this. Example:
starting EF = SV/EDV = 50/100 50%. If EDV increases by 20, EF = 70/120 = 58%.
Most books only consider the left ventricle PV loop but it is important to consider the differences between the left and right ventricles. Below is a PV loop for the right ventricle:
Notice how much less work the RV does in stroke work and that the work of the RV is mainly volume work. The isovolumic contraction and relaxation periods are not pronounced in the RV.
humans have receptors in the circulatory system for pressure (carotid and aortic bodies; cranial nerves IX and X are afferents), volume (chambers of the heart, vena cava, pulm. artery). Volume increase is corrected by SNS and by chambers release of peptide that stimulates sodium secretion by kidneys. ANP is from atrial myocytes. BNP is from ventricular myocytes (called "brain" because it was first isolated from pig brains. In humans, it is produced primarily by the ventricle). BNP pretty good marker for CHF. Volume decrease inhibits above and may trigger thirst receptors via angiotensin II to also help increase volume.
summary figure for renin-angiotensin-aldosterone system (RAAS)
p. 285 beta agonists cause contraction of cardiac muscle but relaxation of smooth muscle. same signal transduction pathway at membrane. In both types of cells cAMP is increased and PKA is activated and intracellular Ca++ is increased. In cardiac muscle this leads to contraction via Troponin C mechanism. Smooth muscle doesn't have Troponin and increased PKA acts to inhibit MLCK and activate MLCP causing relaxation.
http://www.cvphysiology.com/Blood%20Pressure/BP026.htm
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