106 cardiac cycle systole isovolumic valves are closed

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: all of the right atria and from here the AP travels thru both atria to the AV bundle and into the ventricals. 7 Initiation in the atria allows it to pump blood into the ventrical before the strong vetricular contraction and the atria is therefore known as a primer pump AV node may act as the pace maker in the abscence of a fxning SA node Overdrive Suppression •  If you drive a self-excitatory cell at a rate faster than its own inherent rate, you will suppress the cell s own automaticity –  Mechanism may be due to increased activity of Na+/K+ pump creating more negative Er –  Cells of the AV node and purkinje system are under overdrive suppression by the SA node AV node •  Delays the wave of depolarization from entering the ventricle –  allows the atria to contract slightly ahead of the ventricles (.1 sec delay) •  Slow conduction velocity due to smaller diameter fibers •  In absence of SA node, AV node may act as pacemaker but at a slower rate Heart fills with blood during diastole Effect of HR on systole/diastole •  As heart rate (HR) ↑ cycle length (CL) ↓ •  At a resting heart rate systole (S) < diastole (D) •  Both the duration of systole and diastole shorten, but diastole shortens to a greater extent –  At high HR the ventricle may not fill adequately P. 106 Cardiac Cycle •  Systole Isovolumic = valves are closed –  isovolumic contraction –  ejection Mitral are closed and aortic are open •  HR of 75 BPM; CL = .8 sec. S = .3 D = .5 •  HR of 150 BPM; CL = .4 sec. S = .2 D = .2 •  During systole perfusion of the myocardium is restricted by the contracting cardiac muscle compressing blood vessels (especially in LV) Cycle systole= contraction - ejection Diastole = relaxation Coronary flow in left ventricle peaks at onset of diastole •  Diastole Enters diastole phase after relaxation (contraction) –  isovolumic relaxation –  rapid inflow- 70-75% –  diastasis –  atrial systole- 25-30% relaxation Mitral and tricusoid are open Aortic and pulmonary are closed during diastole phase Both valves are closed at both the onset of contraction and onset of 106 106 Onset of Ventricular Contraction •  Isovolumic contraction –  Tricuspid & Mitral valves close •  as ventricular pressure rises above atrial pressure Ejection of blood from ventricles •  Most of blood ejected in first 1/2 of phase •  ventricular pressure peaks and starts to fall off •  ejection is terminated by closure of the semilunar valves (pulmonic & aortic) –  Pulmonic & Aortic valves open •  as ventricular pressure rises above pulmonic & aortic artery pressure During isovolumic contraction there is no emptying as pressure builds in the ventricals During isovolumic relaxation the intraventricular pressure decreases rapidly As pressure builds in the arteries the blood tries to get back into the ventricals but the aortic and pulmonary valves close quickly 8 Ventricular Relaxation •  Isovolumetric (isometric) relaxation-As the ventricular wall relaxes, ventricular pressure (P) falls; the aortic and pulmonic valves close as the ventricular P falls below aortic and pulmonic artery P •  Rapid inflow-When ventricular P falls below atrial...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern