Systole and Diastole – Cardiac Cycle

by Thad Wilson, PhD

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    00:02 The cardiac cycle.

    00:04 Here in the cardiac cycle, we need to break it down into its two most basic forms – that is systole and diastole.

    00:13 So, in terms of systole, what really are we talking about? We’re talking about what's occurring with ventricular contraction.

    00:20 So, contraction is one of the biggest components of systole.

    00:25 Interestingly, though, also, is the ejection of blood comes along with contraction.

    00:31 So, the majority of the time, during the ejection phase of the blood, there will be within systole.

    00:40 However, a little bit of it translates over into diastole.

    00:46 There is a relaxation phase that transitions between systole and diastole.

    00:52 So, what do I mean by relaxation? It is the muscles themselves – cardiac muscle – that is relaxing.

    01:00 So, it's interesting to think about, even when the muscle is relaxing a little bit, you still could be in systole, i.e. pushing blood out because blood being pushed out of the left ventricle is simply a matter of the pressure differential.

    01:16 The other times in which you are in diastole are during the filling phases.

    01:21 And you notice we have some numbers attached to things like ejection and filling.

    01:27 That is because there's a rapid and a reduced ejection and a rapid and a reduced filling.

    01:35 So, all of those kind of items come out when we look at the cardiac cycle.

    About the Lecture

    The lecture Systole and Diastole – Cardiac Cycle by Thad Wilson, PhD is from the course Cardiac Physiology.

    Included Quiz Questions

    1. Active relaxation
    2. Ventricular filling
    3. Ventricular ejection
    4. Active contraction
    5. Ventricular ejection & Active contraction
    1. Systole is the contraction phase and diastole is the relaxation phase.
    2. Diastole is the contraction phaseand systole is the relaxation phase.
    3. Both the contraction and relaxation phaseare termed as diastole.
    4. Systole is exclusively the contraction of atria.
    5. Both the contraction and relaxation phaseare termed as systole.

    Author of lecture Systole and Diastole – Cardiac Cycle

     Thad Wilson, PhD

    Thad Wilson, PhD

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    By Sharon M. on 22. February 2018 for Systole and Diastole – Cardiac Cycle

    excellent clear description told easily thanks so much understand a lot more now