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Blood Flow in the Brain, Lungs, and Heart (Nursing)

by Jasmine Clark

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    00:01 So now let's look at blood flow to special areas in the body.

    00:05 Starting with the brain.

    00:07 Blood flow to the brain must be constant because neurons are intolerant to ischemia, which causes a short of blood and therefore, oxygen coming to the brain.

    00:20 Blood flow to the brain average is about 750 mL/min.

    00:28 The way we control blood flow to the brain is through metabolic controls.

    00:33 So when there is a decreased pH or an increase in the amount of carbon dioxide, we are going to have a marked vasodilation.

    00:43 Very high carbon dioxide levels will depress autoregulatory mechanisms.

    00:51 The brain is very vulnerable under extreme systemic pressure changes.

    00:56 A main arterial pressure of less than 60 mm Hg can lead to syncope or fainting.

    01:04 A mean arterial pressure of greater than 160 mm Hg can result in cerebral edema or swelling of the brain.

    01:15 So now let's look at blood flow to the lungs.

    01:18 To do this, we look at our pulmonary circuit, which is an unusual circuit as the pathway is very short.

    01:25 The arteries and arterioles of pulmonary circuit are going to look more like our veins and venules with thin walls and large lumens.

    01:36 The arterial resistance and pressure in our pulmonary circuit is actually much lower than what we find in our systemic circuit.

    01:45 And this average is about 24/10 mm Hg versus the 120/80 mm Hg that we see in the rest of the body.

    01:57 The autoregulatory mechanisms in the lungs are also opposite of what we see in the body.

    02:03 In the lungs, low oxygen levels actually cause vasoconstriction and high levels promote phase o dilation.

    02:12 This allows for blood to flow to areas that are oxygen-rich and away from areas that have inadequate oxygen supply.

    02:23 When we look at blood flow to the heart, this is going to be influenced by aortic pressures and ventricular pumping.

    02:31 During ventricular systole, our coronary vessels are going to be compressed.

    02:38 Our myocardial blood flow is going to cease and stored myoglobin is going to supply sufficient oxygen.

    02:46 During diastole, our high aortic pressure forces blood through the coronary circulation.

    02:54 At rest, our coronary blood flows at about 250 mL/min.

    03:00 And as controlled by way of myogenic mechanisms.

    03:04 So during strenuous exercise, our coronary vessels are going to dilate in response to the local accumulation of vasodialators.

    03:14 Blood flow is going to increase to about three to four times.

    03:18 And this is going to be important because our cardiac cells use about 60% of the oxygen that are delivered to them.

    03:27 Other cells in our body only use about 25% of the oxygen delivered to them.

    03:33 So increasing our coronary blood flow as a way to provide more oxygen to those coronary cells, especially during strenuous exercise.


    About the Lecture

    The lecture Blood Flow in the Brain, Lungs, and Heart (Nursing) by Jasmine Clark is from the course Cardiovascular System: Blood Vessels – Physiology (Nursing).


    Included Quiz Questions

    1. Marked vasodilation
    2. Marked vasoconstriction
    3. Increased blood pressure
    4. Decreased blood flow

    Author of lecture Blood Flow in the Brain, Lungs, and Heart (Nursing)

     Jasmine Clark

    Jasmine Clark


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