In this video, we're going to continue our lesson on hemodynamics as we focus in on the relationship between blood flow, blood pressure, and resistance. Recall from our last lesson video that blood flow refers to the total volume of blood flowing through any particular point in the cardiovascular system in a given time period, and it's usually expressed in units of milliliters per minute. Blood flow can be symbolized with the capital letter f, which is why we have the f bolded here. Blood flow or f is actually directly driven by a blood pressure gradient or a difference in the blood pressure between two points in the cardiovascular system. Recall from our last lesson video that blood pressure refers to the force that the blood exerts on the walls of the blood vessels, and it's usually expressed in units of millimeters of mercury. The blood pressure gradient can be symbolized as Δp, where the Greek letter delta represents the difference and the letter p represents the blood pressure, which is why we have the p bolded here. The blood pressure gradient is also referred to as the hydrostatic blood pressure.
Again, blood flow or f is directly driven by a blood pressure gradient or Δp, because blood will always flow from areas of high blood pressure toward areas of low blood pressure. However, it's important to note that blood flow, or f, is impacted not only by the blood pressure gradient or Δp but also by the resistance, which refers to any opposition to blood flow, or in other words, how difficult it is for blood to flow through the cardiovascular system. The greater the resistance, the harder it is for blood to flow through. Resistance is symbolized with the capital letter r.
It's essential to understand that these three variables, blood flow or f, blood pressure gradient or Δp, and resistance or r, are interconnected, and changing any one of these variables can impact the others. Blood flow or f is directly proportional to the blood pressure gradient or Δp, which means that the greater the Δp, the greater the blood flow will be. Conversely, blood flow or f is inversely proportional to resistance or r, which means that the greater the value of r, the lower the blood flow will be. Referring to our equation: f = Δp r
If you increase the value of Δp, it will lead to an increase in the blood flow. Conversely, increasing the resistance will decrease the value of the blood flow. This equation shows that blood flow and resistance are inversely proportional with each other.
We can algebraically rearrange this equation to isolate any one of these variables. To isolate the resistance, multiply both sides of the equation by r and divide both sides of the equation by f, resulting in: r = Δp f
To isolate Δp, multiply both sides of the equation by resistance, and you get: Δp = f ⋅ r
This concludes our lesson on the relationship between blood flow, blood pressure gradient, and resistance. We'll be able to get some practice applying these concepts and continue to learn more as we move forward in our course. I'll see you all in our next video.