Blood Flow, Blood Pressure, and Resistance | Anatomy & Physiology
() Acetaminophen increases blood pressure in patients with coronary artery disease. population and their correlation with systemic vascular resistance. Blood pressure may be measured in capillaries and veins, as well as the vessels of the pulmonary . In the venous system, the opposite relationship is true. Arterial hypertension is the result of abnormal flow/resistance relationships. Resistance to outflow consists of different components: the systolic component is the.
So I'm going to draw that as blue. That's the part where now the blood is without oxygen. And then it continues to go and get collected into a venule, which sounds a little bit like the arterial on the other side, right? And we've got a vein over here. And then finally, the blood gets collected in a large vein called the vena cava. And there are actually two vena cavas, so this'll be the superior vena cava.
There's also an inferior vena cava. And the blood flow through this half is, as you would guess, continues to go around. And if I was to try to figure out the pressures, the blood pressures, at different points along the system, I'm going to choose some points that I think would be interesting ones to check.
So it would be good probably to check what the pressure is right at the beginning. And then maybe at all the branch points. So what the pressure is as the blood goes from the aorta to the brachial artery. Maybe as it ends the brachial artery and enters the arterial.
Maybe the beginning and the end of the capillaries. Also from the venue to a vein, and also, wrapping it up, what the pressure is at the end. Now, these numbers, or these pressures, can be represented as numbers, right? Like what is the millimeters of mercury that the blood is exerting on the wall at that particular point in the system?
And earlier, we talked about systolic versus diastolic pressure, and there we wanted to use two numbers, because that's kind of the range, the upper and the lower range of pressure. But now I'm going to do it with one number. And the reason I'm using one number instead of two, is that this is the average pressure over time. So the average pressure over time, for me-- keep in mind my blood pressure is pretty normal.
It's somewhere around over 80 in my arm. So the average pressure in the aorta kind of coming out would be somewhere around 95, and in the artery in the arm, probably somewhere around Again, that's what you would expect-- somewhere between 80 and So 90 is the average, because it's going to be not exactlybecause remember, it's spending more time in diastole and relaxation than in systole.
So it's going to be closer to 80 for that reason. And then if you check the pressure over here by this x, it'd probably be something like, let's say And then as you cross the arterial, the pressure falls dramatically.
So it's somewhere closer to And then here it's about Here it's about Let's say 10 over here. And then at the very end, it's going to be close to a 5 or so. Let me just write that again.
And the units here are millimeters of mercury. So I should just write that. Pressure in millimeters of mercury. That's the units that we're talking about. So the pressure falls dramatically, right? So from 95 all the way to five, and the heart is a pump, so it's going to instill a lot of pressure in that blood again and pump it around and around. And that's what keeps the blood flowing in one direction.
So now let me ask you a question. Let's see if we can figure this out. Let's see if we can figure out what the resistance is in all of the vessels in our body combined. So we talked about resistance before, but now I want to pose this question.
See if we can figure it out. So what is total body resistance? And that's really the key question I want to try to figure out with you. We know that there is some relationship between radius and resistance, and we talked about vessels and tubes and things like that.
But let's really figure this out and make this a little bit more intuitive for us. So to do that, let's start with an equation. And this equation is really going to walk us through this puzzle.
So we've got pressure, P, equals Q times R. Really easy to remember, because the letters follow each other in the alphabet.
And here actually, instead of P, let me put delta P, which is really change in pressure. So this is change in pressure. And a little doodle that I always keep in my mind to remember what the heck that means is if you have a little tube, the pressure at the beginning-- let me say start; S is for start-- and the pressure at the end can be subtracted from one another. The change in pressure is really the change from one part of tube the end of the tube. And that's the first part of the equation.
So next we've got Q. So what is Q? This is flow, and more specifically it's blood flow. And this can be thought of in terms of a volume of blood over time. So let's say minutes. So how much volume-- how many liters of blood are flowing in a minute?
Or whatever number of minutes you decide? And that's kind of a hard thing to figure out actually. But what we can figure out is that Q, the flow, will equal the stroke volume, and I'll tell you what this is just after I write it. The stroke volume times the heart rate.
So what that means is that basically, if you can know how much blood is in each heartbeat-- so if you know the volume per heartbeat-- and if you know how many beats there are per minute, then you can actually figure out the volume per minute, right? With each heartbeat, blood is sent throughout the body, carrying oxygen and nutrients to all the cells in body.
Putting it all together: Pressure, flow, and resistance (video) | Khan Academy
The cardiac cycle is the sequence of events that occurs when the heart beats. Blood pressure is maximum during systole, when the heart is pushing and minimum during diastole, when the heart is relaxed. Vasodilation caused by relaxation of smooth muscle cells in arteries causes an increase in blood flow.
When blood vessels dilate, the blood flow is increased due to a decrease in vascular resistance. Therefore, dilation of arteries and arterioles leads to an immediate decrease in arterial blood pressure and heart rate.
- Pressure and Blood Flow
- Putting it all together: Pressure, flow, and resistance
- Arterial Blood Pressure
Cardiac output is the amount of blood ejected by the left ventricle in one minute. Cardiac output CO is the volume of blood being pumped by the heart, by left ventricle in the time interval of one minute. The effects of vasodilation, how the blood quantity increases and decreases along with the blood flow and the arterial blood flow and resistance on cardiac output is discussed in this review Article.
Keywords Heart; Cardiac cycle; Arteries; Blood flow; Vasodilation; Arterial Resistance; Cardiac output Introduction The circulatory system is composed of the heart and blood vesselsincluding arteries, veins, and capillaries [ 12 ].
Arteries and Veins play an important role in blood circulation along with heart [ 3 ]. The heart is the key organ in the circulatory system [ 4 ]. As a hollow, muscular pump, its main function is to propel blood throughout the body. It usually beats from 60 to times per minute, but can go much faster when necessary. It beats abouttimes a day, more than 30 million times per year, and about 2. With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to every cell.
Blood pressure, blood flow, and resistance
Each day, 2, gallons of blood travel many times through about 60, miles of blood vessels that branch and cross, linking the cells of our organs and body parts. Heart collects the deoxygenated blood from the body and pushes it to the lungs where it becomes oxygenated, and then heart pumps the oxygen rich blood to the body.
Normal functioning of heart is very important to lead a healthy life [ 5 ]. Vasodilation is widening of blood vessels caused by relaxation of smooth muscle cells in the vessel walls particularly in the large arteriessmaller arterioles and large veins thus causing an increase in blood flow [ 6 ].
Arterial dilation leads to an immediate decrease in arterial blood pressure and heart rate [ 7 ]. The relationship between mean arterial pressure, cardiac output and total peripheral resistance TPR gets affected by Vasodilation. The amount of blood that is put out by the left ventricle of the heart in one contraction is called the stroke volume. Numerous cardiovascular afflictions are currently known to be associated with heart including aortic root dilation, aortic regurgitation, mitral regurgitation, myocarditis, heart failure, pericarditis, pericardial effusion [ 8 - 10 ].
Sudden deaths due to cardiac arrest, cardiac stroke, atrioventricular conduction block, and heart failure are reported worldwide [ 11 - 13 ]. Various animals like mouse were used to detect the heart disease [ 14 ]. Cardiovascular disease is one of the most frequent causes of death of women in the world [ 15 - 17 ].
Stroke is the major healthcare problem with higher mortality and morbidity rates [ 18 ].
[Systolic, diastolic and pulse pressure: pathophysiology].
Women are more affected with Atherosclerosis [ 19 ]. At times increase in blood pressure may leads to various kinds of health problems [ 2021 ]. Heart failure patients are at increased risk of sudden death due to ventricular problems [ 22 - 24 ]. Diabetes Mellitus DM is also a main risk factor for heart failure [ 25 - 27 ]. Most of the cardiovascular emergencies are caused by coronary artery disease [ 2829 ].
Echocardiography is the modality of choice for investigation of suspected congenital or acquired heart disease [ 30 - 32 ] Suspected heart disorders and related heart diseases can be investigated using Echocardiogram [ 33 - 35 ].
The frequency of the cardiac cycle is described by the heart rate [ 36 ]. There are two phases of the cardiac cycle. The heart ventricles are relaxed and the heart fills with blood in diastole phase [ 37 ]. The ventricles contract and pump blood to the arteries in systole phase [ 38 ]. When the heart fills with blood and the blood is pumped out of the heart one cardiac cycle gets complete.
The events of the cardiac cycle explains how the blood enters the heart, is pumped to the lungs, again travels back to the heart and is pumped out to the rest of the body [ 39 ]. The important thing to be observed is that the events that occur in the first and second diastole and systole phases actually happen at the same time [ 40 ].
During this first diastole phase, the atrioventricular valves are open and the atria and ventricles are relaxed. From the superior and inferior vena cavae the de-oxygenated blood flows in to the right atrium. The atrioventricular valves which are opened allow the blood to pass through to the ventricles [ 41 ]. The Sino Atrial SA node contracts and also triggers the atria to contract.
The contents of the right atrium get emptied into the right ventricle.
During this first systole phase, the right ventricle contracts as it receives impulses from the Purkinje fibers [ 42 ]. The semi lunar valves get opened and the atrioventricular valves get closed. The de-oxygenated blood is pumped into the pulmonary artery. The back flow of blood in to the right ventricle is prevented by pulmonary valve [ 43 ].
The blood is carried by pulmonary artery to the lungs. There the blood picks up the oxygen and is returned to the left atrium of the heart by the pulmonary veins [ 44 ]. In the next diastolic phase, the atrioventricular valves get opened and the semi lunar valves get closed.
The left atrium gets filled by blood from the pulmonary veins, simultaneously Blood from the vena cava is also filling the right atrium. The Sino Atrial SA node contracts again triggering the atria to contract. The contents from the left atrium were into the left ventricle [ 45 ]. During the following systolic phase, the semi lunar valves get open and atrioventricular valves get closed.
The left ventricle contracts, as it receives impulses from the Purkinje fibers [ 47 ]. Oxygenated blood is pumped into the aorta. The prevention of oxygenated blood from flowing back into the left ventricle is done by the aortic valve.
Aortic and mitral valves are important as they are highly important for the normal function of heart [ 48 ]. The aorta branches out and provides oxygenated blood to all parts of the body. The oxygen depleted blood is returned to the heart via the vena cavae. Left Ventricular pressure or volume overload hypertrophy LVH leads to LV remodeling the first step toward heart failure, causing impairment of both diastolic and systolic function [ 4950 ].
Coronary heart disease [CHD] is a global health problem that affects all ethnic groups involving various risk factors [ 5152 ].