I get that your heart can pump harder and whatnot, but when it’s a fairly closed system pumping the same blood around how does that actually increase the pressure?
In: 12
Your veins are able to contract, this is called hypertension. When enough of the veins contract it leaves less volume for the blood, but like you said the blood isn’t going anywhere, so it pushes against the arterial walls in a measurable way.
Your vessels expand and contract as well. The same amount of flow in a smaller area produces a higher pressure.
Take a standard straw. Have two glasses filled equally, one with water and the other with a milk shake that won’t pour out if held upside down.
Now attempt to drink both with the same force.
In the body, you don’t have significant changes in blood thickness. But there are medicines which act primarily to thin the blood.
The more approximate test would be to have one straw that is clean and another that has gunk all over the inside, then try to drink a mostly melted shake. But I can’t think of an easy way to gunk up the sides of a straw that isn’t gross.
It is like current in an electrical circuit. The volume of blood your heart pumps per minute equals the current ( Amps), your vessels, mostly small segments of arteries before the tissue can contract or relax. This is the resistance(Ohms). The higher the resistance of your vessels, the more pressure is needed to press the blood through for any given volume. The more blood your heart pumps, the higher is the pressure at a given resistance. Blood pressure equals Voltage. U=R x I.
The veins don’t play that much of a role in blood pressure, it’s a more indirect factor as the veins regulate how fast the blood is returned to the heart after passing the tissue. They’re more like a reservoir feeding the pumping heart with the blood needed. Most of your blood, about 80%, is stored in the veins.
Relatively fixed amount of blood, but dynamic size of pipes since blood vessels are not fixed dimensions. Tighter blood vessels equates to high blood pressure.
I don’t know that I would call it “constantly” changing. It does pulse from the pumping of the heart, which is why blood pressure has two numbers, the first being the high-pressure mode when the blood is shoved through the system by a heart contraction, and the second being the pressure in the “relaxed”/heart chamber refilling mode, but if you aren’t changing your state (don’t jump up and start running after sitting down a while, or something), the pressure pattern stays pretty constant.
We have some voluntary control and a lot of involuntary control on the compression of the veins (which are not rigid like glass but more like a rubbery hose) so overall system pressure can be modified by changes in how much the body presses on the veins (like how you can squeeze your neck muscles and make your face turn red because you increased pressure and slowed flow). FLow can be constricted a bit and since the volume of blood flow is “constant” (as per the heart pumping process if heart rate stays unchanged), the pressure rises if space is constricted, speeding up the flow through the system where constricted, usually. Similar pressure changes can happen if the heart increases its rate of pumping, of course.
And of course the blood itself is a viscous liquid so it can change viscosity (resistance to flow) depending on lots of things but mostly chemistry (it is a mix of solids like cells and solution or salty water, in effect), and cause the pressure to change depending on how hard the liquid is resisting its push by the heart.
I think it is important to note, or remember, that the vein system itself is somewhat flexible so the veins do expand and contract a bit in response to pressure during pumping by the heart. Things can happen to the vessels though, over time, and make the vessels a lot less flexible, or even constrict them (arteriosclerosis, hard deposits on the vessels which block flow over time) and thus make pressure increase overall, because vessels can’t expand in response to heart pulses (never mind the parts where the actual open space fills in by plaque or whatever).
Think of your blood vessels being a flexible container, like a water balloon. Your veins expand and contract. Squeeze too much and they reduce the size of the container, making the pressure go up.
I get that your heart can pump harder and whatnot, but when it’s a fairly closed system pumping the same blood around how does that actually increase the pressure?
In: 12
Your veins are able to contract, this is called hypertension. When enough of the veins contract it leaves less volume for the blood, but like you said the blood isn’t going anywhere, so it pushes against the arterial walls in a measurable way.
Your vessels expand and contract as well. The same amount of flow in a smaller area produces a higher pressure.
Take a standard straw. Have two glasses filled equally, one with water and the other with a milk shake that won’t pour out if held upside down.
Now attempt to drink both with the same force.
In the body, you don’t have significant changes in blood thickness. But there are medicines which act primarily to thin the blood.
The more approximate test would be to have one straw that is clean and another that has gunk all over the inside, then try to drink a mostly melted shake. But I can’t think of an easy way to gunk up the sides of a straw that isn’t gross.
It is like current in an electrical circuit. The volume of blood your heart pumps per minute equals the current ( Amps), your vessels, mostly small segments of arteries before the tissue can contract or relax. This is the resistance(Ohms). The higher the resistance of your vessels, the more pressure is needed to press the blood through for any given volume. The more blood your heart pumps, the higher is the pressure at a given resistance. Blood pressure equals Voltage. U=R x I.
The veins don’t play that much of a role in blood pressure, it’s a more indirect factor as the veins regulate how fast the blood is returned to the heart after passing the tissue. They’re more like a reservoir feeding the pumping heart with the blood needed. Most of your blood, about 80%, is stored in the veins.
Relatively fixed amount of blood, but dynamic size of pipes since blood vessels are not fixed dimensions. Tighter blood vessels equates to high blood pressure.
I don’t know that I would call it “constantly” changing. It does pulse from the pumping of the heart, which is why blood pressure has two numbers, the first being the high-pressure mode when the blood is shoved through the system by a heart contraction, and the second being the pressure in the “relaxed”/heart chamber refilling mode, but if you aren’t changing your state (don’t jump up and start running after sitting down a while, or something), the pressure pattern stays pretty constant.
We have some voluntary control and a lot of involuntary control on the compression of the veins (which are not rigid like glass but more like a rubbery hose) so overall system pressure can be modified by changes in how much the body presses on the veins (like how you can squeeze your neck muscles and make your face turn red because you increased pressure and slowed flow). FLow can be constricted a bit and since the volume of blood flow is “constant” (as per the heart pumping process if heart rate stays unchanged), the pressure rises if space is constricted, speeding up the flow through the system where constricted, usually. Similar pressure changes can happen if the heart increases its rate of pumping, of course.
And of course the blood itself is a viscous liquid so it can change viscosity (resistance to flow) depending on lots of things but mostly chemistry (it is a mix of solids like cells and solution or salty water, in effect), and cause the pressure to change depending on how hard the liquid is resisting its push by the heart.
I think it is important to note, or remember, that the vein system itself is somewhat flexible so the veins do expand and contract a bit in response to pressure during pumping by the heart. Things can happen to the vessels though, over time, and make the vessels a lot less flexible, or even constrict them (arteriosclerosis, hard deposits on the vessels which block flow over time) and thus make pressure increase overall, because vessels can’t expand in response to heart pulses (never mind the parts where the actual open space fills in by plaque or whatever).
Think of your blood vessels being a flexible container, like a water balloon. Your veins expand and contract. Squeeze too much and they reduce the size of the container, making the pressure go up.
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