Effect of vasoconstriction and dilation on blood pressure

In summary, vasoconstriction and decreased blood flow have opposite effects on blood pressure, with the former increasing and the latter decreasing it. However, the impact on blood flow due to vasoconstriction is dependent on the velocity and cross-sectional area of the vessel. Additionally, due to the incompressibility of blood, if one site is constricted, the blood must go elsewhere, ultimately returning to the heart. Therefore, blood pressure may not be equal at the site of vasoconstriction compared to an unconstricted site due to factors such as local autoregulation and hormonal control.
  • #1
Jmiz
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One way to regulate blood pressure is through vasoconstriction which in turn increases peripheral resistance, but also decrease the amount of blood that passes through the vessel. These two changes have opposite effects on blood pressure. So is it because the resistance increase effect lead to a greater increase of bP than the effect of having lower volume of blood passing through the constricted vessel, which would in turn decrease bP since less volume lead to less vapor pressure from blood that would act on the vessel walls?

Also since blood flow = velocity times cross area of vessel, what is the impact on blood flow due to vasoconstriction?

Since bP = force exerted on vessel walls by blood, wouldn't bP not be equal at the site of vasoconstriction compared to another unconstricted site?

Thanks
 
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  • #2
If you constrict some veins or arteries, where does the blood go?
 
  • #3
Ultimately, still back to the heart
 
  • #4
Blood is effectively incompressible. If the volume in reduced is some region, it has to go somewhere.
 
  • #5
Jmiz said:
One way to regulate blood pressure is through vasoconstriction which in turn increases peripheral resistance, but also decrease the amount of blood that passes through the vessel. <snip>

There are multiple mechanisms to regulate blood pressure- not just through modulating the peripheral resistance (primarily the arterioles), but also by control over total blood volume. Hormonal control (vasoactive substances) are one mechanism, but there are many including neuronal and local autoregulation. A primary cause of hypertension is increased fluid volume due to excessive resorption of Na in the kidney, which over time leads to increased peripheral resistance.

There are multiple ways to induce high blood pressure: holding blood volume constant and increasing the peripheral resistance, or holding the peripheral resistance constant and increasing blood volume.
 
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What is vasoconstriction and how does it affect blood pressure?

Vasoconstriction is the narrowing of blood vessels, which results in an increase in blood pressure. This occurs when the smooth muscle in the walls of blood vessels contracts, causing the vessels to become narrower and reducing the amount of blood flow through them. This leads to an increase in blood pressure as the heart has to work harder to pump blood through the constricted vessels.

What causes vasoconstriction?

Vasoconstriction can be caused by various factors including hormones, nerve signals, and certain medications. The most common cause is the release of the hormone adrenaline, which triggers vasoconstriction as part of the body's natural "fight or flight" response. Other causes include stress, smoking, and cold temperatures.

How does vasoconstriction affect blood pressure in the short term?

In the short term, vasoconstriction can cause an immediate increase in blood pressure. This is because it reduces the diameter of blood vessels, making it more difficult for blood to flow through them. As a result, the heart has to work harder to pump blood through the constricted vessels, leading to an increase in blood pressure.

What is vasodilation and how does it affect blood pressure?

Vasodilation is the widening of blood vessels, which leads to a decrease in blood pressure. This occurs when the smooth muscle in the walls of blood vessels relaxes, allowing the vessels to become wider and increasing blood flow. As a result, there is less resistance to blood flow, causing a decrease in blood pressure as the heart does not have to work as hard to pump blood through the wider vessels.

What causes vasodilation?

Vasodilation can be triggered by various factors including hormones, nerve signals, and certain medications. The most common cause is the release of nitric oxide, which is a chemical that signals the blood vessels to relax and widen. Other causes include physical activity, heat, and certain drugs such as nitroglycerin.

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