Vasoconstriction (constricting blood vessel) and flow rate?

In summary, the conversation discusses why the speed of blood decreases when blood vessels constrict. The participants consider the relationship between flow rate, volume of blood, and pressure, and suggest that the flow rate may not always remain constant. They also mention the impact of viscous drag and the function of the heart as a pump.
  • #1
shangriphysics
32
1
I was wondering why when the blood vessels constricted the speed of the blood decreased?

I thought that since the flow rate has to be the same, the volume of blood that reaches a smaller area from a bigger area will increase in speed and hence decrease in pressure?

Perhaps is this due to the fact that the volume of blood from a bigger area has to go through many smaller areas at once, and therefore the velocity would decrease because the volume of blood has to go through many tunnels at once?
 
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  • #2
shangriphysics said:
I was wondering why when the blood vessels constricted the speed of the blood decreased?

I thought that since the flow rate has to be the same, the volume of blood that reaches a smaller area from a bigger area will increase in speed and hence decrease in pressure?

Must the flow rate be the same?
 
  • #3
I guess in my hypothetical human body in which the fluids are incompressible, neglible internal friction(viscocity), for each diastolic and cystolic pressure, the pressure would be the same as well as the flow rate.
 
  • #4
In flow through blood vessels (especially capillaries), the pressure change as a result of vessel constriction is negligible compared to the increased pressure from viscous drag. Also, the heart is not a positive displacement pump, so the blood flow rate can change as a result of constrictions. The tendency would be for the blood flow rate to decrease, and the blood pressure to increase.

Chet
 
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Likes shangriphysics
  • #5
Thank you Chet!
 

1. What is vasoconstriction and how does it affect flow rate?

Vasoconstriction is the narrowing of blood vessels, which can decrease the flow rate of blood. This is because when blood vessels are constricted, the space for blood to flow through is reduced, causing a decrease in blood flow.

2. What causes vasoconstriction?

Vasoconstriction can be caused by various factors including hormones, nervous system signals, and certain medications. It is a normal physiological response to regulate blood flow and maintain blood pressure.

3. What are the effects of vasoconstriction on the body?

Vasoconstriction can have both positive and negative effects on the body. On one hand, it can help regulate blood pressure and maintain body temperature. On the other hand, it can also restrict blood flow to certain organs and tissues, leading to potential health issues.

4. How is vasoconstriction related to hypertension?

Hypertension, or high blood pressure, can be caused by vasoconstriction. When blood vessels are constricted, the heart has to work harder to pump blood through the narrowed vessels, resulting in increased blood pressure.

5. Can vasoconstriction be reversed?

Yes, vasoconstriction can be reversed through vasodilation, which is the widening of blood vessels. This can be achieved through various methods such as relaxation techniques, certain medications, and physical activity. However, it is important to address the underlying cause of vasoconstriction to prevent it from occurring again.

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