91 Questions
Which of the following is the primary function of the cardiovascular system?
To provide adequate blood flow to the tissues and organs
What is the goal of short-term control of the cardiovascular system?
Maintenance of cerebral and coronary blood flow
What is the goal of long-term control of the cardiovascular system?
Maintain adequate blood flow to all tissues of the body
Why do kidneys need blood flow in excess of their metabolic needs?
To maintain the concentration of substances in the blood within normal ranges
What is the purpose of blood flow to the skin on some occasions?
To dissipate heat
Which mechanisms are used to regulate blood flow over a long time period?
Both A and B
What are most regulatory mechanisms designed to maintain in the short term?
Normal systemic arterial blood pressure
What is the blood flow needed to meet in the long term?
Metabolic demands of the tissues
Which system contains the largest volume of blood in the body?
Venous system
What is the study of physical factors that determine the flow of blood called?
Hemodynamics
What is the unit of measurement for blood flow?
All of the above
What is the unit of measurement for blood velocity?
Centimeters per second
What is the unit of measurement for blood pressure?
Millimeters of mercury
Which system contains smaller volumes of blood compared to the venous system?
All of the above
What is the primary function of hemodynamics?
To study physical factors of blood flow
What is blood flow defined as?
The volume of blood which moves through a vessel in a unit period of time
What is blood velocity defined as?
The distance a component of the blood moves in a unit period of time
Which equation represents the relationship between vessel diameter, velocity, and flow?
Q = v * A
If blood flow through a vessel is constant while its cross-sectional area is decreased, what happens to its blood velocity?
It increases
What happens to the total cross-sectional area of the vessels as you move distally (away from the heart)?
It increases
Which type of flow is described as having a parabolic velocity profile?
Laminar flow
Where is the blood flow slowest in a vessel with laminar flow?
Closest to the walls
What is the primary purpose of blood flow through the capillaries?
To provide adequate time for diffusion
What is the term used to describe the flow of blood through non-branching vessels, connected end-to-end?
Continuity flow
What is the unit of measurement for blood flow?
Volume/time
Which type of flow is described as having a rapid mixing due to irregular motion of fluid elements?
Turbulent flow
What is the equation used to calculate the Reynolds number (NR)?
NR = ρ * V * D/ η
What does a Reynolds number (NR) value less than 2000 indicate?
Laminar flow
What does a Reynolds number (NR) value greater than 3000 indicate?
Turbulent flow
What is the effect of turbulent flow on resistance?
Resistance is greatly increased
What does turbulent blood flow require to maintain specific flow compared to laminar flow?
Higher perfusion pressure
What factors determine blood density?
Number of cells and large proteins in whole blood
What happens to blood density during hemorrhage?
Decreases
What is blood viscosity a measure of?
Blood stickiness and thickness
What can hematocrit cause during slower flow?
Promotes thrombi formation
What does blood viscosity depend on?
Shear rate, mechanical properties of cellular elements, and composition of plasma
How does low hematocrit affect blood turbulence?
Decreases turbulence
Which type of flow is described as having a parabolic velocity profile?
Laminar flow
What happens to the velocity of blood flow when the diameter of a vessel decreases?
The velocity increases
What is shear highest at in a blood vessel?
The blood vessel wall
What is the term used to describe the aggregation of red blood cells due to low shear?
Rouleaux
What happens to turbulence when blood flows into a suddenly wider diameter vessel?
Turbulence increases
What is the effect of shear on blood viscosity?
Shear decreases blood viscosity
Which of the following is the relationship between blood flow (Q), the pressure gradient along a vessel (ΔP), and vascular resistance (R)?
Q = ΔP / R
What is the force that makes blood flow?
Blood pressure
What is the pressure difference (ΔP) in relation to blood flow through a vessel?
The difference between the proximal and distal pressures
What is the direct relationship between blood flow and the pressure difference across a vessel?
Flow is directly proportional to ΔP
What must be applied to blood in order to make it flow?
Force
What is the unit of measurement for blood flow?
Liters per minute
What is the primary force that makes blood flow through the blood vessels?
Pressure difference
Which of the following is true about the relationship between blood flow and resistance in a vessel?
Blood flow is inversely proportional to resistance
What is the primary means for the physiological regulation of resistance in blood vessels?
Radius of the vessel
What happens to resistance when the radius of a vessel decreases?
Resistance increases
What happens to resistance when the length of a vessel increases?
Resistance increases
What is the primary factor that regulates the radius and therefore the resistance of blood vessels?
Sympathetic nervous system
What is the effect of small changes in the radius of a vessel on resistance?
Small changes in the radius produce large changes in resistance
What happens to blood flow when there is an increase in blood viscosity (η)?
Blood flow decreases
Which equation describes the relationship between pressure, flow, and the determinants of resistance?
Flow = (∆P r4 PI) / (L η 8)
What happens to blood flow when blood viscosity increases?
Blood flow decreases
What is the effect of increased blood viscosity on blood pressure?
Increased blood viscosity increases blood pressure
What is the relationship between resistance and the number of red blood cells?
Resistance is directly proportional to the number of red blood cells
Which equation can be used to estimate the mean arterial blood pressure (MBP)?
MBP = (Systolic BP + 2 Diastolic BP)/3
What is the flow of blood through non-branching vessels, connected end-to-end, called?
Laminar flow
What is the total resistance of the systemic vasculature called?
Total peripheral resistance (TPR)
What happens to blood flow when the internal diameter of a vessel decreases?
Blood flow decreases
What is the primary function of hemodynamics?
To study the physical factors that determine blood flow
What does a Reynolds number (NR) value less than 2000 indicate?
Laminar flow
What is the flow of blood (Q) called?
Cardiac output (CO)
What is the total resistance of the systemic vasculature called?
Total peripheral resistance (TPR)
What is the pressure difference (∆P) across the systemic vasculature called?
Mean arterial pressure (MAP)
What is the equation that relates mean blood pressure (MBP), cardiac output (CO), and total peripheral resistance (TPR)?
MBP = CO TPR
Which type of blood vessel arrangement results in the greatest total resistance?
Series
Which type of blood vessel arrangement results in the least total resistance?
Parallel
Which type of blood vessel arrangement is most common in the cardiovascular system?
Both series and parallel
What is the formula for calculating the total resistance (RT) of resistances in series?
RT = R1 + R2 + R3 + ...
What is the formula for calculating the total resistance (RT) of resistances in parallel?
RT = 1/R1 + 1/R2 + 1/R3 + ...
When blood vessels are arranged in parallel, what can be said about the total resistance compared to the resistance of any individual vessel?
The total resistance is always less
When blood vessels are arranged in series, what can be said about the total resistance compared to the resistance of any individual vessel?
The total resistance is always greater
Which vessels in the kidney are in series with each other?
Glomerular and peritubular capillaries
What is the ratio of the change in volume (ΔV) of a structure to the change in pressure (ΔP) within the structure?
Compliance (C)
Which type of vessels have equal pressure gradients but may have different flows?
Vessels in parallel
What is the measure of stiffness in a vessel?
Reciprocal of compliance (C-1)
Which type of vessels have high compliance and expand easily?
Veins
What happens to arterial compliance with age?
Decreases
What effect does increased sympathetic tone have on venous vessels?
Stiffens them
Which system contains all major organ vasculatures in parallel with each other?
Systemic vasculature
What is the primary function of compliance in the aorta?
Determines the change in pressure during ejection of blood from the heart
What is the effect of increased blood viscosity on blood pressure?
Increases blood pressure
Which vessels in the kidney are in series with each other?
Glomerular and peritubular capillaries
What is the typical relationship between the inlet and outlet pressures of vessels in series?
They are usually different
What is the typical relationship between the total flows of vessels in series?
They must be equal
Study Notes
Cardiovascular System Function
- The primary function of the cardiovascular system is to deliver oxygen and nutrients to tissues and remove waste products.
Short-term and Long-term Control of Cardiovascular System
- The goal of short-term control is to maintain blood pressure and flow to vital organs.
- The goal of long-term control is to regulate blood flow and pressure over a long period of time.
Blood Flow Regulation
- Blood flow is regulated by controlling vessel diameter, velocity, and flow.
- Mechanisms used to regulate blood flow over a long time period include neural and hormonal control.
- In the short term, regulatory mechanisms are designed to maintain arterial blood pressure.
Blood Flow and Pressure
- Blood flow is defined as the volume of blood flowing through a vessel per unit time.
- Blood velocity is defined as the speed at which blood flows through a vessel.
- The unit of measurement for blood flow is mL/min.
- The unit of measurement for blood velocity is cm/s.
- The unit of measurement for blood pressure is mmHg.
Vessel Characteristics
- The systemic circulation contains the largest volume of blood in the body.
- The venous system contains smaller volumes of blood compared to the arterial system.
- The primary function of hemodynamics is to study physical factors that determine blood flow.
Blood Flow and Velocity
- When blood flow through a vessel is constant, and its cross-sectional area decreases, blood velocity increases.
- As you move distally (away from the heart), the total cross-sectional area of the vessels increases.
- Laminar flow is characterized by a parabolic velocity profile.
- Blood flow is slowest in the center of a vessel with laminar flow.
Turbulent Flow
- Turbulent flow is characterized by rapid mixing due to irregular motion of fluid elements.
- The Reynolds number (NR) represents the relationship between vessel diameter, velocity, and flow.
- A Reynolds number (NR) value less than 2000 indicates laminar flow.
- A Reynolds number (NR) value greater than 3000 indicates turbulent flow.
Blood Density and Viscosity
- Blood density is affected by hematocrit and plasma protein concentration.
- Blood viscosity is a measure of its resistance to flow.
- Blood viscosity depends on hematocrit, temperature, and plasma protein concentration.
- Low hematocrit can cause increased blood viscosity during slower flow.
Vascular Resistance
- Vascular resistance is affected by vessel radius, length, and blood viscosity.
- The primary factor regulating vessel radius and resistance is smooth muscle tone.
- The primary means of physiological regulation of resistance in blood vessels is through neural and hormonal control.
Blood Pressure and Flow
- The force that makes blood flow is the pressure difference along a vessel.
- The primary force that makes blood flow through blood vessels is cardiac output.
- The direct relationship between blood flow and pressure difference across a vessel is represented by Ohm's Law (Q = ΔP/R).
Test your knowledge of cardiovascular system regulation under different conditions in this quiz. Explore how blood flow to tissues and organs changes at rest compared to times of increased demand, such as during exercise or fever. Learn about the short-term control mechanisms that help maintain normal systemic arterial blood pressure and ensure adequate blood flow to vital organs like the brain and heart.
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