Cardiovascular System, Biological Fluids, Renal Function (CFR)

These flashcards cover key concepts, definitions, and implications of viscosity and blood flow as discussed in the lecture on the cardiovascular system.

What is viscosity?

Viscosity is the resistance to flow of a fluid.

What are the SI units of viscosity?

The SI units of viscosity are Pascal seconds (Pa.s).

How is viscosity related to the haematocrit ratio?

Viscosity is directly proportional to the haematocrit ratio.

What effects does polycythaemia vera have on blood?

It leads to an overproduction of red blood cells, increasing haematocrit and blood viscosity.

What are the implications of increased blood viscosity?

Increased blood viscosity can lead to circulation problems such as thrombosis and emboli.

How does temperature affect blood viscosity?

As temperature decreases, blood viscosity increases by 2-3 times.

What causes red blood cells to accumulate in the center of arteries?

The Bernoulli-induced pressure differential causes them to be guided toward the central axis.

What is Poiseuille’s Law?

Poiseuille’s Law describes how flow rate depends on pressure difference, viscosity, and the dimensions of a tube.

What is the equation for Poiseuille’s Law?

Q = rac{ riangle P imes r^4}{8 imes L imes
u} where Q is the flow rate, P is the pressure, r is the radius, L is the length, and
u is the viscosity.

What does a decreased radius of a vessel do to blood flow?

It significantly decreases blood flow due to the r^4 dependency in Poiseuille’s Law.

What happens to blood pressure in small vessels?

Blood pressure drop increases significantly in small vessels due to increased surface area and resistance.

What is the volume flow rate of blood in relation to pressure difference?

Volume flow rate (Q) is directly proportional to the pressure difference divided by viscous resistance.

What impact does viscous resistance have on blood flow?

Viscous resistance opposes the flow of blood, affecting circulation and pressure drop along vessels.

Why does the heart have to work harder if an artery narrows?

Atheroma deposits can reduce the radius, increasing resistance and making the heart work 81 times harder.

What is the pressure maintained across blood vessels?

The pressure drop is directly proportional to viscosity and inversely proportional to the fourth power of the radius.

How does viscosity affect the velocity profile of blood flow?

Viscosity produces a velocity profile with higher velocity at the center and lower near the vessel walls.

What implications does high viscosity blood have for circulation?

It can lead to slower blood flow and poor oxygen transport.

What are the maximum and resting pressures in the systemic circulation?

Maximum pressure (systole) is ~120 mm Hg and resting phase (diastole) is ~80 mm Hg.

What is the pressure in the pulmonary system during systole?

Systolic pressure is approximately 25 mm Hg.

What do skeletal muscle pumps do for venous return?

They compress veins, increasing pressure and helping to push blood toward the heart.

What pressure gradient must be maintained for blood to flow?

A difference in pressure must be maintained across the vessel to ensure blood flow continues.

What is a common complication of decreased red blood cells?

Anaemia can lead to poor oxygen transport despite easier circulation.

What occurs to blood viscosity as blood temperature decreases?

Viscosity increases as blood temperature decreases, leading to poorer circulation.

How is blood flow affected by an increase in blood viscosity?

An increase in blood viscosity causes a decrease in flow rate.

What is a major reason for blood pressure drop in arterioles and capillaries?

A major decrease in blood vessel radius results in energy and pressure loss due to viscous forces.

How does Poiseuille's Law relate to narrow vessels?

Narrow vessels lead to significant resistance, impacting flow rate drastically.

What happens to blood at the boundary layer near the vessel walls?

It remains at rest due to frictional forces, which allows plaque to form.

How does the average velocity of blood relate to the radius of the vessel?

Average velocity is affected as radius decreases, impacting overall blood circulation.

What does arterial narrowing imply about cardiac workload?

If arteries narrow, the heart must exert significantly more effort to maintain blood flow.

How does Poiseuille’s Law demonstrate the need for radius maintenance?

Reducing the radius drastically increases the flow resistance, impacting blood pressure and flow.

What is the role of one-way valves in veins?

They ensure blood flows only in the proper direction towards the heart.

What is the significance of internal surface area in smaller vessels?

Greater internal surface area increases friction, affecting pressure and flow dynamics.

What flow rate and pressure drop would create burdens on heart function?

High flow rates with significant pressure drops require increased cardiac output.

How does the principle of continuity apply to blood flow?

The flow rate depends on the average velocity and the cross-sectional area of the vessels.

What health issues can arise from increased blood viscosity?

Increased viscosity can lead to risks of thrombosis, embolisms, and hypertension.

What effect does decreased length of a vessel have on resistance?

Decreased vessel length reduces resistance, allowing easier blood flow.

What can blood viscosity indicate about an individual's health?

High blood viscosity might signal conditions such as polycythaemia vera or dehydration.

How does blood viscosity relate to disease states like arteriosclerosis?

It indicates increased resistance in narrowed vessels, leading to cardiovascular stress.

What does a pressure gradient across a vessel establish for blood flow?

A pressure gradient ensures that blood is pushed through the circulatory system efficiently.

Why is understanding blood viscosity crucial for cardiovascular health?

It affects flow dynamics, oxygen transport, and overall heart workload directly.

What example can demonstrate the practical application of Poiseuille’s Law in medicine?

Using Poiseuille's equation in surgical contexts to assess artery conditions post-operation.