Hemodynamics I

____= the study of physical principles that govern the movement of blood through the human circulatory system

Hemodynamics

The circulatory system is a ___ and ___ circuit

closed, continuous

The circulatory system consists of what? (4)

the pumping generator (heart), arteries (elastic conduits), veins, capillaries

Usually __ liters of blood pass through each vascular segment per minute

5

We must understand that the arterial system distributes ____, ___, ___, ___, and ___ to various organs

nutrients, oxygen, hormones, antibodies, and medications

Power = rate of ___ transferred, describes how fast ___ is done on a system, units: _____

energy, work, watts (joules/sec)

Work = amount of ___ transferred or expended, ___ x ___, units: ___

energy, power x time, Joules

Power and ____ are inversely related

work

Energy = the ability to do ___

work

Energy that is stored and associated with static pressure, ex: energy stored in a spring

Potential Energy

Energy associated with dynamic pressure, related to movement

kinetic energy

A measure of force per unit area

Pressure

Resistance = Ratio of ____ drop across a vessel or flow path per flow, impediment that must be overcome for ___ to occur

pressure, flow

Capacitance =

A measure of the ability to hold charge in volume per change in time (dv/dt), v=volume

Compliance =

ratio of change in volume to a change in pressure (dv/dp)

High compliance means a ___ increase in volume for a ___ increase in pressure

large, small

Incompliant flow paths means a ___ increase in volume for a ___ increase in pressure

slight, significant

Velocity =

speed with which fluid moves in a specific direction (meters/sec)

Viscosity =

A measure of resistance of a fluid to flow due to attraction of molecules

Power: ___ energy is taken in by the device in one form and transformed to ___ energy in another form

input, output

When a force acts on an object and causes it to move through a distance, energy is transferred and ___ is done

work

Work done = ___ transferred

energy

___ energy is energy stored and ready to go

potential

Flow (Q) =

the quantity or volume of fluid flowing at an interval of time

Units for Flow (Q) =

ml/sec or ml/min

Flow (Q) equals ?/?

pressure difference / flow resistance (∆P/R)

Systole = where heart contracts and pumps ______ blood to the organs through the ___ system

oxygenated, arterial

Diastole = where the heart ____ and allows it to fill up with ___

relaxes, blood

During diastole, there is a continued push of blood through the aorta to smaller arteries through the relaxation and contraction of the arterial walls. What is this called?

Windkessel Effect

____ play a major role in maintaining a balance between the blood entering and exiting the venous system

capillaries

Factors affecting bloof flow: is the tensions of ____ within the arteries

blood

What makes blood flow? (2)

the presence energy gradient, blood flows from high pressure to low pressure

the presence energy gradient =

difference in pressure between two points within the vascular system

Arterial system = ___ pressure

high

Avg pressure in Aorta = _____ mmHg, this decreases to ____ mmHg as it flows through arteries and arterioles

100, 40

Pressure in capillaries is about ___ mmHg which is less than in arterioles and greater than in venules

10

The driving force to propel blood is a change in ___

energy

Flow occurs from __ to __ energy

high to low

In the cardiovascular system, energy usually gets converted between ___ and ____ energy

kinetic, potential

Pressure exerted on the vessel walls represents ___ energy

potential

Flow in flow direction in vessels (related to velocity) represents ___ energy

kinetic

Capacity of doing work and overcoming resistance: ____ energy, ____ energy, ____ energy

kinetic, potential, fluid (total)

Energy of motion =

Kinetic energy

Is the ability of blood to do work based on its velocity of motion =

kinetic energy

kinetic energy is a ___ fraction of total ___ energy

small, blood

Kinetic energy is related to the concept of ___ and __ of flow

inertia, velocity

Inertia =

tendency of an object at rest to remain at rest, and tendency for a moving object to continue moving in the direction its going rather than changing

KE = (equation)

1/2 (mv^2)

___ energy is high during exercise or in stenotic situation when velocities are high

Kinetic

What is the main energy in blood flow?

Potential Energy

Energy of something at rest than in motion, and work done when an object is moved from one position to another =

Potential Energy

In hemodynamics, potential energy is a combination of? (2)

Intravascular pressure and Gravitational potential energy

Intravascular pressure is created by continuous __ of the heart and is a dominant source of ___ energy

pumping, potential

Hydrostatic pressure = ___ exerted by a ____ within a closed system (due to the weight of blood when a person in standing)

pressure, fluid

Hydrostatic Pressure (HP) = (equation)

HP=(-)pgh

What do the letters stand for? HP=(-)pgh

p=specific gravity or density, g=acceleration due to gravity, h=height above specific reference point

____ ____ increases distention of blood vessel walls due to the increase in pressure

hydrostatic pressure

Static filling pressure of blood: pressure exists because of the relationship between what?

the amount of blood in a vessel and the elasticity of the vessel walls

Gravitational potential energy = is the work of ____ force

gravitational

Capacity of a quantity of blood to do work based on its position above a specific reference point

Gravitational potential energy

Gravitational energy = ____

mgh (mass, gravity, height)

The higher the body part the higher the ____ energy (think raising your arm above your head)

gravitational

In the cardiovascular system there is a ____ of ___ law, which is no energy lost to __

conservation of energy, heat

Pressure on vessel walls is ___ and force in flow direction is ___

PE, KE

Energy will be converted back in forth between what?

Between kinetic and potential energy

Any decrease in velocity will cause a ___ in KE

decrease

(total) fluid energy is a combination of ___ and ___

KE and PE

Total Fluid Energy = (equation)

Pressure + KE + gravity

Total Fluid Energy = (broken down further equation)

P + 1/2 mv^2 +pgh

(according to Isaac Newton) Ratio of shear stress to shear rate =

Fluid Viscosity

Sheer stress = stress ____ to the face of the material instead of being ____ (normal stress)

parallel, perpendicular

Fluid is located between 2 plates. The shear force divided by the contact areas between the fluid and the plate gives the ___ stress

shear

Shear rate is the difference in ____ between the different layers and can be calculated as the __ of top plate and the difference between the plates ___/___

velocity, velocity, velocity/height

Different layers of blood move with different ____

velocities

Difference in velocity in different layers causes a ___ ___ (friction) between them

shear action

Displacement of one fluid layer with respect to the next = ___ ___

shear rate

Viscosity units =

Pa.s=N.s/m^2 or Posie (dyness.s/cm^2)

Viscosity is a ____ to flow

resistance

In fluid, the resistance come from ___ ___ of the molecules

cohesive forces

The stronger the attraction between the molecules, the more ____ it is for the substance to flow

difficult

Fluid viscosity is ____ dependent

heat

As temperature increase, viscosity ____

decreases

Based on the resistance equation, resistance is proportional to _____

viscosity

Equation for resistance =

R = 8Ln/πrˆ4

Energy is lost in the form of ___ as the layers of RBCs collide and rub against eachother

heat

Energy being lost as heat means ___ losses and changes in ___ as well as ____ losses

viscous, direction, inertial

____ flow can occur from changes in the cardiac cycle, vessel diameter changes, branching, atherosclerosis, and stenosis

Disturbed

Increasing hematocrit increases blood _____

velocity

____ hematocrit decreases the blood velocity

decreasing

Decreasing the vessel size ____ the frictional forces (resistive forces which impede flow) and heat energy losses

increases

Loss is determined by the vessel ___

diameter

VIscous losses are greatest in ___ vessels or capillaries

small

Central flow is almost even with that by the ____

walls

Laminar flow is a good demonstration of viscous energy losses that occur between ___ and the vessel ___ resistance

layers, wall

Disturbed flow also causes loss of ____

energy

Normal blood vessels have ____ endothelial layers

smooth

Normal blood vessels: definitely there are frictional forces but they are ____ and do not affect our measurement accuracy. Here I am not suggesting that frictional energy losses with the walls are negligible

small

Increase in frictional forces can be seen with: vessels with ____ or rough ____ ____

plaque, tunica intimas

Increase in frictional forces can be seen with: vessel ___, ____, ____, ___

branching, kinking, bends, twists

An increase in frictional forces can be seen with: ____ viscosity and ___ flow

higher, higher