Physics lecture 2/27

5

how many liters of blood does the circulatory system contain?

solids, liquids, gases

what 3 categories is matter generally classified into?

fluids*

materials that flow and conform to the shape of their containers

to flow

to move in a stream, continually changing position and possibly direction

the right

what side of the heart is related to the venous system?

the left

what side of the heart is related to the arterial system?

viscosity

the resistance to flow offered by a fluid in motion

ɳ (poise)= kg/m-s

what are the units of viscosity?

viscosity

what is the property of a fluid that resists the force which tends to cause it to flow?

low

is water's viscosity high or low?

high

is honey's viscosity high or low?

50%

viscosity of the blood plasma is about ___% greater than that of water.

5 times

the viscosity of normal blood is about ___(#) times that of water

pressure=force/area

the driving force behind fluid flow

dyne/cm^2

what are the units for pressure?

difference

a pressure _____ is required for flow to occur

direct

what is the relationship between pressure and flow rate?

no

equal pressures = _____ flow

volumetric flow rate

the volume of blood passing a point per unit of time

Q, milliliters/second, mL/s

what is the unit for volumetric flow rate?

Q (mL/s) = ΔP (dyne/cm^2) / resistance to flow (poise)

what is the equation for volumetric flow rate?

R (poise) = ΔP (dyne/cm^2) / Q (mL/s)

what is the equation for viscosity?

the pressure difference (or gradient) and the resistance to flow (viscosity)

what is the volumetric flow rate in a long straight tube determined by?

direct

what is the relationship between pressure and volumetric flow rate?

inverse

what is the relationship between viscosity and volumetric flow rate?

Q=[ΔP π x d^4] / [128 L * ɳ]

What is Poiseuille's equation? *for steady flow in long, straight tubes

R (g/cm^4 -s) = 8 x L (cm) x ɳ (poise) / pi * [r^4 (cm^4)]

flow resistance equation

decrease it by 1/16 its original value

what does doubling the radius of a tube do to its resistance?

increases its resistance by 16 times its original value

what does decreasing the radius of a tube by half do to its resistance?

direct

what's the relationship between tube diameter and flow rate?

inverse

what's the relationship between tube length and flow rate?

low

does the aorta have low or high resistance?

high

do the arterioles have low or high resistance?

50%

how much of the total resistance in the systemic circulation do the arterioles account for?

flow

to move in a stream continually changing position and possibly direction

fluids

a material that flow and conforms to the shape of its container

flow resistance

pressure difference divided by volume flow rate for steady flow

volumetric flow rate

volume of fluid passing a point per unit of time

pressure gradient (slope)

pressure difference divided by distance between the two pressure locations

viscosity

resistance of fluid to flow

pulsatile, phasic, and steady

what are the 3 basic forms of blood flow?

pulsatile blood flow

occurs when blood moves with variable velocity. Blood accelerates and decelerates as a result of cardiac contraction. Seen in arterial circulation.

phasic blood flow

occurs when blood moves with variable velocity. blood accelerates and decelerates as a result of respiration. seen in venous circulation.

steady blood flow

occurs when blood moves at a constant speed or velocity. present in venous circulation when individuals stop breathing for a brief moment

plug, laminar, parabolic, disturbed, turbulent

what are the 5 categories flow can be divided into?

plug flow

flow with all fluid portions traveling with the same flow speed and direction

entrance to a vessel

where does plug flow occur?

unit

plug flow is similar to the motion of a solid object that does not flow but moves as a _____

laminar flow

flow in which fluid layers slide over each other in a smooth, orderly manner, with no mixing between layers

layer

'lamina' = _____ = silent flow

straight and parallel to each other

what describes the streamlines in laminar flow?

center of the tube

where is flow speed at its max in laminar flow?

at tubes walls

where is flow speed at its min in laminar flow?

decreasing

a _____ profile of flow speeds from the center to the wall is present in laminar flow

parabolic flow

a form of laminar flow with a profile in the shape of a parabola

1/2

in parabolic flow, the average flow speed across the vessel is equal to ___(#) the max flow speed

disturbed flow

a form of laminar flow that cannot be describes by straight parallel streamlines

forward

in disturbed flow, particles of fluid flow in the _____ direction

stenosis or at bifurcation

when does disturbed flow occur?

turbulent flow

random, chaotic, swirling, hurricane-like with rotational patterns, multidirectional flow of a fluid with mixing between layers

no

is turbulent flow laminar?

Bruit or murmur

the unusual sound that blood makes when it rushes past an obstruction or stenosis

cardiovascular pathology and elevated blood velocities

what is bruit or murmurs associated with?

transition from high flow speed in narrow channel to slow flow in a broad stream

where does turbulent flow occur?

false! forward net flow is still maintained

T or F

With turbulent flow, net flow can be forward or backward or mixed.

mmmmmmm

what does MPV pulse wave look like when the patient is breathing normal?

iiiiiiiiiiiiiiiiii

what does MPV pulse wave look like when the patient is holding their breath?

1. laminar flow

2. entrance effect: 'plug flow'

3. laminar flow

4. 'steeper' parabolic laminar

5. entrance effect: 'plug flow'

6. exit effect: turbulence

7. laminar flow

what are the 7 steps of flow through a rigid tube?

pulsatile flow (arterial)

non-steady flow that accelerates and decelerates with each cardiac cycle

true

T or F

With pulsatile flow, in distensible vessels, includes added forward flow and/or flow reversal over the cardiac cycle in some locations in the circulation

Windkessel effect

later in the cycle, when the driving pressure is reduced, the compliant vessel is able to contract, producing extended flow later in the pressure cycle

continuity rule

blood is neither created nor destroyed as it flows through a vessel

stenosis

flow speed increases at a _____ and turbulence can occur distal to it

true

T or F

Volumetric flow rate must be constant proximal, within and distal to a stenosis

Poiseuille's law says flow speed decreases with smaller diameters, while continuity rule states flow speed increases with smaller diameters

Why do Poiseuille's law and the continuity rule seem contradictory?

Poiseuille's law-long, straight vessel with no stenosis, refers to entire vessel

continuity rule-refers to diameter of a shorter portion of a vessel (stenosis)

what is the important difference between Poiseuille's law and continuity that accounts for the contradiction?

Bernoulli's equation

assuming there is no energy lost to heat, in a closed system, the energy at point 1 must equal the energy at point 2.

Bernoulli effect

pressure reduction in a region of high-flow speed

inverse

in the Bernoulli effect, what is the relationship between flow speed and pressure?

increase

In the Bernoulli effect, to maintain flow continuity, flow speed must (increase/decrease) through a stenosis

drop

with the Bernoulli effect, does the pressure drop or rise in a stenosis?

Δ P = 4 (flow speed at stenosis)^2

what is the pressure drop formula? (dont need to know)

-change in flow direction

-increased velocity as vessel narrows

-turbulence downstream from stenosis

-pressure gradient across the stenosis

-loss of pulsatility

What are the effects of a stenosis?

Ohms' Law

current = Δ voltage / resistance

the numerator for flow is Δpressure but the numerator for ohms' law is Δvoltage BUT the denominator is resistance for both

what are the similarities and differences between flow and ohms' law?

Doppler effect

A change in frequency caused by motion of a source or reflector