physics chapter 18

what is hemodynamics

the study of blood moving through the circulatory system

what is another name for flow

volume flow rate

what indicates the volume of blood moving during a particular time

flow

what is flow measured in

liters/min

what indicates the speed or swiftness of a fluid moving from one location to another

velocity

what is velocity measured in

cm/s

what are the basic forms of blood flow

pulsatile, phasic, steady

_____ occurs when blood moves with a variable velocity where blood accelerates and decelerates due to cardiac contraction

pulsatile flow

where does pulsatile flow commonly appear

arterial circulation

____ occurs when blood moves at a variable velocity the blood accelerates and decelerates due to respiration

phasic flow

where does phasic flow commonly appear

venous circulation

_______ occurs when a fluid moves at a constant speed or velocity

steady flow

where do we see steady flow

in the venous system when the person stops breathing for a brief moment

laminar flow is when the flow streamlines are ___ and ____

aligned; parallel

what is laminar flow characterized by

layers of blood that travel at individual speeds

where are laminar flow patterns typically found

normal physiological states

what are the two forms of laminar flow

plug flow and parabolic flow

what occurs when all of the layers of blood cells travel at the same velocity

plug flow

what has a bullet shaped profile where velocity is highest in the center of the lumen and gradually decreases going to the vessel walls

parabolic flow

laminar flow is _____ flow

silent

what predicts whether flow is laminar or turbulent

the reynolds number

what is the reynolds number for laminar flow

< 1500

what is characterized by chaotic flow patterns in many different directions at different speeds where the streamlines are often obliterated

turbulent flow

what are the small, hurricane like, swirling, rotational patterns that appear in turbulent flow

eddy current or vortex

what is turbulent flow associated with

cardiovascular pathology and elevated blood velocities

turbulent flow is typically seen ___ to a stenosis

downstream

turbulent flow converts flow energy into other forms like

sound and virbation

what is the sound that is associated with turbulence

murmur or bruit

what is the vibration that is associated with turbulent flow

thrill

what is the reynolds number that is associated with turbulent flow

> 2000

_____ is when blood moves from a regions of higher energy to lower energy

energy gradient

what forms of energy are associated with blood

kinetic, pressure, gravitational

what is the sum of the total energy at a specific location within the circulation

sum of all three forms of energy (kinetic, pressure, gravitational)

what energy is associated with a moving object

kinetic energy

what is kinetic energy determined by

an objects mass and the speed at which it moves

does a heft swiftly moving object have a little or a lot of kinetic energy

a lot

______ is a form of stored or potential energy

pressure energy

____ energy has the ability to do work

potential

pressure is a major form of energy for ___________

circulating blood

how does pressure energy create flow

by overcoming resistance

what type of energy is a form of stored or potential energy that is associated with any elevated object

gravitational energy

as blood flows through the circulation how is energy lost

viscous loss, frictional loss, and inertial loss

what describes the thickness of a fluid

viscosity

is more or less energy lost with movement of high viscosity fluids

more

viscous loss is associated with blood overcoming its ___________

internal stickiness

how is viscosity measured

poise

what determines the viscous energy loss in blood

hematocrit

____ is the percentage of blood made up of red blood cells

hematocrit

when does frictional loss occur

when flow energy is converted to heat as one object rubs against another

when blood slides across the vessel walls that creates heat what is this an example of

frictional loss

energy is ___ when the speed of a fluid changes regardless of whether the fluid speeds up or slows down

lost

_____ relates to the tendency of a fluid to resist changes in its velocity

inertia

when does inertial energy loss occur

pulsatile flow, phasic flow, and when velocity changes after stenosis

velocity ____ as the vessel narrows

increases

where is the maximum velocity found

where the vessel is the narrowest

when blood flows out of the stenosis into a vessel segment of normal diameter does the velocity increase or decrease

decrease

what is the narrowing in the lumen of the vessel

stenosis

turbulence downstream to a stenosis is known as

post-stenotic turbulence

the pressure downstream from the stenosis is ___ compared to the pressure measured upstream to the stenosis

lower

what causes the post-stenotic pressure to decrease

the loss of energy as blood flows through the stenosis

stenosis causes a ___ in flow direction

change

stenosis causes a ____ velocity as the vessel narrows

increased

stenosis causes ___ downstream to the stenosis

turbulence

stenosis causes a __________ gradient across the stenosis

pressure

stenosis causes a ___ of pulsatility

loss

what does bernoulli’s principle describe

relationship between velocity and pressure in a moving fluid

where is bernoulli’s principle derived from

the principle of conservation of energy

the sum of kinetic energy and pressure energy remains _____

constant

within a stenosis where is pressure the lowest

narrowest part of the vessel

what is the law of conservation of energy

energy is neither created nor destroyed it is just converted from one form of energy to another

where is velocity the highest within a vessel with stenosis

the narrowest part of the stenosis

kinetic energy ___ with higher velocities

increases

kinetic energy of blood _____ as blood flow speeds up through the stenosis

increases

as the blood accelerates pressure energy is converted into

kinetic energy

where is pressure energy the lowest

where the vessel/stenosis is most narrow

as blood moves downstream from the stenosis we get a ____ velocity and kinetic energy

reduced

as blood decelerates what happens to the kinetic energy

kinetic energy is converted back to pressure energy

pressure energy ______ in the post-stenotic region

rises

pressure and velocity are ____ related

inversely

flow x resistance = ?

pressure gradient

what can cause pressure gradient to increase

when flow or resistance increases

what can cause flow to increase

when pressure gradient increases or resistance decreases

what does ohms law describe

the movement of electricity through a wire

current x resistance = ?

voltage

electrical resistance is reported in units of

ohms

within the circulatory system the resistance vessels are called

arterioles

veins are ___ walled and ____

thin; collapsible

veins have ___ pressure and are only partially filled with blood

low

veins and arteries are usually ______ resistance vessels

low

when venous flow increases during exercise how does the cross-sectional shape of the vein change

hourglass → oval → round

the flexibility of shapes the veins can take allow veins to accommodate a large volume increase with a very small ___ increase

pressure

as veins become more round the resistance to flow _____, increasing the outflow toward the heart

decreases

what is the pressure related to the weight of blood pressing on a vessel measured at a height above or below the heart level

hydrostatic pressure

what is the unit hydrostatic pressure is reported in

mmHg

hydrostatic pressure introduces an error in measurement based on ___________

the site of measurement

where are pressures accurately measured on the body

level of the heart

pressures are ____ when measurement is taken below the level of the heart

high

pressures are ____ when measurement is taken above the level of the heart

low

_____ means flat on your back

supine

when someone is laying supine the hydrostatic pressure is

zero everywhere