US Physics Q6 Wk5 Exam

the study of blood moving through the circulatory system

hemodynamics

indicates the volume of blood moving during a particular time

flow (volume flow rate)

indicates "how much"

flow (volume flow rate)

units for volume flow rate

volume/time (L/min)

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

velocity

indicates "how fast"

velocity

units for velocity

distance/ time (cm/sec)

three basic forms of blood flow:

- pulsatile

- phasic

- steady

blood moves at a variable velocity; it accelerates and decelerates as a result of cardiac contraction

pulsatile flow

pulsatile flow commonly appears in _______ circulation

arterial

blood moves with a variable velocity; it accelerates and decelerates as a result of respiration

phasic flow

phasic flow commonly appears in _______ circulation

venous

occurs when a fluid moves at a constant speed or velocity

steady flow

present in the venous circulation or when individuals stop breathing for a brief moment

steady flow

when the flow streamlines are aligned and parallel

laminar flow

characterized by layers of blood that travel at individual speeds

laminar flow

two forms of laminar flow:

- plug flow

- parabolic flow

all of the layers and blood cells travel at the same velocity

plug flow

bullet-shaped profile. Velocity is highest in the center of the lumen, and gradually decreases to its minimum at the vessel wall

parabolic flow

AKA silent flow

laminar flow

most common flow seen in arteries

laminar flow

characterized by chaotic flow patterns in many different directions at many different speeds

turbulent flow

small, hurricane-like, swirling, rotational patterns that appear in turbulent flow

eddy/vortex

turbulent flow may be seen downstream from a _______ in a vessel

stenosis

converts flow energy into other forms such as sound or vibration

turbulent flow

sound associated with turbulence

murmur or bruit

tissue vibration associated with turbulence, also described as a palpable murmur

thrill

a unitless number that predicts whether flow is laminar or turbulent

reynold's number

reynold's number above ______ indicates turbulent flow

2000

reynold's number under _____ indicates laminar flow

1500

blood moves from regions of higher energy to lower energy; this is called an

energy gradient

energy is imparted to blood by the contraction of the heart during

systole

3 forms of energy associated with blood:

- kinetic

- pressure

- gravitational

type of energy associated with a moving object

kinetic

kinetic energy is determined by 2 factors:

- object's mass

- the speed at which it moves

heavy/quickly moving objects have _____ kinetic energy

high

light/slowly moving objects have ______ kinetic energy

low

a form of stored or potential energy; the ability to perform work

pressure energy

a major form of energy for circulating blood and creates flow by overcoming resistance

pressure energy

a form of stored or potential energy; associated with any elevated object

gravitational energy

as blood flows through the circulation, energy is lost in 3 ways:

- viscous loss

- frictional loss

- inertial loss

the thickness of a fluid

viscosity

the _______ the fluid, the more viscous it is

thicker

units for viscosity

poise

more energy is lost with movement of _____ viscosity fluids

high

the percentage of blood made up of red blood cells

hematocrit

viscous energy loss is determined by the

hematocrit

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

frictional loss

blood sliding across vessel walls creates heat, causing

frictional loss

energy loss caused by the speed of a fluid changing, regardless of whether the fluid accelerates or decelerates

inertial loss

the tendency of a fluid to resist changes in velocity

inertia

inertial energy loss occurs during 3 events:

- pulsatile flow

- phasic flow

- velocity changes at a stenosis

maximum velocity exists where the vessel is _______ and decreases as the blood flows out of the stenosis into a vessel segment of normal diameter

narrowest

a narrowing in the lumen of a vessel

stenosis

stenosis may cause changes in ______ as blood flows into and out of the narrow portion of the vessel

direction

stenosis may cause increased _______ within the stenosis

velocity

stenosis may cause a turbulence _________ from the stenosis

downstream

stenosis may cause a pressure ________ across the stenosis (pressure downstream is lower than pressure upstream)

gradient

stenosis may cause a conversion of pulsatile flow patterns to ______ flow

steady

describes the relationship between velocity and pressure in a moving fluid

bernoulli's principle

with a steady flow, the sum of all forms of energy is the same ________

everywhere

where kinetic energy is the _____, pressure energy will be the lowest and vise versa

highest

pressure gradient =

flow x resistance

pressure gradient _______ with an increase in flow or resistance

increases

flow _________ with an increase in pressure gradient or a decrease in resistance

increases

ohm's law applies to

electricity

voltage =

current x resistance

resistance vessels are called

arterioles

veins are ____ walled and collapsible

thin

during normal function, veins have a ____ pressure and are only partly expanded with an hourglass shape

low

veins are ______ resistance vessels

low

when venous flow increases with exercise, the cross-sectional shape of a vein changes from hourglass to _____, and then to _____

oval , round

as veins become more round, the resistance to flow ______, which increases outflow toward the heart

decreases

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

hydrostatic pressure

units for hydrostatic pressure

mmHg

pressures are accurately assessed when the measurement is made at heart level. Measurements will be too high if measured _____ the heart, and too low if measured ____ the heart

below , above

when a person is ______ all parts of the body are at the same level as the heart; hydrostatic pressure will be zero everywhere

supine

when a person is standing, at heart level the hydrostatic pressure is _______. Any measured pressure at heart level will be accurate for circulatory pressure

zero

when a person is standing, at locations below heart level hydrostatic pressure is positive. The measured pressure will be ________ than true circulatory pressure

higher

when a person is standing, at locations above the heart hydrostatic pressure is negative. The measured pressure will be ____ than true circulatory pressure

lower

measured pressure =

circulatory pressure + hydrostatic pressure

breathing affects two venous flows:

- venous flow in the legs

- venous return to the heart

located between the abdomen and thorax; the muscle responsible for breathing

diaphragm

during inspiration, the diaphragm moves

downward

during inspiration, the chest cavity expands and ______ pressure in the chest

decreases

during inspiration, negative thoracic pressure creates suction that _______ venous return to the heart

increases

during inspiration, venous flow from the head, arms, and vena cava _______

increases

during inspiration, the diaphragm presses into the abdomen which _______ abdominal pressure

increases

during inspiration, venous flow in the legs _______

decreases

during expiration, the diaphragm moves

upward

during expiration, pressure in the chest ______

increases

during expiration, due to increased thoracic pressure, venous return to the heart ______

decreases

during expiration, venous flow from the head, arms, and vena cava all _______

decrease

during expiration, the diaphragm decompresses the abdomen which causes a ________ in abdominal pressure

decrease

during expiration, there will be an ______ in venous flow from the legs

increase

venous flow in the______ correlates with movement of the diaphragm

legs

changes in venous return to the heart are _______ to those of venous flow in the legs

opposite

Valsalva ________ pressure in the thorax and reduces all venous flows

increases

in a patient standing up:

what is the hydrostatic pressure at the level of the ankle, far below heart level

100 mmHg

in a patient standing up:

what is the hydrostatic pressure at the level of the knee, somewhat below the heart

75 mmHg