Chapter 18 Flashcards
_______ is the study of blood moving through the circulatory system
hemodynamics
______, also called ______, indicates the volume of blood moving during a particular time. This measurement answers the question: how much?
flow, volume flow rate
what are the units of flow?
volume divided by time; liters/min
______ indicates the speed or swiftness of a fluid moving from one location to another. This answers the question: how fast?
velocity
what are the units of velocity?
distance; cm/s
what are the 3 basic forms of blood flow?
pulsatile, phasic, and steady
______ occurs when blood moves with a variable velocity, blood accelerates and decelerates as a result of cardiac contractions; therefore, this commonly appears in the arterial circulation
pulsatile flow
______ also occurs when blood moves with a variable velocity. Blood accelerates and decelerates as a result of respiration; therefore, this often appears in the venous circulation
phasic flow
______ occurs when a fluid moves at a constant speed or velocity. This is present in the venous circulation when individuals stop breathing for a brief moment
steady flow
______ is when the flow streamlines are aligned as parallel. this is characterized by layers of blood that travels at individual speeds. Commonly found in normal physiologic states
laminar flow; The word lamina means layer.
2 forms of laminar flow: ______ flow occurs when all of the layers and blood cells travel at the same velocity
______ flow has a bullet-shaped profile. Center velocity is highest then gradually decreases
Plug
Parabolic
The ______ predicts whether flow is laminar or turbulent.
Reynolds number
The Reynolds number for laminar is less than ______
And for turbulent flow is greater than ______
> 1500
<2000
______ is characterized by chaotic flow patterns in many different directions and at many different speeds, the steam lines are often obliterated
Turbulent flow
Small, hurricane-like, swirling, rotational patterns appear in turbulent flow, this is called an _____ current or a ______
Eddy
Vortex
______ is often associated with cardiovascular pathology and elevated blood velocities, maybe downstream from a significant stenosis in a vessel
Turbulence
Sound associated with turbulence is called a ______ or a ______
Murmur
Bruit
Tissue vibrations associated with turbulence is called a ______, this is also described as a palpable murmur
Thrill
Blood moves from regions of higher energy to lower energy, this is called ______
Energy gradient
Energy is imported to the blood by the contraction of the heart during ____
Systole
The total energy at a specific location within the circulation is the sum of what three energy forms?
Kinetic, pressure, and gravitational
kinetic energy is associated with ______ objects, and is determined by what 2 factors?
moving
an objects mass and the speed at which it moves
pressure energy is a form of ______ or ______ energy. Pressure has the ability to perform work; its for circulating blood and creates flow by overcoming resistance
stored or potential energy
gravitational energy is also a form of stored or potential energy. it is associated with any ______ object
elevated; identical objects at the same height have the same gravitational energy
as blood flows through the circulation, energy is lost in what three ways?
viscous loss, frictional loss, and inertial loss
______ describes the thickness of a fluid
viscosity; more energy is lost with a higher viscosity
what units is viscosity measured?
poise
viscous energy loss in blood is determined by the ______, this is a percentage of blood made up of red blood cells
hematocrit; a normal value is approximately 45%
with ______, hematocrit is reduced, and blood has a reduced viscosity
anemia
______ losses occur when flow energy is converted to heat as one object rubs against another such as blood sliding across vessel walls creating heat
frictional
______ relates to the tendency of a fluid to resist changes in its velocity
inertia
what three events occurs during inertia energy loss?
pulsatile flow, phasic flow, and velocity changes at a stenosis
velocity ______ as the vessel narrows; ______ velocity exists where the vessel is narrowest
increases
maximum
velocity ______ as blood flows out of the stenosis into a vessel segment of normal diameter
decreases
a ______ is a narrowing in the lumen of a vessel
stenosis
- changes in flow direction
- increased velocity as vessel narrows
- turbulence downstream from the stenosis
- pressure gardient across the stenosis
- loss of pulsatility
effects of a stenosis
______ describes the relationship between velocity and pressure in a moving fluid
Bernoulli’s principle; it is derived from the principle of conservation of energy
this principle states that, with a steady flow, the sum of all forms of energy is the same everywhere; AKA the sum of kinetic energy and pressure energy remains constant
conservation of energy
what is the relationship between flow, resistance, and pressure gradient?
pressure gradient = flow x resistance
pressure gradients increases when either?
flow increases or resistances increase
flow increases when either
pressure gradient increases or resistances decreases
what is Ohm’s law?
voltage = current x resistance
pressure in a fluid system is called ______ in an electrical system; flow is called ______; and resistance stays the same
voltage
current
what is the units for electrical resistance?
ohms
in the circulatory system, the resistance vessels are called ______
arterioles
veins, like arteries, are usually ______ resistance vessels
low
when venous inflow increases during exercise, the cross-sectional shape of a vein changes from hourglass to oval and then to round; allowing volume ______ with a very small increase in pressure
increase
pressure related to the weight of blood pressing on a vessel measured at a height above or below heart level
hydrostatic pressure
what are the units for hydrostatic pressure?
mmHg
Hydrostatic pressures are erroneously to ______ when the measurement is made at a location below heart level and ____ if made above heart level
high
low
when a person is supine the hydrostatic pressure is ______ everywhere; this accurately represents true circulatory pressure
zero
what is the equation for measured pressure?
measured pressure = circulatory pressure + hydrostatic pressure
respiration affects venous flow for what 2 reasons?
the venous system is low pressure and muscles responsible for respiration alter pressure in the thorax and the abdomen
breathing affects venous flow in what 2 ways?
venous flow in the legs and venous return to the heart
during inspiration the chest cavity expands creating ______ pressure in the chest; which increases venous flow from the head, arms, and IVC and decreases blood flow in the legs
decreased
during expiration pressure ______ in the chest; reducing venous return to the heart decreasing the flow in the head, arms, and IVC; increases flow in the legs
increases
