Physics Exam #1 Flashcards
Only includes hemodynamics part one powerpoint, not part 2. Part 2 is in iPad.
in terms of the circulatory system, this term describes cardiac function
pulsatility
in terms of the circulatory system, these 2 terms describe the composition of the blood
viscosity
density
in terms of the circulatory system, these 2 terms describe the vascular smooth muscle tone
elasticity
compliance
how many liters of blood does the circulatory system contain?
5 liters (4-8 liters)
normal range for cardiac output is 4-8 liters
how much water makes up plasma?
90%
In blood, these cells dominate.
RBC’s (red blood cells) or erythrocytes
40%
define hematocrit
percentage of erythrocytes in whole blood
what is the term meaning “the percentage of erythrocytes in whole blood”
hematocrit
these cells are larger than erythrocytes and less numerous
WBC’s (white blood cells)
these are smaller than erythrocytes
platelets
what shape are platelets and what do they do?
they are disc shaped
they help with coagulation
In relation to the ultrasound transducer, what do red blood cells do?
they reflect the US beam back to the transducer
a decrease or increase in the hematocrit DIRECTLY correlates to an increase or decrease in the
VISCOSITY (of blood)
what are the units of viscosity
poise
compare the viscosity of blood plasma to water (percentage)
viscosity of blood plasma is about 50% greater than that of water
specifically, “viscosity” has to do with what in relation to a “fluid in motion”?
resistance to flow
what layer of the artery is thicker and has elastic properties
tunica media
why do arteries have an abundance of elastic tissue and less smooth muscle?
to accommodate for the stress of high pressure
arteries are compliant TRUE OR FALSE
TRUE
what is compliance?
the ability of a hollow organ (vessel) to distend and increase volume with increasing pressure
an effect of pulsatile flow
the windkessel effect
what is the windkessel effect
when the pressure pulse forces a fluid into a COMPLIANT vessel such as the aorta, it expands and increases the volume within it….
will show as systolic flow
why can you feel your pulse on your neck or wrist?
windkessel effect
what’s the difference in blood characteristics between anemia and polycythemia
anemia leads to DECREASE in hematocrit & DECREASE in viscosity
polycythemia is an INCREASE in hematocrit & INCREASE in viscosity
to move more viscous fluid requires more
energy
in the circulatory system, energy is lost in the form of…. what rubs against each other…
heat
RBC’s rub against each other… think friction… heat
in regards to the windkessel effect, this event will show as systolic flow
when pressure pulse forces fluid into a compliant vessel (ex. aorta) it expands and increases the volume within it
***recoil is diastolic flow
veins expand in response to
increased transmural pressure
in terms of layers, how are the veins different than arteries
tunica intima - has single layer of endothelial cells
tunica media - thinner than artery, collagen fibers, smooth muscle
are veins more compliant than arteries? why or why not
yes, this is mainly due to their thinner walls (much more elastic too - veins are distensible and can hold large volumes of blood)
known as venous compliance
too compliant though is bad. Could be associated with edema
abnormally compliant veins can be associated with what pathology
edema
what component of the cardiovascular system is known as the “capacitive” component
venous system… “capacitive” because the venous system can store a large “capacity” of blood
what percentage of the body’s blood volume resides in the veins at rest?
65%
veins change shape; talk about it
since they’re elastic they can increase in diameter by an increase in intravascular pressure
they can also decrease diameter by an increase in surrounding tissue pressure.
during exercise the cross sectional shape of a vein changes from hourglass to oval to round
***large volume increase with a very small increase in pressure
when veins expand what decreases or goes down?
resistance to flow decreases!
(this INCREASES outflow toward the heart) - transmural pressure is high
veins empty rapidly and then return to
their typical semi-collapsed state
respiration has a profound effect on these 2 things…
venous pressure and flow
respiration affects venous flow for 2 reasons:
- venous system is low pressure
- muscles responsible for respiration alter pressures in the thorax and the abdomen
anatomically, breathing affects venous flow how (2 ways)
- venous flow in the legs
- venous return to the heart, which comprises venous flow from the head, arms, and flow from the IVC to the heart
a vein at rest is in what kind of state
a semi-collapsed state… veins empty rapidly then return to rest!
flow question as related to breathing: flow INCREASES from the abdominal cavity to the RA and DECREASES from the legs to the abdominal cavity during….
INSPIRATION (remember the sniff test, what happens exactly)
flow question as related to breathing: the return of flow from the legs to the abdomen INCREASES and from the abdomen to the RA DECREASES during…
EXPIRATION
during inspiration the chest cavity __________, diaphragm moves ________, and a __________ pressure is created in the chest.
expands, downward, negative
***negative pressure creates SUCTION that increases venous return to the heart - that’s why venous flow from the head, arms, and vena cava INCREASES during inspiration (more blood flow to head)
but ALSO why is venous blood flow decreased in the legs during inspiration???
because during inspiration, the diaphragm also presses into the abdomen. Abdominal compression INCREASES abdominal pressure and DECREASES venous blood flow in the legs
during expiration the diaphragm moves _______, pressure in the chest is ________. Increase thoracic pressure reduces __________.
upward, increased, venous return to the heart
(rib cage gets smaller as rib muscles relax and the diaphragm decompresses the abdomen - decreases abdominal pressure and increases venous blood flow in the legs)
***thus, venous flow from the head, arms, and the vena cava all DECREASE during expiration (less blood flow to head)
Inspiration five main points
diaphragm moves downward toward the abdomen
thoracic pressure decreases
abdominal pressure increases
venous return to the heart increases
venous flow in legs decreases
Expiration five main points
diaphragm moves upward into thorax
thoracic pressure increases
abdominal pressure decreases
venous return to the heart decreases
venous flow in legs increases
when the calf muscle contracts
venous blood returns to the heart.
what does the effectiveness of the calf muscle pump depend on (2)
depends on the forcefulness of the venous contraction and competence of venous valves
how does the calf muscle pump work…
by shunting blood out of the deep system (veins, venules, capillaries)
explain the calf muscle pump clinically beginning with “muscular contraction…”
“muscular contraction compresses the intramuscular veins and surrounding superficial veins, raising venous pressure and facilitating blood flow towards the heart.”
as blood is moved OUT of the calf veins, these 2 pressures drop
intramural and transmural pressure drops
what will happen if muscle contraction is weak in the calf muscle pump?
less blood is moved out the leg and transmural pressure will remain high — this is why edema occurs in sedentary patients (esp with bad venous valves)
incompetent venous valves are dangerous because
faulty valves allow backward blood flow back down, pulled down by gravity. Blood will be coming into the leg via the arteries faster than it can exit the leg via the veins and then edema happens.
with a normal efficient muscle pump we expect (3)
no flow during rest or low flow
augmented forward flow tip contraction (integrate)
no flow or low flow on relaxation
with an INEFFICIENT muscle pump due to venous incompetence we expect (4)
reflux at rest (retrograde)
augmented flow on contraction
reflux on relaxation
the blood goes back up and then falls back down
Fluid in our body cannot be destroyed, it can only be
CONVERTED by absorption or by being turned into heat
the movement of any fluid medium between 2 points requires 2 things:
a route for fluid to flow (obviously)
a pressure gradient (difference in energy levels) between the two
blood always follows the path of
least resistance
total energy is the sum of these 3 energies:
potential (pressure) energy, kinetic (movement) energy, gravitational energy
pressure energy - created by heart
kinetic energy - energy in motion (mass and speed )
gravitational energy - hydrostatic energy
you have two columns. one is way taller than the other. which one will have a higher hydrostatic pressure?
the taller one
at the level of the heart, the hydrostatic pressure is
0 mmHg
“above” the heart we have a “negative” hydrostatic pressure or decreased pressure
“below” the heart we have a “positive” hydrostatic pressure or increased pressure
what do we mean when we say “blood pressure?”
blood “pressure” is the hydrostatic “pressure” that is exerted by blood on the wall of a blood vessel
blood pressure depends on (3)
- cardiac output
- vascular resistance
- total blood volume
blood pressure depends on #1 and #2
blood pressure = cardiac. output x resistance
in THE SUPINE PATIENT, the hydrostatic pressure is what and why?
it is zero because all parts of the body are at the same level as the heart. A pressure reading on a supine patient is an accurate one; represents true circulatory pressure
In terms of inertia… what is necessary for blood to flow (or any fluid) from one point to another?
a pressure gradient aka energy gradient
**high pressure to low pressure (old knowledge)
define inertia
tendency of an object to resist any change in its motion
as blood move out to the periphery what will it lose?
it will lose energy in the form of heat but the heart pump will keep the inertia
3 types of energy loss (not really lost but converted; either absorbed or converted into heat)
- frictional
- viscous
- inertia
5 things that cause energy loss
- rougher vessel surface
- sharper angles (ex. bends, kinks, twists, branching)
- higher “viscosity” blood aka higher “hematocrit”
- Higher volumetric flow
- increased velocity
define frictional energy loss
every converted to heat from rubbing - blood flow energy loss mainly due to this one
which has greater friction and resistance to flow… a smaller vessel or larger one
smaller vessel
define viscous energy loss (5)
an increase in viscosity leads to an increase in energy loss
if a fluid is thick it moves freely
takes way more energy to move thicker fluid
increase viscosity = decreased velocity
decreased viscosity = increased velocity
define inertial energy loss (4)
fluid resists changes in velocity
changes in speed lead to energy loss
increased or decreased speed - energy loss either way
as blood moves farther out to periphery, energy dissipates in form of heat
what is the driving force behind fluid flow
pressure
in terms of units, what is pressure
force per unit area
equation for pressure is
force divided by area
in a fluid that is not moving, how is pressure distributed?
EVENLY!!!
it is evenly distributed throughout a fluid that is not moving
true or false… pressure exerts its force in ALL directions
true
2 things can generate a pressure gradient in the body
the heart
gravity
a pressure gradient in flow is similar to a pressure gradient in electricity where Voltage = current x resistance. In flow, the equation for a pressure gradient is
flow x resistance
what does Ohm’s Law state?
Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points
electrical resistance is reported in units of ohms. In the circulatory system, the resistance vessels are called
arterioles
define compliance
ability of a vessel to distend and increase volume with increasing pressure
what propels blood along an artery?
the elastic recoil or ARTERIAL COMPLIANCE
missed on exam in calf muscle pump, muscular contraction would lead to an _________ in venous pressure, whereas muscular relaxation would lead to a _________ in venous pressure
increase, decrease
missed on exam capacitance is best described as
a measure of the ability to hold a change in volume per change in time
missed on exam the inverse relationship between pressure and velocity is described as
Bernoullis equation
missed on exam flow resistance depends most strongly on which of the following
flow radius
missed on exam proximal to, at, and distal to a stenosis, WHAT must be constant?
volume flow rate
missed on exam Poiseuille’s Law refers to the flow in a vessel and is determined by what three things?
Resistance, Viscosity, Pressure
