Cardio-Physio-Hemodynamics-Mitov Flashcards
Hemodynamics?
the physical behavior of blood as a fluid.
Hemodynamics examines the interrelationships between: (5 things)
flow, pressure gradients,, resistance, velocity, vessel cross-sectional area
Units of flow
mL/s
Pressure?
Force per unit area, Blood pressure measured in mmHg
Resistance definition and units?
Impedance of flow, mmHg/mL/min -pressure rise associated with an incremental rise in flow
Formula for flow?
Pressure/Resistance which is analogous to Ohm’s law
What is the consequence of too high blood flow?
A too-high flow can damage blood vessels and tissue
What is the consequence of too-low blood flow?
flow that’s too low means tissues served by the blood vessel may not receive sufficient oxygen to function.
What is the pressure that exerts on the walls of the blood vessels?
Blood pressure
Where does blood pressure originate?
With the contraction of the heart
In what 3 ways is blood pressure modified?
altering cardiac activity, vasoconstriction, or vasodilation.
What are the main 3 factors that affect resistance in blood vessels?
vessel length, vessel radius, and blood viscosity
What are the main regions of the circulatory system that generate resistance, due the small caliber of their lumen?
The arterioles and capillary networks
Which vessles in particular are able to rapidly alter resistance by altering their radius through vasodilation or vasoconstriction?
arterioles
What must be overcome in order to maintain blood flow throughout the body?
resistance
Which force overcomes resistance to maintain blood flow?
Pressure
The distribution of blood circulating to the different regions of the body is determined by the output of the and by the contractile state of the resistance vessels (arterioles) of these regions.
left ventricle
systolic arterial pressure
Peak arterial pressure reached during ejection of blood by the heart
Diastolic arterial pressure
Lowest arterial pressure reached during diastole, while the heart is relaxed and filling (not ejecting blood).
Arterial pulse pressure:
The difference between systolic and diastolic arterial pressures; dependent on stroke volume (volume ejected by one ventricle during one contraction), resistance, and arterial compliance.
Mean arterial pressure (MAP):
The average pressure over a complete cardiac cycle of systole and diastole; dependent on peripheral resistance and cardiac output (volume ejected by one ventricle per unit time).
What is the dicrotic notch (incisura)?
Only with aortic pressure
Describe how pressure changes in the cardiovascular system starting in the left atrium?
arterial pressure is a is a useful concept because it can be used to calculate overall blood flow, and thus delivery of nutrients to the various organs. It is a good indicator of perfusion pressure (ΔP).
Mean
What is a good indicator of perfusion pressure (ΔP)?
mean arterial pressure (MAP)
The difference between SBP and DBP is called?
pulse pressure
What are the two major factors that affect the pulse pressure?
(1) the stroke volume output of the heart and (2) the compliance (total distensibility) of the arterial tree.
What is the trend of blood pressure with age?
A gradual increase of SBP, MAP, and DBP
What are the name of the sounds heard when measuring BP?
Korotkoff sounds
Atherosclerosis:
disease of the large and intermediate-sized arteries in which fatty lesions called atheromatous plaques develop on the inside surfaces of the arterial walls.
arteriosclerosis:
general term that refers to thickened and stiffened blood vessels of all sizes.
Low values of systolic and pulse blood pressure have been classically considered hallmark signs of which pathology?
aortic valve stenosis
What is aortic valve stenosis?
narrowing of the aortic valve so that ventricular ejection is impeded.
What causes aortic stenosis?
often occurs as a result of calcium deposits on the leaflets of the aortic valve.
Impaired ventricular ejection, combined with the normal inflow of blood from the left atrium, results in an increased/decreased volume in the left ventricle during diastolic filling.
increased
During aortic stenosis, the increased volume in the left ventricle during diastolic filling can/cannot overcome the resistance caused by the stenotic aortic valve.
can
and allows for partial recovery of left ventricular cardiac output
Left ventricular pressure vs. right ventricular pressure during aortic stenosis?
left ventricular systolic pressures are much higher than aortic systolic pressures
What is patent ductus arteriosus?
The ductus arteriosus (a blood vessel that attaches from the aorta to the pulmonary artery during fetal development after birth) does not close as it should.
a heart valve disease in which the aortic valve does not close tightly, allowing blood to flow from the aorta (the largest blood vessel) into the left ventricle (a chamber of the heart).
Aortic regurgitation
In which pathology does the aortic incinsura dissappear?
aortic regurgitation
Abnormalities in MAP can impact blood and alter the function of the heart.
flow, normal
What is a sustained increase in diastolic blood pressure, a sustained increase in systolic blood pressure, or both.
Hypertension
How do our arteries change as we age?
loss of blood vessel elasticity and decreased compliance of large arteries
Where is the primary focus of damage due to hypertension?
on the left ventricle
What pathology can lead to cardiac hypertrophy, ischemic heart disease, coronary artery disease, kidney disease, and/or stroke?
hypertension
What are some causes of hypertension?
renal artery stenosis, drug use, sleep apnea, and adrenal diseases.
n chronic hypertension, diastolic dysfunction or ineffective left ventricular filling resulting in pulmonary congestion pressure can progress to the right/left side of the heart.
Right side
Right heart failure can then lead to decreased return to the heart, causing increased systemic venous pressures and high hepatic pressures that may impact liver function
venous
right heart failure can then lead to decreased venous return to the heart, causing increased systemic venous pressures and high hepatic pressures that may impact function
liver
What results from high pulmonary vascular pressures with certain lung diseases?
Right ventricular failure, known as cor pulmonale
hypertension can also be caused by left ventricular or valvular dysfunction from systemic hypertension
pulmonary
Study this figure
Another cause of hypotension may occur during conditions such as due to circulating pathogen infections that lead to massive and overwhelming vasodilation as a result of a system-wide immune cytokine responses, or septic shock
sepsis
Sepsis due to circulating pathogen infections that lead to massive and overwhelming vasodilation/vasoconstriction as a result of a system-wide immune cytokine responses, or septic shock
vasodilation
If the cardiovascular system is unable to supply blood to tissues, especially those of the brain and heart, hypoxemia, metabolic failures, and system organ failure (MSOF) can lead to death
multiple
life-threatening condition that results when you lose more than 20 percent (one-fifth) of your body’s blood or fluid supply. This severe fluid loss makes it impossible for the heart to pump a sufficient amount of blood to your body.
Hypovolemic shock
The decrease in blood volume due to hemorrhage produces a decrease/increase in venous return to the heart and a decrease/increase in right atrial pressure.
Decrease, decrease
When hemorrhage occurs, which two components of the vascular system decrease almost immediately?
Cardiac output and arterial pressure.
As a result of hemorrhage, almost immediate reduction of cardiac output and aterial pressure decreases, which aspect has no change?
total peripheral resistance (TPR)
What causes the total peripheral resistance (TPR) to decrease as a result of hemorrhage?
compensatroy responses in the cardiovascular system
What are the 3 compensatory mechanisms as a result of hemorrhage?
- Baroreceptor reflex
- Renin-Angiotensin II -Aldosterone
- Capillaries
What represents the changes in pressure in the arterial system over periods of systole (during which the stroke volume is ejected from the left ventricle) and diastole (during which the heart is refilling and blood in the arterial system continues to flow downstream)?
The arterial pressure wave
Arterial pressure is affected by which 4 things?
- Cardiac output
- stroke volume
- arterial compliance
- peripheral resistance
What is the formula for the rate of flow (Q)?
What does it mean for the smooth muscle in e in the walls of the arterioles is tonically active?
Always contracted
Smooth muscle in arteriole walls are extensively innervated by?
sympathetic adrenergic nerve fibers
What type of receptors are found on the arterioles of several vascular beds (e.g., skin and splanchnic vasculature)?
α1-Adrenergic receptors
What happens when the α1-Adrenergic receptors are activated in vascular smooth muscle?
When activated, these receptors cause contraction, or constriction, of the vascular smooth muscle.
How does the constriction of vasculature (decrease of diameter of the arteriole) affected resistance to blood flow?
Increases resistance to blood flow.
What is the site of highest resistance to blood flow?
arterioles
All/ not all capillaries are perfused with blood at all times.
Not all
Which type of adrenergic receptors are found in arterioles of skeletal muscle?
β2-adrenergic receptors
β2-adrenergic receptors are found in arterioles of skeletal muscle. When activated, these receptors cause constriction/dilation?
Dilation
How to calculate systemic vascular resistance with mean arterial pressure, central venous pressure, and cardiac output?
SVR (aka TRP) = (MAP-CVP)/CO
Systemic vascular resistance (also know as total peripheral resistance) = (mean arterial pressure - central venous pressure)/cardiac output
How is MAP calculated?
MAP is calculated as MAP=DBP+ (SBP-DBP)/3
What is the central point of pulmonary function?
exchange across the barrier that separates the alveolar air and the pulmonary capillary blood.
What drive’s the exchange exchange across the barrier that separates the alveolar air and the pulmonary capillary blood?
Diffusion (Fick’s Law)
Less resistance to stretch = more/less compliance
more
(as in vein walls are thinner and more compliant to hold blood)
Where does the majority of the blood volume come from during compensatory efforts of the body during hemorrhage?
Systemic veins and venules
Which part of the circulatory system has the highest cross-sectional area?
Capillary beds
What part of the circulatory system serves as a major blood volume reservoir?
Veins
Flow to the brain is steady/various and maintained the same/different in rest or exercise.
steady; same
Which part of the nervous system controls blood flow to the various organs?
ANS
Blood flow within each organ changes with body activities, except in the:
Brain
What is velocity?
objects speed in a particlar direction
What is the velocity of blood flow?
rate of displacement of blood per unit time.
How to calculate Area (or cross-sectional area fo a blood vessel or a group of blood vessels):
A = πr2, where r is the radius of a single blood vessel (e.g., aorta) or the total radius of a group of blood vessels (e.g., all of the capillaries)
The velocity of flow should be lowest/highest in vessels with the largest total cross-sectional area (capillaries) and lowest/highest in the vessels with the smallest total cross-sectional area (aorta).
lowest; highest
What is the relationship between velocity and cross-sectional area?
Inverse relationship
As cross-sectional area increases, velocity decreases
Under normal physiological conditions, flow through vessels is governed by which law?
Poiseuille’s law
The the greatest resistance to flow occurs where?
microcirculation, particularly the arterioles
According to Poiseuillie’s law:
Flow is directly/inversely proportional to the longitudinal pressure gradient (inflow pressure minus outflow pressure).
directly prportional
According to Poiseuillie’s law:
Flow is directly/inversely proportional to the fourth power of the radius of the tube?
directly proportional
According to Poiseuillie’s law:
Flow is directly/inversely proportional to the viscosity of the fluid.
inversley proportional
According to Poiseuillie’s law:
Flow is directly/inversely proportional to the length of the tube (vessel)
What is the relationship of resistance to length of tube, viscosity, and radius according to :
Resistance is directly proportional to length of tube.
Resistance is directly proportional to viscosity.
Resistance is inversely proportional to the fourth power of the radius.
What is the most important factor effect flow through a tube?
The radius of the tube.
to blood flow is determined by blood vessel diameter and organization.
Resistance
In a series, increasing resistance to blood flow in any one vessel in the series will increase/decrease the total resistance to blood flow.
increase
The renal and splanchnic circulations have the resistances arranged in series/parallel?
series
The aorta and most other vascular beds have the resistances arranged in parallel/series?
parallel
Opening a new exit route will make it easier for blood to exit the aorta, so adding a new resistance actually decreases/increases the total resistance of the system in parallel?
decreases
What is the reciprocal of resistance?
conductance
What is a measure of the blood flow through a vessel for a given pressure difference?
conductance
The conductance of a vessel increases/decreases in proportion to the fourth power of the diameter?
increases
The farther away the blood is from the vessel wall, faster/slower the flow?
Faster
What occurs if adjacent layers of blood travel at different velocities?
shear
What is a severe consequence of shear?
it breaks up aggregates of red blood cells and decreases blood viscosity.
Where is shear the highest in a blood vessel?
at the wall, where shear rate is normally highest, red blood cell aggregation and viscosity are lowest.
What is laminar or streamline flow through the blood vessel?
flow through vessels occurs in concentric layers that slip over each other, with fastest flow at the center and slowest up against the walls of the vessel.
When streamline flow is disrupted, kinetic energy is squandered on chaotic motion, a pattern known as .
turbulence
Major influencers on Reynolds number (laminar or turbulent flow) are which 2 factors?
- changes in blood viscosity
- changes in velocity of blood flow
Viscosity desribes a liquids resistance to ?
flow
Viscosity and density are the characteristics of a fluid, but there is/is no direct relation between viscosity and density
is no
High Reynolds number is associated with?
turbulent flow
How would a decrease in viscosity affect Reynolds nimber?
A decreased viscosity (e.g. low hematocrit), would increase Reynolds number.
Narrowing of blood vessel, which produces an increase in velocity of flow, would have what effect on Reynold’s number?
Increase Reynolds number
What can happen to RBCs if blood is stationary or barely moving?
, RBCs have time to adhere to each other and form aggregates that resemble stacks of coins (rouleaux).
The tendency for erythrocytes to aggregate at low flow rates depends on the concentration of the larger protein molecules in plasma, especially ?
fibrinogen
Changes in blood viscosity with flow rate are much more/less pronounced when the concentration of fibrinogen is high.
more
RBC aggregates break apart as flow velocity increases/decreases?
increases
What describes how distensible a blood vessel is ?
Capacitance or compliance
Which blood vessels are more compliant?
veins, hence more blood is stored in veins than arteries
What happens to veins as we age?
The energy driving flow during diastole was stored in the elements of the arterial wall by the ventricle during systole.
elastic
So, energy stored in arterial walls during systole drives blood forward during diastole
Arteries with more elastic properties dampen the pulse pressure, this effect is called?
Windkessel effect
