Cardio Physiology Flashcards
Cardiac output
the rate at which blood is pumped from either ventricle. CO of L vent equals the CO of the right because its in series.
Venous return
the rate at which blood is returned to the atria.
How does CO and venous return look when the heart is in steady state
CO from the heart equals venous return to the heart
how is blood flow to organs altered
by the resistance of the blood vessels, especially the arterioles
mitral valves
between the artium and the ventricle. Between the rich side, tricuspid valve, and theft side, the mitral valve.
Semilunar valve
between the left ventricle and the aorta.
When the left ventricle ___, the pressure in the ventricle ___ and the _____ ____ opens to send blood gushing out
contract, increases and the aortic valve
Different mechanisms of cardiac output
CO can RTS, and distribution to organs can change, or CO can inc or dec as the percentage to each organ stays the same, or CO and percent distribution are altered.
how does the pressure of the vena cava compare to the atrium
the vena cava P is higher
How does CO compare between the two ventricles
it is the same!
Hemodynamics
how the blood flows.
Describe the structure and function of arteries.
the aorta is the biggest, they have thick muscle with elastic fibers. THEY ARE UNDER THE HIGHEST PRESSURE.
The volume of blood contained in arteries is the ______ volume
Stressed volume
Describe the structure of arterioles. They are always…?
they are filled with smooth muscle. Always tonically active, which means contracted
What vessel is under the highest resistance
arterioles
What fibers are arterioles innervated by
sympathetic fibers, alpha 1 adrenergic and beta 2 adrenergic.
What do alpha-1 adrenergic receptors do
on arterioles of vascular beds. When stimulated, they cause contraction, or constriction of the Smooth muscle. Constriction causes a decrease in diameter, which causes an increase in resistance.
What do beta-2 adrenergic receptors do
arterioles of skeletal muscle. they cause dilation (relaxation) when activated, which increases diameter, and decreases resistance.
Capillaries
thin walled lined with single layer of endothelial cells and surrounded by a basal lamina. Site for exchange
how do lipid soluble substances versus water soluble substances cross the membrane
lipid soluble cross by dissolving and diffusing across the endothelial cells. Water soluble cross through water filled clefts, or through large pores.
How is it that not all capillaries are filled with blood
there is selective perfusion, which means that they are filled based on metabolic needs. This is controlled by the dilation or constriction of arterioles, which is controlled by the sympathetic innervation.
What vessel contains the largest percentage of blood in the body
veins
The volume of blood in the veins is called the ___ volume
unstressed volume
What do alpha-1 adrenergic receptors in veins do
they cause contraction of the veins, reduces capacitance, and therefore reduces the unstressed volume.
Velocity of blood flow is equal to
Flow (Q)/cross-sectional area (A)
Flow
the volume flow per unit time
Area
cross-sectional areas of the vessel
As area increases, What happens to the velocity
it decreases
Think about why the blood flow velocity makes sense.
velocity will be slower in capillaries, to allow for more time to diffuse, because more area?
How does blood flow
down its pressure gradient, so from high to low.
Flow is equal to
pressure/resistance
Blood flow is directly proportional to…
the pressure difference (pressure gradient)
blood flow is inversely proportional to…
resistance.
An increased resistance means a ____ flow
decreased
Decreasing resistance will ___ flow
increase
Total Peripheral Resistance
TPR. CO = P/R (but P will be the pressure difference between the vena cava and the aorta. [instead of Flow=P/R]
Poiseuille Equation
used to describe the relationship between the resistance, blood vessel diameter and the blood viscosity
Resistance is proportional or inversely proportional to viscosity
proportional
If viscosity increases, what happens to resistance
it increases
Is resistance proportional or inversely proportional to length of the blood vessel?
directly
Is the resistance proportional or inversely proportional to the radius
it is inversely proportional to the fourth power of the radius.
When the radius of a blood vessel decreases, what happens to its resistance?
it increases.
Series vs parallel resistance.
series is considered to be the sum of the remittances of all the vessels with a given organ. And parallel resistance is the distribution of blood flowing from the different branches of the aorta.
blood flow in the CVS is…
laminar
Laminar blood flow…
streamlined. velocity of the blood closest to the vessel wall is zero, and then each successive layer to the interior of the cell increases velocity. so the velocity of the blood at the center of the vessel is the fastest.
Turbulent blood flow. What does this do to the needed pressure.
when there is something like a valve of a clot that disrupts the laminar nature of the flow. There is no parabolic profile to blood flow. AUDIBLE and more pressure or energy is needed to move it.
Korotkoff sounds
turbulent flow!
What can cause turbulent flow. you can hear…?
stenosis, cardiac valve disease. MURMURS
Reynolds number
dimensionless number to see if blood flow is laminar or turbulent. Less than 2000, laminar, above 2000 may be turbulent, above 3000 its definitely turbulent
decreases in viscosity causes ___ in Reynolds number. Give an example of what would cause this
increase. Like decreased hematocrit.
Narrowing of a blood vessel causes a/an _____ in velocity, which will then in turn cause a/an ___ in Reynolds number.
increase, increase.
Anemia is a d/I in hematocrit? How does anemia affect Reynolds number
a decrease. which then causes turbulent flow, and murmurs. Reynolds number is high for anemia, because there is a decrease in viscosity, because less in the blood, and therefore an increase is Reynolds number. Then there is high CO, which will cause an increase in velocity which will increase Reynolds number..
Thrombi and Reynolds number
a blood clot causes an increase in Reynolds number by narrowing the diameter, with an associated increase in velocity, and then an increase in Reynolds number.
What is shear
what happens when blood moves at different velocities. So at the cell wall, there is high shear because at the wall velocity is zero, and at the center velocity increases. So at the center of the vessel, shear is at its lowest.
Compliance and capacitance
is highest in veins, because they can hood more volume at lower lower pressure. Compliance is lower in arteries because they hold less blood than veins, and at higher pressure.
Compliance/capacitane, veins and arteries
Veins are high compliance, and unstressed volume. Arteries are less compliant and have stress volume
What happens when there is a change in compliance in the veins
there is a decrease compliance in the veins, then the veins can hold less blood, blood will shift from the veins to the arteries. Then the unstressed volume will decrease and the stress volume will increase.
why is pressure in the aorta highest
because there is a large blood volume and the low capacitance.
what happens at systole and diastole
during systole, blood is ejected, and during diastole, there is a rest.
Diastolic Pressure
lowest arterial pressure, pressure in the arteries during ventricular relaxation when no blood is being ejected from the left ventricle.
Systolic Pressure
highest arterial pressure when the blood is being ejected from the left ventricle during systole.
What is the dicrotic notch or the incisura
the blip in the arterial pressure curve, when the aortic valve closes. There is a brief moment of retrograde flow from the aorta back to the valve. It briefly decreases the aortic pressure.
Pulse Pressure
the difference between the systolic and the diastolic pressures.
Stroke volume
the volume of blood ejected from the left ventricle on a single beat.
Mean arterial pressure
the average pressure in a complete cardiac cycle. (Diastolic + 1/3 of the PP)
Why is diastolic pressure heavily involved in the MAP
because a greater fraction of the cardiac cycle happens in diastole
PP dampens as it moves into smaller arteries and arterioles. Why?
the resistance of these smaller vessels makes it hard to transmit the PP, and the compliance, capacitance of the vessels, especially veins, dampens the PP.
The PP will change is the ____ changes
stroke volume
Arteriosclerosis
plague deposits in the alls, causing a decreased diameter and makes the walls stiffer and less compliant. because the compliance is created, the SV that is ejected causes a greater change in arterial pressure. Therefore, the systolic pressure, PP and the mean pressure all increase.
Aortic stenosis
aortic valve is narrowed, so the amount of blood that can leave is less. So SV is reduced, and less blood enters the aorta on each beat. So systolic pressure, mean pressure and PP are all decreased.
Aortic regurgitation
blood flow is interrupted, usually by abnormality, and the blood back flows into the aorta. Could be because pressure in the ventricle is low (because there is relaxation of the ventricle) or because the arctic valve isn’t good.
How does the pressure relate in veins and arteries
in veins pressure is much less, due to the resistance of the vessels
Which vasculature is at a lower pressure, the pulmonary or the systemic?
Pulmonary
Which vasculature has a lower resistance
pulmonary
Electrical activation is the cardiac ___ ___ which usually starts in the _____ ___
electric potential, and in the SA node.
Describe the sequence in terms of contraction of the chambers
The atria must contract before the ventricles, and the ventricles must contract from apex to base for a sufficient ejection of blood.
Contractile vs conducting cells
the contractile cells are a majority of the atrial and ventricular tissue, and the conduction cells are in the nodes, internal tracts, bundle of His and Purkinje fibers. Conducting cells are responsible for rapidly spreading the action potentials. Contractile cells are the working cells
How dos an action potential spread throughout the myocardium
- the SA node fires the AP like a pacemaker
- Atrial internal tracts bring the AP to the atria.
- Simultaneously, the AP is Brough to the AV node
- The AV node has a sower conductance, which allows the ventricle to fill with blood
- Bundle of His fibers get the AP and travel fast, then down the Purkinje systems all within the ventricle.
What happens if the AV nodes fire too quickly
there will be decreased ventricular filling, and decreased SV and CO
Normal sinus rhythm. criteria?
patterns and timing of activation of the heart is normal. criteria are:
- AP must originate at the SA node
- SA node impulses must happen at 60-100 impulses per minute.
- Activation of myocardium must happen int he correct sequence
Talk a little about latent pacemakers
the pacemaker of the heart is the SA node because it depolarizes the fastest (probably because there is a smaller AP). The other tissues won’t spontaneously depolarize because the SA node depolarizes faster. But there are conditions that the other tissues can become the pacemakers.
- If the SA node decreases in its firing or is destroyed.
- if firing rate of the latent pacemakers becomes faster than that of the SA node
- the conductance of the firing of AP from the SA node is blocked because of disease
why do the AV nodes have a slow conductance
there is a slow conductance because there slow conduction velocity, which ensures that the ventricles do not activate too early.
Why do the Purkinje fibers conduct quickly?
to make sure the activation of the ventricle is fast to readily and rapidly eject blood.
what does conduction velocity depend on?
it depends on the size of the inward current, the rate of the rise of the upstroke and the cable properties like resistance.
Conduction velocity does not depend on
duration of the AP
effects of the ANS on the heart rate is called…
Chronotropic effects
How do the sympathetic and parasympathetic affect heart rate
sympathetic increases HR and para decreases HR
Positive chronotropic receptors. example
increase heart rate. Sympathetic. NOREPINEPHRINE. activates Beta-1 receptors on the SA node. causes an increase in If, the funny influx of Na, which increases the rate of phase 4 depolarization. More Ca channels are also open, which means there has to be less depolarization to have another AP. Essentially the threshold is lower and there is faster depolarization, so more APs, faster heart rate
Negative chronotropic effects
decrease in heart rate. parasympathetic. ACETYLCHOLINE. there will be a decrease in If after the ACh binds with muscarinic receptors in the SA node. Less If means that the depolarization will take longer. Longer for APs, slows the heart rate. also, hyper polarization happens when there is an increase in K outflux, and an increase in threshold potential.
The effects of the ANS on the conduction velocity is the __
dromotropic effects.
Simulation of the sympathetic NS does what to conduction velocity
increases.
What mechanism causes the increase in conduction velocity
increased Ca inward, which means increased conduction velocity. Shortens the ERP which allows increased firing rate.
How does the parasympathetic affect the conduction velocity
parasympathetic causes a decrease in Ca moving in and an increase in K moving out, so the AP rate is decreased.
isotropism
ability to develop force
positive inotropic effects vs negative
increase both the rate of tension development and and peak tension. the opposite.
How does contractility relate to Ca
the larger the inward movement of Ca and the larger amount of Ca stored, means the larger the Ca in the ICF when released fro the SR, and the greater the contractility.
What do Beta-1 receptors affect
SYMPATHETIC a positive inotropic effect which causes increased peak tension, increased rate of tension development and faster relaxation (shorter twitch)
When there is an increase in heart rate, what happens to contractility
it increases
Why is there an increase in contractility when there is an increase in heart rate.
More APs, more Ca released from the SR, more contraction
Positive staircase effect
AKA Bowditch staircase, or treppe. with each beat after the heart rate doubles, tension builds little by little. This is because there are more action potentials, more Ca entering the cell, and more stored Ca in SR. This goes until maximum Ca storage is achieved.
Postextrasystolic potentiation
Extrasystole = an extra beat. The tension will be higher on THE NEXT beat, and not on that extrasystole beat.
How do cardiac glycosides affect contractility.
these are positive inotropic agents, like digoxin and digitoxin and ouabain. They inhibit the Na-K pump. By inhibiting this, less Na is pumped out of the cell, so intracellular Na increases. This causes the Ca-Na pump to keep calcium in the cell (normally, the pump works by getting energy from the inwardly moving Na down its gradient to pump Ca out of the cell.) so when Na doesn’t have a con gradient to allow sodium to rush in, the pump stops sending Ca out, and the intracellular Ca stays in. Which then increases the tension!
When would cardiac glycosides be used
congestive heart failure. this prevents the ventricles from having a strong enough contraction to eject sufficient SV. So these drugs will increase the Ca in the myocardium, and provide a stronger contraction.
Stroke volume
volume of blood ejected by the ventricle on each beat. The difference between the blood volume in the ventricle before and after ejection. Usually 70ml.
Ejection fraction. what does it also indicate?
the fraction of the end-diastolic volume ejected in each SV. Usually 55%. indicated contractility. As this number increases, so does contractility.
Cardiac output
total volume of blood ejected from each ventricle. CO = SV x HR
What does the Frank Starling relationship state. What relationship does this solidify
that the volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole, which relies on venous return. THIS ENSURES THAT CO MATCHES VENOUS RETURN
in terms of CO, does pressure work or volume work require more energy? give examples
pressure work, because it needs more O2 to pump the blood. Like in stenosis, more P to pump the blood out. Then in volume work, like during strenuous exercise, its volume work to increase the CO.
How does the muscle thickness of the left ventricular wall compared to the right help explain pressure work
the left ventricle has much higher pressure work needs, so it needs more O2 consumption to pass on the blood. Therefore it has a thicker wall to handle that increased need to spend O2 to meet those higher pressure needs.
Explain pressure work in terms of systemic hypertension and the thickness of cardiac walls
This requires the left ventricle to have a lot more pressure work, so the wall hypertrophies to accommodate for the increased O2 consumption from the pressure work.
Law of Laplace
the pressure prelates directly with the thickness of the wall and the tension, and indirectly relates to the radius.
What does the thickness of the ventricular wall say about the pressure it can exert
According to Laplace, the thicker the wall the more pressure it can exert.
What causes an increase in MSP (mean systemic pressure). How does an increase in MSP shift the vascular function curve
an increase in blood volume and a decrease in compliance.
shifts to the right.
What is the driving force of blood flow. Whats its value
mean arterial pressure. Approximately 100 mmHg
The pressure in the major artery serving each organ is ___to Pa/MAP because of the parallel arrangement of arteries off of the aorta
equal
MAP/Pa= ?
CO x TPR
How does chronic hypertension affect the baroreceptors
The baroreceptors do not see elevations in the blood pressure, or they do not think its abnormal. For example, it may have a higher set point, or there may be decreased sensitivity of the baroreceptors.
Where are the cardiovascular centers located in the brain?
The lower 1/3 of the pons and the reticular formation of the medulla.
Parasympathetic affect on HR
it decreases it
Sympathetic affect on HR when talking about baroreceptors
it can…
- inc the SA node to increase HR
- increase contractility of cardiac muscle and SV
- cause vasoconstriction in arterioles which will increase TPR
- vasoconstriction the veins to reduce unstressed volume
