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BRS Cardiovascular Physiology
Terms in this set (215)
Systemic blood flow is caused by the cardiac output of what side of the heart?
Pulmonary blood flow is caused by the cardiac output of what side of the heart?
What vessels contain an extensive amount of elastic tissue and smooth muscle?
What type of volume is contained the arteries, stressed or unstressed?
Which vessel type is the site of highest resistance in the cardiovascular system?
True or False? ß2-ARs are found n arterioles of skeletal muscle.
True or False? Capillaries have the smallest total cross-sectional and surface area of any of the other vessel.
False; In their entirety, capillaries contain the largest total cross-sectional and surface area. It is for this reason the velocity of blood through capillaries is very slow.
Veins are under high or low pressure?
What type of vessel in the cardiovascular system contains the highest proportion of blood?
What is the name given to blood volume in the veins?
What type of adrenergic receptors are associated with veins?
How is velocity related to cross-sectional area?
They are indirectly proportional. When velocity increases, cross-sectional area decreases.
How is velocity related to flow?
They are directly proportional. When velocity increases, flow increase.
What is the equation for velocity of blood flow?
v = Q/A
Where is velocity highest, in the aorta or in the sum of all the capillaries?
The aorta because the total cross-sectional area of the capillaries is much greater than the aorta.
What is important about the low velocity of blood in capillaries?
The low velocity of blood in capillaries is very important because it optimizes the conditions for substance exchange.
How is blood flow related to the pressure gradients (dP)?
Blood flow is directly proportional to pressure gradients. The greater the pressure gradient between two segments of vessel, the greater the flow.
How is flow related to resistance?
Resistance and flow are inversely proportional.
What is the equation for cardiac output?
CO = (MAP - RAP)/TPR; where CO = cardiac output, MAP = mean arterial pressure, RAP = right atrial pressure, & TPR = total peripheral resistance
How are resistance and viscosity related?
Resistance increases with increasing viscosity.
What is viscosity and what determines it in the blood?
Viscosity is a fluids resistance to flow, and in the blood, it is dependent on hematocrit.
How are resistance and the length of a vessel related?
The greater the length of the vessel, the greater the resistance. Resistance and length are directly proportional. This makes sense because there is more chances for the blood to interact with the walls of the vessel and slow down the flow.
How is resistance related to the radius of the vessel?
Resistance is inversely proportional to the fourth power of the radius.
True or False? Arteries arranged in parallel all receive the total blood flow.
False; When vessels are arranged in parallel, they only receive a fraction of the total blood flow.
True or False? The total resistance of arteries in a parallel arrangement is greater than the resistance in anyone vessel alone.
False; Due to parallel arrangement, total resistance is less than any one vessel.
What happens to the total resistance when an artery is added in parallel?
total resistance decreases
What is true about pressure in parallel arteries?
the pressure is the same in each
Where does one see vessels in a series?
blood delivery to organs
How does one calculate the total resistance of blood vessels in a series?
Total resistance for vessels in a series is the sum of each vessel's individual resistance.
In a series arrangement of vessels, which vessel type provides the greatest resistance?
True or False? Blood vessels in series all receive the same total blood flow.
True; This makes sense because when blood vessels are arranged in series, the same amount of blood travels through each vessel because it does not have other avenues like in parallel arrangements.
What happens to pressure as blood travels through vessels in series?
the pressure decreases
What is laminar flow?
When flow is streamlined, smooth.
What is turbulent flow?
When flow is rough and all over the place.
What is Reynold's number?
a value uses to tell whether flow will be laminar or turbulent
What happens to flow as Reynold's number increases?
flow becomes more turbulent
Turbulence results in what type of sound in the vessels?
What increases Reynold's number?
1. Decreased blood viscosity increases Reynold's number, and this makes sense because low viscosity means there are less RBCs to resist a force that causes change.
2. Increased blood velocity causes an increase in Reynold's number. This makes sense because think how hard it is to control a car at 200mph as opposed to 35mph.
Food for thought! If you remember one of these effects on Reynold's number, you will remember both. How is through the relation ship between velocity and viscosity. Velocity is directly related to flow. Flow is inversely proportional to resistance, and resistance is directly proportional to viscosity. Therefore, an increased velocity is often related to a decreased amount of viscosity. Velocity is affected in multiple ways, but this is an easy way to help remember the two.
What is shear?
Shear is the force experienced by blood vessels due to the fact that blood travels at different velocities within a blood vessel.
Where is blood velocity highest in a given vessel?
the center of a vessel
Where is blood velocity close if not zero in a given vessel?
at the walls of a vessel
Where is shear greatest?
Shear is greatest at the walls of the vessel because there is a greater variability of velocity there. The difference between zero and fast is much greater than fast and faster.
What is distensibility?
Distensibility is the ability of a vessel to increase in size; or rather, dilate.
What is compliance/capacitance?
Compliance is the ability of a vessel to hold more or less blood. Compliance and distensibility are related but are not the same thing.
Compliance is highest in what type of vessel?
veins; This makes sense since veins contain the highest portion of blood at any given point in time.
What is elastance?
Elastance is the stiffness of the vessel.
What causes elastance?
the amount of elastic tissue a vessel contains
How is compliance related to elastance?
Compliance and elastance are inversely proportional. This makes sense when you think about elastic waist bands or Spanks. They contain lots of elastic material, which helps hold in the fat instead of letting it expand out.
What is the equation for capacitance?
capacitance = volume/pressure
How is capacitance related to pressure?
Capacitance is indirectly proportional to pressure.
What happens to capacitance with age?
Capacitance decreases with age because vessels become stiffer.
What happens to pressure as it flows from the aorta back to the heart through the vena cava?
Where does one see the greatest decrease in pressure?
One sees the greatest decrease in pressure at the arterioles because they are the site of highest resistance.
True or False? Arterial pressure is pulsatile, not constant.
What is systolic pressure? (no numbers needed)
The highest pressure obtained during the cardiac cycle.
What is diastolic pressure? (no numbers needed)
The lowest pressure obtained during the cardiac cycle.
What is pulse pressure?
the difference between systolic and diastolic pressure
What is the largest determinant of pulse pressure? Why?
Stroke volume is the largest determinant of pulse pressure. This is true because an increased volume of blood leads to an increase in of pressure in the arteries because they are not very compliant. Since systolic pressure increases without an increase in diastolic pressure, the difference between the two is greater and pulse pressure is therefore higher.
What happens to pulse pressure as one ages?
Pulse pressure usually increases as one ages because the stiffness of the vessels increases.
How does one calculated to mean arterial pressure?
add diastolic pressure plus 1/3
What does the P wave signify?
What is the PR interval?
the distance between the P wave and the beginning of the Q wave
What happens to the PR interval when conduction through the SA nodes decreases?
What happens to the PR interval when conduction through the SA node increase?
What does the QRS complex represent?
What is does the QT interval represent?
represents the entire period of ventricular depolarization and repolarization
What does the ST segment represent?
represents the period when the ventricles are depolarized
What does the T wave represent?
What determines the resting membrane potential of cardiac muscle?
K conductance; this is why the resting membrane potential approaches the K equilibrium potential
What is the role of the Na/K-ATPase in cardiac muscle with respects to ions?
maintain ion concentration gradient
What is the resting membrane potential of cardiac muscle?
True or False? Action potentials are shorter than an action potential in the nervous system.
False; They are longer thanks to L-type Ca channels
What causes phase 0 in a cardiac action potential? What starts it?
an increase of Na conductance due to fast-Na channels
What causes phase 1 in a cardiac action potential? What causes the initial repolarization?
increased conductance of K and decreased Na conductance
What causes phase 2 in a cardiac action potential? What causes the plateau?
Phase 2 is caused by the opening of L-type calcium channels which causes an increase in Ca conductance into the cell and an increase in K conductance outward. The opposite movement of Ca and K are nearly equal so the membrane potential does not change.
What does phase 3 represent?
repolarization; Ca conductance increases and K conductance predominates which leads to hyperpolarization
What does phase 4 represent?
the resting potential
The SA node is known as the ____ of the heart?
What is the SA node considered the heart's pacemaker?
It has an unstable resting membrane potential which leads to an action potential
What causes the SA node's unstable resting membrane potential?
the influx of Na into the cell due to funny-Na channels
What type of pacemakers are the AV node and the Purkinje fibers?
What is the importance of the latent pacemakers?
Latent pacemakers take over for the SA node if it is suppressed.
What is the relative rate of depolarization for the different pacemakers of the heart?
SA node > AV node > Purkinje fibers
Why is the SA node normally the pacemaker of the heart?
It spontaneously depolarizes faster than the other two
What causes the upstroke in the action potential of the SA node, Na or Ca?
What turns on the funny-Na channels?
What determines conduction velocity?
size of inward current during the upstroke of an action potential
Where is conduction velocity highest?
Why is conduction velocity slowest in the AV node?
to allow time for ventricular filling
What is the absolute refractory period?
the period of time between the upstroke of the action potential and the end of the plateau when another stimulus cannot cause another action potential
What is the effective refractory period?
period when a conducted action potential is impossible
What is the relative refractory period?
The period right after the absolute refractory period where a stronger stimulus than normal is required to cause an action potential.
What are chronotropic effects?
effects that change heart rate
What is a negative chronotropic effect?
the slowing of heart rate by decreasing SA node firing rate
What is a positive chronotropic effect?
increasing the heart rate by increasing the SA node firing rate
What is a dromotropic effect?
effects conduction velocity, especially in the AV node
True or False? The ventricles have parasympathetic vagal innervation like the SA node, atria and AV node.
Why does a negative chronotropic effect, parasympathetic stimulation, cause a slowing in heart rate?
funny-Na channels are inhibited which causes a slowing in phase 4 depolarization
Why does a negative dromotropic effect cause a decrease in conduction velocity?
Ca conductance inward is decreased
What receptor is stimulated by norepinephrine at the heart?
What is the importance of an intercalated disk in cardiac muscle?
maintance of cell-to-cell adhesion
Where does one find gap junctions in the heart?
at intercalated disks
What is the significance of gap junctions?
They allow rapid conduction of action potentials between cells, so that they contract as one.
True or False? T tubules are extensions of the cell membrane.
What is the significance of T tubules in cardiac muscle?
they carry the action potential
True or False? T tubules in cardiac muscle form dyads with the sarcoplasmic reticulum.
What is the significance of the sarcoplasmic reticulum?
It is the site of calcium storage for excitation-contraction coupling.
What type of receptor is located on the sarcoplasmic reticulum that leads to calcium release?
What is contractility?
the intrinsic ability of cardiac muscle to develop force at a given muscle length
Contractility is also known as what?
What factors increase contractility?
1. heart rate
2. sympathetic stimulation via ß1-ARs
3. cardiac glycosides
Why does increased heart rate cause increased contractility?
An increased heart rate causes an increase in intracellular Ca, which results in greater tension during contraction.
How does sympathetic stimulation increase contractility?
1. increases Ca influx during the plateau
2. inactivates SERCA by phosphorylation of phospholamban
What do cardiac glycosides increase contractility?
Cardiac glycosides inhibit Na/K-ATPase activity, This increase intracellular Na concentrations changing the concentration gradient. Without the Na concentration gradient established by the Na/K-ATPase, the Na/Ca counter-transporter cannot work; therefore, intracellular Ca concentrations are increased. Increased intracellular Ca concentrations lead to greater tension during contraction.
How does parasympathetic stimulation via acetylcholine and muscarinic receptors decrease contractility?
by decreasing inward Ca current the plateau of the action potential
What is preload?
Preload is the tension placed on the cardiac muscle by the end-diastolic pressure which is directly proportional to end-diastolic volume.
What is afterload?
The load which the cardiac muscle must exert its contractile force against. In the left ventricle, it is the aortic pressure, and in the right ventricle, it is the pressure of the pulmonary artery.
What decreases the velocity of cardiac muscle contraction?
How are venous return and cardiac output related?
they are directly proportional
True or False? Increases in end-diastolic volume increase ventricular fiber length, and this leads to increased tension.
What is the Frank-Starling relationship?
Stroke volume/cardiac output increase when venous return/end-diastolic volume increases
With respects to the pressure-volume loop, what does the segment 1-2 represent?
What causes isovolumetric contraction?
Isovolumetric contraction occurs when the ventricle contracts causing an increase in pressure that closes the AV-valves but that is not large enough to open the semilunar valves for ejection.
With respects to the pressure-volume loop, what does the segment 2-3 represent?
The width of the pressure-volume loop is also known as what?
What is the stroke volume?
the amount of blood ejected from the ventricle each beat; Stroke Volume = EDV-ESV
With respects to the pressure-volume loop, what does the segment 3-4 represent?
With respects to the pressure-volume loop, what does the segment 1-4 represent?
An increase in preload is indicated by what change in the pressure-volume loop?
an increase in width; increase in stroke volume
An increase in afterload is indicated by what change in the pressure-volume loop?
a decrease in width; decrease in stroke volume
An increase in contractility is indicated by what change in the pressure-volume loop?
an increase in width; increase in stroke volume
What is the equation for cardiac output?
Cardiac output = stroke volume x heart rate
What is the ejection fraction?
the amount of end-diastolic volume ejected in the stroke volume; ejection fraction = stroke volume/EDV
What is stroke work?
the amount of work per beat
What is stroke work of the left ventricle?
aortic pressure x stroke volume
What is the primary fuel for stroke work?
What increases cardiac oxygen demand?
1. increased afterload
2. increased heart size
3. increased contractility
4. increased heart rate
What is associated with the a wave?
atrial contraction; an increase in atrial pressure
What is associated with the c wave?
The c wave is associated with the back flow of blood into the atria during ventricular contraction and the bulging back of the AV-valves.
What is associated with the v wave?
slow flow of blood into the atria during the end of ventricular contraction when the AV-valves are still closed.
What is associated with the fourth heart sound?
filling of the ventricle by atrial systole
What what is associated with the first heart sound?
closure of the AV-valves
True or False? Blood is ejected during isovolumetric contraction.
False; If blood was ejected, then one of the valves would have to be open and the volume would change.
What causes the aortic valve to open?
When ventricular pressure is greater than the aortic pressure due to contraction, the aortic valve opens.
What is associated with the second heart sound?
closure of the semilunar valves
What causes the dicrotic notch, or incisure, in the aortic pressure tracing?
closure of the aortic valves causes a short increase in pressure
What what is associated with the third heart sound?
rapid ventricular filling, which is passive
What is diastasis?
the longest phase of the cardiac cycle and it is a phase of decreased ventricular filling
What are the steps of the cardiac cycle?
1. Atrial systole
2. Isovolumetric ventricular contraction
3. Rapid ventricular ejection
4. Reduced ventricular ejection
5. Isovolumetric ventricular relaxation
6. Rapid ventricular refilling
What is the baroreceptor reflex?
a fast, neural mechanisms for regulating blood arterial pressure
How are baroreceptors activated?
Where are baroreceptors located?
carotid sinus and aortic arch (respond to increases)
What are the steps for a baroreceptor reflex with respects to a decrease in atrial pressure?
1. decreased atrial pressure causes decreased stretch
2. the carotid sinus nerve decreases firing rate to vasomotor center
3. The vasomotor responds because it sets mean arterial pressure at 100 mm Hg, and a decrease in stretch causes a deviation from 100 mm Hg.
4. sympathetic outflow to the heart and blood vessels increases whereas parasympathetic outflow to the heart and blood vessels decreases
What effects attempt to increase arterial pressure in response to decreased baroreceptor stretch?
1. increased heart rate
2. increased contractility and stroke volume
3. increase in vasoconstriction
What happens to blood pressure with increased angiotensin II levels?
increase in blood pressure
What happens to blood pressure with increased vasopressin levels?
increase in blood pressure
What happens to blood pressure with increased atrial natriuretic peptide levels?
decrease in blood pressure
Where are precapillary sphincters found?
Are true capillaries surrounded by smooth muscle?
How do water-soluble substances pass through capillaries into the surrounding tissues?
via the intracellular clefts
What is type of capillaries in the liver allow for proteins to pass in and out?
How do larger water-soluble substances gain passage?
What is the algebraic expression for capillary hydrostatic pressure?
An increase in Pc favors filtration or resorption?
What determines Pc?
arterial and venous pressures and resistances
What is the algebraic expression for interstitial hydrostatic pressure?
An increase in Pi favors filtration or resorption?
True or False? Pi is normally near zero and is therefore negligible.
What causes oncotic capillary pressure?
the concentration of proteins in the plasma
An increase in oncotic capillary pressure favors filtration or resorption?
A decrease in oncotic capillary pressure favors filtration or resorption?
An increase in oncotic interstitial pressure favors filtration or resorption?
What would cause a decrease in oncotic interstitial pressure?
inadequate lymph function
If the net pressure is positive, is resorption or filtration favored?
filtration is favored
If the net pressure is negative, is resorption or filtration favored?
True or False? Filtration from the capillaries is usually greater than resorption.
How is excess filtrate returned to the circulation?
via the lymph system
What is the significance of one-way flap valves in lymph vessels?
allows for entrance but not exit, and it creates unidirectional flow
Why does edema occur with respects to lymphatic function?
Edema occurs when the interstitial volume is greater than the capacity of the lymph vessels to return it to the circulation.
What is endothelium-derived relaxing factor (EDRF)?
a vasodilator released by endothelial cells
What cNMP is increased due to increased EDRF production?
What is one form of EDRF?
Why does prolonged standing lead to edema in lower extremities?
Blood pools in the veins because of their high compliance. This leads to increased capillary hydrostatic pressure, which results in increased filtration. If the increased filtration exceeds the ability of the lymphatics to return the fluid to the circulation, then edema ensues.
What results when venous return is low?
stroke volume and cardiac output decrease
What happens to arterial pressure due to decreased cardiac output?
Why would someone faint if cardiac output is decreased?
Cerebral arterial pressure may become too low
What is it called when blood pressure decreases with standing?
What does the cardiac function curve depict?
the Frank-Starling relationship for the ventricle
What is shown by a cardiac function curve?
cardiac output is a function of end-diastolic volume
What is depicted by the vascular function curve?
the relationship between venous return and right atrial pressure
What is the mean systemic pressure with respects to the vascular function curve?
where the curve intersects the x-axis
What does the mean systemic pressure equal?
right atrial pressure when there is no flow
What causes an increase the mean systemic pressure?
1. increase in blood volume
2. decrease in venous compliance
With respects to the vascular function curve, what happens to the curve when the mean arterial pressure increases?
shifts to the right
What causes a decrease in mean systemic pressure?
1. decrease in blood volume
2. increase in venous compliance
With respects to the vascular function curve, what happens to the curve when the mean systemic pressure decreases?
shift to the left
What determines the slope of the vascular function curve?
resistance in the arterioles
What does a clockwise rotation in the vascular function curve indicate?
decrease in total peripheral pressure
What is the result of a decrease in total peripheral pressure with respects to venous return?
there is an increase
What does a counterclockwise rotation of the vascular function curve indicate?
an increase in total peripheral pressure
What is the result of an increase in a total peripheral pressure with respects to venous return?
there is a decrease
What is the name of the point where cadiac output curve and a venous return curve intersect?
equilibrium or steady-state point
What is the significance of the steady-state point?
it is the point where cardiac output and venous return are equivalent
Which curve is affected by inotropic agents?
cardiac output curve
What is the result of positive inotropic agents?
increased contractility and increased cardiac output
What happens to the steady-state point when positive inotropic agents are used?
the point shifts to a higher cardiac output and a lower right atrial pressure
Why does right atrial pressure decrease with positive inotropic agents?
because more blood is ejected during each beat
What is the result of negative inotropic agents?
decreased contractility and decreased cardiac output
What happens to the steady-state point when blood volume is increased or venous compliance is decrease?
cardiac output and right atrial pressure increase for the point
What happens to the steady-state point when blood volume is decreased or venous compliance is increased?
cardiac output and right atrial pressure decrease for the point
True or False? An increase in total peripheral resistance results in a decrease in both cardiac output and venous return.
What happens to the cardiac output curve when TPR increases?
it shifts downward which is the result of an increased afterload
What happens to the right atrial pressure when TPR increased?
it stays the same
What happens to the cardiac output curve when TPR decreases?
it shifts upward due to decreased afterload
What happens to right atrial pressure when TPR decreases?