Cardiovascular Physiology Flashcards
Rationale for higher blood velocity in the aorta than in the sum of all of the capillaries?
Aorta: small cross-sectional area
Capillaries: large cross-sectional area
Rationale for large cross-sectional areas in capillaries?
Large cross-sectional areas = lower velocity of blood in the capillaries optimizes the conditions for exchange of substances across capillary wall.
Equation / formula used resistance?
Poiseuille equation:
R= 8nl / πr to the power of 4
Where:
R= resistance
n= viscosity of blood
l= length of blood vessels
r4= radius of blood vessels to the fourth power
Describes the distensibility of blood vessels?
Capacitance ( Compliance)
C= V/P
Where:
C= Capacitance of Compliance (mL/mm Hg)
V= Volume (mL)
P= Pressure (mmHg)
Decrease in venous capacitance effect of unstressed and stress volume?
Decreases unstressed volume and Increases stressed volume by shifting blood from the veins to the arteries.
Effect of decrease AV node conduction on PR interval ?
PR interval increases
Refers to the increase force of contraction in a stepwise fashion as the intracellular calcium increases cumulatively?
Positive Staircase / Bowditch Staircase / Treppe
- increased heart rate increases the force of contraction in a stepwise fashion as the intracellular calcium increases cumulatively over several beats.
Refers to the beat that occurs after an extrasystolic beat that has increased force of contraction?
Post-extrasystolic potentiation
- the beat that occurs after an extrasystolic beat has increased force of contraction because “extra” Ca has entered the cells during the extrasystole.
70kg man, has a Resting O2 consumption of 250mL / min; Systemic arterial O2 of 0.20ml O2/ mL; Systemic mixed venous O2 of 0.15mL O2/mL ; Heart rate of 72 beats/ min.
What is the Cardiac Output?
What is the stroke volume?
CO= 5000mL/min
SV= 69.4 mL / beat
CO= O2 consumption / O2 pulmonary artery- O2 pulmonary veins
CO= 250ml/min / (0.20 - 0.15) = 5000ml/ min?
SV= CO / HR
SV= 5000ml /72 beats / min
SV= 69.44 mL / beat
At the arteriolar end of capillary:
Capillary HP: 30mmHg
Capillary OP: 28 mmHg
Interstitial HP : 0 mmHg
Interstitial OP: 4mmHg
Filtration or Absorption?
Filtration
(30mmHg- 0mmHg ) - (28mmHg-4mmHg)
= +6mmHg
At the venous end of capillary:
Capillary HP: 16mmHg
Capillary OP: 28 mmHg
Interstitial HP : 0 mmHg
Interstitial OP: 4mmHg
Filtration or Absorption?
Absorption
(16-0)-(28-4)
= - 8 mmHg
Response of vessels in myogenic hypothesis during an increase in perfusion pressure?
Vasoconstriction
- without vasoconstriction, blood flow would increase as a result of increased pressure
50% narrowing of an artery leads to how much decrease in blood flow?
Decrease to 1/16
-if the radius is decreased by 1/2 , then the resistance would increase by 2(4) of 16. But since blood flow is inversely proportional to resistance , flow will decreased to 1/16.
Cardiac contractility compensation during change from supine to standing position?
Increased contractility
Baroreceptors detect the decrease in arterial pressure and thus activated the sympathetic outflow and decreases parasympathetic outflow.
SBP is highest in which vessel?
Choices:
a. Renal artery
b. Renal vein
c. Aorta
d. Pulmonary artery
Renal artery
-pressure on the venous side is lower than the arteria side. Systolic pressure is slightly higher in the downstream arteries than in the aorta because of the reflection of pressure waves at branch points.
Where is the pacemaker?
(-) P wave, (+) QRS complex, (+) T wave
AV Node
The absent P wave indicates that the atrium is not depolarizing and therefore, the pacemaker can not be in the SA Node. Both QRS & T wave are positive, indicating that the depolarization and repolarization of the ventricles occured in the normal sequence.
Increase in ejection fraction causes decrease in what cardiac parameter ?
ESV
In ventricular extrasytoles , what is extrasystolic beats effect on pulse pressure?
Decrease pulse pressure because stroke volume is decreased.
In ventricular extrasystoles, next normal contractions effect on pulse pressure ?
Increased pulse pressure because the contractility of the ventricle is increased.
True or False.
On the extrasystolic beat, pulse pressure decreases because there is an inadequate ventricular filling time, the ventricle beats too soon.
True
True or False.
Postextrasystolic contraction produces increased pulse pressure because contractility is increased.
True
True or False.
Extra Ca enters the cell during the extrasystolic beat.
True
Increase in contractility causes ________ in CO for given end-______ volume.
Increased in cardiac output for a given end-diastolic volume.
________ contraction occurs during ventricular systole, before the aortic valve opens.
Isovolumetric contraction
In isovolumetric contraction, ventricular pressure _________, But volume remains__________ because blood cannot be ejected into the aorta against a closed valve.
Choices
a. Constant , Increased
b. Constant , Deceased
c. Increase, Decreased
d. Increased , Constant
e. Decreased, Constant
Increased , Constant
From points 1-4, locate the isovolumic contraction?
Points 1-2
From points 1-4, locate where the Aortic valve closes?
Point 3
From points 1-4 , locate what point where all the valves are closed.
Point 3
Points 1-4: Locate the Isovolumic relaxation
Points 3-4
Points 1-2 : Isovolumic contraction
Points 1-4. Locate the first heart sound.
Point 1
The _____ heart sound corresponds to the closure of the AV valves.
First
Absorption or Filtration?
Capillary HP = 30mmHg
Capillary OP = -2mmHg
Interstitial HP= 25mmHg
Interstitial OP= 2 mmHg
Filtration
[(30-(-2)] - [(25-2)]
= 32 - 23
= +9mmHg
What is the rate of water flow across the capillary wall?
Capillary HP = 30mmHg
Capillary OP = -2mmHg
Interstitial HP= 25mmHg
Interstitial OP= 2 mmHg
Kf x net pressure = 0.5 x 9mmHg = 4.5mL / min
Kf= 0.5
Net pressure = 9
Net pressure = [(30-(-2)] - [(25-2)]
= 32 - 23
= +9mmHg
Factors of turbulent blood flow? (3)
- Decreased viscosity
- Increased velocity
- Partial occlusion of a blood vessel
66 M, S/P Sympathectomy , experiences a great fall in arterial pressure upon standing up. Explanation?
A suppressed response of the baroreceptor mechanism.
Normal baroreceptor mechanism responds to a decrease in arterial pressure through the vasomotor center by increasing sympathetic outflow and decreasing parasympathetic outflow; In sympathectomy , sympathetic component baroreceptor mechanism is absent.
Normal baroreceptor mechanism responds to a __________ in arterial pressure through the vasomotor center by ___________ sympathetic outflow and __________ parasympathetic outflow.
a. Decrease, decreasing, increasing
b. Increase, increasing, decreasing
c. Decrease, increasing , decreasing
d. Increase, decreasing, increasing
Decrease, Increasing , Decreasing
Ventricles are completely depolarized in which portion of the ECG?
ST Segment
Pulmonary blood flow is greater than aortic blood flow in which type of shunt?
Left to right ventricular shunt
The change indicated by the dashed lines on the cardiac output/ venous return curves shows?
Increased mean systemic filling pressure.
The shift in the venous return curve to the right is consistent with an increase in blood volume as a consequence , mean systemic filling pressure.
2 P waves preceding each QRS complex. Interpretation?
Decreased conduction through the AV Node.
This pattern indicates that only every other P wave is conducted through the AV node to the ventricle.
Compensatory change in the carotid sinus during acute decrease in arterial blood pressure?
Decreased firing rate of the carotid sinus nerve.
Decrease parasympathetic outflow.
Tendency for an edema to occur will be increased by ______ venous pressure?
Increased venous pressure
Edema occurs when more fluid is filtered out of the capillaries than can be returned to the circulation by the lymphatics.
Rationale for inspiratory split of the second heart sound.
The aortic valve closes before the pulmonic valve.
Rationale for decrease in total peripheral resistance during exercise?
Increase in local metabolites on skeletal muscle arterioles causes vasodilation.
Increase in arteriolar resistance, without a change in any other component. Effect on arterial pressure?
An increase in arterial pressure
What is the patients cardiac output?
HR : 70 bpm
Systemic Arterial O2: 0.24 ml O2 / mL
Mixed Venous O2: 0.16 mL O2/mL
Whole body O2 consumption: 500mL / min
Ans: 6.25 L per min
CO= 500mL / (0.24-0.16)
CO= 6250 mL/ min or 6.2L /min
Result of an inward Na+ current?
Upstroke of the action potential in atria, ventricles and purkinje fibers .
Result of an inward Ca+ current?
Upstroke in SA node
True or False.
End diastolic volume and Right atrial Pressure are related and can be used interchangeably.
True
Rationale for why the greatest pressure decrease occurs across the arterioles?
They have the greatest resistance.
True or False.
The greater the distance is ,the greater the decrease in arterial pressure.
True
Pulse pressure is determined by what cardiac parameter?
Determined by Stroke volume
-pulse pressure is the difference between the highest and lowest arterial pressue; reflects the volume ejected by the left ventricle.
______________ is the difference between the highest and lowest arterial pressure; reflects the volume ejected by the_________ ventricle.
a. Pulse pressure , Right Ventricle
b. Pulse pressure, Left Ventricle
c. Stroke Volume , Right Ventricle
d. Stroke Volume , Left Ventricle
Pulse Pressure, Left Ventricle