Cardiovascular System (Test 2) Flashcards
Where is the bicuspid or mitral valve located?
between the left atrium and the left ventricle
What is ECG (electrocardiogram)?
An ECG is a graphic illustration of the Cardiac conduction system.
What causes the P wave in an ECG pattern?
Depolarization of atrial muscle fibers
In the ECG, during which wave does ventricular repolarization occur?
T wave
Can ECG be useful for determining a patient’s cardiac output stroke volume heart sounds end-diastolic volume?
No. ECG would be useful for determining the heart rate
What is most responsible for the plateau of cardiac action potential?
Both calcium and potassium channels
Which cells have pacemaker potential?
The sino-atrial nodal cells have the pacemaker potential.
What determines the cardiac output?
Stroke volume multiplied by heart rate
What is the ratio of stroke volume and end-diastolic volume?
Ejection fraction
What are some indices of ventricular performance?
stroke volume, stroke work, cardiac output, cardiac work
What is the most important factor in influencing the amount of blood pumped by the ventricle?
Venous return
Which two great vessels bring deoxygenated blood back to the heart?
The superior and inferior venae cavae.
When does the first heart sound occur?
The first heart sound occurs during the phase of isovolumetric contraction.
What is the correct sequence for the path of the cardiac impulse?
S-A node, A-V node, bundle of His, Purkinje fibers.
Where does the bundle of His and its branches located?
The bundle of His and its branches is located in the interventricular septum
What are most responsible for phase 0 of a cardiac action potential?
Sodium channels
What events cause cardiacmyocyte repolarization?
Calcium channels begin to close while more potassium channels open; potassium rapidly leaves the cell
What relationship is defined by Frank-Starling’s law of the heart?
End–diastolic volume and stroke volume
The opening of which channel in the autorhythmic cell (pace maker cells) is responsible for the huge positive spike in membrane potential?
L-type calcium channel
What is the typical stroke volume for an adult at rest?
70 (or 80) mL.
Which two heart chambers pump oxygenated blood?
The left atrium and the left ventricle
When does the atrial systole occur?
Towards the end of ventricular diastole
Due to what event does the second heart sound occur?
Closing of the semilunar valves
What does the heart rate dependent on?
Rate of pacemaker potential
Which structure has the slowest conduction velocity of the cardiac impulse?
AV nodal fibers
What is the correct sequence for the blood flow in the heart?
Right heart, tricuspid valve, right ventricle, pulmonic valve, pulmonary circulation, left atria, mitral valve, left ventricle, aortic valve, aorta
What is the result from delay of spread of electrical activation from atria to ventricles?
The delay allows atrial contraction to push an additional amount of blood into the ventricle before it contracts
Which heart valves open (or close) during the diastole and systole of heart cycle?
In diastolic phase, AV valves (bicuspid and tricuspid) open and semilunar valves close. In systolic phase, AV valves close and semilunar valves open.
What changes in the ventricular pressure during isovolumic contraction phase of cardiac cycle?
The begin of ventricular contraction causes leaflets of the mitral valve to close, continuation of ventricular muscle contraction will increases ventricular pressure very rapidly until it exceeds aortic pressure.
What is the β adrenergic effect on the ventricular myocyte’s function?
It increases cAMP/PKA signal pathway which activates L-type calcium channels. Also, it causes release of free calcium from the
sarcoplasmic reticulum. The general result is to increase muscle contractility.
What is the effect of activation of the baroreceptor reflex during hemorrhage?
Increase in heart rate due to activation of sympathetic tone on the vasculature
If the systolic arterial pressure is 125 mmHg and the diastolic arterial pressure is 85 mmHg, what is the estimated mean arterial pressure?
98 mmHg
Mean Arterial Pressure (MAP)
MAP=Diastolic Pressure + (1/3)(Systolic-Diastolic)
What is the effect of nitric oxide on vascular smooth muscle cell function?
Nitric oxide (NO) contributes to arteriolar vasodilation in the basal state
What is active hyperemia?
increasing blood flow of an organ when its metabolic activity increases
Where does the slowest velocity of blood flow occur?
Capillaries
What happens to the capillary hydrostatic pressure when arteriolar constriction?
Decreases
Where does the highest vascular resistance in the cardiovascular system occur?
Arterioles, where the large decrease in pressure within the systemic circulation take place
What is the effect on the heart rate by decreasing parasympathetic stimulation?
Heart rate increases
What mechanism by which the exchange of lipid-soluble substances (including CO2 and O2) across the capillary membrane occur?
Diffusion
How do you determine the resistance to flow in a blood vessel?
R=(8Lviscosity)/(pi*r^4)
Sum to determine total resistance for vessels arranged in series. Sum the inverse to determine total resistance in parallel.
Is flow in microcirculation assumed to be steady?
Yes
Where is Nitric Oxide released from?
Arteriolar endothelial cells
What does the Starling’s Law of Filtration predict?
Fluid movement=K*[(P_inside-P_outside)-(O_inside-O_outside)]
Less filtration if tissue hydrostatic pressure (Interstitial, PIF) increases; more filtration if plasma osmotic pressure decreases; Less filtration if the filtration coefficient decreases
Is blood composed of approximately the same number of red blood cells and white blood cells?
No. Red blood cells constitute about 45% of whole blood volume. White blood cells make >1% of blood in a normal individual.
Why is there decreased hematocrit in microcirculation?
The parabolic velocity profile in arterioles and venules with velocity higher near the center of the vessel; deformable red blood cells tend to be found more often closer to the center and away from the wall of the arterioles; plasma that near the wall of the arterioles tends to move more slowly.
What types of cells are in microvessel other than hematic cells?
Endothelial cells, pericytes and smooth muscle cells
What is the myogenic and metabolic vasodilator hypotheses of autoregulation?
Myogenic autoregulation depends on stretch activated ion channels in vascular smooth muscle that, when stretched, allow Ca2+ ions to enter and induce contraction. Metabolic autoregulation is thought to
be due, in part, to substances produced in the tissue, in proportion to metabolism, which are vasoactive (cause contraction or relaxation of vascular smooth muscle).
What is The Fahraeus effect?
More red blood cells in arterioles than capillaries
What percent of blood is carried by capillaries?
At any given moment capillaries contain 5% of the circulation blood volume
How close are cells from capillary?
Diffusion distances are very small; most cells are not more than 0.1 mm away from a capillary
What is the effect of venous constriction on the capillary hydrostatic pressure?
Increased
What is the relationship between the arteriolar vasodilators production and the local oxygen level?
The production of vasodilators in inversely proportion to local oxygen levels
Endothelial cells produce Nitric Oxide in response to what?
shear stress
If the diameter of an arteriole decreases by a factor of two and the pressure drop across it and the viscosity remain constant, how much the flow through the arteriole will decrease?
By a factor of 16
What is the effect of sympathetic stimulation on capillary hydrostatic pressure?
Decreased
What factors determine the changes in mean arterial pressure?
cardiac output and/or total peripheral resistance
Does parasympathetic stimulation control arteriolar resistance?
No or minimal
How does a long-term regulation of blood pressure by kidney occur?
It regulates blood volume by adjusting salt and water excretion
What is flow autoregulation?
Maintaining blood flow nearly constant in the face of pressure change
What vascular region has the least amount of smooth muscle?
capillaries
What is the most important factor in determining vascular resistance?
vascular diameter
What are the nonadrenergic, noncholinergic autonomic neurons?
a third subsystem of neurons that use nitric oxide as a neurotransmitter have been described and found to be integral in autonomic function, particularly in the gut and the lungs
Where is the most blood in the cardiovascular system?
veins
How does the vasodilator production relate to local oxygen level?
inversely proportional
Are endothelial cells involved in the myogenic response?
no
