Cardiac output and venous return

The normal intrapleural pressure is ____ mmHgm which is the normal external cardiac pressure.

-4

Normal right atrial pressure (PRA) for healthy adults= ____ mmHg

0

Normal resistance to venous return (RVR) for healthy adults= ____ mmHg per L/min of blood flow

1.4

Why does stroke volume progressively diminish as atrial pacing frequency (HR) gradually increases?

Because of the reduced time for ventricular filling

With an increase in total peripheral resistance (TPR), a new equilibrium point is established. What are the affects on cardiac output, venous return, and right atrial pressure?

Both cardiac output and venous return decrease but right atrial pressure remains unchanged

Cardiac output is frequently stated as ______, which is the cardiac output per square meter of body surface area.

Cardiac index (CI)

The quantity of blood pumped into the aorta each minute by the heart. The sum of the blood flows to all the tissues of the body

Cardiac output

The cardiac function curve is a plot of the relationship between:

Cardiac output of the left ventricle and right atrial pressure

Measurement of cardiac output using the Oxygen Fick Principle. (Equation)

Cardiac output= oxygen absorbed by lungs/arteriovenous oxygen difference

Accumulation of a large quality of fluid in the pericardial cavity around the heart with resultant increase in external cardiac pressure and shifting of the curve to the right.

Cardiac tamponade

How does an increase in total peripheral pressure (TPR) change the venous return curve? How does an increase in total peripheral pressure (TPR) change the cardiac output curve?

Counterclockwise rotation of venous return curve. Downward shift of the cardiac output curve.

The cardiac function curve or cardiac output curve is based on the Frank-Starling relationship for the _____

Left ventricle

Degree of filling of systemic circulation (measured by the ________ pressure), is a factor affecting venous return to the heart from the systemic circulation because it is the force that forces the systemic blood towards the heart (this is the pressure measured everywhere in the systemic circulation when all flow of blood is stopped)

Mean systemic filling

The ________ pressure rises at the onset of heavy exercise. This effect results partly from the sympathetic stimulation that contracts the veins and other capacitive parts of the circulation. In addition, tensing of the abdominal and other skeletal muscles of the body compresses many of the internal vessels, causing a still greater increase in said pressure.

Mean systemic filling

Pressure in the vasculature if the heart stopped and pressures equilibrare at the capillary

Mean systemic pressure

Max _____ stimulation results in the cardiac output rising to about double normal but the right atrial pressure hardly changes.

Sympathetic

Stretch of the right atrium initiates a nervous reflex called the _____ reflex. Passes first to the vasomotor center of the brain and then back to the heart by way of the sympathetic nerves and vagi, ______ (increases or decreases) the HR

Bainbridge, increases

Increase in right atrial pressure produces increase in cardiac output. However, this "matching" occurs only up to a point: when right atrial pressure reaches a value of approx. _____ mmHg, cardiac output can no longer keep up with venous return and the cardiac function curve levels off. Max level of cardiac output is approx. _____ L/min

4, 9

Normal venous return for healthy adults= _____ L/min

5

For young, healthy men, resting cardiac output averages about ____ L/min. For women, this value is about ____ L/min

5.6, 4.9

Normal mean systemic filling pressure (Psf) for healthy adults= ____ mmHg

7

As shown in the Venous Return Curve, when the hearts pumping capability becomes diminished and causes the right atrial pressure to rise, the backward force of the rising atrial pressure on the veins of the systemic circulation ______ (increases or decreases) venous return of blood to the heart.

Decreases

An increase in total peripheral resistance (TPR) has what affect on cardiac output and venous return?

Decreases cardiac output and venous return

An increase in resistance to venous return twice normal rotates the Venous Return Curve _____ to one-half as great a slope

Downward

The intersection of the curves whee cardiac output and venous return are equal is called the __________. Gives a normal value for cardiac output of ____ L/min and a right atrial pressure of ____ mmHg

Equilibrium point, 5, 0

As venous return increases... right atrial pressure, end-diastolic volume, and end-diastolic fiber length increase. Increase in end-diastolic fiber length produces a(n) _____ (increase or decrease) in cardiac output

Increase

The lower the pressure in the right atrium, the higher the pressure gradient between the systemic arteries and the right atrium leading to _____ (increase of decrease) venous return

Increase

A rise in HR leads to a(n) ____________ into myocardial cells and this influx enhances myocardial contractility

Increase in the net influx of Ca2+ per minute

Increased quantities of blood flow into the heart stretches the walls of the heart chambers that causes cardiac muscle to contract with _____ (increased or decreased) force

Increased

During heavy exercise, the increased level of the cardiac output curve results almost entirely from sympathetic stimulation of the heart that causes: _____ and ______

Increased HR, increased strength of contraction

Stretch of the sinus node in the wall of the right atrium has what affect on HR?

Increases HR

What affect does sympathetic stimulation have on systemic circulation?

Increases Psf because of contraction of the peripheral vessels and increases the resistance to venous return

By the Frank-Starling mechanism, an increase in end-diastolic volume produced what affect in cardiac output

Increases cardiac output

As opposed to HR and myocardial contractility which are strictly cardiac factors, ______ and ______ are factors that are mutually dependent on function of the heart and vasculature.

Preload (end diastolic pressure), afterload (aortic pressure)

______ and _____ are called coupling factors because they constitute a functional coupling between the heart and blood vessels

Preload (end diastolic pressure), afterload (aortic pressure)

equation for cardiac output

Qh (cardiac output)= SV (stroke volume) x HR

A rise in intrapleural pressure shifts the cardiac output drive to the ____ by the same amount

Right

The Venous Return Curve relates venous return to ______

Right atrial pressure

Vascular Function Curve (venous return curve) depicts the inverse relationship between venous return and

Right atrial pressure

______ is a factor affecting venous return to the heart from the systemic circulation because it exerts a backward force on the veins to impede flow of blood from the veins into the right atrium.

Right atrial pressure

Increases in blood volume increase mean systemic filling pressure which shifts the venous return curve to the _____. A new intersection/equilibrium point is established at which both the cardiac output and right atrial pressure are ______ (increased or decreased)

Right, increased

True or false: 2/3 of the so called resistance to venous return is determined by venous resistance and about 1/3 is determined by the arteriolar and small artery resistance

True

True or false: resistance to blood flow between the peripheral vessels and the right atrium (resistance to venous return) is one of the three principal factors that affect venous return to the heart fro systemic circulation

True

True or false: sympathetic stimulation affects both he heart and the systemic circulation

True

A decrease in resistance to venous return to one-half normal allows twice as much flow of blood and therefore rotates the Venous Return Curve _____ to twice as great a slope.

Upward

As Psf (mean systemic filling pressure) increases, how does the Venous Return Curve shift?

Upward and to the right

Formula for calculating venous return

VR=Psf-PRA/RVR (VR is venous return, Psf is the mean systemic filling pressure, PRA is the right atrial pressure, and RVR is the resistance to venous return)

The quality of blood flowing from veins into right ventricle

Venous return