Mastering A&P The Heart

During which of these stages are the aortic and pulmonary valves open?

2b

Calculate the mean arterial pressure (MAP) for a patient whose systolic blood pressure is 120 mm Hg and diastolic blood pressure is 70 mm Hg.

87- Mean arterial pressure (MAP) is calculated by dividing the pulse pressure by three and adding the result to the diastolic pressure. The pulse pressure is the difference between the systolic and diastolic pressures.

Select the correct partial path. This path is part of the complete blood flow pathway. You should be able to trace flow starting in any location.

All systemic veins return oxygen-poor venous flow to the right atrium, through the tricuspid to the right ventricle, and up and out the pulmonary semilunar valve to the pulmonary trunk and pulmonary arteries to the capillaries of the lungs. Returning oxygen-rich blood flowing through pulmonary veins enters the left atrium, passes through the mitral valve to the left ventricle, and flows out through the aortic semilunar valve into the aorta and on to systemic capillaries. Congratulations on completing blood flow through the two-sided heart, identifying oxygen-rich and oxygen-poor locations, and preparing yourself for knowledge you will use again and again!

Most of the decrease in ventricular volume takes place during which phase of the cardiac cycle?

As the ventricles contract, blood is forced through the semilunar valves and out into the arteries, resulting in a reduction in ventricular blood volume. At the end of this phase, ventricular volume is at a minimum−the "end-systolic volume" (ESV).

Atrial pressure is greater than ventricular pressure during which phase of the cardiac cycle

Blood always flows from high to low pressure. During atrial contraction, blood flows from atria (high pressure) to ventricles (low pressure). Similarly, this same pressure gradient exists during ventricular filling.

Which of the following is NOT correct regarding the relationship between pressure, flow, and resistance in the cardiovascular system?

Blood flow (F) is directly proportional to the difference in blood pressure (ΔP) between two points in the circulation-that is, the blood pressure, or hydrostatic pressure, gradient. Consequently, when ΔP increases, blood flow increases, and when ΔP decreases, blood flow declines. On the other hand, blood flow is inversely proportional to the total peripheral resistance (TPR) in the systemic circulation; if TPR increases, blood flow decreases.

Isovolumetric relaxation is characterized by which of the following?

During isovolumetric relaxation, all valves into and out of the ventricles remain closed. This prevents blood from flowing backward through the heart.

During the ventricular ejection phase of the cardiac cycle, which of the following is true?

During ventricular ejection, blood flows from the ventricles into the arteries. To do so, the blood must pass through the semilunar valves, which must be open during this phase. Narrowing of the left semilunar valve reduces blood flow out of the heart, a disease condition known as aortic stenosis.

Most of the increase in left ventricular volume takes place during what phase of the cardiac cycle

During ventricular filling the AV valves remain open, which allows blood to flow from the atria into the ventricles. The passive flow of blood during this phase (before atrial contraction) accounts for roughly 80 percent of the increase in ventricular volume.

An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __

Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.

Which of the following is equivalent to the ventricular volume during isovolumetric contraction?

Isovolumetric contraction occurs at the beginning of ventricular systole when the ventricular volume is at its maximum value−the end diastolic volume (EDV). Because no volume changes occur during isovolumetric contraction, ventricular volume remains at this value throughout the phase.

Which of the following is equivalent to the ventricular volume during isovolumetric relaxation?

Isovolumetric relaxation occurs at the beginning of ventricular diastole when the ventricular volume is at its minimum value−the end systolic volume (ESV). Because no volume changes occur during isovolumetric relaxation, ventricular volume remains at this value throughout the phase.

Which of the following is involved in long-term regulation of blood pressure?

Long-term control of blood pressure is achieved through direct and indirect renal mechanisms. The kidneys regulate blood pressure indirectly via the renin-angiotensin-aldosterone mechanism, which also involves ADH. In response to low blood pressure, increased release of renin results in increased synthesis of angiotensin II (Ang II). Ang II stimulates secretion of ADH and aldosterone, which work together to promote increased salt and water reabsorption by the kidneys. This in turn decreases urine output and gradually increases blood volume and pressure (assuming the individual is also consuming fluid). The increased thirst that accompanies the fall in blood pressure is due in part to the stimulation of the hypothalamic thirst center by Ang II.

As your skeletal muscles contract during physical activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action?

More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore a larger cardiac output.

Increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume.

Stroke volume (the volume of blood ejected from the ventricle during systole) is equal to the difference between EDV (the volume of blood in the ventricle before it contracts) and ESV (the volume of blood remaining in the ventricle after it contracts). Increasing EDV will result in a larger stroke volume; however, increasing ESV will result in a smaller stroke volume.

When the atria contract, which of the following is true?

The ventricles are in diastole.Atrial contraction fills each of the ventricles to their maximum capacity−the end diastolic volume (EDV). This occurs towards the end of ventricular diastole while the ventricles are still relaxed.

How would a decrease in blood volume affect both stroke volume and cardiac output?

Yes, a decreased blood volume would decrease the end diastolic volume, thus lowering the stroke volume. Although this would initially lead to a decrease in the cardiac output, heart rate would increase because of increased activity of the sympathetic nervous system in an effort to maintain cardiac output.

How would an increase in the sympathetic nervous system increase stroke volume?

Yes, an increase in sympathetic nervous system activity would increase contractility (by increasing available calcium), thus increasing stroke volume. Contractility causes an increase in stroke volume by decreasing end systolic volume; it does not change end diastolic volume.

Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.

Yes, higher pressure in the atria than in the ventricles forces the AV valves to open and blood moves into the ventricles.

Increased pressure in the ventricles would close what valve(s)?

Yes, increased pressure in the ventricles would close the AV valves.

Which of the following is correct about the filling of the ventricles?

Yes, most of the ventricular filling is passive; atrial contraction adds just a little more blood.

The heart is actually (one, two, or three) pumps?

Yes, the right side of the heart pumps to/from the lungs (pulmonary circuit) and the left side of the heart pumps to/from the rest of the body (the systemic circuit).

Which of the following would increase heart rate?

epinephrine and norepinephrine

Which of the following would increase cardiac output?

epinephrine. Sympathetic stimulation leads to the release of epinephrine and norepinephrine, both of which increase heart rate and increase contractility, which increases stroke volume. Increasing heart rate and stroke volume increases cardiac output.

In what direction does blood flow through the heart?

from a region of high pressure to a region of low pressur

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling

isovolumetric contraction, ventricular ejection, isovolumetric relaxation

Which heart chamber receives blood from the pulmonary veins?

left atrium

Which chamber pumps oxygenated blood out the aorta to the systemic circuit?

left ventricle

Which chamber receives blood from the superior and inferior vena cavae?

right atrium

Which heart chamber pumps unoxygenated blood out the pulmonary trunk?

right ventricle

The influence of blood vessel diameter on total peripheral resistance is ________.

significant because resistance is inversely proportional to the fourth power of the vessel radius

The pulse pressure is ________

systolic pressure minus diastolic pressure

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during ____

ventricular diastole

Ventricular pressure is greater than aortic pressure during which phase of the cardiac cycle?

ventricular ejection

At what point during the cardiac cycle does the AV valve close?

when ventricular pressure becomes greater than atrial pressure