A&p Review Of Heart

The correct answer lists the specific layers that make up the heart. The incorrect answers either list incorrect components or different types of tissues that do not compose the layers of the heart.

The pericardium is the thin, fibrous sac that encases the heart, composed of two layers: the visceral pericardium and the parietal pericardium. These layers create the pericardial space around the heart.

The pericardial fluid serves to lubricate the surface of the heart, preventing friction and allowing for smooth contractions during systole.

During diastole, the heart undergoes a relaxation phase where all four chambers relax simultaneously, enabling the ventricles to fill with blood in preparation for the next contraction. This process is crucial for the heart to efficiently pump blood throughout the body.

Unlike diastole, atrial and ventricular systole are not simultaneous events. Atrial systole occurs first, just at the end of diastole, followed by ventricular systole.

The atrioventricular valves separate the atria from the ventricles, while semilunar, pulmonary, and aortic valves are involved in the circulation of blood from the heart to the rest of the body.

During diastole, the tricuspid and mitral valves are open to allow blood flow from the atria to ventricles, and they only close as ventricular systole begins.

The correct term for the valves described in the question is 'semilunar'. Atrioventricular valve has two leaflets, bicuspid valve has two cusps or leaflets, and tricuspid valve has three cusps or leaflets. Only semilunar valves have three leaflets shaped like half-moons.

The valve between the right ventricle and the pulmonary artery is known as the pulmonic valve, as it prevents the backflow of blood from the pulmonary artery into the right ventricle. The other options provided are different valves present in the heart but are not specifically located between the right ventricle and the pulmonary artery.

The valve between the left ventricle and the aorta is known as the aortic valve. The other options - pulmonary, tricuspid, and mitral valves are located in different parts of the heart and serve different functions.

The semilunar valves are forced open during ventricular systole as blood is ejected from the right and left ventricles into the pulmonary artery and aorta. During diastole, the semilunar valves are closed to prevent backflow of blood.

The correct answer is SA node firing rate of 60 to 100 impulses per minute, as it is responsible for generating electrical impulses in the heart to initiate each heartbeat. The AV node, Bundle of His, and Purkinje fibers also play important roles in the conduction of electrical signals in the heart, but they are not the primary pacemaker like the SA node.

The AV node coordinates the incoming electrical impulses from the atria and after a slight delay relays the impulse to the ventricles. The SA node is the pacemaker of the heart, located in the right atrium. The Purkinje fibers are specialized fibers that conduct the electrical stimulus to the myocardium. The Bundle of His is a collection of heart muscle cells specialized for electrical conduction.

If the SA node malfunctions, the AV node generally takes over the pacemaker function of the heart at its inherently lower rate.

When both the SA and AV nodes fail, the ventricular pacemaker site takes over with an inherent bradycardic rate of 30 to 40 impulses per minute.

The correct answer refers to the phases of the cardiac cycle where systole corresponds to the contraction phase and diastole corresponds to the relaxation phase.

Cardiac output specifically refers to the amount of blood pumped by each ventricle during a given period, which is calculated by multiplying the stroke volume (volume of blood pumped by one ventricle in a single contraction) by the heart rate. The other terms mentioned represent different aspects of the cardiovascular system but do not directly relate to the specific definition of cardiac output.

The amount of blood ejected per heartbeat is determined by stroke volume, which is the volume of blood pumped from the left ventricle per beat. Stroke volume is a critical component of cardiac output.

Parasympathetic impulses from the vagus nerve slow down the heart rate, while sympathetic impulses increase it. Therefore, the correct answer is 'slow'.

Preload is the degree of stretch of the ventricular cardiac muscle fibers at the end of diastole, which directly affects stroke volume. Afterload refers to the pressure that the heart must work against to eject blood during systole. Contractility is the intrinsic ability of the heart to generate force. Compliance refers to the ability of a cardiac chamber to expand to accommodate filling without a significant increase in pressure.

Preload refers to the stretching of the heart muscle (myocardium) at the end of diastole, just before contraction. It is an important component of cardiac function related to the volume of blood in the ventricle at the end of diastole. LVEDP is a measure of the pressure in the left ventricle at the end of diastole, indicating the extent of filling and stretching of the ventricle. Other terms like stroke volume, cardiac output, and right atrial pressure are related to different aspects of cardiac function but not specifically to preload.

The Frank-Starling (or Starling) law of the heart describes the relationship between the volume of blood returning to the heart and the contraction strength for optimal cardiac output.

Preload refers to the amount of blood in the ventricles at the end of diastole. A reduction in the volume of blood returning to the ventricles will decrease preload.

Afterload is the resistance of the systemic or pulmonary blood pressure to ventricular ejection, which impacts stroke volume. Preload refers to the initial stretching of the cardiac muscle fibers prior to contraction. Contractility is the strength of the heart's contraction. Heart rate is the number of heartbeats per unit of time.

Contractility specifically refers to the force generated by the contracting myocardium, whereas end-diastolic volume, stroke volume, and cardiac output are related but different concepts in cardiac physiology.