Cardiovascular System: The Heart

Flashcards covering anatomy, conduction, action potential, cardiac cycle, cardiac output, and physiological concepts of the heart based on Tortora Chapter 20.

What is the primary function of the heart acting as a pump?

It moves blood through the pulmonary and systemic circulations.

Where is the heart located in the body, and how is its mass distributed relative to the midline?

The heart lies in the mediastinum, and about two-thirds of its mass is left of the body's midline.

What are the primary functions of the fibrous pericardium?

It is a tough outer layer that helps protect, anchor, and prevent overstretching of the heart.

What are the three layers of the heart wall in order from outer to inner?

Epicardium, myocardium, and endocardium.

From which major vessels does the right atrium receive deoxygenated blood?

Superior and inferior venae cavae.

Where does the right ventricle pump deoxygenated blood?

Through the pulmonary trunk to the lungs.

Where does the left atrium receive oxygenated blood from?

From the pulmonary veins.

Which heart chamber has the thickest myocardium and why?

The left ventricle, because it must generate higher pressure to pump blood through the entire body.

What is the endocardium and what structure is it continuous with?

It is a smooth inner lining of the heart chambers and valves, continuous with the lining of large vessels.

What are the names and locations of the two atrioventricular (AV) valves?

Tricuspid valve (between right atrium and right ventricle) and bicuspid/mitral valve (between left atrium and left ventricle).

What are the names and locations of the two semilunar valves?

Pulmonary valve (between right ventricle and pulmonary trunk) and aortic valve (between left ventricle and aorta).

Which structures prevent AV valve cusps from inverting during ventricular contraction?

Chordae tendineae and papillary muscles.

What valve closures produce the S1 and S2 heart sounds?

S1 is mainly caused by AV valve closure; S2 is mainly caused by semilunar valve closure.

What is the correct pathway of blood flow through the heart and lungs, starting from the body?

Body \rightarrow Venae cavae \rightarrow Right atrium \rightarrow Right ventricle \rightarrow Lungs (via pulmonary trunk/arteries) \rightarrow Left atrium \rightarrow Left ventricle \rightarrow Aorta \rightarrow Body.

What structural features of cardiac muscle allow electrical signals to spread rapidly between cells?

Intercalated discs containing gap junctions.

What is the functional advantage of cardiac muscle's long refractory period?

It prevents tetanus, allowing the heart chambers to relax and refill between contractions.

What is the sequence of structures in the cardiac conduction system?

SA node \rightarrow AV node \rightarrow AV bundle \rightarrow Bundle branches \rightarrow Purkinje fibers.

Why is there a brief delay at the AV node during cardiac electrical conduction?

To allow the atria to finish contracting before the ventricles contract.

What ionic movements occur during the three phases of the ventricular action potential?

1. Rapid depolarization: $\text{Na}^+$ enters. 2. Plateau: $\text{Ca}^{2+}$ enters while $\text{K}^+$ leaves. 3. Repolarization: $\text{Ca}^{2+}$ channels close and $\text{K}^+$ outflow restores resting potential.

What electrical activity in the heart corresponds to the P wave, QRS complex, and T wave on an ECG?

P wave = atrial depolarization; QRS complex = ventricular depolarization; T wave = ventricular repolarization.

How long is one cardiac cycle at a resting heart rate of $75\,\text{beats/min}$?

About $0.8\,\text{s}$.

What occurs during the three phases of the cardiac cycle?

Atrial systole: atria contract to add final blood to ventricles. Ventricular systole: ventricles contract and eject blood. Relaxation period: all chambers relax and ventricles refill.

What is the mathematical equation used to calculate Cardiac Output?

$$\text{Cardiac Output (CO)} = \text{Stroke Volume (SV)} \times \text{Heart Rate (HR)}$$

What is the cardiac output when stroke volume is $70\,\text{mL/beat}$ and heart rate is $75\,\text{beats/min}$?

$$70\,\text{mL/beat} \times 75\,\text{beats/min} \approx 5.25\,\text{L/min}$$

What is preload, and how is it related to the Frank–Starling law?

Preload is the amount of ventricular filling/stretch before contraction; greater stretch increases force and stroke volume according to the Frank–Starling law.

How does contractility affect stroke volume, and what increases contractile force?

Greater contractile strength at the same preload increases stroke volume; positive inotropic effects increase force.

How is afterload defined, and what impact does higher afterload have on blood ejection?

Afterload is the pressure the ventricle must overcome to eject blood; higher afterload tends to make ejection harder.

How do sympathetic and parasympathetic nerves regulate heart function?

Sympathetic stimulation increases heart rate and contractility, while parasympathetic (vagus) stimulation decreases heart rate.

What are the clinical consequences of reduced coronary blood flow versus complete coronary artery obstruction?

Reduced flow causes myocardial ischemia, while complete obstruction causes myocardial infarction.

From which germ layer and during which week of embryonic development does the heart begin to form?

The heart begins developing from mesoderm in the third week.