Cardiovascular and Nervous System

The autonomic nervous system regulates involuntary visceral functions: heart rate (cardiac innervation), respiratory rate (respiratory centers), and blood pressure (vasomotor control). Memory and intelligence are cognitive functions regulated by the central nervous system (cerebral cortex, hippocampus), not the autonomic system.

The first heart sound (S1) is the "lubb" sound caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of systole. The second heart sound (S2) is the "dupp" sound caused by semilunar valve closure at the end of systole.

Correct statement. Average cardiac output is 5.3 liter per minute.

Cardiac output is defined as the volume of blood pumped by each ventricle per minute, calculated as the product of heart rate (beats per minute) and stroke volume (blood pumped per beat). Option B is nonsensical, C lacks the formula, and D describes stroke volume, not cardiac output.

The coronary sinus is a major coronary vein. It returns the majority of the left ventricular blood flow to the right atrium. The coronary sinus orifice of the right atrium is the aperture via which approximately 90% venous drainage of the heart is returned to the circulation by the coronary sinus.

The pericardium and parietal pleura are innervated by the phrenic nerve (C3-C5). This explains why pericarditis pain is typically retrosternal and may radiate to the shoulder (via C3-C5 dermatomal distribution). The phrenic nerve mediates the pain sensation from these structures.

The c-wave in the jugular venous pulse occurs due to bulging of the closed tricuspid valve into the right atrium during early ventricular systole (isovolumetric contraction). This creates a small rise in atrial pressure. It is distinct from the a-wave (atrial contraction) and v-wave (atrial filling against closed tricuspid valve).

When changing from standing to lying down, gravity no longer pulls blood downward into the legs, so venous return to the heart increases immediately. Heart rate may transiently decrease due to increased baroreceptor firing, not increase. Cerebral blood flow is relatively stable in both positions due to autoregulation. Pulmonary blood flow distribution becomes more uniform in the supine position.

Mitral valve prolapse is characterized by myxomatous degeneration of the valve leaflets, which involves accumulation of glycosaminoglycans and disruption of collagen fibers. This makes the leaflets floppy and prolapsed. Hyalinization and fibrinoid necrosis are not typical findings in MVP.

Mitral valve prolapse is pathologically characterized by myxomatous degeneration, where the valve leaflets become floppy and redundant due to accumulation of glycosaminoglycans in the connective tissue. This causes the valve to billow backward into the left atrium during systole. Hyalinization is seen in aging valves, while fibrinoid necrosis occurs in vasculitis.

Tetralogy of Fallot (TOF) consists of four essential components: ventricular septal defect (VSD), right ventricular outflow tract obstruction (typically infundibular/subvalvular pulmonary stenosis), overriding aorta, and right ventricular hypertrophy. Valvular pulmonic stenosis is NOT part of the classic tetrad - the obstruction is infundibular (subvalvular) rather than at the valve itself. This distinction is important for surgical planning and prognosis.

ECG (Electrocardiogram) records the electrical activity of the heart from electrodes placed on the skin. It shows the cardiac cycle (P wave, QRS complex, T wave) and is essential for diagnosing arrhythmias, myocardial infarction, conduction defects, and electrolyte imbalances. EEG (Electroencephalogram) is for brain electrical activity. Kidney function tests (creatinine, BUN) and liver function tests assess those organs. ECG is exclusively cardiac.

The P wave in an ECG represents the depolarization of atrial muscle tissue, which is the electrical event that precedes atrial contraction. Option A incorrectly states it represents contraction itself - the ECG records electrical activity, not mechanical contraction. The QRS complex represents ventricular depolarization.