Examkin

Soru

Zorluk: OrtaHuman Physiology, Health, and Diseases

Consider the following statements regarding human cardiac physiology and blood circulation:

1. The Sinoatrial (SA) node functions as the primary pacemaker of the heart because it generates impulse discharges at the highest intrinsic frequency.
2. The Atrioventricular (AV) node introduces a slight physiological delay in signal transmission, ensuring atria contract completely before ventricular systole begins.
3. The coronary sinus collects deoxygenated blood from the myocardium and empties directly into the left atrium.

Which of the statements given above are correct?

  1. 1 and 2 onlyCevap
  2. B
    2 and 3 only
  3. C
    1 and 3 only
  4. D
    1, 2 and 3

Cevap

1 and 2 only
Statements 1 and 2 accurately describe cardiac physiology. The Sinoatrial (SA) node acts as the natural pacemaker because it generates action potentials at the highest frequency. The Atrioventricular (AV) node introduces a essential physiological delay (~0.1 s) to allow the ventricles to fill completely before contracting. Statement 3 is incorrect because the coronary sinus drains deoxygenated blood from the heart wall into the right atrium, not the left atrium.

Adım Adım Çözüm

1
Evaluate Statement 1 regarding cardiac pacemaking.
Statement 1 is correct. Located in the right atrium, the SA node exhibits the highest rhythmicity (70-80 impulses per minute) and paces the heart.
The intrinsic depolarization rate of the SA node overrides slower secondary pacemakers in the conduction system.
2
Evaluate Statement 2 regarding conduction delay at the AV node.
Statement 2 is correct. Impulse propagation slows down significantly (approx. 0.1 second delay) at the AV node.
This delay ensures complete atrial emptying and optimal ventricular filling prior to ventricular contraction.
3
Evaluate Statement 3 regarding myocardial venous drainage.
Statement 3 is incorrect. The coronary sinus collects deoxygenated blood from the cardiac veins and opens into the right atrium.
All systemic deoxygenated venous return, including coronary venous drainage, enters the right atrium, while the left atrium exclusively receives oxygenated blood from the lungs.

Anahtar Kavram

Cardiac Conduction System and Coronary Circulation
Bu soruyu puanla

Konular

Human Physiology, Health, and Diseases

Bu konudan daha fazla soru