Nokea
The heart wall receives blood from the
- A. blood flowing through it
- B. coronary arteries
- C. cardiac veins
- D. pulmonary arteries
Correct Answer: B
Rationale: The heart wall (myocardium) is supplied oxygenated blood by coronary arteries (B) branching from the aorta. Blood in chambers (A) doesn’t nourish the wall, cardiac veins (C) drain it, and pulmonary arteries (D) supply lungs.
You may also like to solve these questions
Granulocytes that protect against infections caused by parasitic worms
- A. Neutrophils
- B. Eosinophils
- C. Basophils
- D. Lymphocytes
Correct Answer: B
Rationale: Eosinophils (B) target parasites with toxic granules.
Least blood pressure is at:
- A. Vein
- B. Vena cava
- C. Aorta
- D. Capillary
Correct Answer: B
Rationale: The vena cava (B) has the lowest pressure (~0-5 mmHg) as blood returns to the heart. Veins (A, ~10 mmHg), capillaries (D, ~20 mmHg), and aorta (C, ~100 mmHg) have higher pressures.
Which structure in the heart initiates action potentials that stimulate contraction of the heart at constant rate of about 100 beats per minute?
- A. Cardiac accelerator nerves
- B. Atrioventricular node
- C. Cardiovascular center
- D. Sinoatrial node
Correct Answer: D
Rationale: The SA node (D) initiates action potentials at ~100 bpm, though vagal tone slows it to 60-80 bpm in vivo. AV node (B) is slower (~40-60 bpm), nerves (A) and center (C) modulate.
A hormone that is significantly involved in regulation of blood volume is:
- A. ACTH
- B. osmoretic hormone
- C. ADH
- D. LH
Correct Answer: C
Rationale: Antidiuretic hormone (ADH) regulates blood volume by promoting water reabsorption in the kidneys, increasing plasma volume. ACTH affects cortisol, and LH is reproductive; 'osmoretic hormone' is not a standard term.
Which of the following statements is false?
- A. Hematocrit is the ratio of red blood cells found in the blood
- B. Polycythemia is indicated if the hematocrit is exceptionally high
- C. RBCs, WBCs, and platelets are whole cells found in blood
- D. A monocyte is a type of white blood cell
Correct Answer: C
Rationale: Platelets (C) are fragments, not whole cells; others are true.