CMH Lahore Medical & Dental Entry Biology: Circulation MCQs

CMH Lahore Medical & Dental Entry Biology: Circulation MCQs — sample questions

1. Question 1

   Q1. During strenuous exercise, which blood vessel is primarily responsible for supplying oxygenated blood to the skeletal muscles?

   • A) Arterioles
   • B) Venules
   • C) Capillaries
   • D) Arteries

   Answer: Arterioles

   Explanation: Arterioles regulate blood flow to capillaries; they are primary suppliers of oxygenated blood to muscles during exercise. Venules collect deoxygenated blood.

2. Question 2

   Q2. What is the primary function of the sinoatrial (SA) node in the heart?

   • A) To conduct impulses to the ventricles
   • B) To initiate heartbeats
   • C) To regulate blood pressure
   • D) To filter blood

   Answer: To initiate heartbeats

   Explanation: The SA node acts as the heart's natural pacemaker, initiating heartbeats. The AV node conducts impulses to ventricles.

3. Question 3

   Q3. Which structure in the heart prevents backflow of blood from the ventricles to the atria?

   • A) Semilunar valves
   • B) Atrioventricular valves
   • C) Chordae tendineae
   • D) Papillary muscles

   Answer: Atrioventricular valves

   Explanation: Atrioventricular valves prevent backflow from ventricles to atria. Semilunar valves prevent backflow from arteries to ventricles.

4. Question 4

   Q4. What is the term for the pressure exerted by blood on the walls of blood vessels?

   • A) Blood pressure
   • B) Osmotic pressure
   • C) Hydrostatic pressure
   • D) Turgor pressure

   Answer: Blood pressure

   Explanation: Blood pressure is the pressure exerted by blood on vessel walls. Hydrostatic pressure is a related concept but not specific to blood.

5. Question 5

   Q5. Which type of blood vessel has the thickest walls relative to their lumen diameter?

   • A) Arteries
   • B) Veins
   • C) Capillaries
   • D) Arterioles

   Answer: Arteries

   Explanation: Arteries have thick walls to withstand high pressure from the heart. Veins have thinner walls and larger lumens.

6. Question 6

   Q6. What is the primary function of the lymphatic system in relation to circulation?

   • A) To return interstitial fluid to the bloodstream
   • B) To filter blood
   • C) To produce red blood cells
   • D) To regulate blood pressure

   Answer: To return interstitial fluid to the bloodstream

   Explanation: The lymphatic system returns interstitial fluid to the bloodstream, aiding circulation. It does not filter blood or produce red blood cells.

7. Question 7

   Q7. During diastole, what happens to the atrioventricular valves?

   • A) They remain closed
   • B) They open to allow blood flow into the ventricles
   • C) They are forced shut
   • D) They become incompetent

   Answer: They open to allow blood flow into the ventricles

   Explanation: During diastole, atrioventricular valves open, allowing blood to flow into ventricles. They close during ventricular systole.

8. Question 8

   Q8. What is the name of the valve located between the right atrium and right ventricle?

   • A) Tricuspid valve
   • B) Pulmonary valve
   • C) Mitral valve
   • D) Aortic valve

   Answer: Tricuspid valve

   Explanation: The tricuspid valve is between the right atrium and ventricle. The mitral valve is between the left atrium and ventricle.

9. Question 9

   Q9. Which factor increases peripheral resistance in blood vessels?

   • A) Vasodilation
   • B) Vasoconstriction
   • C) Increased blood viscosity
   • D) Both B and C

   Answer: Both B and C

   Explanation: Both vasoconstriction and increased blood viscosity increase peripheral resistance. Vasodilation decreases resistance.

10. Question 10

    Q10. The 'lub' sound heard during a heartbeat is due to the closure of which valves?

    • A) Semilunar valves
    • B) Atrioventricular valves
    • C) Pulmonary valves
    • D) Aortic valves

    Answer: Atrioventricular valves

    Explanation: The 'lub' sound is due to the closure of atrioventricular valves. 'Dub' sound is due to semilunar valves closure.

11. Question 11

    Q11. What is the effect of increased sympathetic stimulation on heart rate?

    • A) Decreased heart rate
    • B) Increased heart rate
    • C) No effect on heart rate
    • D) Variable effect

    Answer: Increased heart rate

    Explanation: Increased sympathetic stimulation increases heart rate. Parasympathetic stimulation decreases heart rate.

12. Question 12

    Q12. Which blood vessel carries deoxygenated blood from the heart to the lungs?

    • A) Pulmonary artery
    • B) Pulmonary vein
    • C) Aorta
    • D) Coronary artery

    Answer: Pulmonary artery

    Explanation: The pulmonary artery carries deoxygenated blood to the lungs. Pulmonary veins carry oxygenated blood back to the heart.

13. Question 13

    Q13. What is the term for the exchange of substances between the blood and tissue cells?

    • A) Diffusion
    • B) Osmosis
    • C) Capillary exchange
    • D) Active transport

    Answer: Capillary exchange

    Explanation: Capillary exchange refers to the exchange of substances between blood and tissue cells. Diffusion is a related process.

14. Question 14

    Q14. Which condition is characterized by a low red blood cell count or low hemoglobin level?

    • A) Anemia
    • B) Polycythemia
    • C) Leukemia
    • D) Thrombocytopenia

    Answer: Anemia

    Explanation: Anemia is characterized by low red blood cell count or hemoglobin. Polycythemia is an increased red blood cell count.

15. Question 15

    Q15. What is the primary role of the coronary circulation?

    • A) To supply oxygenated blood to the lungs
    • B) To supply oxygenated blood to the heart muscle
    • C) To supply oxygenated blood to the brain
    • D) To supply oxygenated blood to the liver

    Answer: To supply oxygenated blood to the heart muscle

    Explanation: Coronary circulation supplies oxygenated blood to the heart muscle. It is essential for the heart's function.

16. Question 16

    Q16. Which part of the heart's conduction system is responsible for delaying the impulse?

    • A) SA node
    • B) AV node
    • C) Bundle of His
    • D) Purkinje fibers

    Answer: AV node

    Explanation: The AV node delays the impulse, allowing the atria to fully contract before ventricular contraction begins.

17. Question 17

    Q17. What is the effect of increased potassium ion concentration on heart function?

    • A) Increased heart rate
    • B) Decreased heart rate
    • C) Arrhythmias
    • D) Cardiac arrest

    Answer: Arrhythmias

    Explanation: Increased potassium can lead to arrhythmias. High levels can cause cardiac arrest. It affects the heart's electrical activity.

18. Question 18

    Q18. Which type of capillary is characterized by the presence of pores or fenestrae?

    • A) Continuous capillaries
    • B) Fenestrated capillaries
    • C) Sinusoidal capillaries
    • D) Discontinuous capillaries

    Answer: Fenestrated capillaries

    Explanation: Fenestrated capillaries have pores, allowing for increased exchange of substances. Continuous capillaries lack these pores.

19. Question 19

    Q19. What is the term for the movement of blood through the heart and blood vessels?

    • A) Circulation
    • B) Respiration
    • C) Excretion
    • D) Digestion

    Answer: Circulation

    Explanation: Circulation refers to the movement of blood through the heart and vessels. Respiration involves gas exchange.

20. Question 20

    Q20. Which chamber of the heart receives deoxygenated blood from the body?

    • A) Right atrium
    • B) Left atrium
    • C) Right ventricle
    • D) Left ventricle

    Answer: Right atrium

    Explanation: The right atrium receives deoxygenated blood from the body via the vena cava. Left atrium receives oxygenated blood from lungs.