NEET Biology Body Fluids and Circulation MCQs Set 11

Multiple Choice Questions (MCQs) for NEET Biology: Body Fluids and Circulation

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Multiple Choice Questions

Question 1: The correct route through which impulse travels in the heart is
(a) SA node → Purkinje fibres → bundle of His → AV node → heart muscles
(b) SA node → AV node → bundle of His → Purkinje fibres → heart muscles
(c) AV node → bundle of His → SA node → Purkinje fibres → heart muscles
(d) AV node → SA node → Purkinje fibres → bundle of His → heart muscles
Show Answer & Explanation

Answer: (b) SA node → AV node → bundle of His → Purkinje fibres → heart muscles

Explanation:
1. SA node (wave of contraction get originated at SA node) ↓ AV node ↓ Bundle of His ↓ Purkinje's fibre (now, the impulse stimulates the ventricles to contract simultaneously).

Question 2: Bundle of His is a network of
(a) Muscle fibres distributed throughout the heart walls
(b) Muscle fibres found only in the ventricle wall
(c) Nerve fibres distributed in ventricles
(d) Nerve fibres found throughout the heart
Show Answer & Explanation

Answer: (b) Muscle fibres found only in the ventricle wall

Explanation:
1. Bundle of His are muscle fibres which originate from AV node and present on the each ventricle wall.

Question 3: The cardiac pacemaker in a patient fails to function normally. The doctors find that an artificial pacemaker is to be grafted in him. It is likely that it will be grafted at the site of
(a) Atrioventricular bundle
(b) Purkinje system
(c) Sinoatrial node
(d) Atrioventricular node
Show Answer & Explanation

Answer: (c) Sinoatrial node

Explanation:
1. Sinoatrial node is also called pacemaker because it is the site which generates the maximum number of action potential i.e., 70–75 min–1 and is responsible for initiating and maintaining the rhythmic contractile activity of the heart.

Question 4: Impulse of heart beat originates from
(a) SA node
(b) AV node
(c) Vagus nerve
(d) Cardiac nerve
Show Answer & Explanation

Answer: (a) SA node

Explanation:
1. SA node is also known as pacemaker because the contraction of atria is initiated and activated by SA node.

Question 5: Rate of heart beat is determined by
(a) Purkinje fibres
(b) Papillary muscles
(c) AV-node
(d) SA-node
Show Answer & Explanation

Answer: (d) SA-node

Explanation:
1. It is the site which generates the maximum number of action potential i.e. 70–75 min–1 and is responsible for initiating and maintaing the rhythmic contractile activity of the heart.

Question 6: The heart sound ‘dup’ is produced when
(a) Mitral valve is closed
(b) Semilunar valves at the base of aorta get closed
(c) Tricuspid valve is opened
(d) Mitral valve is opened
Show Answer & Explanation

Answer: (b) Semilunar valves at the base of aorta get closed

Explanation:
1. The first heart sound 'LUBB' is produced by closure of bicuspid and tricuspid valves.
2. The second heart sound 'DUP' is produced by closure of aortic and pulmonary semilunar valves.

Question 7: At the end of joint diastole ventricle is
(a) Completely filled by blood
(b) Two third filled by blood
(c) One third filled by blood
(d) Completely empty
Show Answer & Explanation

Answer: (b) Two third filled by blood

Explanation:
1. During joint diastole, in the beginning of the ventricle diastole there is first rapid filling due to opening of AV valves then the blood fills into ventricles with slow pace called diastasis or slow filling.
2. Due to this, ventricle is two-thirds filled by blood.
3. Remaining 1/3rd is filled during atrial contraction.

Question 8: When the heart muscles receive insufficient oxygen, it is indicated in the ECG as
(a) Enlarged P-wave
(b) Depressed S-T segment
(c) Flattened T-wave
(d) Both (2) & (3)
Show Answer & Explanation

Answer: (d) Both (2) & (3)

Explanation:
1. S-T segment is elevated in acute myocardial infarction and depressed when the heart muscle receives insufficient oxygen.
2. T wave is flat when heart muscle receives insufficient oxygen as in atherosclerotic heart disease and it may be elevated when the body's potassium level is increased.

Question 9: In what way pulmonary artery is different from pulmonary vein?
(a) Its lumen is broad
(b) Its wall is thick
(c) It has valves
(d) It does not possess endothelium
Show Answer & Explanation

Answer: (b) Its wall is thick

Explanation:
1. Artery has thick wall, blood flows with more pressure.
2. Thickness of artery is due to tunica media.

Question 10: In veins, valves are present to check backward flow of blood flowing at
(a) Atmospheric pressure
(b) High pressure
(c) Low pressure
(d) All of these
Show Answer & Explanation

Answer: (c) Low pressure

Explanation:
1. Artery have high pressure Veins have low pressure, thin walls.

Question 11: Fastest distribution of some injectible material/medicine with no risk of any kind can be achieved by injecting it into the
(a) Muscles
(b) Arteries
(c) Veins
(d) Lymph vessels
Show Answer & Explanation

Answer: (c) Veins

Explanation:
1. This is so because veins carry blood towards the heart and then heart pumps blood to all organs.

Question 12: The thickening of walls of arteries is called
(a) Arteriosclerosis
(b) Arthritis
(c) Aneurysm
(d) Both (2) & (3)
Show Answer & Explanation

Answer: (a) Arteriosclerosis

Explanation:
1. Arteriosclerosis : Thickening of walls due to calcification in old age.
2. Arthritis : It is a disorder in which inflammation of the joints occurs.
3. It is characterized by pain, swelling, redness, heat.
4. Aneurysm : Abnormal widening and ballooning of a portion of an artery due to weakness in the wall of blood vessel.

Question 13: Which of the following cannot be taken as a feature of open type circulatory system?
(a) Low pressure system
(b) Well regulated blood supply to different organs
(c) Blood returns to the heart slowly
(d) Non formation of capillaries
Show Answer & Explanation

Answer: (b) Well regulated blood supply to different organs

Explanation:
1. Well-regulated blood supply to different organs occurs in closed circulatory system, in which blood flows in the blood vessel.

Question 14: Which of the following blood vessels bypass are present in the circulatory system before birth?
(a) Foramen ovale
(b) Fossa ovalis
(c) Ductus arteriosus
(d) Both (1) & (3)
Show Answer & Explanation

Answer: (d) Both (1) & (3)

Explanation:
1. Before birth, the major portion blood from the right side bypasses the pulmonary circulation through foramen ovale and ductus arteriosus.
2. At the time of birth with the start of breathing, these bypass cease to act.
3. Foramen ovale closes to become fossa ovalis.
4. Ductus arteriosus closes to become ligamentum arteriosum.

Question 15: Isovolumetric systole is duration between
(a) Closure of AV valve and opening of semilunar valve
(b) Closure of semilunar valve and opening of AV valve
(c) Closure of tricuspid and closure of bicuspid valve
(d) Closure of tricuspid and opening of bicuspid valve
Show Answer & Explanation

Answer: (a) Closure of AV valve and opening of semilunar valve

Explanation:
1. During isovolumetric contraction volume of blood does not change even though ventricular continue contracting.

Question 16: High level of which ions change the strength of contraction
(a) Ca2+
(b) K +
(c) Na+
(d) All of these
Show Answer & Explanation

Answer: (d) All of these

Explanation:
1. Elevated blood level of K+ or Na+ decreases heart rate and contractility An excess of Ca2+ increases heart rate.

Question 17: Assertion (A): The cardiac impulse which originates from SA node in mammalian heart cannot spread directly from atria to ventricles.
Reason (R): In mammalian heart there is no continuity between cardiac muscle fibres of atria and those of ventricles except AV bundles.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

Explanation:
1. SA node → AV node → Bundle of His → Bundle branch → Purkinje fibre → Ventricle wall.

Question 18: Assertion (A): First phase of ventricular filling is rapid and causes 3rd sound of heart.
Reason (R): It is because of auricular systole.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (c) Assertion is true but the Reason is false.

Explanation:
1. It is because of opening of AV valve.

Question 19: Assertion (A): Dub is a long and sharp sound.
Reason (R): It is caused by closing of atrio ventricular valves.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (d) Both Assertion and Reason are false.

Explanation:
1. Dup has high pitch and of short duration.

Question 20: Assertion (A): Portal system consists of veins which start from capillaries and end into capillaries.
Reason (R): All vertebrates have hepatic portal system.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

Explanation:
1. A unique vascular connection exists between the digestive tract and liver called hepatic portal system.

Question 21: Assertion (A): Left ventricle pumps blood at a much higher pressure to all body parts involved in systemic circulation.
Reason (R): The muscular wall of the left ventricle is two to four times as thick as the wall of right ventricle.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.

Explanation:
1. Left ventricle has thickest wall.

Question 22: Assertion (A): Endocardium provides a smooth lining for the inside of the heart and covers the valves of the heart.
Reason (R): Endocardium is continuous with the endothelial lining of the large blood vessels associated with the heart and the rest of the cardiovascular system.
(a) Both Assertion and Reason are true and the Reason is a correct explanation of the Assertion.
(b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) Both Assertion and Reason are false.
Show Answer & Explanation

Answer: (b) Both Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

Explanation:
1. Inner wall of heart is endocardium.

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