NEET Biology Body Fluids and Circulation MCQs Set 18

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Chapter-wise Objective Questions: Body Fluids and Circulation

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Multiple Choice Questions

Question 1: In which state is iron present in haemoglobin?
(a) Ionic
(b) Fe2+
(c) Fe3+
(d) None of the above
Show Answer & Explanation

Answer: (b) Fe2+

Explanation:
1. Haem contains ferrous (Fe2+) iron, which binds oxygen reversibly.

Teacher's Note:
1. Fe3+ gives methaemoglobin which cannot carry O2.

Question 2: Megakaryocytes:
(a) Produce leucocytes
(b) Form blood platelets
(c) Are carriers of oxygen
(d) Are carriers of carbon dioxide
Show Answer & Explanation

Answer: (b) Form blood platelets

Explanation:
1. Platelets are cytoplasmic fragments shed from megakaryocytes.

Teacher's Note:
1. Platelets live about 7 to 10 days.

Question 3: During blood clotting, fibrin is produced by:
(a) Thrombin
(b) Prothrombin
(c) Liver
(d) Proteolysis only
Show Answer & Explanation

Answer: (a) Thrombin

Explanation:
1. Thrombin converts soluble fibrinogen into insoluble fibrin threads.

Teacher's Note:
1. Prothrombin is the inactive precursor of thrombin.

Question 4: The number of erythrocytes per mm3 of human blood is:
(a) 4 million
(b) 5 million
(c) 6 million
(d) 0.5 million
Show Answer & Explanation

Answer: (b) 5 million

Explanation:
1. A healthy adult has about 5 to 5.5 million RBC per mm3.

Teacher's Note:
1. The WBC count is 6000 to 8000 per mm3.

Question 5: The valves of the heart are attached to the papillary muscles by:
(a) Columnae carneae
(b) Chordae tendineae
(c) Tendinae
(d) Pectinati muscles
Show Answer & Explanation

Answer: (b) Chordae tendineae

Explanation:
1. Fibrous cords, the chordae tendineae, connect the cusps of the tricuspid and bicuspid valves to papillary muscles.

Teacher's Note:
1. They prevent valves from turning inside out.

Question 6: In cyanosis, the colouration of body parts appears:
(a) Bluish
(b) Yellowish
(c) Reddish
(d) Brownish
Show Answer & Explanation

Answer: (a) Bluish

Explanation:
1. Poor oxygenation of blood gives a bluish colour to skin and mucous membranes.

Teacher's Note:
1. Jaundice gives a yellow colour.

Question 7: Which of the following animals has the highest heart rate per minute?
(a) Elephant
(b) Whale
(c) Man
(d) Mouse
Show Answer & Explanation

Answer: (d) Mouse

Explanation:
1. Smaller animals have a higher metabolic rate and heart rate, up to several hundred per minute in a mouse.

Teacher's Note:
1. The elephant has about 25 beats per minute.

Question 8: Which has the thickest walls?
(a) Right auricle
(b) Left auricle
(c) Right ventricle
(d) Left ventricle
Show Answer & Explanation

Answer: (d) Left ventricle

Explanation:
1. The left ventricle pumps blood to the whole body at high pressure.

Teacher's Note:
1. It is the thickest chamber of the heart.

Question 9: Blood supply to the heart musculature is via:
(a) Cardiac artery
(b) Coronary artery
(c) Aorta
(d) Pulmonary vein
Show Answer & Explanation

Answer: (b) Coronary artery

Explanation:
1. The coronary arteries arise from the aorta and supply the cardiac muscle.

Teacher's Note:
1. Blockage causes myocardial infarction.

Question 10: The remnant of the foramen ovale (fossa ovalis) is located in the:
(a) Inter-atrial septum
(b) Interventricular septum
(c) Between pulmonary and aortic arches
(d) Superior vena cava
Show Answer & Explanation

Answer: (a) Inter-atrial septum

Explanation:
1. In the foetus, the foramen ovale is an opening between the atria. After birth it closes, leaving the fossa ovalis.

Teacher's Note:
1. Ductus arteriosus is between the pulmonary artery and the aorta.

Question 11: The connection between the pulmonary and aortic arches in the foetus is:
(a) Ligamentum arteriosum
(b) Ductus arteriosus
(c) Foramen ovale
(d) All of the above
Show Answer & Explanation

Answer: (b) Ductus arteriosus

Explanation:
1. The ductus arteriosus bypasses the foetal lungs and becomes the ligamentum arteriosum after birth.

Teacher's Note:
1. Do not confuse it with the foramen ovale.

Question 12: The mitral valve is supported by:
(a) Bundle of His
(b) Ductus arteriosus
(c) Foramen ovale
(d) Chordae tendineae
Show Answer & Explanation

Answer: (d) Chordae tendineae

Explanation:
1. The mitral (bicuspid) valve cusps are held by chordae tendineae.

Teacher's Note:
1. It guards the left atrioventricular opening.

Question 13: Which of the following is a congenital heart disease?
(a) Patent ductus arteriosus
(b) Patent foramen ovale
(c) Ventricular septal defect
(d) All of these
Show Answer & Explanation

Answer: (d) All of these

Explanation:
1. All three are defects present from birth.

Teacher's Note:
1. They cause mixing of oxygenated and deoxygenated blood.

Question 14: The largest and thickest heart chamber is the:
(a) Left ventricle
(b) Left atrium
(c) Right atrium
(d) Right ventricle
Show Answer & Explanation

Answer: (a) Left ventricle

Explanation:
1. The left ventricle has the thickest wall to pump blood into the aorta.

Teacher's Note:
1. Its wall is about three times thicker than the right ventricle.

Question 15: The pacemaker is the:
(a) Instrument for measuring heart beat
(b) Instrument for measuring pulse rate
(c) Atrioventricular node that provides impulse for heart beat
(d) Sinoatrial node that provides impulse for heart beat
Show Answer & Explanation

Answer: (d) Sinoatrial node that provides impulse for heart beat

Explanation:
1. The SA node, in the wall of the right atrium, initiates the heartbeat.

Teacher's Note:
1. Its rate is about 70 to 75 per minute.

Question 16: The tricuspid valve is found between the:
(a) Sinus venosus and right auricle
(b) Right auricle and right ventricle
(c) Left ventricle and left auricle
(d) Ventricle and aorta
Show Answer & Explanation

Answer: (b) Right auricle and right ventricle

Explanation:
1. The tricuspid valve guards the right atrioventricular opening.

Teacher's Note:
1. The mitral valve guards the left opening.

Question 17: Which sequence represents the origin and conduction of the heartbeat?
(a) AV node, bundle of His, SA node, Purkinje fibres
(b) SA node, Purkinje fibres, AV node, bundle of His
(c) Purkinje fibres, AV node, AV node, bundle of His
(d) SA node, AV node, bundle of His, Purkinje fibres
Show Answer & Explanation

Answer: (d) SA node, AV node, bundle of His, Purkinje fibres

Explanation:
1. The impulse starts at the SA node, goes to the AV node, then through the bundle of His and its branches to the Purkinje fibres.

Teacher's Note:
1. The AV node delays the impulse slightly.

Question 18: The hormone that stimulates the heart beat is:
(a) Insulin
(b) Adrenaline
(c) Glucagon
(d) Gastrin
Show Answer & Explanation

Answer: (b) Adrenaline

Explanation:
1. Adrenaline increases the heart rate and the force of contraction.

Teacher's Note:
1. It acts through the sympathetic system.

Question 19: The heart beat is accelerated by:
(a) Sympathetic nerves and noradrenaline
(b) Cranial nerves and adrenaline
(c) Cranial nerves and acetylcholine
(d) Sympathetic nerves and acetylcholine
Show Answer & Explanation

Answer: (a) Sympathetic nerves and noradrenaline

Explanation:
1. Sympathetic nerves release noradrenaline, which raises the heart rate.

Teacher's Note:
1. The vagus (parasympathetic) nerve releases acetylcholine and slows the heart.

Question 20: The heart sound 'dup' is produced when:
(a) The mitral valve opens
(b) The mitral valve closes
(c) The semilunar valves at the base of the aorta close
(d) The tricuspid valve opens
Show Answer & Explanation

Answer: (c) The semilunar valves at the base of the aorta close

Explanation:
1. The second sound is produced when the semilunar valves close at the end of ventricular systole.

Teacher's Note:
1. The first sound 'lub' is from closure of the AV valves.

Question 21: When the heartbeat is slower than normal, the condition is called:
(a) Bradycardia
(b) Tachycardia
(c) Hypocardia
(d) Nicacardia
Show Answer & Explanation

Answer: (a) Bradycardia

Explanation:
1. Bradycardia means a heart rate below 60 per minute.

Teacher's Note:
1. Tachycardia is a fast heart rate.

Question 22: The 'lubb' and 'dupp' heart sounds are due to:
(a) Opening of heart valves
(b) Action of papillary muscles
(c) Closing of heart valves
(d) Activity of the pacemaker
Show Answer & Explanation

Answer: (c) Closing of heart valves

Explanation:
1. Lubb is the closure of the AV valves, and dupp is the closure of the semilunar valves.

Teacher's Note:
1. Sounds are heard with a stethoscope.

Question 23: The normal cardiac output is about:
(a) 15 litres per minute
(b) 5 litres x 72 per minute
(c) 5 litres per minute
(d) 5/72 litre per minute
Show Answer & Explanation

Answer: (c) 5 litres per minute

Explanation:
1. Cardiac output = stroke volume (about 70 mL) x heart rate (about 72) = about 5 litres per minute.

Teacher's Note:
1. Cardiac output is the volume pumped by each ventricle per minute.

Question 24: Acetylcholine causes:
(a) Bradycardia
(b) Tachycardia
(c) Both
(d) None
Show Answer & Explanation

Answer: (a) Bradycardia

Explanation:
1. Acetylcholine from the vagus nerve decreases the heart rate.

Teacher's Note:
1. It acts on the SA node.

Question 25: The first heart sound, 'lubb', occurs:
(a) At the end of systole
(b) At the end of diastole
(c) At the beginning of ventricular systole
(d) At the beginning of ventricular diastole
Show Answer & Explanation

Answer: (c) At the beginning of ventricular systole

Explanation:
1. The AV valves close at the start of ventricular systole to give 'lubb'.

Teacher's Note:
1. It is longer and louder than 'dupp'.

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Body Fluids and Circulation Objective Questions & Solutions for NEET Biology

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