NEET Biology Body Fluids and Circulation MCQs Set 14

Biology Objective Questions and Answers: Body Fluids and Circulation

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Access the complete set of multiple-choice questions for Body Fluids and Circulation below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official NEET textbooks.

Multiple Choice Questions

Question 1: An open circulatory system is found in
(a) annelids and chordates
(b) only vertebrates
(c) arthropods and molluscs
(d) only fishes
Show Answer & Explanation

Answer: (c) arthropods and molluscs

Explanation:
1. In open circulation blood is pumped through large vessels into open spaces (sinuses), as in arthropods and molluscs.

Teacher's Note:
1. Annelids and chordates have closed circulation.

Question 2: Which animals have a heart that pumps only deoxygenated blood?
(a) Amphibians
(b) Fishes
(c) Birds
(d) Mammals
Show Answer & Explanation

Answer: (b) Fishes

Explanation:
1. Fish have a two-chambered heart that pumps deoxygenated blood to the gills, so circulation is single.

Teacher's Note:
1. Birds and mammals have a four-chambered heart and double circulation.

Question 3: Amphibians and most reptiles have a heart with
(a) two atria and one ventricle
(b) one atrium and two ventricles
(c) two atria and two ventricles
(d) one atrium and one ventricle
Show Answer & Explanation

Answer: (a) two atria and one ventricle

Explanation:
1. A three-chambered heart has two atria and a single ventricle, so blood mixes.

Teacher's Note:
1. Crocodiles have a four-chambered heart.

Question 4: The valve between the right atrium and right ventricle is the
(a) bicuspid valve
(b) tricuspid valve
(c) semilunar valve
(d) Eustachian valve
Show Answer & Explanation

Answer: (b) tricuspid valve

Explanation:
1. The right atrio-ventricular opening has a valve of three muscular flaps, the tricuspid valve; the left has the bicuspid or mitral valve.

Teacher's Note:
1. Semilunar valves guard the aorta and pulmonary artery.

Question 5: The pacemaker of the heart is the
(a) atrio-ventricular node
(b) bundle of His
(c) Purkinje fibres
(d) sino-atrial node
Show Answer & Explanation

Answer: (d) sino-atrial node

Explanation:
1. The SA node generates the maximum number of action potentials, about 70 to 75 per minute.

Teacher's Note:
1. It is located in the upper right corner of the right atrium.

Question 6: The correct path of impulse conduction in the heart is
(a) AV node, SA node, bundle of His, Purkinje fibres
(b) SA node, bundle of His, AV node, Purkinje fibres
(c) Purkinje fibres, bundle of His, AV node, SA node
(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 spreads from the SA node over the atria to the AV node, then down the bundle of His and its branches into the Purkinje fibres.

Teacher's Note:
1. This coordinates ventricular contraction.

Question 7: Heart rate from an ECG can be found by counting the number of
(a) P waves only in a cycle
(b) T waves in an hour
(c) ST segments
(d) QRS complexes per minute
Show Answer & Explanation

Answer: (d) QRS complexes per minute

Explanation:
1. Each QRS complex corresponds to one ventricular contraction, so counting them gives the heart rate.

Teacher's Note:
1. Normal rate is about 72 per minute.

Question 8: Duration of one cardiac cycle in a healthy human at rest is about
(a) 0.5 second
(b) 1.2 second
(c) 0.8 second
(d) 2 seconds
Show Answer & Explanation

Answer: (c) 0.8 second

Explanation:
1. At a heart rate of 72 per minute, one cycle lasts about 0.8 second.

Teacher's Note:
1. Ventricular systole lasts 0.3 s and diastole 0.5 s.

Question 9: Cardiac output of a healthy person is about
(a) 70 mL per minute
(b) 500 mL per minute
(c) 50 L per minute
(d) 5000 mL per minute
Show Answer & Explanation

Answer: (d) 5000 mL per minute

Explanation:
1. Cardiac output is stroke volume (about 70 mL) times heart rate (about 72), roughly 5 litres per minute.

Teacher's Note:
1. Athletes have a greater cardiac output.

Question 10: The first heart sound (lub) is associated with closure of the
(a) semilunar valves
(b) Eustachian valve
(c) tricuspid and bicuspid valves
(d) coronary valve
Show Answer & Explanation

Answer: (c) tricuspid and bicuspid valves

Explanation:
1. The first sound is caused by closure of the AV valves at the start of ventricular systole; the second (dub) by closure of semilunar valves.

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

Question 11: The second heart sound (dub) is associated with closure of the
(a) tricuspid valve
(b) bicuspid valve
(c) semilunar valves
(d) AV valves
Show Answer & Explanation

Answer: (c) semilunar valves

Explanation:
1. At the start of ventricular diastole the semilunar valves close, producing the dub.

Teacher's Note:
1. Lub is longer and louder.

Question 12: Atherosclerosis is the narrowing of arteries due to deposition of
(a) iron and zinc
(b) urea only
(c) glycogen
(d) calcium, fat and cholesterol
Show Answer & Explanation

Answer: (d) calcium, fat and cholesterol

Explanation:
1. Deposits of calcium, fat and cholesterol and fibrous tissue narrow arterial lumen, causing coronary artery disease.

Teacher's Note:
1. It affects blood supply to heart muscles.

Question 13: Parasympathetic neural signals ______ the heart rate and ______ the cardiac output.
(a) increase, increase
(b) decrease, decrease
(c) decrease, increase
(d) increase, decrease
Show Answer & Explanation

Answer: (b) decrease, decrease

Explanation:
1. The parasympathetic system (acetylcholine) reduces heart rate and cardiac output; the sympathetic system (noradrenaline) raises them.

Teacher's Note:
1. Adrenal medullary hormones also raise cardiac output.

Question 14: The vessel carrying the highest concentration of urea out of the liver is the
(a) hepatic artery
(b) hepatic portal vein
(c) hepatic vein
(d) pulmonary vein
Show Answer & Explanation

Answer: (c) hepatic vein

Explanation:
1. Urea is made in the liver from ammonia and leaves through the hepatic vein.

Teacher's Note:
1. The hepatic portal vein carries nutrient-rich blood to the liver.

Question 15: In the human body, veins differ from arteries in that veins
(a) are thick walled and carry blood away from the heart
(b) have narrow lumen
(c) never have valves
(d) have valves in the lumen and wider lumen
Show Answer & Explanation

Answer: (d) have valves in the lumen and wider lumen

Explanation:
1. Veins carry blood toward the heart, have thinner walls, a wider lumen and valves to prevent backflow.

Teacher's Note:
1. Arteries are thick walled and carry blood away from the heart.

Question 16: Sympathetic neural signals are mediated by ______ and ______ the heart rate.
(a) acetylcholine, increase
(b) noradrenaline, decrease
(c) acetylcholine, decrease
(d) noradrenaline, increase
Show Answer & Explanation

Answer: (d) noradrenaline, increase

Explanation:
1. The sympathetic nervous system releases noradrenaline and increases heart rate and cardiac output.

Teacher's Note:
1. The parasympathetic system releases acetylcholine and decreases them.

Question 17: Joint diastole is the phase in which
(a) both atria contract
(b) both ventricles contract
(c) all four chambers of the heart are relaxed
(d) only the left atrium relaxes
Show Answer & Explanation

Answer: (c) all four chambers of the heart are relaxed

Explanation:
1. Joint diastole lasts about 0.4 second, with atria and ventricles all in diastole.

Teacher's Note:
1. Blood flows passively into the ventricles during this time.

Question 18: The human heart is described as myogenic because
(a) it is initiated by the brain
(b) the heartbeat is initiated by the SA node in the heart muscle itself
(c) it needs nerves to start beating
(d) it is controlled by hormones only
Show Answer & Explanation

Answer: (b) the heartbeat is initiated by the SA node in the heart muscle itself

Explanation:
1. Human heartbeat is initiated by the SA node, a specialised cardiac muscle region, so it is myogenic; the nervous system only modifies it.

Teacher's Note:
1. In molluscs the heartbeat is neurogenic.

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