Class 9 Circulatory System Mock Test (ICSE)

Topics in Circulatory System

• Structure of the heart
• Heart rate, stroke volume and cardiac output
• Mechanism of blood circulation
• Blood and its components
• Benefits of exercise on the circulatory system

Circulatory System practice questions with answers

1. Q1Multiple choice·1 mark
   Which blood vessel carries oxygenated blood from the lungs back to the left atrium of the heart?

   1. (a)Superior vena cava
   2. (b)Pulmonary vein
   3. (c)Aorta
   4. (d)Pulmonary artery
   Show answer and step marks

   1. Correct option: (b) Pulmonary vein+1

   Answer: (b)
2. Q2Multiple choice·1 mark
   How does regular long-term endurance training typically affect the resting heart rate of an individual?

   1. (a)Decreases it, leading to athletic bradycardia
   2. (b)Increases it significantly
   3. (c)Causes erratic and irregular fluctuations
   4. (d)Keeps it completely unchanged
   Show answer and step marks

   1. Correct option: (a) Decreases it, leading to athletic bradycardia+1

   Answer: (a)
3. Q3Multiple choice·1 mark
   What is the typical resting stroke volume of an untrained healthy adult human during physical rest?

   1. (a)$5\text{ L}$
   2. (b)$120\text{ mL}$
   3. (c)$70\text{ mL}$
   4. (d)$50\text{ mL}$
   Show answer and step marks

   1. Correct option: (c) $70\text{ mL}$+1

   Answer: (c)
4. Q4Multiple choice·1 mark
   Which component of human blood is primarily responsible for the transport of oxygen from the lungs to body tissues?

   1. (a)Red blood cells
   2. (b)Blood platelets
   3. (c)White blood cells
   4. (d)Plasma
   Show answer and step marks

   1. Correct option: (a) Red blood cells+1

   Answer: (a)
5. Q5Long answer·4 marks
   (a) Define cardiac output and state its average resting value for a healthy adult. (b) Calculate the cardiac output per minute of an athlete during a heavy workout whose heart rate is $150\text{ beats/min}$ and stroke volume is $120\text{ mL/beat}$.
   Show answer and step marks

   1. Definition of cardiac output: The volume of blood pumped out by each ventricle of the heart per minute.+1
   2. State average resting value: Approximately $5\text{ L/min}$ (or $5000\text{ mL/min}$)+1
   3. Formula and substitution: $\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume} = 150 \times 120$+1
   4. Final calculation with proper units: $18000\text{ mL/min}$ or $18\text{ L/min}$+1

   Answer: (a) Cardiac output is the volume of blood pumped out by each ventricle of the heart per minute; at rest it is about $5\text{ L/min}$. (b) $150 \times 120 = 18000\text{ mL/min} = 18\text{ L/min}$.
6. Q6Long answer·4 marks
   Define heart rate, stroke volume, and cardiac output. Calculate the cardiac output per minute for an individual whose heart rate is $75$ beats per minute and stroke volume is $70$ mL per beat. Express your final answer in litres per minute.
   Show answer and step marks

   1. Definition of heart rate: The number of times the heart beats per minute.+0.5
   2. Definition of stroke volume: The volume of blood pumped out by each ventricle of the heart during a single heartbeat.+0.5
   3. Definition of cardiac output: The volume of blood pumped out by each ventricle of the heart per minute.+1
   4. Formula: $\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume}$.+1
   5. Substitution and calculation: $75 \times 70 = 5250 \text{ mL/min} = 5.25 \text{ L/min}$.+1

   Answer: Heart rate: number of heartbeats per minute. Stroke volume: volume of blood pumped by each ventricle in one beat. Cardiac output: volume of blood pumped by each ventricle per minute ($=$ heart rate $\times$ stroke volume). Cardiac output $= 75 \times 70 = 5250\text{ mL/min} = 5.25\text{ L/min}$.

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