EXERCISES

Q1. Name the components of the formed elements in the blood and mention one major function of each of them.
Answer: The formed elements make up about 45% of blood and include three main components:

1. Erythrocytes (RBCs): Carry oxygen and carbon dioxide with the help of haemoglobin.
2. Leucocytes (WBCs): Protect the body by fighting infections and destroying foreign organisms.
3. Platelets (Thrombocytes): Help in the clotting of blood and prevent excessive blood loss.

Q2. What is the importance of plasma proteins?
Answer: Plasma proteins form about 6–8% of plasma and have different functions:

• Fibrinogen: Helps in blood clotting.
• Globulins: Take part in body defense mechanisms.
• Albumins: Maintain osmotic balance and regulate blood volume.

Q3. Match Column I with Column II.
Answer:
(a) Eosinophils → (iii) Resist infections
(b) RBC → (v) Gas transport
(c) AB group → (ii) Universal recipient
(d) Platelets → (i) Coagulation
(e) Systole → (iv) Contraction of heart

Q4. Why do we consider blood as a connective tissue?
Answer: Blood is called a connective tissue because it has a fluid matrix called plasma, in which formed elements (RBCs, WBCs, and platelets) are suspended. Like other connective tissues, it connects different body parts by transporting gases, nutrients, hormones, and wastes between them.

Q5. What is the difference between lymph and blood?
Answer: The difference between lymph and blood are-

1. Blood is a red-coloured fluid due to the presence of haemoglobin, whereas lymph is colourless as it lacks haemoglobin.
2. Blood contains both RBCs and WBCs, while lymph has no RBCs and mainly lymphocytes.
3. The protein content of blood is high (about 6–8%), whereas in lymph, it is comparatively low.
4. Blood circulates through a closed system of arteries and veins, while lymph flows through lymphatic vessels.
5. Functionally, blood transports gases, nutrients, and hormones, whereas lymph plays a vital role in immunity and in returning tissue fluids to the bloodstream.

Q6. What is meant by double circulation? What is its significance?
Answer: Double circulation means that blood flows through the heart twice during one complete circulation of the body. This system consists of two parts —

1. Pulmonary circulation: It carries deoxygenated blood from the right ventricle to the lungs for oxygenation and then brings oxygenated blood back to the left atrium.

2. Systemic circulation: It carries oxygenated blood from the left ventricle to all the body tissues and returns deoxygenated blood to the right atrium.

The significance of double circulation is that it  keeps the oxygenated and deoxygenated blood completely separate, ensuring efficient oxygen supply to all body parts. It helps maintain a high metabolic rate and is especially important for birds and mammals that require continuous and high energy for their activities.

Q7. Write the differences between:
(a) Blood and Lymph
(b) Open and Closed system of circulation
(c) Systole and Diastole
(d) P-wave and T-wave
Answer:

(a) Blood and Lymph

(b) Open and Closed Circulatory System

(c) Systole and Diastole

(d) P-wave and T-wave

Q8. Describe the evolutionary change in the pattern of heart among the vertebrates.
Answer: The heart of vertebrates shows gradual evolution toward complete separation of oxygenated and deoxygenated blood:

Q9. Why do we call our heart myogenic?
Answer: Our heart is called myogenic because it can generate its own rhythmic contractions without external stimulation. The cardiac muscles (especially in nodal tissue) produce action potentials on their own, making the heart autoexcitable.

Q10. Sino-atrial node is called the pacemaker of our heart. Why?
Answer: The Sino-atrial node (SAN) is called the pacemaker because it generates the maximum number of impulses (about 70–75 per minute). It initiates and maintains the rhythmic heartbeat by controlling the rate of contraction.

Q11. What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?
Answer: The Atrio-ventricular node (AVN) receives impulses from the SAN and passes them to the ventricles with a short delay, allowing the atria to contract completely before the ventricles do. The Atrio-ventricular bundle (Bundle of His) carries the impulses rapidly through its branches and Purkinje fibres to all parts of the ventricles, ensuring their coordinated contraction.

Q12. Define a cardiac cycle and the cardiac output.
Answer:

• Cardiac cycle: The sequence of events in one heartbeat, including systole and diastole of both atria and ventricles. It lasts about 0.8 seconds in a person with a heart rate of 72 beats per minute.
• Cardiac output: The amount of blood pumped by each ventricle in one minute. It is calculated as:
  Cardiac Output = Stroke Volume × Heart Rate
  Average value ≈ 70 mL × 72 = 5 litres per minute.

Q13. Explain heart sounds.
Answer: Two main heart sounds are heard during each cardiac cycle:

• First sound (“lub”): Produced by the closure of tricuspid and bicuspid valves at the beginning of ventricular systole.
• Second sound (“dub”): Produced by the closure of semilunar valves at the beginning of ventricular diastole.
  These sounds help doctors detect abnormalities in heart function.

Q14. Draw a standard ECG and explain the different segments in it.
Answer: An ECG (Electrocardiogram) records the electrical activity of the heart during a cardiac cycle. It shows three main waves: