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Biology - The Circulatory System

Grade 10ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Blood Composition: Blood consists of plasma (55%) and formed elements (45%) including Erythrocytes (RBCsRBCs), Leukocytes (WBCsWBCs), and Thrombocytes (Platelets).

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Hemoglobin (HbHb): An iron-containing pigment in RBCsRBCs that binds with oxygen to form Oxyhemoglobin (Hb(O2)4Hb(O_2)_4) for transport.

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Double Circulation: The human heart follows a double circulation path consisting of Pulmonary circulation (Heart →\rightarrow Lungs →\rightarrow Heart) and Systemic circulation (Heart →\rightarrow Body →\rightarrow Heart).

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Heart Valves: The Tricuspid valve (right side) and Bicuspid/Mitral valve (left side) prevent backflow into the atria. Semilunar (SLSL) valves prevent backflow into the ventricles.

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Blood Pressure: Represented as SystolicDiastolic\frac{Systolic}{Diastolic}, typically 12080\frac{120}{80} mmHgmmHg. Systole refers to contraction and Diastole refers to relaxation.

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Hepatic Portal System: A unique venous connection where the hepatic portal vein carries nutrient-rich blood from the gastrointestinal tract to the Liver before reaching the Systemic circulation.

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RhRh Factor: An antigen found on the surface of RBCsRBCs. If present, the blood is Rh+Rh^+; if absent, it is Rh−Rh^-.

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Pacemaker: The Sino-atrial (SASA) node initiates the electrical impulse, followed by the Atrio-ventricular (AVAV) node, Bundle of His, and Purkinje fibers.

📐Formulae

Cardiac Output (CO)=Stroke Volume (SV)×Heart Rate (HR)Cardiac\ Output\ (CO) = Stroke\ Volume\ (SV) \times Heart\ Rate\ (HR) International standard unit is L/minL/min.

Hb+4O2⇌Hb(O2)4Hb + 4O_2 \rightleftharpoons Hb(O_2)_4 (Reversible binding of Oxygen to Hemoglobin)

Pulse Pressure=Systolic Pressure−Diastolic PressurePulse\ Pressure = Systolic\ Pressure - Diastolic\ Pressure

CO2+H2O→Carbonic AnhydraseH2CO3⇌H++HCO3−CO_2 + H_2O \xrightarrow{Carbonic\ Anhydrase} H_2CO_3 \rightleftharpoons H^+ + HCO_3^- (Transport of CO2CO_2 in plasma)

💡Examples

Problem 1:

Calculate the Cardiac Output of a person whose heart beats 7272 times per minute (72 bpm72\ bpm) and pumps out 70 mL70\ mL of blood per beat.

Solution:

CO=72×70=5040 mL/min=5.04 L/minCO = 72 \times 70 = 5040\ mL/min = 5.04\ L/min

Explanation:

Cardiac output is the volume of blood pumped by the left ventricle per minute. It is the product of the heart rate (HRHR) and the stroke volume (SVSV).

Problem 2:

During a medical check-up, a student's blood pressure is recorded as 130/90 mmHg130/90\ mmHg. Identify the Systolic pressure and calculate the Pulse Pressure.

Solution:

Systolic Pressure = 130 mmHg130\ mmHg. Pulse Pressure = 130−90=40 mmHg130 - 90 = 40\ mmHg.

Explanation:

The numerator represents the pressure during ventricular contraction (SystoleSystole), and the difference between systolic and diastolic pressure is defined as the pulse pressure.

Problem 3:

Explain why an Rh−Rh^- person cannot receive Rh+Rh^+ blood during a second transfusion.

Solution:

The Rh−Rh^- body produces anti-RhRh antibodies after the first exposure. In a second transfusion, these antibodies cause agglutination of the Rh+Rh^+ RBCsRBCs.

Explanation:

The RhRh factor acts as an antigen. Sensitization occurs during the first contact, and the subsequent immune response leads to clumping of blood cells.