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Life Processes and Living Things - The human circulatory system

Grade 5IGCSE

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

🔑Concepts

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The Heart: A muscular organ that acts as a pump. It has four chambers: the right atrium, right ventricle, left atrium, and left ventricle.

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Blood Vessels: There are three main types: Arteries (thick walls, carry blood away from the heart), Veins (thinner walls, have valves, carry blood to the heart), and Capillaries (tiny vessels for exchange).

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Blood Composition: Blood is made of Red Blood Cells (transport O2O_2 using hemoglobin), White Blood Cells (defend against pathogens), Platelets (clotting), and Plasma (liquid part).

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Gas Exchange: Blood transports oxygen (O2O_2) from the lungs to the cells for respiration and carries carbon dioxide (CO2CO_2) back to the lungs to be exhaled.

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Double Circulatory System: Humans have two circuits: the pulmonary circuit (heart →\rightarrow lungs →\rightarrow heart) and the systemic circuit (heart →\rightarrow body →\rightarrow heart).

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Pulse Rate: The number of times the heart beats per minute (bpm). It increases during exercise to deliver more O2O_2 to muscles.

📐Formulae

Heart Rate (bpm)=Total Number of HeartbeatsTime in Minutes\text{Heart Rate (bpm)} = \frac{\text{Total Number of Heartbeats}}{\text{Time in Minutes}}

Pulse Rate∝Physical Activity Intensity\text{Pulse Rate} \propto \text{Physical Activity Intensity}

Cardiac Output=Stroke Volume×Heart Rate\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}

💡Examples

Problem 1:

A student measures their pulse for 3030 seconds and counts 4040 beats. Calculate their heart rate in beats per minute (bpm).

Solution:

8080 bpm

Explanation:

Since there are 6060 seconds in a minute, we multiply the 3030-second count by 22. Calculation: 40×6030=8040 \times \frac{60}{30} = 80.

Problem 2:

Why does the concentration of CO2CO_2 increase in the blood as it passes through the muscles during exercise?

Solution:

Due to cellular respiration.

Explanation:

During exercise, muscles require energy. Cells use O2O_2 and glucose to produce energy, creating CO2CO_2 as a waste product. This CO2CO_2 diffuses into the blood to be transported away.