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Human Body Systems - The Circulatory System

Grade 7IB

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

🔑Concepts

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The heart is a muscular organ that acts as a double pump: the right side pumps deoxygenated blood to the lungs (Pulmonary Circulation), and the left side pumps oxygenated blood to the body (Systemic Circulation).

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Blood vessels are categorized into three types: Arteries (carry blood away from the heart at high pressure), Veins (carry blood toward the heart at low pressure and contain valves), and Capillaries (allow for the diffusion of O2O_2, CO2CO_2, and nutrients).

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Blood is composed of four main components: Plasma (liquid medium), Red Blood Cells (contain hemoglobin to carry O2O_2), White Blood Cells (immune response), and Platelets (blood clotting).

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Gas exchange occurs in the capillaries of the lungs where CO2CO_2 leaves the blood and O2O_2 enters, and in the body tissues where O2O_2 is delivered to cells for aerobic respiration: C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}.

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The heartbeat is controlled by electrical impulses, and the pulse rate represents the number of times the heart beats per minute (BPMBPM).

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Hemoglobin (HbHb) binds with oxygen in the lungs to form oxyhemoglobin: Hb+4O2⇌Hb(O2)4Hb + 4O_2 \rightleftharpoons Hb(O_2)_4.

📐Formulae

Heart Rate (BPM)=Number of BeatsTime in Seconds×60\text{Heart Rate (BPM)} = \frac{\text{Number of Beats}}{\text{Time in Seconds}} \times 60

Cardiac Output (Q)=Stroke Volume (SV)×Heart Rate (HR)\text{Cardiac Output (Q)} = \text{Stroke Volume (SV)} \times \text{Heart Rate (HR)}

Blood Pressure (BP)=Systolic PressureDiastolic Pressure\text{Blood Pressure (BP)} = \frac{\text{Systolic Pressure}}{\text{Diastolic Pressure}}

💡Examples

Problem 1:

A student measures their pulse after running and counts 3030 beats in 1515 seconds. Calculate their heart rate in BPMBPM.

Solution:

Heart Rate=3015×60=120 BPM\text{Heart Rate} = \frac{30}{15} \times 60 = 120 \text{ BPM}

Explanation:

To find the beats per minute, we divide the observed beats by the time interval and multiply by 6060 seconds. Alternatively, since 1515 seconds is 14\frac{1}{4} of a minute, we can multiply 30×4=12030 \times 4 = 120.

Problem 2:

Why is the wall of the left ventricle significantly thicker than the wall of the right ventricle?

Solution:

The left ventricle must generate enough pressure to pump blood through the Aorta to the entire systemic circuit, whereas the right ventricle only pumps blood to the nearby lungs.

Explanation:

Greater muscle mass allows the left ventricle to create the high pressure (PP) required to overcome the resistance of the long systemic pathways to the head and limbs.

Problem 3:

Identify the chemical change that occurs when Red Blood Cells reach the lungs.

Solution:

Deoxygenated hemoglobin (HbHb) binds with inhaled oxygen (O2O_2) to form Hb(O2)4Hb(O_2)_4.

Explanation:

In the high-oxygen environment of the alveoli, hemoglobin has a high affinity for O2O_2, allowing the blood to become 100%100\% saturated for transport to the tissues.