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Transport in Animals - Heart structure and function

Grade 11IGCSEBiology

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

🔑Concepts

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The heart is a muscular pump divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle. The septum separates the oxygenated blood on the left side from the deoxygenated blood on the right side to prevent mixing.

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Mammals have a double circulatory system. The pulmonary circuit carries deoxygenated blood to the lungs to pick up O2O_2 and release CO2CO_2, while the systemic circuit carries oxygenated blood to the rest of the body.

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The muscular wall of the left ventricle is significantly thicker than the right ventricle. This is because the left ventricle must generate enough pressure to pump blood around the entire body, whereas the right ventricle only pumps blood to the lungs.

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Valves (atrioventricular and semilunar) ensure the one-way flow of blood through the heart. They open and close in response to pressure changes during the cardiac cycle.

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The coronary arteries supply the heart muscle itself with oxygenated blood. If these become blocked (Coronary Heart Disease), the supply of O2O_2 and glucose is restricted, which can lead to a heart attack (myocardial infarction).

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Heart rate is measured in beats per minute (bpm) and increases during exercise to provide more O2O_2 and glucose to respiring muscles and to remove CO2CO_2 faster.

📐Formulae

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

Heart Rate (bpm)=60Time for one cardiac cycle (seconds)\text{Heart Rate (bpm)} = \frac{60}{\text{Time for one cardiac cycle (seconds)}}

💡Examples

Problem 1:

An individual has a resting heart rate of 7272 beats per minute and a stroke volume of 70 cm370\text{ cm}^3. Calculate their Cardiac Output in dm3/mindm^3/min.

Solution:

Cardiac Output=72×70=5040 cm3/min\text{Cardiac Output} = 72 \times 70 = 5040\text{ cm}^3/min In dm3/min:50401000=5.04 dm3/min\text{In } dm^3/min: \frac{5040}{1000} = 5.04\text{ dm}^3/min

Explanation:

Cardiac output is the volume of blood pumped by the heart per minute. First, multiply the heart rate by the stroke volume, then divide by 10001000 to convert from cm3cm^3 to dm3dm^3.

Problem 2:

Calculate the heart rate if one complete cardiac cycle (heartbeat) takes 0.80.8 seconds.

Solution:

Heart Rate=600.8=75 bpm\text{Heart Rate} = \frac{60}{0.8} = 75\text{ bpm}

Explanation:

To find the number of beats in a minute, divide the total seconds in a minute (6060) by the duration of a single beat (0.8 s0.8\text{ s}).

Heart structure and function - Revision Notes & Key Diagrams | IGCSE Grade 11 Biology