Human Heart Physiology Quiz
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Questions and Answers

What is the approximate resting heart rate of an adult human?

  • 100 beats/min
  • 50 beats/min
  • 72 beats/min (correct)
  • 195 beats/min

    • Which of the following has the highest typical heart rate?

  • Mouse (correct)
  • Trained Athlete
  • Human
  • Elephant

    • Where does the contraction of heart muscle initially begin?

  • In the aortic valve
  • In the ventricles
  • In the sino-atrial (SA) node (correct)
  • In the left atrium

    • What is the effect of sympathetic nerve fibers on heart rate?

    <p>Sympathetic fibers increase heart rate by up to 100% (D)</p> Signup and view all the answers

    What is the primary role of the sino-atrial (SA) node?

    <p>To act as the heart's pacemaker initiating heart beat. (A)</p> Signup and view all the answers

    How does the parasympathetic nervous system affect heart rate?

    <p>It decreases heart rate by up to 30% (D)</p> Signup and view all the answers

    What is the approximate number of times the human heart beats in an average lifespan?

    <p>2.6 billion (D)</p> Signup and view all the answers

    What causes the two atria to contract simultaneously?

    <p>Contraction wave spreads rapidly from the SA node across both atria (D)</p> Signup and view all the answers

    What percentage of blood flows directly from the atria to the ventricles before atrial systole occurs?

    <p>70% (B)</p> Signup and view all the answers

    What is the approximate blood pressure at the start of the large arteries?

    <p>100 mmHg (B)</p> Signup and view all the answers

    What is the approximate blood pressure in the vena cavae?

    <p>0 mmHg (A)</p> Signup and view all the answers

    What is the intrinsic rate of the SA node, in the absence of the ANS input?

    <p>100 beats/min (B)</p> Signup and view all the answers

    What is the typical volume of blood ejected from each ventricle during ventricular systole, also known as the stroke volume?

    <p>70 ml (B)</p> Signup and view all the answers

    What causes the dicrotic notch?

    <p>The backflow of blood from the aorta into the ventricles (D)</p> Signup and view all the answers

    What is the term for the volume of blood remaining in each ventricle after ventricular systole?

    <p>End-systolic volume (A)</p> Signup and view all the answers

    In which vessel is the blood pressure approximately 85 mmHg?

    <p>Arterioles (B)</p> Signup and view all the answers

    What is the average cardiac output in liters per minute?

    <p>5 liters (B)</p> Signup and view all the answers

    What is the approximate blood pressure at the start of the capillaries?

    <p>25 mmHg (D)</p> Signup and view all the answers

    According to the Frank-Starling Law of the Heart, what primarily influences stroke volume?

    <p>Venous return to the atria (D)</p> Signup and view all the answers

    What happens to pulse pressure as blood flows through smaller arteries?

    <p>It becomes less. (C)</p> Signup and view all the answers

    Approximately how many seconds pass between the closing of the atrioventricular valves, and the opening of the semilunar valves?

    <p>0.02 to 0.03 seconds (A)</p> Signup and view all the answers

    What is the initial cause of blood being pumped into the ventricles during the cardiac cycle?

    <p>Atrial contraction from the sino-atrial node (D)</p> Signup and view all the answers

    What is the pulse pressure?

    <p>The difference between systolic and diastolic pressures (C)</p> Signup and view all the answers

    What event immediately follows the maximal systolic pressure?

    <p>A sharp drop in pressure, called the incisura (A)</p> Signup and view all the answers

    What is the primary effect of increased end-diastolic pressure on the heart, according to the Frank-Starling law?

    <p>Increased stroke volume (A)</p> Signup and view all the answers

    How does exercise typically affect the Frank-Starling curve?

    <p>It shifts the curve upwards and to the left (D)</p> Signup and view all the answers

    In a failing heart, what happens to the amount of blood remaining in the heart after contraction?

    <p>The amount increases (A)</p> Signup and view all the answers

    What physiological effect can result from the damming of blood in the veins due to heart failure?

    <p>Dyspnea and oedema (A)</p> Signup and view all the answers

    What is the primary reason for a decline in cardiac output during heart failure?

    <p>Reduced pumping ability of the heart (C)</p> Signup and view all the answers

    What does an electrocardiogram (ECG) record?

    <p>The electrical activity of the heart (C)</p> Signup and view all the answers

    What is the relationship between ventricular contraction force and end-diastolic pressure, within physiological limits?

    <p>Increased end-diastolic pressure increases contraction force (C)</p> Signup and view all the answers

    Which of these is NOT a direct consequence of heart failure, as described in the text?

    <p>Increased blood flow to organs (B)</p> Signup and view all the answers

    What is the primary function of the annulus fibrosus in the heart?

    <p>To act as an electrical insulator, preventing direct conduction between atria and ventricles. (B)</p> Signup and view all the answers

    What is the typical time delay between atrial and ventricular contraction due to the annulus fibrosus?

    <p>0.11 seconds (A)</p> Signup and view all the answers

    Which structure normally serves as the only electrical link between the atria and the ventricles?

    <p>The AV node (D)</p> Signup and view all the answers

    What is the function of the His-Purkinje system?

    <p>To transmit the impulse from the AV node to the ventricular muscle. (C)</p> Signup and view all the answers

    What is the conduction velocity of the Purkinje fibers?

    <p>4 meters per second (D)</p> Signup and view all the answers

    Which term describes the contraction of the heart chambers during the cardiac cycle?

    <p>Systole (C)</p> Signup and view all the answers

    What is the typical duration of one complete cardiac cycle?

    <p>0.8 seconds (B)</p> Signup and view all the answers

    What is the typical, resting heart rate in beats per minute?

    <p>70 bpm (D)</p> Signup and view all the answers

    What role do the left and right pulmonary arteries play in circulation?

    <p>They send blood to the lungs. (A)</p> Signup and view all the answers

    How does blood exit the left ventricle?

    <p>Through the aortic semilunar valve. (C)</p> Signup and view all the answers

    Which structure separates individual cardiac muscle cells?

    <p>Intercalated discs (C)</p> Signup and view all the answers

    What characteristic allows cardiac muscle to contract rhythmically without external stimulation?

    <p>It is myogenic. (C)</p> Signup and view all the answers

    What part of the brain regulates heart rate?

    <p>Medulla oblongata (C)</p> Signup and view all the answers

    What is the approximate duration of the refractory period in cardiac muscle?

    <p>0.25 – 0.3 seconds (C)</p> Signup and view all the answers

    What is the main function of the aorta in the circulatory system?

    <p>To distribute oxygenated blood to the body. (A)</p> Signup and view all the answers

    What does the term 'syncytium' refer to in cardiac muscle physiology?

    <p>Interconnected cardiac cells. (B)</p> Signup and view all the answers

    Study Notes

    Cardiovascular System, Biological Fluids, Renal Function

    • CFR.5 The Heart: Structure, physiology, cardiac cycle, arterial blood pressure, cardiac failure

    Learning Outcomes

    • Describe the features of the human heart and its role in systemic and pulmonary circulatory systems
    • Identify the external features of the human heart, major arteries, veins, compartments, cardiac muscle, orientation and location in the body
    • Describe the internal features of the heart: atria, ventricles, septum, bicuspid and tricuspid valves, semilunar valves, sinoatrial node
    • Explain the cardiac cycle stages (systole, diastole, stroke volume, cardiac output, Frank-Starling law)
    • Discuss blood pressure measurements, and different levels detected in different parts of the systemic circulation (aorta vs vena cava)

    The Heart

    • The heart circulates blood
    • Found in the thorax, within its own pericardial cavity
    • Attached to the walls of the pericardium where great vessels enter/exit
    • Pericardium is lined by mesothelium (simple squamous epithelium), forming part of the pericardial membrane
    • Epicardium is the outer covering of the heart, covered by mesothelium

    The Heart Structure (Diagram)

    • External and internal structures labelled
    • Atria, ventricles, septum, valves identified
    • Aorta, superior and inferior vena cava, pulmonary arteries and veins

    Structure of the Heart (Diagram)

    • Diagram of the heart's internal structure with numbered labels
    • Include major components and vessels in labelled diagram

    Systemic and Pulmonary Circulation (Diagram)

    • Diagram illustrating the pathways of blood flow in both circulatory systems in the body
    • Label major vessels and organs in both circuits

    Cardiac Muscle Physiology

    • Coordination of muscular contraction is vital for proper heart function
    • Cardiac muscle is striated, but arranged into individual cells separated by areas of intercalated discs
    • Intercalated discs have numerous gap junctions which allow free diffusion of ions between cells
    • Cardiac muscle is myogenic, meaning it contracts rhythmically and continuously without external stimulation
    • Functions as a syncytium (action potentials spreading from cell to cell)
    • Refractory period: 0.25 - 0.3 seconds; no further contraction during this period

    Nervous Control of the Heart - CV Center

    • Heart rate regulated by the cardiovascular/ cardiac centre in the medulla oblongata which responds to pressure receptors in the walls of blood vessels
    • Input to the centre includes from higher brain centres, proprioceptors, baroreceptors and chemoreceptors
    • Output to effectors increase nerve impulses leading to heart rate changes
    • Blood vessels vasoconstrict/vasodilate

    Heart Rate

    • Varies widely in different mammals; generally lower in larger animals
    • Adult human heart: ~72 beats per minute
    • Can rise to 195 beats per minute under stress
    • Trained athletes tend to have lower resting heart rates (~50 beats per min)

    Physiology of the Heart

    • Contraction begins spontaneously in the sinoatrial (SA) node in the right atrium near the superior vena cava entry
    • SA node (pacemaker)
    • Consists of modified cardiac muscle mixed with nerve fibres of the autonomic nervous system (sympathetic and parasympathetic/vagus nerve)

    Physiology of the Heart

    • Heart beat originates spontaneously at the SA node due to its myogenic nature
    • SA node generates 100 beats per minute
    • Autonomic nervous system can 'slow down' or 'speed up' heart rate (change frequency)
    • Sympathetic fibres increase heart rate by up to 100%
    • Parasympathetic fibres decrease heart rate by up to 30%

    Excitatory and Conductive System

    • SA node initiates the heartbeat, and sends signals via the conducting system to stimulate contractions

    • Bundle Of His/atrioventricular bundle (start of the system)

    • Right bundle branch

    • Left bundle branch

    • Purkinje fibres (end of system): conduct impulses and allow both ventricles to contract simultaneously at ~4m/s

    Cardiac Cycle

    • Contraction (systole) and relaxation (diastole) of heart chambers; period from end of one contraction to the end of the next is the cardiac cycle
    • Typically 70 beats per minute in healthy adults (slowed by parasympathetic nervous system)
    • One complete cycle ~0.8 seconds
    • Human heart beats approximately 2.6 billon times in an average lifespan

    Cardiac Cycle

    • Starts with atrial contraction initiating by the SA node
    • Blood normally flows continuously into the atria from vena cavae and pulmonary vein
    • ~70% of atrial blood flows directly into the ventricles while ~30% is pushed into ventricles by atrial systole
    • Delay in transmission through the AV node causes a pause between atrial systole and ventricular systole

    Cardiac Cycle

    • During ventricular diastole, the ventricles fill to a volume of 120-130ml
    • Ventricular Systole: Pressure rise leads to atrioventricular valve closure, followed by semilunar valve opening
    • 70ml ejected per contraction, the stroke volume;
    • remaining volume is end-systolic volume (~50-60 ml).

    Cardiac Output

    • Volume of blood ejected into the aorta (or right ventricle) per minute
    • Calculated as Stroke Volume x Heart Rate
    • Normal approx. 5 Litres/min
    • Can increase to 25 Litres/min under stress

    Frank-Starling Law of the Heart

    • Intrinsic ability of the heart to adapt to changing loads of inflowing blood
    • Ventricles are elastic and can expand to accommodate a larger volume of blood
    • All blood coming to heart is pumped
    • Relationship between Ventricle end-diastolic pressure (LVEDP) and Stroke Volume (SV)

    Blood Pressure

    • Left ventricle drives blood around arteries
    • Measured using a sphygmomanometer
    • Typical reading in healthy adults: 120/80 mmHg (systolic/diastolic)
    • Systolic pressure: highest blood pressure reading
    • Diastolic pressure: lowest blood pressure reading

    Blood Pressure

    • Mean Arterial Pressure (MAP) = Diastolic + (1/3rd Systolic - Diastolic)
    • Aorta: 100mmHg
    • Arterioles: 85 mmHg
    • Capillaries: 25mmHg
    • Vena Cavae: 0 mmHg

    Blood Pressure - Systemic Circulation

    • Pulse pressure: difference between systolic and diastolic pressure readings
    • Pulse pressure decreases as blood passes through smaller arteries and disappears in capillaries (~1mmHg)

    Blood Pressure

    • Maximal systolic pressure ends with a sharp drop (incisura/dicrotic notch) during ventricular diastole due to backflow
    • The rapid closure of aortic semilunar valves causes a brief rebound (notch)

    Learning Resources

    • Sherwood. Human Physiology (Chapters 9 & 10)
    • Solomon. Biology (Chapter 44)
    • Chiras. Human Biology (6th Edition, Chapters 5 & 6)

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    CFR 5 Heart WT 2024-25 PDF

    Description

    Test your knowledge on the physiology of the human heart with this quiz. Topics include resting heart rates, the role of the sino-atrial (SA) node, and blood pressure readings. Perfect for students studying biology or health sciences.

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