Cardiac Physiology and Function Quiz
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Questions and Answers

What prevents fast Na+ channels from reopening immediately after being activated?

  • They require a change in ion concentration.
  • They take time to recharge before activation.
  • They can only be opened by hormonal signals.
  • They close a fraction of a second after opening. (correct)

    • What is the primary function of the pacemaker potential in the cells of the SAN?

  • To inhibit the generation of action potentials.
  • To increase resting membrane potential rapidly.
  • To cause spontaneous depolarization over time. (correct)
  • To create a resting state without fluctuation.

    • How frequently do the SAN cells generate action potentials at rest?

  • Every 1 second
  • Every 1.5 seconds
  • Every 0.8 seconds (correct)
  • Every 2 seconds

    • What role does calcium play in excitation-contraction coupling within cardiac muscle cells?

    <p>Calcium converts electrical signals into mechanical energy.</p> Signup and view all the answers

    How can the firing rate of action potentials in the AVN be influenced?

    <p>By sympathetic and parasympathetic nerve input.</p> Signup and view all the answers

    What is the formula for calculating stroke volume?

    <p>SV = EDV - ESV</p> Signup and view all the answers

    What is the typical end diastolic volume (EDV) at rest?

    <p>130ml</p> Signup and view all the answers

    What happens to the venous return during physical activity?

    <p>It increases due to the skeletal muscle pump.</p> Signup and view all the answers

    Which of the following statements correctly describes cardiac output during mild exercise?

    <p>Cardiac output is approximately 10 L/min.</p> Signup and view all the answers

    What impact does increased preload have on the heart?

    <p>It allows the heart muscle to stretch more.</p> Signup and view all the answers

    What is the primary function of gap junctions in cardiac muscle tissue?

    <p>They allow for rapid transmission of action potentials between cells.</p> Signup and view all the answers

    What characteristic allows myocardial cells to spontaneously generate action potentials?

    <p>Automaticity</p> Signup and view all the answers

    What separates the atria from the ventricles in the heart?

    <p>Fibrous tissue</p> Signup and view all the answers

    What is the role of desmosomes in cardiac muscle cells?

    <p>They tightly hold cells together.</p> Signup and view all the answers

    Which ions primarily influence the phases of the cardiac action potential?

    <p>Na+, K+, and Ca++</p> Signup and view all the answers

    What term describes the heart functioning as a single unit due to interconnected muscle cells?

    <p>Syncytium</p> Signup and view all the answers

    Which statement accurately describes the cardiac muscle's electrical characteristics?

    <p>Cardiac muscle can transmit action potentials rapidly between cells.</p> Signup and view all the answers

    What is the significance of the pacemaker potential generated by spontaneous depolarization in cardiac cells?

    <p>It regulates heart rate.</p> Signup and view all the answers

    What role does calcium play in myocyte contraction?

    <p>It activates tropomyosin complexes.</p> Signup and view all the answers

    Who developed the galvanometer to show that tracings can be produced by action potentials?

    <p>William Einthoven</p> Signup and view all the answers

    What does Einthoven's Triangle help to determine?

    <p>Which lead will best show certain electrical activity</p> Signup and view all the answers

    What primarily generates the electrical trace seen in an ECG?

    <p>Action potentials traveling through heart muscle</p> Signup and view all the answers

    Which of the following factors influences how the ECG trace varies?

    <p>Direction of travel of action potentials</p> Signup and view all the answers

    What can be inferred from the term 'vector' in the context of cardiac action potentials?

    <p>It has both magnitude and direction.</p> Signup and view all the answers

    What represents the average direction of the impulse during an action potential in the heart?

    <p>Electrical vector</p> Signup and view all the answers

    What is indicated by the small depolarizing wave fronts during an action potential?

    <p>They generate electrical currents in the heart.</p> Signup and view all the answers

    What is a major consequence of left ventricular hypertrophy due to hypertension?

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

    Which of the following is considered a modifiable risk factor for hypertension?

    <p>Overweight/obesity</p> Signup and view all the answers

    The response to injury hypothesis primarily relates to which vascular condition?

    <p>Atherosclerosis</p> Signup and view all the answers

    Which of the following is least likely to cause secondary hypertension?

    <p>Chronic tobacco use</p> Signup and view all the answers

    Which condition is most directly associated with hypertension of renal origin?

    <p>Renovascular disease</p> Signup and view all the answers

    What is a common effect of chronic hypertension on blood vessels in the body?

    <p>Atherosclerosis development</p> Signup and view all the answers

    What initial event does the response to injury hypothesis identify in the development of atherosclerosis?

    <p>Injury to the epithelium</p> Signup and view all the answers

    Which of the following complications is directly associated with damage to capillaries due to hypertension?

    <p>Oedema</p> Signup and view all the answers

    What primarily determines systolic blood pressure?

    <p>The characteristics of stroke volume ejected by the heart</p> Signup and view all the answers

    What is the function of elastic tissue in blood vessels during systole?

    <p>It absorbs pressure to prevent a sharp rise in vessel pressure</p> Signup and view all the answers

    What occurs without the elastic recoil of blood vessels?

    <p>Dramatic fall in pressure and blood flow between beats</p> Signup and view all the answers

    What mechanism primarily regulates blood pressure in an acute setting?

    <p>Baroreceptor reflex</p> Signup and view all the answers

    How does arterial pressure affect the firing rate of baroreceptor neurons?

    <p>Increased arterial pressure leads to increased firing rate</p> Signup and view all the answers

    What long-term mechanism primarily maintains blood pressure?

    <p>Renin-angiotensin-aldosterone mechanism</p> Signup and view all the answers

    What is referred to as Windkessel’s effect?

    <p>Continuous blood flow in the aorta despite intermittent heart pumping</p> Signup and view all the answers

    What role do stretch-sensitive sensory nerve endings have in blood pressure regulation?

    <p>They provide feedback to lower blood pressure when it is high</p> Signup and view all the answers

    Study Notes

    Cardiac Physiology

    • The heart is a dual pump within one organ, each side having an atrium and ventricle.
    • It pumps blood from low-pressure veins to high-pressure arteries.
    • Right ventricle output enters the pulmonary artery.
    • Left ventricle output enters the aorta.
    • Output is under intrinsic control but can be regulated by autonomic nerves and hormones.

    Blood Pressure

    • Pulmonary circuit pressure is approximately 28/8 mmHg.
    • Systemic circuit pressure is approximately 120/80 mmHg.

    Heart Valves and Circulation

    • Heart valves control unidirectional blood flow.
    • Bicuspid (mitral) valve opens and closes, regulating blood flow between left atrium and ventricle.

    Cardiac Cycle

    • The cardiac cycle is the coordinated sequence of electrical and mechanical events from one heartbeat to the next.
    • It includes atrial and ventricular relaxation (diastole) and contraction (systole).

    Heart Valves

    • The bicuspid valve is open when relaxed, closed when the papillary muscles contract.

    Electrical Activity

    • The heartbeat originates from the sinoatrial (SA) node.
    • Depolarization of the heart follows a defined pathway from the SA node until the ventricles are fully depolarized.
    • Atrial and ventricular depolarization and repolarization can be tracked using an electrocardiogram (ECG).

    Phases of the Cardiac Cycle

    • Atrial systole.
    • Ventricular systole (first phase).
    • Ventricular systole (second phase).
    • Ventricular diastole (early).
    • Ventricular diastole (late).

    Heart Valves and Circulation

    • The tricuspid and mitral valves are associated with atrial and ventricular contraction and relaxation.

    Cardiac Muscle

    • Cardiac muscle is a syncytium, allowing coordinated contraction of the entire myocardial mass.
    • Desmosomes tightly connect the muscle cells, while intercalated discs contain gap junctions for signal transmission.
    • Cardiac cells exhibit automaticity, capable of self-depolarization and generating pacemaker potentials.

    Action Potentials of Cardiac Muscle

    • Action potentials in cardiac tissue demonstrate characteristics including rapid depolarization, plateau phase, and repolarization.

    Excitation-Contraction Coupling

    • During excitation-contraction coupling, a chemical signal (Ca^2+) converts an electrical signal into mechanical force and induces contraction.

    Pacemaker Potentials

    • Pacemaker potentials are the slow, spontaneous depolarizations that initiate the heartbeat cycle in the sinoatrial node (SAN).
    • These potentials are related to the rhythmic opening and closing of certain specific ion channels (funny channels and Ca^2+ channels).

    Cardiac Myocyte Action Potential

    • The cardiac myocyte action potential differentiates from other action potentials through a plateau phase, which helps prevent tetany.
    • Calcium-induced calcium release (CICR) amplifies the initial calcium influx to achieve robust myofiber contraction.

    Secondary Hypertension

    • Secondary hypertension often has an identifiable cause (e.g., kidney disease, pheochromocytoma).

    Regulation of Stroke Volume

    • Preload: The extent of stretch of the heart muscle before contraction.
    • Afterload: The pressure against which the heart must pump to eject blood.
    • Contractility: The ability of the heart muscle to contract forcefully.

    Frank-Starling Mechanism

    • The Frank-Starling mechanism describes how an increase in end-diastolic volume leads to an increase in stroke volume.
    • The mechanism is based on the length-tension relationship of cardiac muscle fibers.

    Physiological Basis of Starling's Law

    • Increased stretch/preload increases the overlap of actin and myosin fibers.
    • This allows a greater number of cross-bridges to form and results in increased cardiac contractility.

    Systemic Hypertension

    • Systemic hypertension is elevated blood pressure.
    • Blood pressure is affected by both cardiac output and systemic vascular resistance (SVR)
    • Increased stiffness of the large arteries due to calcification is a contributing factor to the rise in blood pressure with age.
    • Decreased baroreceptor sensitivity and increased sympathetic nervous system activity also contribute to age-related blood pressure changes.

    Neural Control of Heart Rate

    • The autonomic nervous system (sympathetic and parasympathetic) plays a crucial role in regulating heart rate and myocardial contraction.

    Electrocardiogram (ECG)

    • The ECG is a graphical record of the electrical activity of the heart.
    • Action potentials create electrical currents that can be detected at the body’s surface.
    • P wave, QRS complex, PR interval, and PR segments represent distinct phases and are used in clinical diagnosis.

    Atherosclerosis

    • Atherosclerosis is the hardening and narrowing of the arteries due to plaque buildup.
    • Early stages involve injury to the endothelium.
    • Plaque formation involves the infiltration of lipoproteins (mainly LDL cholesterol) into the artery wall, triggering an inflammatory response.
    • The plaque evolves and potentially rupture, causing vessel occlusion.

    Vasodilation and Vasoconstriction

    • Vasodilation and vasoconstriction are autonomic responses that regulate blood flow distribution to various body parts.

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    Related Documents

    Cardiac Physiology PDF - UM1011

    Description

    Test your knowledge on cardiac physiology with this quiz. It covers topics such as action potentials in the SAN, stroke volume calculations, and the effects of physical activity on cardiac output. Challenge yourself to understand the mechanisms behind heart function and regulation.

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