Cardiac Physiology
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Questions and Answers

What is the blood pressure in the pulmonary circuit?

  • 28/8 mmHg (correct)
  • 100/70 mmHg
  • 120/80 mmHg
  • 150/100 mmHg

    • Which side of the heart pumps blood into the pulmonary artery?

  • Right atrium
  • Left atrium
  • Left ventricle
  • Right ventricle (correct)

    • What is the sequence of blood flow from the organs to the heart?

  • Organs -> Veins -> Right atrium (correct)
  • Veins -> Left atrium -> Left ventricle
  • Organs -> Arteries -> Right atrium
  • Veins -> Right atrium -> Right ventricle

    • What is the output of the left ventricle?

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

    What is the normal blood pressure in the systemic circuit?

    <p>120/80 mmHg</p> Signup and view all the answers

    What fills the left ventricle?

    <p>Oxygenated blood</p> Signup and view all the answers

    What is the sequence of blood flow from the heart to the organs?

    <p>Left ventricle -&gt; Aorta -&gt; Organs</p> Signup and view all the answers

    What regulates the output of the heart?

    <p>Both intrinsic and extrinsic control</p> Signup and view all the answers

    What is the function of desmosomes in cardiac muscle?

    <p>To hold the muscle cells together tightly</p> Signup and view all the answers

    What is the term for the ability of cardiac muscle cells to function together as a single unit?

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

    What is the purpose of the fibrous tissue that separates the atria from the ventricles?

    <p>To electrically isolate the atria from the ventricles</p> Signup and view all the answers

    What is the term for the electrical potential difference between the inside and outside of a cell?

    <p>Transmembrane potential (TMP)</p> Signup and view all the answers

    What is the main function of ion channels in cardiac muscle cells?

    <p>To maintain ionic concentration gradients and charge differentials</p> Signup and view all the answers

    What is the term for the ability of an ion channel to only allow a specific type of ion to pass through?

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

    What is the term for the ability of an ion channel to open and close in response to changes in the transmembrane potential?

    <p>Voltage-sensitive gating</p> Signup and view all the answers

    What is the term for the movement of ions down their concentration gradient?

    <p>Chemical potential</p> Signup and view all the answers

    What is the term for the ability of cardiac muscle cells to spontaneously depolarize?

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

    What is the purpose of the action potential in cardiac muscle cells?

    <p>To allow action potentials to pass from one cell to the next</p> Signup and view all the answers

    What is the effect of increased stretch of ventricular muscle on the formation of cross-bridges?

    <p>Increased formation of cross-bridges</p> Signup and view all the answers

    What is the effect of sympathetic stimulation on the sinoatrial (SA) node action potential?

    <p>Increases the rate of phase 4 depolarization</p> Signup and view all the answers

    What is the effect of parasympathetic stimulation on the heart rate?

    <p>Decreases the heart rate</p> Signup and view all the answers

    What is the importance of the Frank-Starling effect?

    <p>Allows the heart to adapt its pumping capacity to changes in venous return and arterial blood pressure</p> Signup and view all the answers

    What is the effect of inotropic agents such as adrenaline on the heart?

    <p>Increases the contractility of the heart</p> Signup and view all the answers

    What is the effect of aging on the blood vessels?

    <p>They stretch less when blood is pumped into them, increasing pressure and afterload</p> Signup and view all the answers

    What is the role of the sympathetic nervous system on the heart?

    <p>Increases heart rate and contractility</p> Signup and view all the answers

    What is the role of the parasympathetic nervous system on the heart?

    <p>Decreases heart rate but has little effect on contractility</p> Signup and view all the answers

    What is the normal resting heart rate?

    <p>About 70bpm</p> Signup and view all the answers

    What is the effect of increased intracellular Ca2+ on the heart?

    <p>Increases the contractility of the heart</p> Signup and view all the answers

    What is the effect of parasympathetic nerve stimulation on pacemaker cells?

    <p>Decrease the rate of influx of Na+ through funny channels</p> Signup and view all the answers

    What is the effect of sympathetic nerve stimulation on pacemaker cells?

    <p>Increase the rate of influx of Na+ through funny channels</p> Signup and view all the answers

    What is the function of baroreceptors in the carotid artery?

    <p>To detect changes in blood pressure</p> Signup and view all the answers

    What is the equation for blood pressure?

    <p>BP = CO x SVR</p> Signup and view all the answers

    What determines systolic blood pressure?

    <p>Characteristics of stroke volume being ejected by the heart and the ability of the aorta to stretch</p> Signup and view all the answers

    What is the function of elastic tissue in blood vessel walls?

    <p>To absorb pressure and prevent a sharp rise in pressure</p> Signup and view all the answers

    What is the primary mechanism for blood pressure regulation in an acute setting?

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

    What causes vasoconstriction?

    <p>Increase in sympathetic nerve activity</p> Signup and view all the answers

    What is the main change in the large arteries with age that contributes to hypertension?

    <p>Increased stiffness due to arteriosclerotic lesions and calcification</p> Signup and view all the answers

    What is the effect of vasoconstriction on blood flow?

    <p>Decreases blood flow</p> Signup and view all the answers

    What is the primary mechanism of blood pressure regulation in chronic hypertension?

    <p>Elevated systemic vascular resistance</p> Signup and view all the answers

    What is the effect of aging on blood pressure?

    <p>Blood pressure increases with age</p> Signup and view all the answers

    What is the type of hypertension that has an identifiable cause?

    <p>Secondary hypertension</p> Signup and view all the answers

    What is the result of the inflammatory response in the pathogenesis of atherosclerosis?

    <p>All of the above</p> Signup and view all the answers

    What is a common effect of hypertension on the body?

    <p>Stroke due to brain haemorrhage</p> Signup and view all the answers

    What is a risk factor for essential hypertension?

    <p>Genetic factors</p> Signup and view all the answers

    What is the term for the initial event in the pathogenesis of atherosclerosis according to the response to injury hypothesis?

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

    What is a consequence of dysfunctional endothelium in hypertensive patients?

    <p>Decreased sensitivity to NO</p> Signup and view all the answers

    What is the common underlying mechanism of various diseases, including ischaemic heart disease, cerebrovascular disease, and renal disease?

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

    What is a characteristic of atherosclerotic plaques?

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

    What does the P wave on an ECG trace primarily represent?

    <p>Depolarization of atrial muscle cells</p> Signup and view all the answers

    Which part of the ECG represents ventricular depolarization?

    <p>QRS complex</p> Signup and view all the answers

    What is indicated by a prolonged PR interval on an ECG?

    <p>AV block</p> Signup and view all the answers

    How is stroke volume calculated?

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

    What initiates the pacemaker potential in the SAN cells?

    <p>Sodium entry through funny channels</p> Signup and view all the answers

    What represents the resting membrane potential on an ECG?

    <p>Isoelectric line</p> Signup and view all the answers

    What does the height of the R wave in the QRS complex suggest?

    <p>Strength of ventricular depolarization</p> Signup and view all the answers

    How often does the sinoatrial node generate action potentials at rest?

    <p>Every 0.8 seconds</p> Signup and view all the answers

    What influences the preload of the heart?

    <p>Extent of stretch of the heart muscle</p> Signup and view all the answers

    What is the role of calcium during the action potential in cardiac muscle cells?

    <p>To couple electrical excitation to contraction</p> Signup and view all the answers

    Which type of calcium channels play a primary role in calcium-induced calcium release?

    <p>L-type calcium channels</p> Signup and view all the answers

    What is the approximate end diastolic volume (EDV) of the ventricles at rest?

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

    What does the T wave on an ECG represent?

    <p>Ventricular repolarization</p> Signup and view all the answers

    What triggers the rapid depolarization in pacemaker cells after the threshold is reached?

    <p>Calcium influx through long-lasting channels</p> Signup and view all the answers

    Which of the following is NOT a factor influencing stroke volume?

    <p>Heart rate</p> Signup and view all the answers

    What effect do sympathetic and parasympathetic nerves have on the sinoatrial node?

    <p>They can modulate the rate of action potential generation.</p> Signup and view all the answers

    What type of channel opens first as the membrane potential begins to depolarize in the SAN?

    <p>Funny channels</p> Signup and view all the answers

    What is indicated by Einthoven's Triangle in cardiac physiology?

    <p>It helps identify which lead best shows electrical activity.</p> Signup and view all the answers

    Which ion is primarily responsible for repolarization during the cardiac action potential?

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

    What characterizes the plaque in the marginal branch of the coronary artery?

    <p>Large lipid-rich necrotic core with a thin fibrous cap</p> Signup and view all the answers

    Which lipid component is primarily modified and contributes to the development of arterial plaque?

    <p>Low-density lipoprotein (LDL)</p> Signup and view all the answers

    What is the consequence of a thin fibrous cap on an atherosclerotic plaque?

    <p>Increases risk of rupture and thrombosis</p> Signup and view all the answers

    What initial injury initiates the process of plaque formation in coronary arteries?

    <p>Vascular endothelial injury due to inflammation or physical stress</p> Signup and view all the answers

    What type of cells form the 'fatty streak' in the arterial wall?

    <p>Lipid-filled foam cells derived from macrophages</p> Signup and view all the answers

    Which of the following describes the role of smooth muscle cells in plaque development?

    <p>They migrate to create a fibrous cap on the plaque</p> Signup and view all the answers

    What process involves macrophages ingesting modified LDL within the arterial wall?

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

    What is a significant characteristic of fibrotic plaque in coronary arteries?

    <p>It is calcified and hard</p> Signup and view all the answers

    What is the name of the phase during which the heart relaxes and refills with blood?

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

    Which valve closes during ventricular isovolumetric contraction?

    <p>Mitral valve</p> Signup and view all the answers

    What is the role of the pulmonary veins in the circulatory system?

    <p>Carry oxygenated blood from the lungs to the heart</p> Signup and view all the answers

    What are the two main categories of heart failure?

    <p>Systolic and Diastolic</p> Signup and view all the answers

    What is the primary mechanism that causes pressure changes within the heart during the cardiac cycle?

    <p>Electrochemical changes in the myocardium</p> Signup and view all the answers

    What event occurs immediately after the mitral valve closes during the cardiac cycle?

    <p>Isovolumetric ventricular contraction</p> Signup and view all the answers

    Which of the following is NOT a phase of the cardiac cycle?

    <p>Isovolumetric atrial relaxation</p> Signup and view all the answers

    What is the primary function of the heart valves?

    <p>To prevent the backflow of blood</p> Signup and view all the answers

    Where does mixed venous blood, returning from the body, enter the heart?

    <p>Right atrium</p> Signup and view all the answers

    What is the correct order of the events in the cardiac cycle?

    <p>Ventricular relaxation, atrial contraction, ventricular contraction, atrial relaxation</p> Signup and view all the answers

    Study Notes

    The Cardiovascular System

    • The heart is a dual pump with two atria and two ventricles, pumping blood from low-pressure veins to high-pressure arteries.
    • The right ventricle pumps blood into the pulmonary artery, while the left ventricle pumps blood into the aorta.
    • The output of the heart is controlled by intrinsic mechanisms and can be regulated by autonomic nerves and hormones.
    • Blood pressure in the pulmonary circuit is approximately 28/8 mmHg, while in the systemic circuit it is approximately 120/80 mmHg.

    Cardiac Cycle

    • The cardiac cycle includes a complete relaxation and contraction of both atria and ventricles.
    • The cycle consists of:
      • Diastole (relaxation phase)
      • Systole (contraction phase)
    • Pressure changes occur within the heart during the cardiac cycle, directing blood flow through different chambers and the body.
    • Valves within the heart regulate blood flow.

    Electrical Activity of the Heart

    • The heart has distinct electrical characteristics.
    • Intercalated discs allow action potentials to pass to adjacent cells, allowing the heart muscle to function as a syncytium.
    • Myocardial cells can spontaneously depolarize, generating a pacemaker potential.

    Action Potential of the Heart

    • Phases of the cardiac action potential:
      1. Rapid depolarization
      2. Early rapid repolarization
      3. Plateau phase
      4. Final rapid repolarization
    • Ion channels regulate the movement of ions across the cell membrane, controlling the action potential.

    Pacemaker Potentials

    • Pacemaker potentials are generated by the sinoatrial (SA) node, which depolarizes over time, triggering an action potential.
    • The SA node can be influenced by sympathetic and parasympathetic nerves to increase or decrease heart rate.

    Excitation-Contraction Coupling

    • Excitation-contraction coupling is the process by which an electrical action potential leads to contraction of cardiac muscle cells.
    • Calcium is the crucial mediator that couples electrical excitation to physical contraction.

    Electrocardiography (ECG)

    • The ECG is an electrical trace resulting from action potentials in all heart muscle fibers.
    • The ECG varies depending on the direction of travel, whether cells are depolarizing or repolarizing, and the size of the change in potential.

    Events of the Cardiac Cycle

    • The cardiac cycle can be divided into:
      • P wave (atrial depolarization)
      • QRS complex (ventricular depolarization)
      • PR interval (atrial muscle depolarization to ventricular depolarization)
      • PR segment (atrial muscle repolarization)

    Cardiac Output

    • Cardiac output is the product of stroke volume and heart rate.
    • Regulation of stroke volume:
      • Preload (extent of stretch of the heart muscle)
      • Afterload (pressure against which the heart needs to pump)
      • Contractility (ability of the muscle to produce a force)
    • The Frank-Starling mechanism: an increase in blood returning to the heart increases end-diastolic volume, leading to increased stretching and increased force of contraction.

    Neural Control of the Heart Rate

    • Neural control of the heart is regulated by sympathetic and parasympathetic divisions of the autonomic nervous system.
    • The autonomic nervous system regulates heart rate, conduction velocity, force of contraction, and coronary blood flow.
    • Sympathetic and parasympathetic stimulation have opposite effects on the sinoatrial (SA) node action potential, influencing heart rate.

    Chronotropic Effects

    • Positive chronotropic effects: increases in heart rate, mediated by the sympathetic nervous system.
    • Negative chronotropic effects: decreases in heart rate, mediated by the parasympathetic nervous system.### Neural Factors Affecting the Heart
    • The sympathetic nervous system (SNS) increases heart rate and contractility
    • The parasympathetic nervous system (PNS) decreases heart rate but has little effect on contractility
    • Resting heart rate is approximately 70bpm, which is reduced from 100bpm by 'vagal tone'

    Effects of Autonomic Nervous System on Pacemaker Cells

    • Parasympathetic nervous system:
      • Decreases rate of Na+ influx through funny channels
      • Decreases Ca2+ influx
      • Increases time taken for pacemaker potential to reach threshold for action potential
    • Sympathetic nervous system:
      • Increases rate of Na+ and Ca2+ influx
      • Increases pacemaker potential development, leading to cardiac action potentials

    Baroreceptors and Chemoreceptors

    • Baroreceptors (carotid artery):
      • Stimulated by increased blood pressure
      • Decreases heart rate and stroke volume
      • Increases parasympathetic activity and decreases sympathetic activity
    • Chemoreceptors (carotid body):
      • Stimulated by increased PCO2 and/or decreased PO2
      • Increases heart rate and stroke volume
      • Increases sympathetic activity and decreases parasympathetic activity

    Systemic Hypertension

    • Defined as the pressure of blood moving through the arterial system
    • Blood pressure (BP) = cardiac output (CO) x systemic vascular resistance (SVR)
    • Systolic BP is largely determined by characteristics of stroke volume (SV) being ejected by the heart and the ability of the aorta to stretch to accommodate SV

    Elastic Tissue in Blood Vessels

    • When blood is pushed into vessels, elastic tissue is stretched
    • Elasticity 'absorbs' pressure, preventing a sharp rise in pressure
    • Between heart beats, elastic tissue recoils, maintaining continuous blood flow

    Regulation of Blood Pressure

    • Regulated by autonomic and hormonal mechanisms
    • Baroreceptor reflex:
      • Primary mechanism for blood pressure regulation in acute settings
      • Acts as a buffer for changes in posture and acute changes in blood volume
    • Renin-angiotensin-aldosterone mechanism:
      • Maintains long-term blood pressure
      • Can reset or downregulate the baroreceptor reflex to a higher setpoint

    Blood Pressure and Age

    • Arterial pressure rises with advancing age
    • Increased stiffness of large arteries due to arteriosclerotic lesions and calcification
    • Decreased baroreceptor sensitivity
    • Increased responsiveness to sympathetic nervous system activity
    • Alteration in renin-angiotensin-aldosterone system relationships

    Hypertension

    • Age-related changes:
      • Increased stiffness of large arteries
      • Decreased baroreceptor sensitivity
      • Increased responsiveness to sympathetic nervous system activity
    • Primary hypertension:
      • 95% of all cases
      • Has no identifiable cause
    • Secondary hypertension:
      • 5-10% of all cases
      • Has an identifiable cause (e.g. kidney disease, adrenal cortical disorders)

    Effects of Hypertension on the Body

    • Stroke due to brain hemorrhage
    • Damage to capillaries in the eye, leading to eyesight damage
    • Edema
    • Left ventricular hypertrophy, leading to heart failure
    • Damage to kidney blood vessels, leading to renal failure
    • Injury to artery walls, precipitating atherosclerosis

    Risk Factors for Hypertension

    • Essential/primary hypertension:
      • Excess salt consumption
      • Overweight/obesity
      • Alcohol consumption
      • Inactivity
      • Smoking
      • Age
      • Race
      • Genetic factors
    • Secondary hypertension:
      • Renal disease
      • Excess aldosterone
      • Pheochromocytoma
      • Other disorders

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    Learn about the structure and function of the heart, including its dual pump system, blood pressure, and circulation pathways. Understand how the heart pumps blood from low pressure veins to high pressure arteries and how output is controlled.

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