Physiology of the Heart
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Questions and Answers

How are preload, end-diastolic volume and filling pressure related?

  • As filling pressure of ventricles increases, this increases the preload. This then increases the end-diastolic volume.
  • As filling pressure of ventricles increases, this increases the end-diastolic volume. This then increases the preload.
  • An increase in end-diastolic volume is followed by an increase in filling pressure. This increases the preload.
  • As the end-diastolic volume of the ventricles increases, this increases the preload which ultimately causes an increase in filling pressure. (correct)
  • As the preload increases, the end-diastolic volume increases as a result. The filling pressure is not involved.

    • What is afterload?

  • The force which causes aortic regurgitation
  • The force against which an atrium pumps to eject blood
  • The force against which a ventricle pumps to eject blood (correct)
  • The velocity of blood flow in the aorta after being ejected from the left ventricle
  • The increased stretch in the outflow tracts which provide a resistance to ejection of blood from the ventricles

    • What is the Frank-Starling Law of the heart?

  • The total energy liberated at each heartbeat is determined by the systolic volume of the heart and muscle fibre length at the beginning of contraction.
  • The total energy liberated at each heartbeat is determined by the diastolic volume of the heart and muscle fibre length at the beginning of contraction. (correct)
  • The total energy liberated at each heartbeat is determined by the diastolic volume of the heart and muscle fibre length at the beginning of relaxation.
  • The total energy liberated at each heartbeat is determined by the diastolic volume of the heart and muscle fibre length at the beginning of relaxation.
  • The total energy liberated at each heartbeat is determined by the diastolic volume of the heart and muscle fibre length at the end of contraction.

    • What are the 3 components of troponin?

    <p>TnC, TnT and TnI</p> Signup and view all the answers

    Which of these statements pertaining to calcium sensitivity is true?

    <p>An increase in calcium binding sites leads to increased contractility</p> Signup and view all the answers

    Which one of the following is true for normal ranges of right atrial pressure and mean arterial blood pressure?

    <p>In the normal ranges of RAP and mABP, CO is controlled by RAP but not mABP/afterload.</p> Signup and view all the answers

    What type of capillary allows large molecules, such as proteins, to diffuse readily across the capillary wall?

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

    Small lipophobic molecules, such as water and ions, cannot diffuse across the lipid bilayer. They can cross between cells (intercellular clefts) in continuous capillaries but have to diffuse across what to be able to get into the clefts?

    <p>Glycocalyx - A glycoprotein layer on the basolateral surface of the endothelium</p> Signup and view all the answers

    Filtration and absorption of fluid are almost perfectly balanced. Fluid filtration is driven by 2 pressure gradients, one of which is a hydrostatic pressure gradient. The hydrostatic pressure gradient drives water in which direction?

    <p>From the capillaries into the interstitium as there is higher hydrostatic pressure at the venous than arteriolar end of capillaries</p> Signup and view all the answers

    What creates an osmotic pressure gradient across capillary walls?

    <p>The high protein concentration in the interstitium</p> Signup and view all the answers

    Which of the following is true?

    <p>Anatomic dead space includes all of the lung, but not the alveoli or respiratory bronchioles and has a typical volume of 150ml.</p> Signup and view all the answers

    In an average healthy adult male, tidal volume is roughly...

    <p>500ml</p> Signup and view all the answers

    During the expiratory process...

    <p>Alveolar pressure &gt; mouth pressure</p> Signup and view all the answers

    What is internal respiration?

    <p>The exchange of gases between blood, interstitial fluid &amp; cells.</p> Signup and view all the answers

    How does air move into the alveoli during inspiration?

    <p>Air moves down a concentration gradient as the atmospheric pressure is less than the alveolar pressure.</p> Signup and view all the answers

    The following statements are correct, EXCEPT

    <p>Most vascular beds constrict during haemorrhage to maintain blood flow to the brain and heart</p> Signup and view all the answers

    Sympathetic nerve firings cause constriction in the following structures, EXCEPT:

    <p>Salivary glands</p> Signup and view all the answers

    What is likely to be the compensatory mechanism activated by heart failure?

    <p>Activation of renin-angiotensin-aldosterone system</p> Signup and view all the answers

    Parasympathetic activation increases total peripheral resistance

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

    How is the mean blood pressure calculated?

    <p>The mean blood pressure is calculated as the time weighted average of the systolic and diastolic blood pressures or 2/3 x DBP plus 1/3 x SBP</p> Signup and view all the answers

    Which of the following is NOT true:

    <p>Noradrenaline acts on Beta-2 receptors</p> Signup and view all the answers

    Where are the baroreceptor reflexes found?

    <p>Carotid sinuses and aortic arch</p> Signup and view all the answers

    The following statements are true, EXCEPT:

    <p>Beta-1 decrease cardiac contractility</p> Signup and view all the answers

    What is the equation which relates cardiac output to blood pressure?

    <p>Cardiac output x heart rate</p> Signup and view all the answers

    What is the substance that the endothelium releases which relaxes the surrounding muscle and is also referred to as the endothelium derived relaxing factor (EDRF)?

    <p>Nitric Oxide</p> Signup and view all the answers

    What is the neurogenic model of control of blood pressure?

    <p>The SNS can contribute to the long term control of blood pressure as well as the kidneys</p> Signup and view all the answers

    Nitric Oxide is produced by an enzyme called ENOS. What is endothelial nitric oxide synthase stimulated by?

    <p>a rise in L-arginine concentration</p> Signup and view all the answers

    What is Guyton's hypothesis?

    <p>The stabilisation of blood pressure over the long term is due to there being a constant extracellular fluid volume which requires there to be a constant sodium content in the body</p> Signup and view all the answers

    Nitric Oxide causes the relaxation of vascular smooth muscle cells. On these cells, what does the opening of potassium cells cause?

    <p>They cause the cells to hyperpolarise and lead to closure of voltage gated sodium channels causing contraction of smooth muscle</p> Signup and view all the answers

    What does introducing L-MNNA to your system mean?

    <p>It's a blocker of ENOS reducing nitric oxide synthesis and leads to a fall in blood flow</p> Signup and view all the answers

    Which artery is generally used to measure blood pressure?

    <p>Brachial artery</p> Signup and view all the answers

    Which substance(s) can cause Endothelium-derived hyperpolarisation?

    <p>hydrogen peroxide and epoxy accosted trienoic acid</p> Signup and view all the answers

    Why does the pressure wave become larger as it moves down the arterial tree?

    <p>Arterial stiffness</p> Signup and view all the answers

    What is the effect of 'Rho kinase' in smooth muscle contraction?

    <p>Ca2+ sensitisation</p> Signup and view all the answers

    What is the speed in which blood cells move at?

    <p>19cm/s</p> Signup and view all the answers

    Define BP

    <p>The time-weighted average of the systolic and diastolic pressure</p> Signup and view all the answers

    Which one of the following is a major contributor to the total peripheral resistance?

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

    Which of the following occurs as a long term response to a low Blood pressure?

    <p>Increase Na reabsorption</p> Signup and view all the answers

    Stabilisation of blood pressure in the long term is due to

    <p>Maintenance of a constant ECF volume</p> Signup and view all the answers

    Which of the following is responsible for the long term regulation of blood pressure

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

    Which stem cell is used for Jane's stem cell transplantation?

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

    Why does heart rate decrease with increasing heart size?

    <p>Bigger ventricles take longer to fill</p> Signup and view all the answers

    What is cardiac output essentially proportional to?

    <p>Metabolic demand</p> Signup and view all the answers

    Where is the sinoatrial node located?

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

    Which pacemaker in the heart has the fastest intrinsic rate?

    <p>Sinoatrial node</p> Signup and view all the answers

    Hermann Stannius used frog hearts to demonstrate the sinus venosus contains a secondary slower pacemaker.

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

    What enables stroke volume to increase from moderate to high heart rates when exercising?

    <p>Increased preload and heart contraction strength</p> Signup and view all the answers

    Which of the following is not a feature of a P cell?

    <p>Is essentially just an empty bag of membrane</p> Signup and view all the answers

    Why is the funny current considered unusual?

    <p>This inward current is activated when the membrane potential hyperpolarizes</p> Signup and view all the answers

    What is a totipotent stem cell?

    <p>A stem cell that can divide to produce all cell types of an organism</p> Signup and view all the answers

    Which of the following is the correct order of haematopoiesis?

    <p>Self-renewal, committed cells, developmental pathway, differentiated functional cell</p> Signup and view all the answers

    Which of the following statements regarding red blood cells is false?

    <p>Red blood cells have a nucleus</p> Signup and view all the answers

    Which of the following statements is true regarding the site of haematopoiesis?

    <p>Haematopoiesis in an adult occurs in the interstitium between the medullary vascular sinuses of the bone marrow</p> Signup and view all the answers

    What is the diameter of a normoblast?

    <p>6-8μm</p> Signup and view all the answers

    What is the lifespan of an Eosinophil?

    <p>Several days</p> Signup and view all the answers

    How long does it take for an Eosinophil to leave circulation once released from bone marrow?

    <p>Leave circulation within 8-12 h of release from bone marrow</p> Signup and view all the answers

    What is the diameter of a platelet?

    <p>2-4μm</p> Signup and view all the answers

    What is the lifespan of a macrophage?

    <p>Months/years</p> Signup and view all the answers

    Which of the following is not a symptom of anaemia?

    <p>High blood pressure</p> Signup and view all the answers

    Which of the following molecules control red blood cell production?

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

    Which of the following statements is true?

    <p>Folates are cofactors in the synthesis of purines and pyrimidines</p> Signup and view all the answers

    Which of the following statements is false?

    <p>Low oxygen levels in blood stimulate kidneys to produce erythropoietin</p> Signup and view all the answers

    What is the diameter of the majority of lymphocytes?

    <p>6-9 μm</p> Signup and view all the answers

    What type of anaemia involves a disturbance of proliferation and differentiation of erythroblasts?

    <p>Impaired production</p> Signup and view all the answers

    Which of the following is NOT an example of intrinsic abnormalities leading to anaemia?

    <p>Increased oxidative stress</p> Signup and view all the answers

    In terms of treatments for anaemia, which of the following does folic acid treat?

    <p>Megaloblastic anaemia</p> Signup and view all the answers

    Which of the following is the correct statement regarding red blood cell production?

    <p>The penultimate precursor is the normoblast, which has a loosely-condensed nucleus, which gets ejected, entering the blood as a reticulocyte</p> Signup and view all the answers

    Which of the following blood groups contains A antigen on cells and β antibody in plasma?

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

    Which of the following are not complications of blood transfusions?

    <p>Iron deficiency</p> Signup and view all the answers

    A pregnant woman with Rh- Blood Type is at risk of developing antibodies to the D Antigen, which could lead to Haemolytic Disease in her next child. This sensitisation can occur during various scenarios. Which of the following situations is a potential cause of Rh Sensitisation in an Rh- Individual?

    <p>Giving Birth to an Rh+ Child</p> Signup and view all the answers

    During a scheduled blood transfusion for a patient undergoing major surgery, the medical team carefully monitors for potential complications. Which of the following is NOT a complication that could occur during a blood transfusion?

    <p>Iron Overload</p> Signup and view all the answers

    After a serious accident, a patient requires an emergency blood transfusion. Upon examination, the patient's blood type is found to be of Blood Type AB. The Medical Team needs to select the compatible blood type to ensure a successful transfusion. Which blood types can the patient with Blood Type AB safely receive?

    <p>Blood Types A, B, AB, and O</p> Signup and view all the answers

    A patient's blood tests reveal high levels of eosinophil and after further tests, is diagnosed with malaria which is a parasitic infection. Which one of the following statements is incorrect about eosinophils?

    <p>Leave circulation within 8-12 hours of release from bone marrow</p> Signup and view all the answers

    A GP has ordered a FBC for a patient with suspected iron deficiency anaemia. The test comes back with an abnormally low red blood cell count. Which of the following statements is correct about red blood cells?

    <p>They are biconcave discs which decrease the surface area and allow deformation</p> Signup and view all the answers

    Which of the following factors contributes to increased airway resistance that can make breathing more difficult in asthma?

    <p>Constriction of bronchial smooth muscles</p> Signup and view all the answers

    How can the findings of FEV1, FVC, and FEV1/FVC ratio allow you to distinguish between an obstructive and a restrictive lung disease?

    <p>Obstructive: FEV1 decreased, FVC decreased or normal, and FEV1/FVC ratio decreased; Restrictive: FEV1 decreased or normal, FVC decreased, and FEV1/FVC ratio normal or increased</p> Signup and view all the answers

    What is the role of surfactant as alveoli shrink in 'Newborn Respiratory distress syndrome'?

    <p>Surface surfactant concentration increases so there is a higher tendency for alveoli to collapse</p> Signup and view all the answers

    According to the diagram of a ventricular action potential displayed below, what does the phase marked '2' refer to?

    <p>Slow voltage gated Ca2+ (in) channels closing</p> Signup and view all the answers

    Why has the ventricular action potential evolved over a long duration?

    <p>Shorter durations protect against reentrant arrhythmias</p> Signup and view all the answers

    In the sino-atrial (SA) node, what dominates the upstroke of the action potential when slow diastolic depolarisation accelerates to a threshold before firing?

    <p>Funny current (If)</p> Signup and view all the answers

    Why is the 'funny current (If)' termed 'funny'?

    <p>It is an inward current that activates when the cell membrane gets more negative</p> Signup and view all the answers

    What is the absolute refractory period?

    <p>The period of time where another action potential is impossible, regardless of the size of the stimulus</p> Signup and view all the answers

    Which kinase is principally activated by Beta-1 adrenoreceptors?

    <p>Protein Kinase A</p> Signup and view all the answers

    What is the principal mechanism triggering Ca release from cardiac muscle sarcoplasmic reticulum?

    <p>Ca-induced Ca release</p> Signup and view all the answers

    What does the P-Q interval tell us in an electrocardiogram (ECG)?

    <p>Atrial conduction and AV nodal delay</p> Signup and view all the answers

    What type of drug changes the force of heart contractions?

    <p>Inotropic agents</p> Signup and view all the answers

    What is the effect of a positively lusitropic drug on the heart?

    <p>A decrease in the rate of relaxation</p> Signup and view all the answers

    Which of the following is true of an ECG?

    <p>An AV block can affect the QRS duration</p> Signup and view all the answers

    Which cardiac structure does X correspond to?

    <p>Tricuspid Valve</p> Signup and view all the answers

    Which of the following is NOT a feature of atrioventricular valve function?

    <p>Opening and closing due to cardiac myocyte contraction</p> Signup and view all the answers

    Which of the following is the correct sequence of events for stage 1 of systole?

    <p>Left atrial pressure &gt; Left ventricular pressure; mitral valve opens; blood flows into left ventricle</p> Signup and view all the answers

    In order to measure pressure and volume changes that occur in a cardiac cycle, in which segment of a heart is a catheter inserted into?

    <p>Left ventricle</p> Signup and view all the answers

    Venous pulse can be divided into a number of components, these in order are...

    <p>Y wave, A wave, C wave, X wave, V wave</p> Signup and view all the answers

    Hydrostatic pressure...

    <p>Is relative to heart level</p> Signup and view all the answers

    Study Notes

    Haematopoiesis

    • A totipotent stem cell is one that can divide to produce all cell types of an organism.
    • The correct order of haematopoiesis is: self-renewal, developmental pathway, committed cells, differentiated functional cell.
    • Red blood cells:
      • Have a biconcave shape
      • Are approximately 7 μm in diameter
      • Do not have a nucleus
      • Respire anaerobically
      • Are removed by the liver and spleen
    • Site of haematopoiesis:
      • In a fetus, it occurs in the liver throughout intrauterine life
      • In an adult, it occurs in the bone marrow

    Erythrocytes

    • Normoblasts have a diameter of 6-8 μm
    • Eosinophils:
      • Have a lifespan of several days
      • Leave circulation within 2-6 hours of release from bone marrow
    • Platelets have a diameter of 1-2 μm

    Anaemia

    • Causes of anaemia:
      • Impaired production
      • Increased destruction (haemolytic)
      • Blood loss
    • Folic acid treats megaloblastic anaemia
    • Vitamin B12 deficiency causes anaemia, but folic acid does not treat it

    Blood Groups and Transfusions

    • Blood groups:
      • A and B antigens on cells, corresponding antibodies in plasma
      • AB blood type can receive A, B, AB, and O blood types
    • Complications of blood transfusions:
      • Blood type incompatibility
      • Transmission of infection
      • Fever
      • Impaired clotting
    • Rh sensitisation:
      • Occurs when an Rh- individual is exposed to Rh+ blood
      • Can lead to haemolytic disease in subsequent pregnancies

    Cardiac Cycle

    • Heart rate decrease with increasing heart size due to ventricular conduction taking longer to propagate
    • Cardiac output is essentially proportional to body size
    • Stroke volume decreases at very high heart rates due to less time for ventricular filling
    • High heart rate is associated with poor prognosis in patients with cardiovascular disease

    Initiation of the Heartbeat

    • Hermann Stannius used frog hearts to demonstrate that the primary pacemaker in the frog heart was the sinus venosus, but when that is isolated, the atria contains a secondary slower pacemaker.
    • The sinoatrial node is located in the right atrium and has the fastest intrinsic rate
    • Features of a P cell include:
      • Poorly differentiated
      • Few mitochondria
      • Numerous membrane invaginations called caveolae
      • Large cell size

    Control of Cardiac Output

    • The funny current (a key player of the membrane clock theory) is considered unusual because it is an inward current activated when the membrane potential repolarises

    • cAMP increases the effect of the funny current, and sympathetic stimulation increases heart rate

    • Ivabradine is the only specific bradycardiac agent licensed for clinical use### Cardiac Conduction and ECG

    • Bundle Branch Block: a delayed wave of excitation in the ventricle, suggesting an issue with conduction down the His Bundle.

    • Ischaemia: the ventricle is not firing off potentials as it should, causing a change in the PR interval.

    • Genetic mutation: a change in the action potential duration and hence the PR interval, due to a mutation in ion channels.

    • Myocardial infarction: a reduced action potential in the ventricles, affecting contraction.

    Pacemakers and Heart Rate

    • Hierarchy of pacemakers: sinus node, atrioventricular node, His bundle, Purkinje fibres.
    • Digoxin: a drug that slows down heart rate.

    ECG and Cardiac Cycle

    • Q wave: represents depolarisation of the ventricular walls.
    • Atrial depolarisation: represented by the P wave on an ECG.
    • Ejection fraction: the percentage of blood pumped out of the ventricle with each contraction.

    Cardiac Cycle

    • Sequence of events for stage 1 of systole: left atrial pressure > left ventricular pressure, pulmonary valve opens, and blood flows into the left ventricle.
    • Pressure-Volume loop: shows the pressure and volume changes that occur in a single cardiac cycle.

    Venous Pulse and Pressure

    • Components of the venous pulse: A wave, C wave, V wave, X wave, Y wave.
    • C wave: caused by the transmitted carotid pulse.
    • X wave: related to atrial relaxation.
    • A wave: right atrial contraction.
    • V wave: corresponds to venous filling when the tricuspid valve is open.
    • Hydrostatic pressure: relative to heart level, and higher in the foot when standing.

    Heart Sounds and Murmurs

    • "Lub" heart sound: associated with the closure of the atrioventricular valves.
    • "Dup" heart sound: due to the closure of the semilunar valves.
    • Gallop rhythm: when systolic pressure is raised and S2 and S3 can be heard as a gallop.
    • Heart murmurs: due to turbulence in the blood and caused by valve stenosis or regurgitation.

    Control of Cardiac Output

    • Factors that affect cardiac output: preload, afterload, contractility, and heart rate.
    • Preload: the degree of stretch of a ventricle immediately before it contracts at the end of diastole.
    • Afterload: the force against which a ventricle pumps to eject blood.
    • Frank-Starling Law: the total energy liberated at each heartbeat is determined by the diastolic volume of the heart and therefore by the muscle fibre length at the beginning of contraction.

    Troponin and Calcium Sensitivity

    • Components of troponin: TnC, TnT, and TnI.
    • Length-dependent activation: occurs in cardiac muscle only, and is contributed to by separation of myofilaments.
    • Calcium sensitivity: an increase in calcium binding sites leads to increased contractility.Here are the study notes for the provided text:
    • Muscle Physiology*

    Titin's Role in Muscle Function

    • Titin interacts with both myosin and actin
    • Thought to be responsible for increased sensitivity of TnC to calcium
    • Increased sarcomere length pulls on titin, drawing the actin and myosin closer together, increasing force by increasing access of actin headgroups to myosin, which favors the formation of cross bridges
    • Titin acts on myosin binding protein C

    Heart Function

    Blood Pressure and Cardiac Output

    • It takes less pressure to fill the right ventricle than the left ventricle because the right ventricular wall is thinner and more compliant
    • An increase in end-diastolic pressure (EDP) increases the stroke volume by increasing the force of contraction by the cardiac muscle, but this is not considered an increase in contractility
    • In the normal ranges of right atrial pressure (RAP) and mean arterial blood pressure (mABP), CO is controlled by both RAP and mABP/afterload
    • An increase in afterload causes a decrease in cardiac output (CO) at very high levels of mABP
    • Preload for the right side of the heart is equivalent to central venous pressure (CVP)

    Compensatory Mechanisms in Heart Failure

    • During heart failure, cardiac output may decrease to a level which is insufficient to provide enough blood for the body's metabolic needs
    • Compensatory mechanisms that may be activated include:
      • Activation of the sympathetic nervous system (SNS) to increase heart rate and cardiac contractility
      • Activation of the renin-angiotensin-aldosterone system (RAAS) to increase fluid retention
      • Venoconstriction to increase central venous pressure (CVP)
      • Increased contractility of the heart

    Control of Blood Pressure

    Baroreceptor Reflexes

    • Baroreceptor reflexes are found in the carotid sinuses and aortic arch
    • These reflexes help to regulate blood pressure

    Equations Relating to Blood Pressure

    • Mean blood pressure (MBP) is calculated as the time-weighted average of the systolic and diastolic blood pressures or 2/3 x diastolic blood pressure (DBP) plus 1/3 x systolic blood pressure (SBP)
    • Cardiac output (CO) is related to blood pressure by the equation: CO x total peripheral resistance (TPR) = MBP

    Neurogenic Model of Blood Pressure Control

    • The sympathetic nervous system (SNS) can contribute to the long-term control of blood pressure, along with the kidneys

    Guyton's Hypothesis

    • The stabilisation of blood pressure over the long term is due to there being a constant extracellular fluid volume, which requires there to be a constant sodium content in the body

    Measurement of Blood Pressure

    • Blood pressure is typically measured in the radial artery
    • The pressure wave becomes larger as it moves down the arterial tree due to arterial stiffness

    Contributors to Total Peripheral Resistance

    • Arterioles are the major contributors to total peripheral resistance (TPR)

    Long-term Regulation of Blood Pressure

    • The kidneys are responsible for the long-term regulation of blood pressure

    Pressure Natriuresis

    • Pressure natriuresis is the phenomenon by which an increase in blood pressure leads to an increase in sodium excretion

    Factors Affecting Blood Pressure

    • Sodium intake can affect blood pressure
    • Increased sodium levels can lead to an increase in blood pressure
    • Decreased sodium levels can lead to a decrease in blood pressure

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    Description

    This quiz assesses your understanding of the heart's physiology, including preload, afterload, and the Frank-Starling Law. It also covers troponin and calcium sensitivity.

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