Cardiac Physiology Overview
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Questions and Answers

Which of the following best describes the relationship between after-load and stroke volume?

  • Increased after-load directly increases stroke volume.
  • Decreased after-load enhances stroke volume.
  • After-load indirectly decreases stroke volume initially but can increase it over time. (correct)
  • After-load does not impact stroke volume.
  • How does pharmacological intervention influence the ventricular function curve?

  • Only negative inotropic agents shift the curve to the right.
  • All agents uniformly shift the curve to the left.
  • The curve remains unchanged regardless of the agent used.
  • Positive inotropic agents shift the curve to the right indicating increased contractility. (correct)
  • Which statement about the Frank-Starling relationship is accurate?

  • It focuses primarily on the effects of negative inotropic agents.
  • Increased end-diastolic volume leads to increased contractility. (correct)
  • It describes the effect of arterial pressure on stroke volume.
  • It is determined solely by external factors affecting muscle length.
  • Which of the following correctly identifies a characteristic of negative inotropic agents?

    <p>They weaken the force of contraction in cardiac muscle.</p> Signup and view all the answers

    What mechanism assists in the return of blood to the heart from the venous system?

    <p>Skeletal muscle contractions during physical activity.</p> Signup and view all the answers

    Which factor primarily influences the preload of the heart?

    <p>Ventricular wall thickness</p> Signup and view all the answers

    What is the primary mechanism by which the skeletal muscle pump aids in venous return?

    <p>Creating pressure gradients through muscle contraction</p> Signup and view all the answers

    How does the Frank-Starling Law describe cardiac contractions?

    <p>They increase with initial fibre length and stretch.</p> Signup and view all the answers

    What effect does reduced ventricular compliance have on preload?

    <p>It decreases preload.</p> Signup and view all the answers

    What is the typical stroke volume of the heart at rest?

    <p>70 ml/beat</p> Signup and view all the answers

    Which channel blocker is known to have a direct negative chronotropic effect?

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

    In the context of cardiac output, what does stroke volume represent?

    <p>The volume of blood ejected with each ventricular contraction.</p> Signup and view all the answers

    Which factor does NOT affect stroke volume?

    <p>Capillary permeability</p> Signup and view all the answers

    What role do one-way valves play in the venous system?

    <p>Prevent backflow of blood toward the extremities</p> Signup and view all the answers

    How does skeletal muscle contraction influence venous return?

    <p>It compresses veins, promoting blood flow towards the heart</p> Signup and view all the answers

    Which factor contributes to the venous return mechanism during respiration?

    <p>A decrease in chest cavity pressure during inspiration</p> Signup and view all the answers

    What is the primary effect of increased venous return on cardiac output?

    <p>Increases end diastolic volume</p> Signup and view all the answers

    What happens to the valves in the veins during calf muscle contraction?

    <p>They open to allow blood to flow back to the heart</p> Signup and view all the answers

    What is affected by the skeletal muscle pump mechanism?

    <p>Blood flow dynamics in the venous system</p> Signup and view all the answers

    Which statement about venous return is accurate?

    <p>It is unidirectional due to venous valves</p> Signup and view all the answers

    How does cardiac output relate to venous return?

    <p>Higher venous return typically increases cardiac output</p> Signup and view all the answers

    Match the terms with their definitions related to venous return:

    <p>O2 poor blood = Blood that is rich in carbon dioxide (CO2) O2 rich blood = Blood that has high levels of oxygen (O2) Cardiac Output = Volume of blood pumped out per minute Stroke Volume = Volume of blood pumped out of the heart in one contraction</p> Signup and view all the answers

    Match the mechanisms affecting venous return:

    <p>One-way valves = Prevent backflow of blood in veins Skeletal muscle contractions = Aid in the compression of large veins Respiration = Acts like a pump during chest cavity pressure changes Calf muscle contraction = Can open and close venous valves during movement</p> Signup and view all the answers

    Match the blood types with their oxygen and carbon dioxide levels:

    <p>O2 poor blood = CO2 rich blood O2 rich blood = CO2 poor blood Systemic blood = Transports oxygen to body tissues Pulmonary blood = Carries carbon dioxide to lungs for exhalation</p> Signup and view all the answers

    Match the terms with their relationship to venous return:

    <p>End Diastolic Volume = Volume of blood in ventricles before contraction Pulmonary Venous Return = The flow of oxygenated blood back to heart from lungs Valves in veins = Prevent backflow and ensure unidirectional flow of blood Compression of veins = Facilitated by surrounding muscle contraction</p> Signup and view all the answers

    Match the following factors with their effects on venous return:

    <p>Chest cavity pressure = 5 mmHg less during inspiration aids venous return Skeletal muscle pump = Enhances blood flow back to the heart One-way valves = Essential for maintaining direction of venous blood flow Calf muscle action = Compresses veins aiding in venous return</p> Signup and view all the answers

    Match the components of venous return with their characteristics:

    <p>Blood flow caused by muscle contraction = Facilitates the return of blood to the heart Valves prevent backflow = Essential for maintaining venous return efficiency Respiratory pump = Influences pressure gradient during breathing One-way valves in veins = Act as gates controlling blood flow direction</p> Signup and view all the answers

    Match the physiological processes with their influences on venous return:

    <p>Contraction of calf muscles = Helps to compress veins Inspiration = Creates negative pressure in thorax enhancing venous return Valves in veins = Prevent backflow during venous return Skeletal muscle activity = Increases effectiveness of venous return</p> Signup and view all the answers

    Match the following terms with their correct definitions:

    <p>Pre-load = Myocardial sarcomere length before contraction Stroke Volume = Volume of blood ejected in each ventricular contraction End Diastolic Volume (EDV) = Volume of the ventricle when relaxed End Systolic Volume (ESV) = Volume of the ventricle when fully contracted</p> Signup and view all the answers

    Match the following terms with their related muscle type:

    <p>Skeletal muscle = Contains both thick and thin filaments Cardiac muscle = Contraction by sliding of filaments Both muscle types = Use myosin and actin Cardiac muscle only = Exhibits no descending limb in length-tension</p> Signup and view all the answers

    Match the following cardiac mechanisms with their descriptions:

    <p>Frank-Starling Law = Strength of cardiac contraction based on initial fibre length Negative chronotropic effect = Slows heart rate Positive inotropic effect = Increases strength of heart contractions Ventricular compliance = Ability to stretch and accommodate blood volume</p> Signup and view all the answers

    Match the following physiological concepts with their implications:

    <p>Increased venous return = Enhances stroke volume Reduced compliance = Decreases pre-load Hypertrophy = Reduces pre-load due to wall thickening Cardiac activation = Variable and affects stroke volume</p> Signup and view all the answers

    Match the following heart conditions with contributing factors:

    <p>Heart failure = Not due to excessive stretch Increased EDV = Improves stroke volume Altered Ca2+ sensitivity = Influences contraction strength Pericardial compliance = Affects pre-load readings</p> Signup and view all the answers

    Match the following cardiac output components with their equations:

    <p>Stroke Volume = $EDV - ESV$ Cardiac Output = $Heart Rate \times Stroke Volume$ Total blood volume = Affects preload indirectly Ventricular filling = Influences EDV</p> Signup and view all the answers

    Match the following drugs or mechanisms to their effects:

    <p>Atenolol = Beta-blocker that slows heart rate Calcium channel blockers = Direct negative chronotropic effect Increased blood volume = Enhances pre-load Decreased respiration = Reduces intra-thoracic pressure</p> Signup and view all the answers

    Match the following agents with their category:

    <p>Digitalis = Cardiac Glycosides Epinephrine = Catecholamines Diltiazem = Calcium channel blockers Beta blockers = Negative inotropic agents</p> Signup and view all the answers

    Match the following neurotransmitters to their sympathetic or parasympathetic roles:

    <p>ACh = Parasympathetic NE = Sympathetic Epinephrine = Sympathetic Dopamine = Parasympathetic</p> Signup and view all the answers

    Match the following receptors with their corresponding signaling pathways:

    <p>b1 = Increases cAMP M2 = Decreases cAMP Calcium channels = Facilitates calcium influx K-ACh channels = Inhibits pacemaker activity</p> Signup and view all the answers

    Match the following terms with their correct definitions related to cardiac contractility:

    <p>Positive inotropes = Increase myocardial contractility Negative inotropes = Decrease myocardial contractility Calcium Pump = Regulates intracellular Ca levels cAMP = Mediates effects of beta-adrenergic stimulation</p> Signup and view all the answers

    Match the following terms to their effects on cardiac function:

    <p>Increase in intracellular Ca = Enhances contractility Activation of PKA = Increases phosphorylated proteins Beta receptor activation = Increases heart rate Calcium channel blockade = Decreases contractility</p> Signup and view all the answers

    Match the following vascular terms with their correct descriptions:

    <p>Vasoconstriction = Narrowing of blood vessels due to smooth muscle contraction Vasodilation = Widening of blood vessels due to smooth muscle relaxation Hydrostatic Pressure = Pressure exerted by fluid at rest Oncotic Pressure = Pressure that draws fluid into the capillaries</p> Signup and view all the answers

    Match the following types of blood vessels with their primary function:

    <p>Arterioles = Regulate blood flow to capillary beds Capillaries = Site of exchange between blood and tissues Venules = Collect blood from capillaries to form veins Lymphatic vessels = Transport lymph fluid back to circulation</p> Signup and view all the answers

    Match the following terms related to capillaries with their characteristics:

    <p>Metarterioles = Connect arterioles to capillaries Pre-capillary sphincters = Control blood flow into capillaries Thoroughfare channel = Direct pathway from arterial to venous system Interstitial fluid = Fluid between blood plasma and tissue cells</p> Signup and view all the answers

    Match the following pressures with their impact on fluid movement:

    <p>NFP = +10 mmHg = Fluid filtration out of capillaries NFP = 0 mmHg = No net fluid movement NFP = -7 mmHg = Fluid reabsorption into capillaries CHP &gt; BCOP = Fluid movement out of capillaries</p> Signup and view all the answers

    Match the following components of the circulatory system with their roles:

    <p>Aorta = Largest artery carrying blood from the heart Medium Arteries = Distribute blood to specific organs Large Veins = Return blood to the heart Arterioles = Control blood flow and pressure</p> Signup and view all the answers

    Match the following fluid dynamics terms with their definitions:

    <p>Bulk flow = Movement of fluid due to pressure differences Filtration Pressure = Net pressure determining movement out of capillaries Colloid Osmotic Pressure = Pressure due to proteins in blood plasma Hydrostatic Pressure = Pressure from fluid within the capillaries</p> Signup and view all the answers

    Match the following types of fluid to their characteristics:

    <p>Lymph = Fluid that circulates in the lymphatic system Plasma = Liquid component of blood containing proteins and electrolytes Interstitial fluid = Fluid surrounding tissue cells Blood = Fluid connective tissue that transports nutrients and gases</p> Signup and view all the answers

    Match the following physiological processes with their descriptions:

    <p>Perfusion = Supply of blood to tissues Filtration = Movement of fluid out of capillaries Reabsorption = Movement of fluid back into capillaries Drainage = Return of excess interstitial fluid via lymphatic vessels</p> Signup and view all the answers

    Match the following blood supply routes with their descriptions:

    <p>Arterioles = Main regulators of blood flow to capillary beds Capillaries = Microscopic vessels where exchange occurs Venules = Small vessels that gather blood from capillaries Lymphatic vessels = Return excess fluid to the bloodstream</p> Signup and view all the answers

    Match the following terms related to vascular structure with their definitions:

    <p>Smooth muscle = Layer responsible for contraction and regulation of blood pressure Endothelial cells = Line the interior of blood vessels Elastic fibers = Allow blood vessels to stretch and recoil Basement membrane = Supportive layer beneath endothelial cells</p> Signup and view all the answers

    Match the following components to their roles in blood flow regulation:

    <p>Pre-capillary sphincters = Regulate blood entry into capillary beds Arterioles = Control resistance to blood flow Capillary walls = Facilitate exchange of substances Venules = Begin the collection of deoxygenated blood</p> Signup and view all the answers

    Match the following aspects of lymphatic function with their roles:

    <p>Lymphatic drainage = Removes excess interstitial fluid Immune response = Filters pathogens via lymph nodes Nutrient absorption = Transports lipids from the digestive tract Fluid balance = Maintains homeostasis between blood and interstitial fluid</p> Signup and view all the answers

    Match the following terms related to pressure gradients in capillaries:

    <p>CHP = Capillary hydrostatic pressure BCOP = Blood colloid osmotic pressure NFP = Net filtration pressure Effective filtration pressure = Determines fluid movement across capillary walls</p> Signup and view all the answers

    Match the following processes with their descriptions:

    <p>Venoconstriction = Activation of smooth muscle in veins Cardiac suction = Atrial pressure drops during ventricular contraction Skeletal muscle pump = Compression of veins aiding blood return Respiratory pump = Pressure variation in the chest during breathing</p> Signup and view all the answers

    Match the components of cardiac output with their definitions:

    <p>Stroke Volume (SV) = Amount of blood pumped per heartbeat Heart Rate (HR) = Number of beats per minute Cardiac Output (CO) = Total blood flow from the heart per minute mmHg = Unit of measurement for blood pressure</p> Signup and view all the answers

    Match the types of blood vessels with their characteristics:

    <p>Arteries = Carry blood away from the heart Veins = Contain one-way valves to prevent backflow Capillaries = Main site for fluid exchange Arterioles = Regulate blood flow to tissues</p> Signup and view all the answers

    Match the autonomic nervous system effects with their functions:

    <p>Sympathetic activation = Increases heart rate and force of contraction Parasympathetic activation = Decreases heart rate Vasoconstriction = Constriction of blood vessels for increased pressure Vasodilation = Dilation of blood vessels to enhance blood flow</p> Signup and view all the answers

    Match the elements of blood pressure regulation with their functions:

    <p>Baroreceptor reflexes = Detect changes in blood pressure Chemoreceptor reflexes = Monitor oxygen and carbon dioxide levels Adrenaline release = Increases heart rate and blood pressure Long-term regulation = Involves kidney function and fluid balance</p> Signup and view all the answers

    Match the features of veins with their functions:

    <p>One-way valves = Prevent backflow of blood Smooth muscle innervation = Controlled by the sympathetic nervous system Larger lumen = Facilitates easy blood return to the heart Compliance = Ability to stretch and accommodate varying volumes</p> Signup and view all the answers

    Match the mechanisms of venous return with their descriptions:

    <p>Muscle contractions = Compress veins to push blood Respiration = Creates a pressure gradient aiding return Venoconstriction = Reduces vein diameter to push blood back Cardiac suction = Helps draw blood into the heart with negative pressure</p> Signup and view all the answers

    Match the components of vascular anatomy with their corresponding types:

    <p>Aorta = Largest artery in the body Small arteries = Distribute blood to capillaries Capillaries = Exchange sites for nutrients and waste Venules = Collect blood from capillaries back to veins</p> Signup and view all the answers

    Study Notes

    Heart Rate & Contractility

    • Atenolol is a beta-blocker that slows down heart rate.
    • Calcium channel blockers like verapamil have a direct negative chronotropic effect, meaning they decrease heart rate.

    Stroke Volume

    • Stroke volume (SV) is the amount of blood ejected from the heart during each contraction.
    • SV = End Diastolic Volume (EDV) - End Systolic Volume (ESV).
    • Resting SV is typically around 70 ml/beat.

    Cardiac Length-Tension Relationship

    • Cardiac muscle contraction is caused by the sliding of thick (myosin) and thin (actin) filaments, similar to skeletal muscle.
    • Key difference: there is no descending limb on the length-tension curve for cardiac muscle.

    Factors Affecting Stroke Volume

    • Pre-load: Refers to the myocardial sarcomere length before contraction.
      • Approximated by EDV (end diastolic volume).
      • Influenced by:
        • Ventricular filling: affected by intra-thoracic pressure, respiration, and blood volume.
        • Ventricular and pericardial compliance: reduced compliance decreases pre-load.
        • Ventricular wall thickness: hypertrophy decreases pre-load.
    • After-load: The force the ventricles must overcome to eject blood.
      • Sum of elastic and kinetic forces.
      • Primary forces opposing ejection are arterial blood pressure and vascular tone.
      • Increased arterial resistance initially decreases stroke volume, but compensatory mechanisms increase it over time.
    • Contractility: Influences the inherent strength of heart muscle contraction during systole.
      • Pharmacological agents can affect contractility.
        • Negative inotropic agents weaken contraction.
        • Positive inotropic agents strengthen contraction.
        • The F-S curve shifts to the right with negative inotropy and to the left with positive inotropy.
        • The dashed line on the F-S curve indicates where maximal contractility has been exceeded.

    Venous Return

    • Venous return is the flow of blood back to the heart through the veins.
    • Directly affects:
      • End Diastolic Volume (EDV): Volume of blood in the ventricles before contraction.
      • Stroke Volume: Volume of blood pumped out with each beat.
      • Cardiac Output: Volume of blood pumped out per minute.

    Mechanisms of Venous Return

    • One-way valves prevent backflow.
    • Compression of large veins: Facilitated by skeletal muscle contractions.
    • Respiration: Acts as a pump, creating a pressure difference between the chest and atmosphere during inspiration, pulling blood back to the heart.

    Venous Return in the Legs

    • One-way valves and skeletal muscle contractions in the calves are crucial for returning blood back to the heart.
    • Valve opens during calf muscle contraction, squeezing blood upwards and preventing backflow when muscle relaxes.

    The Vasculature

    • The vasculature consists of blood vessels, including arteries, arterioles, capillaries, venules, and veins.
    • Arteries transport oxygenated blood away from the heart, while veins return deoxygenated blood to the heart.
    • Arterioles are the smallest arteries, responsible for controlling blood flow to capillaries.
    • Capillaries are the smallest blood vessels, facilitating gas exchange between blood and tissues.
    • Venules are small veins collecting blood from capillaries.

    Circulation and Lymph

    • Blood flow is driven by blood pressure.
    • Arteries and arterioles regulate blood pressure, directing blood flow to specific tissues.
    • Capillaries facilitate fluid exchange between blood and the interstitial fluid.
    • Lymphatic vessels collect excess interstitial fluid and return it to the circulatory system.
    • The venous system returns deoxygenated blood to the heart.

    Blood Pressure Regulation

    • Blood pressure is regulated by cardiac output and peripheral resistance.
    • Cardiac output is the volume of blood pumped by the heart per minute.
    • Stroke volume is the volume of blood ejected by the ventricle during each contraction.
    • Baroreceptors and chemoreceptors detect changes in blood pressure and blood chemistry, sending signals to the autonomic nervous system to adjust heart rate and blood vessel diameter.
    • Long-term blood pressure regulation involves hormonal mechanisms and renal mechanisms.
    • Hypertension is high blood pressure, often caused by dysfunction of the cardiovascular system.

    Cardiac Output

    • Cardiac output (CO) is calculated using the formula: CO = SV x HR.
    • CO represents the amount of blood pumped by the heart per minute.
    • SV is the volume of blood ejected during each heart beat.
    • HR is the number of heart beats per minute.

    Autonomic Nervous System Regulation of Cardiac Output

    • The sympathetic nervous system increases heart rate and force of contraction.
    • The parasympathetic nervous system decreases heart rate and force of contraction.
    • The sympathetic nervous system causes vasoconstriction, while the parasympathetic nervous system causes vasodilation in most blood vessels (excluding the penis and clitoris).
    • The adrenal medulla releases adrenaline and noradrenaline, further increasing heart rate and force of contraction.

    Heart Rate

    • Heart rate is the number of ventricular contractions per minute.
    • Certain drugs, like atenolol and calcium channel blockers, have a negative chronotropic effect on heart rate.

    Cardiac Output: Stroke Volume

    • Stroke volume (SV) is the volume of blood ejected from the ventricle during each contraction.
    • SV is calculated as the difference between end-diastolic volume and end-systolic volume.
    • The Frank-Starling Law of the heart states that the strength of cardiac contraction is directly proportional to the initial length of the cardiac muscle fibers.

    Stroke Volume (Factors influencing)

    • Preload: myocardial sarcomere length just prior to contraction. Affected by:
      • Ventricular filling: Influenced by intra-thoracic pressure, respiration, and blood volume.
      • Ventricular and pericardial compliance: Reduced compliance decreases preload.
      • Ventricular wall thickness: Hypertrophy decreases preload.

    Factors Affecting Cardiac Contractility

    • Intracellular calcium concentration determines myocardial contractility.
    • Factors influencing intracellular calcium levels affect contractility.
    • Positive inotropic agents increase contractility:
      • Cardiac glycosides (digitalis): Block Na-K ATPase.
      • Catecholamines (epinephrine, norepinephrine, isoproterenol): Activate beta-adrenergic receptors.
    • Negative inotropic agents decrease contractility:
      • Beta-blockers: Block beta-adrenergic receptors.
      • Diltiazem and verapamil: Block DHPR Ca channels.

    Autonomic Regulation of Cardiac Contractility

    • The sympathetic nervous system increases myocardial contractility through norepinephrine and beta-1 receptors.
    • The parasympathetic nervous system decreases myocardial contractility through acetylcholine and M2 receptors.

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    Description

    This quiz covers fundamental concepts of cardiac physiology, focusing on heart rate, stroke volume, and the cardiac length-tension relationship. It examines the effects of various medications like Atenolol and calcium channel blockers, as well as factors influencing stroke volume.

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