Bio 13.1 part 2 Heart Conduction System and Cardiac Cycle
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Bio 13.1 part 2 Heart Conduction System and Cardiac Cycle

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Questions and Answers

What is the primary function of the bundle branches in the heart's conduction system?

  • To generate electrical signals
  • To monitor the heart's electrical activity
  • To carry the conduction signal toward the heart's apex (correct)
  • To divide into Purkinje fibers

    • Which phase of the cardiac cycle involves cardiac muscle relaxation and lower pressure in the heart?

  • Arrhythmia
  • Repolarization
  • Diastole (correct)
  • Systole

    • What does an electrocardiogram (ECG) record?

  • Electrical activity of the heart (correct)
  • The heart's contraction strength
  • Blood flow rate through the arteries
  • Pressure changes within the heart

    • What is the correct sequence of contraction during the cardiac cycle?

    <p>Atria contract, followed by ventricular contraction</p> Signup and view all the answers

    What is the main role of Purkinje fibers in the heart's conduction system?

    <p>To propagate the electrical signal from the AV node</p> Signup and view all the answers

    Which component of the cardiac conduction system provides a delay in signal transmission?

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

    What event occurs during systole in the cardiac cycle?

    <p>Blood is pumped out of the heart</p> Signup and view all the answers

    What do the characteristic wave patterns on an ECG correspond to?

    <p>Depolarization or repolarization of heart regions</p> Signup and view all the answers

    What is the normal blood pressure reading for healthy adults at rest?

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

    What does the term 'hypertension' refer to?

    <p>Higher than normal blood pressure</p> Signup and view all the answers

    What does pulse pressure measure?

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

    What does the mean arterial pressure (MAP) represent?

    <p>The average pressure in an artery during one cardiac cycle</p> Signup and view all the answers

    Which of the following factors can lead to an increase in arterial blood pressure?

    <p>Increased peripheral resistance due to vasoconstriction</p> Signup and view all the answers

    How does blood pressure vary based on blood flow into and out of arteries?

    <p>It increases when more blood enters than leaves the arteries</p> Signup and view all the answers

    What physiological change contributes to blood pressure fluctuations in arteries?

    <p>Alternating systole and diastole of the heart</p> Signup and view all the answers

    Why is mean arterial pressure calculated differently than simply averaging systolic and diastolic pressures?

    <p>Diastole lasts longer than systole</p> Signup and view all the answers

    What is the primary function of the thin walls of capillaries?

    <p>To enable exchange of materials between blood and tissues</p> Signup and view all the answers

    How does the circulatory system regulate blood flow to specific body regions?

    <p>By altering the amount of blood flow to that region</p> Signup and view all the answers

    Where is blood pressure at its highest within the systemic circuit?

    <p>In the aorta</p> Signup and view all the answers

    What primarily opposes blood flow in the circulatory system?

    <p>Total peripheral resistance (TPR)</p> Signup and view all the answers

    What happens to blood pressure as blood moves through the vasculature?

    <p>It decreases due to friction and vessel length</p> Signup and view all the answers

    Which factors can increase total peripheral resistance (TPR)?

    <p>Increase in blood vessel length</p> Signup and view all the answers

    What is blood flow (Q) defined as?

    <p>The volume of blood moving through a structure in a given time</p> Signup and view all the answers

    Which statement about capillary structure is incorrect?

    <p>Capillaries have thick walls for robust support</p> Signup and view all the answers

    What is the primary function of vasodilation in thermoregulation?

    <p>To allow heat to be dissipated to the environment</p> Signup and view all the answers

    Which division of the autonomic nervous system decreases heart rate?

    <p>Parasympathetic division</p> Signup and view all the answers

    How does the cardiovascular system respond when internal body temperature falls?

    <p>By vasoconstriction of surface capillaries</p> Signup and view all the answers

    What role does norepinephrine play in heart function?

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

    What mechanism allows local blood flow regulation independent of external signals?

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

    Which hormone is released by the adrenal medulla in response to sympathetic nervous system activity?

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

    What effect do local conditions, such as CO2 concentration, have on blood flow?

    <p>They influence arteriole diameter</p> Signup and view all the answers

    What is the effect of the sympathetic division on the heart?

    <p>Increases both heart rate and contraction force</p> Signup and view all the answers

    What primarily regulates total peripheral resistance (TPR) in the circulatory system?

    <p>Blood vessel diameter</p> Signup and view all the answers

    What happens to blood flow (Q) when the pressure gradient (ΔP) increases?

    <p>Q increases</p> Signup and view all the answers

    Which part of the circulatory system accounts for the majority of total peripheral resistance (TPR)?

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

    What structures encircle some capillaries and can regulate blood flow through capillary beds?

    <p>Precapillary sphincters</p> Signup and view all the answers

    What is the relationship between blood vessel diameter and total peripheral resistance (TPR)?

    <p>Inversely proportional</p> Signup and view all the answers

    During which physiological process do arterioles typically decrease in diameter?

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

    Which of the following factors remains constant over short periods, such as hours, in blood flow regulation?

    <p>Blood vessel diameter</p> Signup and view all the answers

    What occurs when precapillary sphincters constrict?

    <p>Blood flow is decreased to the capillary bed</p> Signup and view all the answers

    What is the primary function of the atria in the heart?

    <p>To transfer blood into the adjoining ventricles</p> Signup and view all the answers

    Why is the left ventricle the most muscular chamber of the heart?

    <p>It pumps blood throughout the body over significant distances</p> Signup and view all the answers

    What prevents blood from flowing back into the atria from the ventricles?

    <p>Atrioventricular (AV) valves</p> Signup and view all the answers

    What structure connects cardiac muscle cells and allows for rapid ion passage?

    <p>Gap junctions</p> Signup and view all the answers

    What is the primary reason for the thick walls of the ventricles compared to the atria?

    <p>To generate high pressure for blood transport</p> Signup and view all the answers

    What is the primary characteristic of a portal system in the body?

    <p>It connects two capillary beds in series.</p> Signup and view all the answers

    What causes the decrease in hydrostatic pressure as blood moves through a capillary?

    <p>Friction as blood passes through the capillary.</p> Signup and view all the answers

    What mechanism primarily drives bulk flow across capillary walls?

    <p>Hydrostatic and oncotic pressures.</p> Signup and view all the answers

    What effect does the larger combined cross-sectional area of capillaries have on blood velocity?

    <p>It reduces blood velocity significantly.</p> Signup and view all the answers

    How does oncotic pressure affect fluid movement in capillaries?

    <p>It causes water to move towards areas of higher protein concentration.</p> Signup and view all the answers

    What is the primary effect of the signal carried by Purkinje fibers on the heart's function?

    <p>It initiates ventricular contraction at the apex of the heart.</p> Signup and view all the answers

    What happens during diastole in the cardiac cycle?

    <p>Cardiac muscle relaxes, allowing blood to enter the heart.</p> Signup and view all the answers

    How does the electrocardiogram (ECG) monitor the heart?

    <p>It records electrical activity during heartbeats.</p> Signup and view all the answers

    What is the significance of the delay in signal transmission mediated by the AV node?

    <p>It ensures complete filling of the ventricles before they contract.</p> Signup and view all the answers

    Which phase of the cardiac cycle involves the highest pressure within the heart?

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

    What is generated from the data collected by electrodes on the body during heart monitoring?

    <p>An electrocardiogram (ECG).</p> Signup and view all the answers

    What sequence does ventricular contraction follow in the cardiac cycle?

    <p>It begins at the heart's apex and moves superiorly.</p> Signup and view all the answers

    What initiates the closing of the AV valves during the cardiac cycle?

    <p>Increase in pressure in the contracting ventricles</p> Signup and view all the answers

    What sound does the 'dup' heart sound represent in the cardiac cycle?

    <p>Closure of the semilunar valves</p> Signup and view all the answers

    Which factor affects cardiac output (CO) the most directly?

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

    How is stroke volume (SV) defined in the context of the heart's function?

    <p>The volume of blood pumped from the ventricle during one contraction</p> Signup and view all the answers

    What is the role of the sinoatrial (SA) node in heart function?

    <p>It generates electrical signals for contraction</p> Signup and view all the answers

    During what phase does ventricular contraction begin?

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

    What does cardiac output (CO) equal when given a heart rate of 75 beats per minute and a stroke volume of 70 mL?

    <p>5,250 mL/min</p> Signup and view all the answers

    What type of blood does the pulmonary circuit carry?

    <p>Oxygen-poor blood</p> Signup and view all the answers

    Which phase of the cardiac cycle corresponds with the opening of the semilunar valves?

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

    What event primarily regulates the sequence of contraction in the heart?

    <p>Electrical signals from the SA node</p> Signup and view all the answers

    Study Notes

    Heart Conduction System

    • The AV bundle divides into two bundle branches, carrying the signal within the ventricular wall towards the apex.
    • Bundle branches further divide into Purkinje fibers, transmitting the signal superiorly within the ventricular walls.
    • This signal initiates ventricular contraction, starting at the apex and moving towards the atria.
    • Electrocardiogram (ECG) monitors heart electrical activity through electrodes placed on the body's surface.
    • ECG records depolarization and repolarization of specific heart regions.

    Cardiac Cycle

    • The cardiac cycle involves two phases: diastole and systole.
    • Diastole involves cardiac muscle relaxation, reducing heart pressure, allowing blood to enter.
    • Systole involves cardiac muscle contraction (first atria, then ventricles), increasing pressure and pumping blood out.

    Blood Flow Regulation

    • The circulatory system distributes materials effectively to specific body regions by regulating blood flow.
    • Blood flow, the volume of blood moving through a structure at a given time, is driven by pressure differences.
    • Blood moves from areas of higher pressure to areas of lower pressure, following the pressure gradient.
    • Blood flow is influenced by a pressure gradient (ΔP) and total peripheral resistance (TPR).

    Total Peripheral Resistance (TPR)

    • TPR is the total friction encountered by blood as it moves through the circulatory system.
    • TPR is influenced by blood viscosity, blood vessel length, and blood vessel diameter.
    • Increased viscosity, length, or decreased diameter increase TPR.

    Blood Flow Equation

    • Blood flow (Q) is directly proportional to pressure gradient (ΔP) and inversely proportional to TPR:
      • Q = ΔP / TPR
    • Arterioles primarily regulate TPR through vasoconstriction and vasodilation.

    Capillary Beds

    • Capillary beds are networks of capillaries receiving blood from an arteriole and delivering it to a venule.
    • Microcirculation, blood flow through the capillary bed, is regulated by the diameter of the supplying arteriole.
    • Precapillary sphincters, smooth muscle cells surrounding capillary entrances, can constrict, diverting blood flow away from the capillary bed.

    Blood Pressure

    • Blood pressure is measured as a ratio of systolic (highest) to diastolic (lowest) pressure.
    • Normal blood pressure for adults is below 120/80 mm Hg.
    • Hypertension is higher than normal blood pressure.
    • Hypotension is lower than normal blood pressure.

    Arterial Blood Pressure

    • Arterial blood pressure fluctuates due to cardiac systole and diastole.
    • Pulse is the rhythmic stretching and recoiling of arteries due to these pressure fluctuations.
    • Pulse pressure is the difference between diastolic and systolic pressures.
    • Mean Arterial Pressure (MAP) represents the average pressure over one cardiac cycle.

    Factors Affecting Arterial Blood Pressure

    • Increased blood flow into arteries or decreased blood flow out of arteries raise blood pressure.
    • Increased cardiac output, arteriole vasoconstriction, or increased total blood volume increase blood pressure.

    Circulation and Thermoregulation

    • Blood carries a significant amount of heat, which is regulated through blood flow control.
    • Vasodilation increases blood flow near the skin surface, releasing heat when body temperature rises.
    • Vasoconstriction decreases blood flow to the skin surface, retaining heat when body temperature falls.

    Endocrine and Nervous Control of Circulation

    • Extrinsic controls, originating from the nervous and endocrine systems, regulate the cardiovascular system.
    • Autonomic nervous system (ANS) regulates heart rate and contractility.

    Sympathetic Nervous System

    • The sympathetic division increases heart rate and contractility by releasing norepinephrine.

    Parasympathetic Nervous System

    • The parasympathetic division decreases heart rate but has little effect on contractility by releasing acetylcholine.

    Endocrine Control

    • Hormones like epinephrine released by the adrenal medulla stimulate heart rate and contractility.

    Autoregulation

    • Local conditions within an organ or tissue can influence local blood flow, a mechanism called autoregulation.
    • This regulates blood flow to specific regions based on local needs.

    Heart Structure and Function

    • The heart has right and left sides operating as separate pumps
    • Right side pumps blood to the lungs; left side pumps blood to the rest of the body
    • The heart consists of four chambers:
      • Two atria: thin walled, receive blood
      • Two ventricles: thick walled, pump blood out
    • Valves ensure unidirectional blood flow:
      • Atrioventricular (AV) valves: between atria and ventricles
      • Semilunar valves: between ventricles and major arteries
    • Heart muscle cells are connected by intercalated discs:
      • Gap junctions allow electrical signals to spread quickly
      • Desmosomes prevent cells from pulling apart during contraction

    The Cardiac Conduction System

    • The heart's electrical activity is regulated by a specialized conduction system:
      • Begins at the sinoatrial (SA) node (pacemaker)
      • Travels through the atria, AV node, bundle of His, bundle branches, and Purkinje fibers
    • The AV node delays signal transmission allowing the atria to contract before the ventricles
    • Ventricular contraction begins at the apex and progresses towards the base, efficiently pushing blood towards the arteries

    The Cardiac Cycle

    • The cardiac cycle consists of two phases:
      • Diastole: relaxation, heart fills with blood
      • Systole: contraction, heart pumps blood out
    • Heart sounds "lub-dup" are generated by valve closure:
      • "Lub": AV valves close at the beginning of ventricular systole
      • "Dup": semilunar valves close at the beginning of ventricular diastole

    Cardiac Output

    • Cardiac output (CO) is the amount of blood pumped by a ventricle per minute
    • It depends on:
      • Heart rate (HR): beats/minute
      • Stroke volume (SV): blood pumped per beat
    • Formula: CO = HR x SV

    Blood Circulation

    • Two circuits:
      • Pulmonary circuit: right heart to lungs
      • Systemic circuit: left heart to body
    • Portal systems: specialized pathways with two capillary beds in series, allow substances to move between body regions
    • Blood velocity slowest in capillaries:
      • Increases time for material exchange
      • Occurs due to increased total capillary surface area

    Material Exchange in Capillaries

    • Material exchange occurs by:
      • Diffusion
      • Endocytosis
      • Exocytosis
      • Bulk flow (mass movement of fluid)
    • Bulk flow is driven by hydrostatic pressure (HP) and oncotic pressure (OP):
      • HP: pressure exerted by fluid on vessel walls
      • OP: pressure created by large molecules (proteins) in fluid

    Thermoregulation

    • The cardiovascular system helps regulate heat:
      • Vasodilation: widening arterioles to increase blood flow close to skin surface, aiding heat dissipation
      • Vasoconstriction: narrowing arterioles to decrease blood flow, retaining heat in the body core

    Extrinsic Control of Circulation

    • The cardiovascular system is regulated by:
      • Extrinsic controls: signals from the nervous and endocrine systems
      • Autoregulation: local factors affecting blood flow within specific organs or tissues
    • The autonomic nervous system (ANS) regulates heart rate and contractility:
      • Sympathetic division: increases heart rate and contractility (releases norepinephrine)
      • Parasympathetic division: decreases heart rate (releases acetylcholine)
    • Hormones (like epinephrine) also influence heart function

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    Description

    Test your knowledge on the heart's conduction system and the cardiac cycle. This quiz covers the function of the AV bundle, bundle branches, Purkinje fibers, and the phases of the cardiac cycle. Assess your understanding of blood flow regulation and ECG monitoring.

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