Cardiac Muscle Contraction and Depolarization Quiz
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Questions and Answers

What factor has the most influence on blood flow in vessels?

  • Blood viscosity
  • Vessel diameter (correct)
  • Tube length
  • Pressure gradient

    • Which type of cardiac muscle cells have a pacemaker potential and membrane potential that 'never rests'?

  • Calcium channels
  • Membrane potential is not relevant
  • Myocardial Contractile Cells
  • Myocardial Autorhythmic Cells (correct)

    • What slows down blood flow in vessels?

  • Pressure gradient
  • Tube length
  • Blood viscosity (correct)
  • Vessel diameter

    • Which factor affecting blood flow remains relatively constant?

    <p>Blood viscosity</p> Signup and view all the answers

    In terms of blood flow, what does resistance primarily depend on?

    <p>Vessel diameter, tube length, and blood viscosity</p> Signup and view all the answers

    Which type of cardiac muscle cells have a different looking action potential due to calcium channels?

    <p>Myocardial Contractile Cells</p> Signup and view all the answers

    Which of the following is NOT a factor that affects blood flow?

    <p>'Never rests' pacemaker potential</p> Signup and view all the answers

    Which hormone enhances heart rate and contractility?

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

    What type of cells in the heart contribute to the generation of the heart's electrical signal?

    <p>'Never rests' pacemaker potential cells</p> Signup and view all the answers

    Which factor increases heart rate and enhances the effects of norepinephrine and epinephrine?

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

    What is a common age-related change affecting the heart?

    <p>Sclerosis and thickening of valve flaps</p> Signup and view all the answers

    Which congenital heart defect involves a narrowed aorta?

    <p>Coarctation of the aorta</p> Signup and view all the answers

    What is a common arrhythmia disorder related to age and underlying heart disease?

    <p>Atrial fibrillation</p> Signup and view all the answers

    What is the most common disorder that involves the superior part of the interventricular septum failing to form?

    <p>Ventricular septal defect</p> Signup and view all the answers

    Which ion concentration must be maintained for normal heart function?

    <p>$Ca^{2+}$</p> Signup and view all the answers

    'Tetralogy' in 'Tetralogy of Fallot' refers to how many defects?

    <p>$4$</p> Signup and view all the answers

    What is the purpose of gap junctions in cardiac muscle cells?

    <p>To ensure the heart contracts as a unit</p> Signup and view all the answers

    What happens when depolarization opens voltage-gated fast Na+ channels in cardiac myocytes?

    <p>Reversal of membrane potential from -90 mV to +30 mV</p> Signup and view all the answers

    What prolongs the depolarization phase (plateau) in cardiac muscle cells?

    <p>Surge of Ca2+ ions</p> Signup and view all the answers

    What is responsible for the repolarization phase in cardiac muscle cells?

    <p>Inactivation of Ca2+ channels and opening of K+ channels</p> Signup and view all the answers

    What role do slow Ca2+ channels play during cardiac muscle contraction?

    <p>Maintain depolarization in plateau phase</p> Signup and view all the answers

    What is the function of automaticity in cardiac cells?

    <p>Self-excitability or spontaneous depolarization</p> Signup and view all the answers

    Which event causes the sarcoplasmic reticulum (SR) to release Ca2+ in cardiac muscle cells?

    <p>Depolarization wave in T tubules</p> Signup and view all the answers

    What is responsible for the long absolute refractory period (250 ms) in cardiac myocytes?

    <p>Fast Na+ channel inactivation</p> Signup and view all the answers

    What is a common way patients describe an arrhythmia?

    <p>As a palpitation or fluttering sensation in the chest</p> Signup and view all the answers

    What is one of the symptoms patients may experience due to arrhythmias?

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

    What is a frequent cause of arrhythmia according to the text?

    <p>Coronary artery disease</p> Signup and view all the answers

    What happens when cardiac cells lack oxygen according to the text?

    <p>They become depolarized</p> Signup and view all the answers

    What can ectopic foci lead to in the heart?

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

    What is altered impulse conduction commonly associated with within the heart?

    <p>Reentry that leads to abnormal conduction</p> Signup and view all the answers

    What can ectopic foci cause in terms of heartbeats?

    <p>Premature beats</p> Signup and view all the answers

    How do ectopic foci impact the normal pacemaker activity of the SA node?

    <p>Replacing it with another pacemaker</p> Signup and view all the answers

    What is the function of intercalated discs in cardiac cells?

    <p>Allow branching of the myocardium</p> Signup and view all the answers

    Which structure is responsible for fast cell-to-cell signals in cardiac cells?

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

    What is the main function of the intrinsic cardiac conduction system?

    <p>Initiate and distribute impulses to coordinate heart contraction</p> Signup and view all the answers

    What characterizes pacemaker-autorhythmic cells in the heart?

    <p>Unstable resting potentials with open slow Na+ channels</p> Signup and view all the answers

    What event leads to the rising phase of the action potential in cardiac cells?

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

    What causes repolarization in cardiac cells after depolarization?

    <p>Inactivation of Ca2+ channels and opening of voltage-gated K+ channels</p> Signup and view all the answers

    What is responsible for the slow depolarization known as pacemaker potential?

    <p>Opening of Na+ channels and closing of K+ channels</p> Signup and view all the answers

    What leads to repolarization in cardiac cells after depolarization?

    <p>Closing of Na+ channels and opening of K+ channels</p> Signup and view all the answers

    What is the final stage of maturation for red blood cells?

    <p>Nucleus incorporation</p> Signup and view all the answers

    Which organelle in red blood cells is responsible for transporting iron into the mitochondria?

    <p>Endoplasmic reticulum (ER)</p> Signup and view all the answers

    What is the main function of hemoglobin in red blood cells?

    <p>Carrying oxygen</p> Signup and view all the answers

    Which component is NOT found in mature red blood cells?

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

    What remarkable transformation do erythrocytes undergo during maturation?

    <p>Exclusion of Golgi bodies</p> Signup and view all the answers

    What is the role of mitochondria in developing erythrocytes?

    <p>Transporting iron</p> Signup and view all the answers

    What makes veins more compliant compared to arteries?

    <p>One-way valves</p> Signup and view all the answers

    What is the primary function of erythrocytes in the bloodstream?

    <p>Carrying oxygen</p> Signup and view all the answers

    How do nutrients like glucose and amino acids leave the capillaries in the body?

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

    What is the main mechanism through which CO2 moves at the capillary bed?

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

    Where are small proteins or amino acids dissolved when they leave the capillaries?

    <p>Interstitial space</p> Signup and view all the answers

    What is the main function of elastic fibers in venous vessels compared to arteries?

    <p>To store blood</p> Signup and view all the answers

    What mainly differentiates venous vessels from arterial vessels?

    <p>Muscle composition</p> Signup and view all the answers

    Where does the blood go after leaving the venules?

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

    What is the primary role of the venous circulation within the body?

    <p>To store blood</p> Signup and view all the answers

    What does the ST segment represent in an ECG?

    <p>A resting membrane potential</p> Signup and view all the answers

    Which part of the ECG signifies that the ventricle is depolarized?

    <p>R wave</p> Signup and view all the answers

    What does the Q wave indicate on an ECG?

    <p>Movement of action potential through the bundle branch fibers</p> Signup and view all the answers

    Why are 12 to 32 leads used in clinical ECGs rather than just three leads?

    <p>To provide electrical views of the heart from multiple angles</p> Signup and view all the answers

    What is the primary benefit of using ECG to monitor cardiac rhythm and rhythm disturbances?

    <p>Tracking changes in ventricular depolarization</p> Signup and view all the answers

    What can be inferred if an ECG shows electrical aberrations?

    <p>Ischemic tissue or necrotic zones</p> Signup and view all the answers

    What does each ECG lead provide?

    <p>An electrical view from different parts of the heart</p> Signup and view all the answers

    Why is the interval between the P and R waves a straight line on an ECG?

    <p>&quot;Slowed impulse at the A-V node&quot;</p> Signup and view all the answers

    What would happen if all blood vessels were completely dilated and fixed at a certain diameter according to the text?

    <p>All tissues would be maximally perfused.</p> Signup and view all the answers

    What local factors can cause vascular smooth muscle to dilate and increase blood flow?

    <p>CO2, H+, K+, and adenosine</p> Signup and view all the answers

    What is an important function of the sympathetic nervous system in relation to blood vessel diameter?

    <p>Causes constriction of blood vessels</p> Signup and view all the answers

    What factor causes muscle contraction to lead to increased perfusion in working muscles?

    <p>Release of adenosine</p> Signup and view all the answers

    What is the main role of smooth muscle surrounding arteries and veins anatomically?

    <p>To respond to tissue need</p> Signup and view all the answers

    What effect do CO2, H+, K+, and adenosine have on vascular smooth muscle?

    <p>Relax and dilate the vessels</p> Signup and view all the answers

    How do blood vessels ensure efficient distribution of blood flow according to the text?

    <p>By constantly altering their diameter based on tissue need</p> Signup and view all the answers

    What is the primary function of the layer of smooth muscle surrounding arteries and veins?

    <p>To respond to tissue need for altered perfusion</p> Signup and view all the answers

    What effect does nitric oxide have on smooth muscle?

    <p>Inhibits SERCA pump</p> Signup and view all the answers

    How does a reduction in vascular diameter affect blood flow to tissues downstream?

    <p>Decreases flow due to increased resistance</p> Signup and view all the answers

    Where is the site of greatest control of resistance in the arterial tree?

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

    What is the primary determinant of flow to the tissue?

    <p>Vessel radius</p> Signup and view all the answers

    Which factor increases total peripheral resistance (TPR) and reduces flow?

    <p>Decreased vascular diameter</p> Signup and view all the answers

    What increases vascular diameter during exercise?

    <p>Increased metabolites from skeletal muscle</p> Signup and view all the answers

    Why do arterioles play a significant role in controlling resistance?

    <p>Due to their smaller relative cross-sectional area</p> Signup and view all the answers

    What determines the resistance to flow primarily in blood vessels?

    <p>Blood viscosity</p> Signup and view all the answers

    Study Notes

    Blood Flow Factors

    • Blood flow in vessels is most influenced by pressure gradients.
    • Factors that slow down blood flow include vascular resistance and blood viscosity.
    • Blood vessel diameter remains relatively constant, influencing flow resistance.
    • Resistance primarily depends on vessel diameter, length, and blood viscosity.

    Cardiac Muscle Cells

    • Pacemaker cells possess a resting membrane potential that never rests, capable of generating spontaneous action potentials.
    • Cardiac muscle cells exhibit different action potentials due to calcium channels primarily found in atrial and ventricular muscle cells.
    • Hormones like norepinephrine and epinephrine enhance heart rate and contractility.
    • Automaticity in cardiac cells allows for rhythmic contraction without external stimuli.

    Heart Defects and Disorders

    • Tetralogy of Fallot refers to four congenital defects affecting the heart.
    • Coarctation of the aorta is a congenital heart defect characterized by a narrowed aorta.
    • Common age-related changes affecting the heart include fibrosis and reduced cardiac output, leading to arrhythmias.

    Cardiac Action Potentials

    • Fast Na+ channels opening during depolarization lead to rapid overshoot in action potentials of cardiac myocytes.
    • Slow Ca2+ channels contribute to the prolonged depolarization phase known as the plateau in cardiac muscle cells.
    • Repolarization in cardiac muscle is primarily driven by the opening of potassium channels.

    Electrical Signals in Heart

    • Gap junctions facilitate direct electrical communication between cardiac cells, allowing for synchronized contractions.
    • Ectopic foci can disrupt normal pacemaker activity, leading to irregular heartbeats or arrhythmias.
    • Intercalated discs in cardiac cells connect adjacent cells and assist in the transmission of electrical impulses.

    Red Blood Cell Maturation

    • Erythroblasts enter the final stage of maturation into red blood cells as they lose their nucleus.
    • Hemoglobin in red blood cells is responsible for oxygen transport, while mitochondria in developing erythrocytes produce ATP.
    • Mature red blood cells lack organelles such as nuclei and mitochondria.

    Capillary Exchange

    • Nutrients like glucose and amino acids move from capillaries via diffusion, while CO2 predominantly moves out through passive diffusion.
    • Small proteins or amino acids that leave capillaries dissolve in the interstitial fluid surrounding tissues.

    Vascular Dynamics

    • Compliance refers to veins being more flexible than arteries due to less smooth muscle and elastic fiber content.
    • Local factors like increased CO2 and acidosis cause vascular smooth muscle to relax, enhancing blood flow.
    • The primary determinant of blood flow to tissues is the degree of resistance in arterioles.

    ECG Insights

    • The ST segment in an ECG represents the isoelectric period between ventricular depolarization and repolarization.
    • The P-R interval provides insights into atrioventricular conduction and timing of electrical signals.
    • Utilization of multiple leads in clinical ECGs ensures comprehensive monitoring of the heart's electrical activity and rhythm disturbances.

    Vascular Control

    • Smooth muscle surrounding arteries and veins plays a critical role in regulating vessel diameter and blood flow.
    • Nitric oxide causes relaxation of vascular smooth muscle, contributing to vasodilation.
    • During exercise, increased metabolic demands lead to vasodilation, enhancing blood flow to active muscle tissues.

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    Description

    Test your knowledge on the process of cardiac muscle contraction and depolarization, including topics like rhythmic depolarization, automaticity, gap junctions, refractory period, and ion channel activation.

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