Cardiovascular System Overview

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Questions and Answers

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

  • To separate blood from different circuits
  • To receive blood returning to the heart (correct)
  • To pump blood out of the heart
  • To prevent backflow of blood during contraction

Which structure prevents backflow from the pulmonary artery into the right ventricle?

  • Aortic valve
  • Mitral valve
  • Pulmonic valve (correct)
  • Tricuspid valve

Which layer of the heart is the outermost component?

  • Endocardium
  • Myocardium
  • Epicardium (correct)
  • Pericardium

What distinguishes the ventricles from the atria?

<p>Ventricles are the lower chambers of the heart. (D)</p> Signup and view all the answers

Which valve is responsible for preventing backflow from the aorta into the left ventricle?

<p>Aortic valve (C)</p> Signup and view all the answers

What causes the plateau phase during the action potential in cardiac muscle cells?

<p>Slow influx of Ca++ (B)</p> Signup and view all the answers

What is the resting potential of the cardiac membrane?

<p>-90 mV (A)</p> Signup and view all the answers

During atrial systole, which valves are involved in the blood flow from the atria to the ventricles?

<p>Tricuspid and mitral valves (D)</p> Signup and view all the answers

What occurs during ventricular systole in the cardiac cycle?

<p>Blood is forced into blood vessels through semilunar valves (A)</p> Signup and view all the answers

How is the action potential spread among cardiac muscle cells?

<p>Via gap junctions in intercalated discs (A)</p> Signup and view all the answers

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

<p>To generate the electrical impulse for contraction (B)</p> Signup and view all the answers

Which characteristic of the pacemaker cells refers to their ability to transmit impulses to adjacent cells?

<p>Conductivity (C)</p> Signup and view all the answers

During which phase of action potential does rapid depolarization occur due to Na+ influx?

<p>Phase 0: rapid depolarization (A)</p> Signup and view all the answers

What is the approximate resting membrane potential of myocardial fibers?

<p>-90 mV (B)</p> Signup and view all the answers

What happens at the AV node during impulse conduction?

<p>The impulse is generally delayed (A)</p> Signup and view all the answers

Which structure begins within the apex of the heart and extends through the ventricles?

<p>Purkinje fibers (D)</p> Signup and view all the answers

What is the threshold membrane potential that initiates upon reaching a rapid influx of Na+?

<p>-40 mV (A)</p> Signup and view all the answers

What is the correct sequence of typical impulse conduction in the heart?

<p>SA node → AV node → bundle of His → Purkinje fibers (B)</p> Signup and view all the answers

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Flashcards

Heart chambers

The heart is composed of four chambers: two upper atria and two lower ventricles. The atria receive blood and pump it to the ventricles, while the ventricles pump blood out of the heart.

Heart valves

The heart valves are like one-way doors, ensuring blood flows in the right direction. They open and close based on pressure changes during heart contractions.

Pulmonary circuit

The pulmonary circuit is the pathway between the heart and lungs, where blood picks up oxygen and releases carbon dioxide.

Systemic circuit

The systemic circuit carries oxygen-rich blood from the heart to the body and returns deoxygenated blood back to the heart.

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Coronary circuit

The coronary circuit supplies blood to the heart muscle itself, providing oxygen and nutrients for its own function.

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Automaticity

The ability of pacemaker cells to generate an electrical impulse without external stimulation.

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Conductivity

The ability of pacemaker cells to pass the electrical impulse to the next cell in the conduction system.

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Contractility

The ability of heart muscle cells to shorten in response to an electrical impulse, leading to contraction.

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Sinoatrial (SA) node

The primary pacemaker of the heart, generating impulses between 60 and 100 times per minute.

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Atrioventricular (AV) node

Located low in the right atrium, it slows down the impulse conduction between the atria and ventricles, ensuring coordinated contraction.

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Bundle of His

Found in the interventricular septum, it divides into right and left branches, carrying the electrical impulse from the AV node to the ventricles.

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Purkinje fibers

Located within the apex of the heart, these fibers spread throughout the ventricles, causing their powerful contraction.

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Typical impulse conduction

The normal sequence of events that initiate and transmit electrical impulses through the heart: SA node-AV node-Bundle of His-Purkinje fibers.

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Repolarization phase

The phase of the cardiac action potential where sodium channels close and potassium channels open, leading to a rapid decrease in membrane potential.

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Depolarization phase

The initial phase of the cardiac action potential, characterized by a rapid influx of sodium ions into the cell. This causes the membrane potential to become more positive.

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Plateau phase

The plateau phase of the cardiac action potential is characterized by a slower influx of calcium ions, prolonging the depolarized state. This is crucial for muscle contraction.

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Diastole

The period in the cardiac cycle where the heart chambers relax and fill with blood.

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Systole

The period in the cardiac cycle when the heart chambers contract and pump blood out.

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Study Notes

Cardiovascular System Overview

  • The average adult has 4-6 liters of blood.
  • Blood is circulated throughout the body in a closed system.
  • Blood always flows in a forward direction.

Heart Anatomy and Components

  • Heart: Size of a closed fist, located in the mediastinum between the second and sixth ribs.
  • Heart Chambers: Four chambers: two atria and two ventricles.
  • Heart Valves: Four valves (two atrioventricular and two semilunar valves), separating atria from ventricles and preventing backflow.
  • Heart Wall Layers: Three layers: epicardium (outer), myocardium (middle), and endocardium (inner).
  • Pulmonary Circuit: Blood flow between the heart and lungs.
  • Systemic Circuit: Blood flow to and from the rest of the body.
  • Coronary Circuit: Blood flow to the heart.
  • Atria: Two upper chambers that receive blood returning to the heart and pump it to the ventricles.
  • Ventricles: Two lower chambers that receive blood from the atria and pump blood to the rest of the body.
  • Heart Valves: Control the flow of blood through the heart. Different valves have different functions preventing backflow in the heart.

Cardiac Cycle and Conduction System

  • Cardiac Cycle: The period from the start of one heartbeat to the initiation of the next.
    • Components: Atrial systole, Atrial diastole, Ventricular systole
  • Atrial systole: Contraction of both atria simultaneously pushes blood into ventricles.
  • Atrial diastole: Relaxation of atria.
  • Ventricular systole: Contraction of ventricles forces blood into the pulmonary artery and aorta.
  • Conduction System: Specialized cells that generate and conduct electrical impulses, controlling the heart's rhythmic contractions.
    • Components: Sinoatrial (SA) node, Atrioventricular (AV) node, Bundle of His, Purkinje fibers.
    • Functions: Create, distribute, and control the timing of electrical impulses during heartbeats.
  • Sinoatrial (SA) Node: Normal pacemaker of the heart, generating impulses between 60 and 100 times per minute.
  • Atrioventricular (AV) Node: Slows impulse conduction between atria and ventricles.
  • Bundle of His: Carries impulses into the ventricles.
  • Purkinje Fibers: Spread impulses to the ventricular walls.

Cardiac Muscle Electrical Activity (Action Potential)

  • Electrical Activity: Myocardial fibers generate and conduct electrical impulses to enable contraction.
    • Phases: Rapid depolarization, initial rapid repolarization, plateau, repolarization and resting.
  • Resting Membrane Potential: Approximately -90 mV
  • Rapid depolarization: Influx of Na+ ions
  • Initial rapid repolarization: Closure of Na+ channels, opening of K+ channels
  • Plateau: Influx of Ca++ ions
  • Repolarization: Closure of Ca++ channels, efflux of K+ ions
  • Resting potential: Membrane potential maintained at -90 mV.
  • Gap junctions: Interconnected cardiac muscle cells allowing for synchronized contraction

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