Cardiac Physiology Quiz

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

The natural pacemaker of the heart is the ______ node.

Sinoatrial

Cardiac myocytes are interconnected by structures called ______ disks.

intercalated

The ______ junctions in cardiac myocytes link cells electrically.

gap

Desmosomes connect intermediate filaments from two adjacent ______.

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

Cardiac contraction has an absolute requirement for ______ influx through L-type Ca 2+ channels.

<p>Ca 2+</p> Signup and view all the answers

The heart consists of a right heart that pumps blood through the ______.

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

Each atrium acts as a weak primer pump for the ______.

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

The heart is composed of three major types of cardiac muscle: atrial muscle, ventricular muscle, and specialized ______ muscle fibers.

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

The duration of contraction in cardiac muscle is much longer than in ______ muscle.

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

The specialized fibers exhibit automatic rhythmical ______ discharge in the form of action potentials.

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

Gap junctions enable passive diffusion of various compounds, like metabolites, water, and ions, up to a molecular mass of ______ Daltons.

<p>1000</p> Signup and view all the answers

A gap junction channel consists of twelve ______ proteins.

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

Adherens junctions are constructed from ______ and catenins.

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

At the adherens junctions, the opposing membranes become separated by approximately ______ nm.

<p>20</p> Signup and view all the answers

The action potential of cardiac muscle averages about ______ millivolts.

<p>105</p> Signup and view all the answers

During each heartbeat, the intracellular potential rises from about ______ millivolts to about +20 millivolts.

<p>-85</p> Signup and view all the answers

The plateau in the action potential of cardiac muscle is due to the opening of fast sodium channels and slow ______ channels.

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

The presence of a plateau in the action potential causes ventricular contraction to last as much as ______ times longer in cardiac muscle than in skeletal muscle.

<p>15</p> Signup and view all the answers

The action potential in skeletal muscle is primarily caused by opening of large numbers of fast ______ channels.

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

The prolonged action potential and plateau in cardiac muscle are due to differences in membrane properties compared to ______ muscle.

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

Flashcards

What are the two pumps of the heart?

The heart is essentially two pumps: the right heart, which circulates blood to the lungs, and the left heart, which pumps blood to the rest of the body. Each heart is divided into an atrium and a ventricle.

What are the roles of the atria and ventricles?

The atria are weaker chambers that help move blood into the stronger ventricles. These ventricles are the main chambers that propel the blood, either to the lungs (right ventricle) or to the body (left ventricle).

What are the types of muscle in the heart?

Cardiac muscle is found in three main types: atrial muscle, ventricular muscle and specialized excitatory and conductive muscle fibers. These specialized fibers are responsible for the heart's rhythm.

How is the contraction of cardiac muscle different from skeletal muscle?

Atrial and ventricular muscle contract similarly to skeletal muscle, but with a longer contraction duration. This means they can hold a contraction longer.

Signup and view all the flashcards

What is the purpose of the specialized fibers in the heart?

Specialized excitatory and conductive fibers generate electrical impulses that control the heart's rhythm. They are weakly contractile due to fewer contractile fibrils.

Signup and view all the flashcards

What is the role of cardiac conductive muscle fibers?

Specialized cardiac muscle fibers form a network responsible for generating and conducting electrical impulses throughout the heart, ensuring coordinated contraction.

Signup and view all the flashcards

What is the function of gap junctions in cardiac muscle?

These junctions link adjacent cardiac muscle cells electrically, allowing for rapid transmission of electrical impulses throughout the heart.

Signup and view all the flashcards

What do desmosomes do in cardiac muscle?

Desmosomes in cardiac muscle provide mechanical linkage between cells, preventing them from tearing apart during contraction.

Signup and view all the flashcards

What is the interaction of adherens junctions with the actin cytoskeleton?

Adherens junctions bind the intercalated disc to the actin cytoskeleton in cardiac muscle, ensuring coordinated contraction.

Signup and view all the flashcards

How does calcium influence cardiac muscle contraction?

Cardiac muscle contraction requires calcium influx through L-type calcium channels, unlike skeletal muscle which relies primarily on intracellular calcium release.

Signup and view all the flashcards

What are gap junctions?

Special channels between cells that allow direct passage of small molecules and ions.

Signup and view all the flashcards

What are cadherins?

Transmembrane proteins that connect adjacent cells, forming a bridge between their cytoskeletons.

Signup and view all the flashcards

What are catenins?

Proteins that link cadherins to the actin cytoskeleton within a cell.

Signup and view all the flashcards

What are adherens junctions?

A type of cell junction that is characterized by the presence of cadherins and catenins, creating a strong connection between cells.

Signup and view all the flashcards

What is an action potential?

A rapid change in membrane potential that occurs in excitable cells, like cardiac muscle.

Signup and view all the flashcards

What is the plateau phase of an action potential?

The phase of the action potential where the membrane potential remains depolarized for a prolonged period.

Signup and view all the flashcards

Why is the action potential in cardiac muscle longer than in skeletal muscle?

The action potential in cardiac muscle is longer than in skeletal muscle due to the opening of slow calcium channels.

Signup and view all the flashcards

What is the significance of the long action potential in cardiac muscle?

The prolonged action potential in cardiac muscle ensures a longer contraction duration, crucial for efficient heart pumping.

Signup and view all the flashcards

What are specialized fibers in the heart?

Specialized excitatory and conductive fibers generate electrical impulses that control the heart's rhythm.

Signup and view all the flashcards

What is the difference between the function of specialized fibers and contractile muscle in the heart?

The heart's rhythm is generated by specialized fibers, while the contractile force comes from atrial and ventricular muscle.

Signup and view all the flashcards

Study Notes

The Heart and its Disorders

  • The heart is two separate pumps
  • A right heart that pumps blood through the lungs
  • A left heart that pumps blood through peripheral organs
  • Each heart is a pulsatile two-chamber pump
  • Composed of an atrium and a ventricle
  • Atria are weak primer pumps for the ventricles
  • Ventricles provide the main pumping force
  • Blood flows through the pulmonary circulation (right ventricle)
  • Blood flows through the peripheral circulation (left ventricle)

Learning Objectives

  • Understanding heart tissue and its functions
  • Cardiac cycle and ECG
  • Disorders of the heart and treatments

Anatomy of the Heart

  • Figure 9-1 shows a diagram of the heart's structure
  • The structure includes the aorta, pulmonary artery, pulmonary vein, left atrium, mitral valve, aortic valve, left ventricle, superior vena cava, right atrium, pulmonary valve, and tricuspid valve, right ventricle, and inferior vena cava.
  • Shows the course of blood flow through the heart's chambers and heart valves

Physiology of Cardiac Muscle

  • The heart contains three major types of cardiac muscle: atrial, ventricular, and specialized excitatory/conductive muscle fibers.
  • The specialized fibers control the heart's rhythmical beating
  • Atrial and ventricular muscle contract similar to skeletal muscle, but contraction duration is longer.
  • Specialized excitatory and conductive fibers contract weakly due to fewer contractile fibrils
  • These fibers exhibit automatic rhythmical electrical discharges (action potentials) or conduct action potentials through the heart.
  • This function helps the excitatory system of the heart control the rhythmical beating of the heart.

Cardiac Conductive Muscle Fibers

  • The heart has a special system for rhythmical electrical impulses for contraction
  • Conducts impulses rapidly to the heart's different parts.
  • Key areas include the Sinoatrial (SA) node (pacemaker in right atrium), Atrioventricular (AV) node (junction between atria and ventricles), Bundle of His (conducts impulses from AV to ventricles), Purkinje fibers (spread throughout ventricles for coordinated contraction).

Cardiac Myocytes

  • Cardiac myocytes are shorter, branched, interconnected cells
  • Intercalated disks connect the cells, containing desmosomes (mechanical), adherens junctions (mechanical link to actin cytoskeleton), and gap junctions (electrical link)
  • Cardiac muscle is striated, with similar thin and thick filaments like skeletal muscle.
  • Calcium influx through L-type Ca2+ channels is crucial for cardiac contraction

Desmosomes

  • Connect intermediate filaments from adjacent cardiomyocytes
  • Formed by a dense protein complex in intercalated disks
  • Major players: transmembrane cadherins (e.g., desmogleins, desmocollins), cytoplasmic anchors (e.g. plakophilins, plakoglobin), and cytoskeletal adaptors (e.g., desmoplakin)

Gap Junctions

  • Essential for chemical and electrical coupling of neighboring cells
  • Intercellular channels connecting cytoplasm
  • Allow passive diffusion of compounds (up to ~1000 daltons) like metabolites, water, and ions.
  • Formed from connexin proteins (12 total, 6 from each cell forming a hemi-channel, connexon)

Adherens Junctions

  • Composed of cadherins and catenins
  • Cadherins zip cells together (homophilic)
  • Link to actin cytoskeleton via catenins
  • Cell membranes become separated by 20 nm.

Action Potentials in Cardiac Muscle

  • Ventricular muscle fiber action potential averages ~105 millivolts
  • Initial spike followed by a plateau (~0.2 seconds) then repolarization.
  • The plateau in the action potential extends ventricular contraction ~15 times longer than in skeletal muscle.
  • Plateau is caused by the opening of both fast sodium channels and slow calcium (calcium-sodium) channels.

Velocity of Signal Conduction in Cardiac Muscle

  • Velocity of signal conduction in atrial/ventricular muscle fibers is ~0.3-0.5 m/sec.
  • Much slower than in large nerve fibers, (~1/250th) and skeletal muscle fibers (~1/10th)
  • Purkinje fibers have a conduction velocity as high as 4m/sec, allowing for rapid conduction throughout the heart.

The Cardiac Cycle

  • Events from one heartbeat to the next
  • Initiated by spontaneous action potential generation in the sinus node
  • Delay of more than 0.1 second for the cardiac impulse to travel from atria to the ventricles.
  • The cardiac cycle has a period of relaxation (diastole) and contraction (systole) to fill with and pump blood.

Consequences of A-V Block

  • With sudden A-V bundle block, the Purkinje system delay intrinsic rhythmical impulses for 5 to 20 seconds
  • During this delay, the ventricles fail to pump blood, causing the person to faint.
  • This delayed pickup is called Stokes-Adams syndrome
  • Prolonged delay can cause death.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

More Like This

Cardiac Muscle Cell Contractions
24 questions
Cardiac Physiology Overview
32 questions

Cardiac Physiology Overview

GlimmeringPeachTree avatar
GlimmeringPeachTree
Cardiac Physiology Quiz
39 questions

Cardiac Physiology Quiz

PolishedVeena6642 avatar
PolishedVeena6642
Use Quizgecko on...
Browser
Browser