Heart pt 2

• myocardial infarction (MI)


  A complete obstruction to blood flow in a coronary artery also called as heart attack
• intercalated discs


  The ends of cardiac muscle fibers connect to neighboring fibers by irregular transverse thickenings of the sarcolemma called
• desmosomes


  Anchoring junctions that prevent cells from being pulled apart
• gap junctions


  allow muscle action potentials to conduct from one muscle fiber to its neighbors
• autorhythmic fibers


  Specialized cardiac muscle fibers that repeatedly generate action potentials that trigger heart contractions
• • cells that repeatedly and rhythmically generate action potentialsPACEMAKER CELLS -

  autorhythmic cells
• sets the rhythm for the contraction of entire heart

  pacemaker
• • the route that delivers action potentials throughout the heart muscle
  • a network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart

  cardiac conduction system
• The next phase of an action potential in a contractile fiber is the ______, a period of maintained depolarization

  plateau
• The recovery of the resting membrane potential during the _______ phase of a cardiac action potential resembles that in other excitable cells

  repolarization
• • a complete heartbeat consisting of contraction and relaxation of both atria and both ventricles
  • both atria relax, ventricles contract
  • both atria contract, ventricles relax

  cardiac cycle
• the phase of CONTRACTION of a chamber of the heart

  systole
• the phase of RELAXATION of a chamber of the heart


  diastole
• record of the electrical activity of the heart

  electrocardiogram
• instrument used to record the electrical activity of the heart

  electrocardiograph
• • atrial depolarization
  • The first, called the ____, is a small upward deflection on the ECG

  P wave
• • The second wave, begins as a downward deflection, continues as a large, upright, triangular wave, and ends as a downward wave.
  • represents rapid ventricular depolarization, as the action potential spreads through ventricular contractile fibers.

  QRS complex
• • The third wave is a dome-shaped upward deflection called the
  • It indicates ventricular repolarization and occurs just as the ventricles are starting to relax

  T wave
• • Analysis of an ECG also involves measuring the time spans between waves, which are called...

  intervals or segments
• is the time from the beginning of the P wave to the beginning of the QRS complex. It represents the conduction time from the beginning of atrial excitation to the beginning of ventricular excitation

  P-Q interval
• begins at the end of the S wave and ends at the beginning of the T wave, represents the time when the ventricular contractile fibers are depolarized during the plateau phase of the action potential

  S-T segment
• extends from the start of the QRS complex to the end of the T wave. It is the time from the beginning of ventricular depolarization to the end of ventricular repolarization

  Q-T interval
• a person wears a battery operated monitor that records an ECG continuously for 24 hours

  continuous ambulatory electrocardiography
• lasts about 0.1 sec, the atria are contracting. At the same time, the ventricles are relaxed


  Atrial Systole
• volume of blood in the ventricle at the end of diastole

  end-diastolic volume (EDV)
• ventricular contraction


  ventricular systole
• period of time when cardiac muscle fibers are contracting and exerting force but not shortening

  isovolumetric contraction
• period of time when both semilunar valves are open and blood begins to leave the heart

  ventricular ejection
• volume of blood remaining in each ventricle after systole

  end-systolic volume (ESV)
• • The amount of blood ejected from the heart in one contraction
  • the volume ejected per beat from each ventricle, equals end-diastolic volume minus end-systolic volume: SV = EDV − ESV

  Stroke volume
• the rebound of blood off the closed cusps of the aortic valve

  dicrotic wave
• period when all four valves are closed and ventricular blood volume does not change

  isovolumetric relaxation
• the act of listening to sounds within the body, is usually done with a stethoscope

  Auscultation
• is the volume of blood ejected from the lef ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute

  Cardiac output (CO)
• the volume of blood ejected by the ventricle during each contraction, multiplied by the heart rate (HR), the number of heartbeats per minute

  stroke volume (SV)
• is the difference between a person's maximum cardiac output and cardiac output at rest

  Cardiac reserve
• the degree of stretch on the heart before it contracts

  preload
• the forcefulness of contraction of individual ventricular muscle fibers

  contractility
• the pressure that must be exceeded before ejection of blood from the ventricles can occur

  afterload
• Within limits, the more the heart fills with blood during diastole, the greater the force of contraction during systole. This relationship is known as the

  Frank-Starling law of the heart