Heart Physiology 2 Flashcards
Define syncytium
One cellular mass formed by the fusion of smaller cells or nuclei division
Structures attaching adjacent cardiac myocytes
Intercalated Discs
Name the 2 types of membrane junctions found in intercalated discs
1) Desmosomes
2) Gap Junctions
Where are action potentials in the heart initiated?
at the SA node (in right atrium by superior vena cava)
Action potentials in the heart open intramembrane protein channels, allowing which ion to enter the myoplasm and trigger muscle contraction?
Calcium
What is the approximate duration of a ventricular cardiac action potential?
~.25-.30 sec
(250-300 msec)
What is the amplitude of a typical ventricular muscle cell action potential? What is the resting potential? What is the peak?
1) Amplitude ~110-120
2) Resting potential ~ -90mV
3) Peak Potential ~+20-30mV
Label the following ventricular action potential diagram.
Label this Wiggers Diagram; Draw your own
What is typical left atrial pressure?
10-15 mmHg
The P wave indicates what event?
Atrial Contraction
What is peak left ventricular pressure during systole?
120 mmHg
What is the nadir of left ventricular pressure during diastole?
0 mmHg
What is peak aortic pressure during systole?
120 mmHg
What is the nadir of aortic diastolic pressure?
80 mmHg
When might you hear a split heart sound?
When 2 AV valves close at different times. Or when 2 semilunar valves close at different times.
What is end-diastolic volume of the left ventricle?
~135mL
What is end-systolic volume of the left ventricle?
~65 mL
What is the source of heart sound 1?
Closing of Mitral and Tricuspid (AV) valves
What is the source of heart sound 2?
Closing of aortic and pulmonary (semilunar) valves.
Describe what an EKG is really measuring.
Measures extracellular electric potential AT BODY SURFACE induced by cardiac action potential that travels through body fluid and reaches the electrodes. Amplitude of actual EKG is only 1-2 mV while heart cell amplitude is ~120mV
The T wave indicates what event?
Ventricular Repolarization
The space between the P wave and Q wave indicates what process?
AV nodal delay
The space between the S and T wave indicates what process?
Uniform depolarization accross ventricle - Ventricular Action Potential Plateau
Describe systolic events.
Systole begins with QRS action potential leading to contraction of ventricles. Mitral valve closes because of increased left ventricular pressure and isovolumetric contraction occurs until aortic valve opens and blood is ejected from the ventricle. Systole ends when the aortic valve opens.
Describe diastolic events.
**Diastole begins when aortic valve closes and isovlumetric relaxation occurs until mitral valve opens. The ventricles then fill because of a pressure differential and the contraction of the atria. Diastole ends when the mitral valve closes after a ventricular contraction begins. **
What is the pacemaker of the heart?
Sinoatrial node
What is the purpose of the Sodium/Calcium Exchange protein?
Creates very large calcium concentration differential between inside and outside of cell
What is the resting potential of cardiac myocytes bothe in atria and ventricles?
~-90mV
What are fast response action potentials?
Ventricular/atrial/Purkinje fiber action potentials
What are slow-response action potentials?
SA and AV node action potentials
What is the name of the abnormal bypass tract connecting the atria and ventricles parallel to the AV node?
Bundle of Kent
Label this diagram
Label this
What are some causes of heart arrhythmia?
1) SA node is too slow and pacemaker activity of AV node or Purkinje fibers occurs
2) Presence of bypass tracts paralell with AV node
3) Conduction block that re-routes action potential pathway
4) Reentrant loop - self-sustaining electrical current in part of heart
