02/05 Flashcards
1% of cardiomyocytes are
Pacemaker cells
Describe pacemakers
- Can spontaneously depolarize
- No resting membrane potential
What is the pacemaker of the heart?
The SA node
The SA node depolarizes at
80 to 100 beats per minute
The Av node depolarizes at
40 to 60 beats per minute
Purkinje fibers depolarize at
20 to 40 beats per minute
The cells of the atria are connected via
Gap junctions
What are the three phases of AP in cardiomyocytes?
- Depolarization
- Plateau Phase
- Repolarization
Why does skeletal muscle experience tetany?
It has a short refractory period
How is the refractory period in cardiac muscles?
Long
The heart rate is set by
The rate of depolarization / AP generation
What is displayed by an EKG / ECG?
Waves show what is happening in the heart with respect to depolarization and repolarization
What is the P wave?
The first wave that shows first electrical activity and is associated with atrial depolarization
What is the QRS complex wave?
Wave associated with ventricular depolarization and atrial repolarization
What is the T wave?
Wave that shows ventricular repolarization
What does the P-R interval say?
How long it takes for AP to get transmitted through whole conduction system
Systole means
Contraction
Diastole means
Relaxation
80% of the blood in the ventricles is filled
Passively
What happens during Isovolumetric contraction?
Both AV and SL valves are closed
Isovolumetric contraction happens when
Ventricles contract
What happens during Ventricular Dejection?
Pressure in ventricles is enough to open SL valves and blood is ejected out of the ventricles
When ventricles relax there is
Isovolumetric relaxation
What happens during isovolumetric relaxation?
All valves are closed and there is atrial relaxation
