Heart Flashcards
What is the cardiac cycle?
Events occuring from one heartbeat to the next.
Define end diastolic volume
Amount of blood in ventricles before systolic ( or filling in )
Define end systolic volume
Lowest volume of blood in ventricle during cardiac cycle, at end of contraction.
Ejection fraction
fraction of EDV ejected per cardiac cycle
Describe the electrical conduction pathway in the heart
SA node –> AV node –> Bundle of His –> Bundle Branch –> purkinje fibers
Describe intercalated disc:
Heart cells connected by discs working as one functional organ in synchronization.
Describe a gap junction
Intercellular connection between cells that connects cytoplasm of 2 cells to allow electrical impulses to pass directly.
What is the Frank-Starling Mechanism?
Heart automatically pumps incoming blood . The amount pumped is determined by the rate of blood flow into the heart.
Increase volume of blood stretches ventricles causing cardiac muscle to contract more forcefully.
What is preload?
Pressure as ventricles fill with blood at end of diastole.
What is afterload?
Afterload refers to the forces that oppose ejection of blood out of the chamber.
Name 2 similarities of Cardiac and Skeletal Contraction
Both striated with myosin/actin.
Both have the t-tubule mechanism acting on sarcoplasmic reticulum.
Name 3 differences of Cardiac and Skeletal Contraction
T tubule Mechanism has direct diffusion of Ca++ for larger amounts of storage.
Action potential has cardiac muscle plateau for longer time of contraction than skeletal mm.
Strength of contraction varies and is dependent on extracellular Ca++.
Ability of cardiac muscle to depolarize and contract is extrinsic or intrinsic?
Intrinsic
Does the SA node have small or large fibers?
Small diameter
Are there contractile muscle fibers in the SA node?
Almost none.
Where does the SA node connect to?
Atrial muscle fibers.
Cell membranes of the SA node are naturally ____ to NA+ and CA++? Why?
LEAKY. Less negative resting membrane potential for easier SELF excitation.
SA node and AV node make up which part on an ECG?
P-wave
Bundle branches make up which part on an ECG?
Q aspect
Purkinje fibers make up which part on an ECG?
QRS
Events that occur within the cardiac cycle are..
1) Chamber and vessel blood volume changes
2) Chamber and vessel blood pressure changes
3) Electrical activity
4) Heart sounds occur
5) Valve opening/closing
What is the p-wave?
depolarization of atrial tissue
What is the QRS complex?
depolarization of ventricular tissue, repolarization of atrial tissue
What is the t-wave?
repolarization of the ventricles; relaxation
