16 Electrophysiology of the Heart Flashcards
-this allows the cardiac muscle fibers to act as a functional syncytium so that the atria and ventricles can contract as a unit
-provides low resistance for the spread of excitation from one cell to another
gap junctions
Type of muscle that is involuntary and striated
Cardiac muscle
____ muscle fibers are shorter and less circular than ____ muscle fibers.
Cardiac
skeletal
-Adjacent cardiac myocytes are joined end to end by ____
-contain desmosomes and gap junctions
intercalated discs
What hold cells together
Desmosomes
In cardiac muscle cells, action potentials are conducted from ____ while in skeletal muscle cells, action potentials are conducted along the length of a ____
cell to cell
single fiber
Propagation is slow in this muscle because of gap junctions and the small diameter of fibers
cardiac muscle
Propagation is fast in this muscle because of the larger diameter fibers
skeletal muscle
The movement of extracellular Ca2+ through the plasma membrane and T tubules into sarcoplasm stimulates the release of Ca2+ from the sarcoplasmic reticulum
calcium-induced calcium release (CICR)
What are the Action Potential stages in Cardiac Muscle
Depolarization
Plateau
Repolarization
Refractory period
refers to all events associated with blood flow through the heart from the start of one heartbeat to the beginning of the next
The Cardiac Cycle
During a cardiac cycle, each
heart chamber goes through two divisions
systole
diastole
This represents ventricular filling
Diastole
This represents ventricular contraction/ejection
systole
Which valve closure causes the “lub” heart sound
Atrioventricular valves (tricuspid & mitral valve)
Which valve closure causes the “dub” heart sound
Semilunar valves (pulmonary & aortic valves)
involves listening to body sounds, usually with a stethoscope
Auscultation
The first heart sound is produced when the ventricles ____ and the ____ valves close
contract
AV
The second heart sound is produced when ventricular ____ begins and the ____ valves close
relaxation
semilunar
It is a prolonged series of auditory vibrations emanating from the heart or blood vessels that may occur at different times during the cardiac cycle
Cardiac murmurs
What are the 3 Cardiac murmurs
Systolic murmurs
Diastolic murmurs
Continuous murmurs
murmurs (between S1 and S2) result as blood regurgitates through incompetent AV (mitral and tricuspid) valves, or as blood is ejected through the semilunar (aortic and pulmonary) valves or a ventricular septal defect.
Possible causes of this murmur include aortic stenosis, pulmonic stenosis, mitral insufficiency, tricuspid insufficiency, interventricular septal defect, interatrial septal defect, and functional (physiologic) murmurs and Tetralogy of Fallot.
Systolic murmurs
A murmur heard after S2 is designated as diastolic. While pure diastolic murmurs are extremely rare in dogs and cats, they are not uncommon in horses. These murmurs are observed in mitral or tricuspid stenosis, pulmonic insufficiency, aortic insufficiency, and innocent diastolic murmurs.
Diastolic murmurs
This murmur is continuous during systole and diastole. In the patent ductus arteriosus (PDA), the fundamental pathophysiologic event is the shunting of blood through the patent duct. The flow direction is usually from the left (aorta) to the right (pulmonic artery) side because of the pressure gradient, but with larger ducts, which are uncommon, the flow ceases or can even be from the right to the left side (so-called reversed PDA).
Continuous murmurs
-Record of electrical events in the myocardium that can be correlated with mechanical events
-With each beat, an electrical impulse (or “wave”) travels through the heart
electrocardiogram (ECG)
electrical voltages generated by the heart are recorded by the ____ from the surface of the body. P, Q, R, S, and T waves are reflected
electrocardiograph
(wave) is the spread of depolarization through the atria, and this is followed by atrial contraction
P wave
(waves) represent the depolarization of the ventricles (contraction of the ventricles)
QRS waves
(wave) shows the repolarization of the ventricles
T wave
interval that extends from the start of atrial depolarization to the start of ventricular depolarization (QRS complex) contract and begins to relax
PR interval or PQ interval
interval that is the time required for ventricles to undergo a single cycle of depolarization and repolarization. This interval can be lengthened by electrolyte disturbances, conduction problems, coronary ischemia, and myocardial damage
Q-T interval
