Electrical Conduction
Strands and clumps of specialized cardiac muscle contain only a few myofibrils, and are located throughout the heart. These areas initiate and distribute impulses through the myocardium
Cardiac Conduction System
The ability of cells to respond to electrical impulses
Excitability
Effect of the strength of contraction
inotropic effect
Occurs when alpha receptors are stimulated, resulting in vasoconstriction
Alpha effect
Process of electrical discharge and flow of electrical activity
Depolarization
6 parts of Cardiac Conduction system
1) Sinoatrial node (SA)
2) Atrioventricular node (AV)
3) Bundle of HIS,
4) Right bundle Branch
5) Left Bundle branch
6) Purkinje Fibers
The ability of the cells to conduct electrical impulses
conductivity
Sense changes in the chemical composition of the blood
Chemoreceptors
Occurs when beta receptors are stimulated, resulting in increased inotropic, dromotropic and chronotropic states
Beta effect
Once cardiac cells depolarize, they begin to return to their resting or polarized state
Repolarization
Is a small mass of specialized tissue just beneath the epicardium in the right atrium. Located near the opening of the superior vena cava with fibers continuous with those of the atrial syncytium. Generates the heart's rhythmic contractions -- often referred to as the pacemaker.
Sinoatrial (SA) node
Cardiac cells possess an ability to generate an impulse to contract even when there is no external nerve stimulus
automaticity
Respond to changes in pressure, usually within the heart or main arteries.
Baroreceptors
May be given as a cardiac drug; has a greater stimulatory effect on beta receptors
Epinephrine
Early phase of repolarization -- cell contains such a large concentration of ions that it cannot be stimulated to depolarize
Absolute refractory period
Impulses originating in the SA travel through the right and left atria -- resulting in atrial contraction. Then travels to the ____, located in the right atrium adjacent to the septum, beneath the endocardium where it transiently slows.
Atrioventricular (AV) node
effect of the rate of contraction
Chronotropic effect
Slows the heart rate
Parasympathic stimulation
may be given as a cardiac drug; has predominant stimulatory actions on alpha receptors
Norepinephrine
In latter phase or repolarization -- cells are able to respond to a stronger than normal stimulus
Relative refractory period
Electrical stimulus goes from AV and continues towards the ____; a continuation of the AV.
Bundle of HIS
Effect of rate of electrical conduction
Dromotropic Effect
Sympathetic Stimulation
The resting cell normally has a net negative charge with respect to the outside of the cell
Polarized state
Used to record electrical changes in the myocardium during the cardiac cycle
Electrocardiogram (ECG)