Electrical Properties of the Heart and Conduction System Flashcards
SA Node
Sinoatrial Node. Normal site of origin of the electrical impulse. The hearts natural pacemaker. SA node travels through the right and left atria resulting in the atrial contraction.
AV Node
Atriocentricular node. Transiently slows electrical impulse.
Bundle of His
A continuation of the AV node. Bundle branches procede the Bundle of His.
Pukinje Fibers
Fibers that go to the left and right ventricles.
Excitability
The ability of cells to respond to electrical impulses.
Conductivity
The ability of cells to conduct electrical impulses.
Intrinsic Automaticity
The ability to generate an impulse to contract without the need of a nerve stimulus. (CARDIAC CELLS)
Chronotropic State
Hearts rate of contraction (monitored by various systems in the body)
Dromotropic State
Hearts rate of electrical conduction (monitored by various systems in the body)
Inotropic State
Hearts strength of contraction (monitored by various systems in the body)
Chemoreceptors
Detect chemical changes in the blood.
Baroreceptors
Sense the pressure in the heart or arteries.
Contractility
Strength of heart muscle contraction.
Parasympathetic Stimulation
Slows heart by affecting AV node
Sympathetic Stimulation
Alpha OR Beta effects; depending on what nerve receptor is stimulated.
ALPHA effects
Alpha receptors are stimulated resulting in vasoconstriction
BETA effects
Beta receptors are stimulated resulting in increased inotropic,dromotropic, and chronotropic states.
Epinephrine
Hormone that has a greater stimulatory effect on BETA receptors.
Norepinephrine
Hormone that has a greater stimulatory effect on ALPHA receptors.
Electrolytes
IONS. Charged chemicals.
Na+
Sodium. Concentration is greater OUTSIDE of the cell.
K+
Potassium. Concentration is greater INSIDE of the cell.
Ca2+
Calcium.
Electrical Potential
Cellular Electrical Charged difference across the membrane. Measured in Millivolts.
Resting Cell
Negative Electrical Pote - Extracellular space is more positively charged than the intracellular space.
Polarized State
Resting cells normally have a NET negative charge with respect to the outside of the cell.
Depolerization
Heart cell gets a stimulus from the conduction system. Sodium (Na+) rushes in, along with some calcium (Ca2+). Changing the charge of the cell. Makes the intracellular slightly positive charged.
Repolarization
The process in which the cell can get back to the POLERIZED state (net negative).Depolerization slows down…Potassium (k+) starts to flow out of the cell, and the sodium potassium pump starts to activate based on the charge needs of the cell to keep it at a polarized state (net negative).
Absolute Refractory Period
EARLY phase of repolarization when the cell contains a large concentration of ions that it cannot be stimulated to depolerize.
Relative Refractory Period
LATE stage of repolarization, cells are able to respond to a stronger stimulus.
ECG
Electrocardio gram a graphic recording of the electrical activity of the heart
P wave
Occurs first. Represents the electrical impulse through the atria
P-R
Flat line between the p and r… Represents the time delay within the AV node
QRS
QRS complex. Represents the DEPOLARIZATION of the ventricle contraction.
ST segment
The pause after the QRS complex. This is where repolarization is beginning.
T
Represents completion of REPOLARIZATION.
Cardiac Cycle
From contraction of the myocardium to the next contraction
Systole
Ventricular contraction. Blood is pumped to the body (systemic) and lungs (pulmonary) via contraction of the ventricles.
Afterload
Pressure in the AORTA.
Stroke volume
Amount of blood ejected into the aorta from the left ventricle per contraction
Cardiac output
Expressed as the volume of blood pumped through the circulatory system in one minute. LITERS PER MINUTE
Heart rate X stroke volume = cardiac output (lpm)
