Chapter 3 Flashcards
Responsible for controlling the rate and rhythm of the heart by coordinating regular depolarization and are found in the electrical conduction system of the heart
Specialized group
Responsible for generating the physical contraction of the heart muscle
Myocardial working cells
Refers to the point at which a stimulus will produce a cell response
Threshold
The ability of cardiac pacemakers cells to generate their own electrical impulses spontaneously without external (or nervous) stimulation
Automatically
The ability of cardiac cells to respond to an electrical stimulus, a characteristic shared by all cardiac cells
Excitability
The ability of cardiac cells to receive an electrical stimulus and then transmit it to other cardiac cells
Conductivity
The ability of cardiac cells to shorten and cause cardiac muscle contraction in response to an electrical stimulus (also referred to as rhythmicity)
Contractility
A substance or compound whose molecules dissociate into charged components, or ions, when placed in water, producing positively and negatively charged ions
Electrolyte
An ion with a positive charge
Cation
An ion with a negative charge
Anion
Location and function of automaticity
SA node, AV junction, purkinje network fibers.. Electrical
Location and function of excitability
All cardiac cells.. Electrical
Location and function of conductivity
All cardiac cells.. Electrical
Location and function of contractility
Myocardial muscle cells.. Mechanical
(K)
Potassium
(Na)
Sodium
(Ca)
Calcium
(Mg)
Magnesium
Three major cations that affect cardiac function
Potassium (K), sodium (Na), and calcium (Ca)
Anion examples
Phosphorus (P) and chloride (CI)
What plays a major roll in cardiac depolarization and repolarization
Potassium (K)
What plays a vital roll in depolarization of the myocardium
Sodium
An increase in sodium blood levels is known as
Hypernatremia
A sodium deficit is known as
Hyponatremia
An increase in potassium blood levels is known as
Hyperkalemia
A deficit in potassium blood levels is known as
Hypokalemia
State of a cardiac cell in which the inside of the cell membrane is negative compared with the outside of the cell membrane; exists when cardiac cells are in the resting state
Resting membrane potential
Change in polarity; a five phase cycle that produces changes in the cell membranes electrical charge; caused by a stimulation of myocardial cells which extends across the myocardium; propagated in an all-or-none fashion
Action potential
Cardiac muscle cell groups that are connected together and function collectively as a unit
Syncytium
Resting state of a cardiac cell, wherein the inside of the cell is electrically negative relative to the outside of the cell
Polarized state
The ability of the cell membrane to change to allow the movement of ions
Permeability
Electrical occurrence normally expected to result in myocardial contraction; involves the movement of ions across cardiac cell membranes, resulting in positively polarity inside the cell membrane
Depolarization
Process whereby the depolarized cell is polarized and positive charges are again on the outside and negative charges are on the inside of the cell; a return to the resting state
Repolarization
What has an important function in myocardial depolarization and myocardial contraction
Calcium
An increase in calcium blood levels is known as
Hypercalcemia
A calcium deficit is defined as
Hypocalcemia
At the cells resting state potassium ion concentration is greater
Inside the cell
In the resting state of the cardiac cell sodium ions is greater
Outside the cell
The refractory period of atrial muscle lasts approximately
.15 seconds
The ventricular muscle contracts at approximately
.25 to .3 seconds thus atrial contractions can be much faster
Stage of cell activity in which the cardiac cell cannot spontaneously depolarize
Absolute refractory period
The period when repolarization is almost complete, and the cardiac cell can be stimulated to contract prematurely if the stimulus is much stronger than normal
Relative refractory period
