Question | Answer |
What are the neuromuscular aspects of the conduction system? | 1 - Action potential; 2 - Resting potential; 3 - Cardiac cell membrane; 4 - Automaticity / Excitability; 5 - Depolarization / Repolarization |
What does action potential mean? | First step in the chain of events leading to contraction. ( +30 - +40 mv) |
What does resting potential mean? | Period between contractions. Inside of the cell is negative relative to the outside |
What does cardiac cell membrane mean? | Cell membrane must allow sodium in for contraction. |
What does automaticity mean? | Ability of the pacemaker cells to generate their own electrical impulses spontaneously (Characteristic is specific to the pacemaker cells.) |
What does excitability mean? | Ability of the cardiac cells to respond to an impulse. (Characteristic is shared by all cardiac cells) |
What does conductivity mean? | Ability of the cardiac cells to receive an electrical impulse & transmit it to other cardiac cells. (Characteristic is shared by all cardiac cells) |
What does contractility mean? | Ability of the myocardial cells to shorten and cause muscle contraction. (Characteristic is specific to myocardial cells) |
Which cardiac cell characteristic is considered a mechanical function of the heart? | Contractility |
What are automaticity, excitability and conductivity characteristics considered? | Electrical functions of the heart |
What is another name for phase zero (0)? | Depolarization |
What is another name for phase 1? | Start of Repolarization |
What is another name for phase 2? | Plateu (Repolarization continues) |
What happened at the end of phase 3 and the start of phase 4? | Sodium pump activated |
What is happening during phases 1 - 3? | Potassium is leaving the cell |
What does TMP stand for? | Threshold membrane potential |
What is the normal range for TMP (Threshold Membrane potential)? | -60 to -70 mv |
What is the total number of phases for a cardiac action potential? | 5 |
Where is the sinoatrial node located? | In the wall of the upper right atrium near the inlet of the superior vena cava. |
What is the normal range of impulse discharges in the SA node? | 60 - 100 beats per min |
Describe a cardiac cell - | They are long and narrow and many are brached |
Define cation - | An ion with a positive charge |
Define anion - | An ion with a negative charge |
What kind of ion is potassium (K+)? | Primary intracellular ion with a negative charge |
What kind of ion is sodium (N+)? | Primary extracellular ion with a positive charge |
What is another name for periods of stimulation? | Depolarization |
What is another name for periods of rest? | Repolarization |
Define P-wave - | Depicts atrial depolarization or the spread of the impulse from the SA node throughtout the atria |
PR-interval - | Represents the time from the onset of atrial depolarization to the onset of ventricular depolarization |
Define PR-segment - | The short isoelectric line between the end of the P-wave to the beginning of the QRS complex |
What is the PR-Segment used for? | As a baseline to evaluate elevation or depression of the ST segment |
QRS complex - | Depicts ventricular depolarization or the spread of the impulse throughtout the ventricles |
ST-Segment - | Represents the end of ventricular depolarization & the beginning of ventricular repolarization |
T-wave - | Represents the latter phase of ventricular repolarization |
QT-interval - | Represents both ventricular depolarization & repolarization |
What are the three types of muscle tissues? | 1 - Skeletal; 2 - Visceral; 3 - Cardiac |
Describe skeletal muscle tissues - | Striated; Responses to commands |
Describe visceral muscle tissues - | Smooth; Involuntary |
Describe cardiac muscle tissue - | Striated; Involuntary (can generate its own electrical output) |
What is the normal range for RMP (resting membrane potential)? | -80 to -90 mv |
What makes up the His-Purkinje System? | Bundle of His, Right and Left bundle branches & Purkinje Fibers |
What does PEA stand for? | Pulseless Electrical Activity |
What does a cardiac cycle consist of? | One heart beat or one P,QRS & T sequence |
How is the delay of the AV node represented on the ECG tracing? | The flat line of the PR interval |
What are the threee main functions of the AV node? | Slow conduction of the electrical impulse; Serve as a backup pacemaker to the SA node; Block some impulses when the rate is high |
What does ANS stand for? | Autonomic Nervous System |
What are the two majior divisions of the automatic nervous system? | 1 - Sympathetic nervous system; 2 - Parasympathetic Nervous System |
Which division of the ANS is the brake? | Parasympathetic |
What kind of receptor is the parasympathetic Nervous system? | Cholinergic |
What does Acetylcholine do to the ANS? | Decrease in the Heart rate, conduction, contractility (SA/AV) |
Which division of the ANS speeds things up? | Sympathetic |
What kind of receptor is the Sympathetic nervous system? | Adranergic |
What does norepihephrine do to the ANS? | Increases Heart Rate, conduction, & contractility |
Heart Rate = | Chronotropic (from chrono-, meaning time; Affecting the rate of rhythmic movements) |
Conduction = | Dromotropic |
Contractility = | Inotropic |