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What is automaticity?
- Ability of cardiac pacemaker cells to spontaneously initiate an electrical impulse without being stimulated by a nerve.
- Is nice because it acts as a backup if a node drops out.
- Can be bad if a rogue cell initiates a new heart beat.
- *very unique to cardiac cells.
What is excitability?
Ability of cardiac muscle cells to respond to an outside stimulus.
Ability to pass electricial current from cell to cell.
Abilty of cell to respond with contraction by shortening.
True/False: Brain and heart can utilize ATP for energy for repolarization of cells.
- Heart and brain can only use O2 for repolarization which is why escemia is so bad for them.
How is calcium involved in action potentials?
Ca+ is involved in contractility.
Which elyte acts as an acid?
Why is sodium important to cardiac action potentials?
- Because sodium is the first to cross the membrane to depolarize the cell.
- Digoxine is the most popular sodium channel drug.
What do action potentials during depolarization look like?
- ECG is just an average of all action potentials at any give time.
- DOES NOT MEASURE ACTUAL, MECHANICAL FUNCTION, ONLY ELECTRICAL ACTIVITY.
What do you need to know about the SA node?
- Rate = 60-100
- Clinically known as "sinus," i.e., NSR (normal sinus rhythm.)
- May create P wave.
What do you need to know about the AV node?
- Normal rate = 40-60/min
- Acts as a filter to prevent overstim from SA
- Will appear on ECG when no P wave but has a narrow QRS.
What is Atrial kick?
Atrium squirts blood into ventricles creating "extra" volume in ventricles-->^cardiac output.
What do you need to know about IVR
(Idioventricular pacer cells)
- Does not play into atrial kick.
What can a pt look like when he/she has low cardiac output?
- Do not rely on BP as measure of CO
- Skin is cool (no circulation to SQ tissue)
- Skin has gray tone
- Diaphoresis, “cool clammy” feel
- May or may not have ↑ JVD (good thing to document).
- Low urine output
- Change in LOC
- Orthostatic BP
- Positional Orthopnea
- Rhythm disturbances
- May have chest pain or discomfort
- Tachycardia if not on Beta-Blocker type drug
Assessment skills are vital to put the picture together.