CARDIO-conduct Flashcards
Which cell set basic cardiac rhythm?
Pacemaker cells- Independent of neurons. triggers electrical conduction for chambers to contract. Located in bundles called Sinoatrial (sinus- atrium R-superior. Can pump on its own w/o CNS +/-. More + -55mv vs 90mv cardiac cell
Which cell carry the signal from pacemaker cells?
Conducting cell
This cell contracts the chambers?
Contracting cell
What is purpose of AV node?
collect and integrate signal from the sinoatrial node and trigger the impulse to stimulate ventricular contraction. Purposeful delay for filling time.
Where is the bundle of His?
Atrioventricular septum, inferior to Atium
What forks at the end of Bundle of HIS?
L and R bundle branches within ventricular septum.
What fibers wrap around towards apex into the ventriuclar wall?
Purkinje fibers- conducting cells, carry signal only
Nerve cells conduct electrical signal, how is it carried?
Action potential- diff of electical voltage inside and outside cell. AT REST- membrane is NEG. Inside K NEG. Outside is POS Ca, Na
How do contracting cells work?
MSK- internal cytoplasm of cell, chemcial, ion, electrolye, will trigger contraction via ions w/in cell membrane that move in and out
What is theory of cell membrane channels?
Nerve conducts electricity to cell membrane channles _open_closed_inactivated_closed_open. Not all or none. Channels occur in 2-3 states
What cause the movement btwn channels?
Cell membranes Action potential/Electical voltage. AFTER PUMP- Membrane neg charged
What is depolarization?
Positive Membrane potential in HEART after pumping blood out, then resting Membrane NEG. -55mV_NA influx INC to more + 30 mv
What occurs at ++30mV?
Contraction
During the plateue phase what is happening with Na, CA, K?
Na- DEC not going in.channel closed. Ca channel open but SLOW influx. 3. K- DEC not moving inside to outside.
During repolarizatin, what ions are moving?
Relaxing repolarization. Ca closed, stops moving inside. K-close, bring cell membrane back to NEG and resting.
How are channels gated/opened?
Ligands- binding of protein or chemical signal that starts chain reaction 2. Voltage gate via ions, electrolytes- THRESHOLD state
what occurs when threshold is met in pacemaker cells?
Threshold- predominant ion channel opening via electrical voltage. Gates are proteins. Spontaneous and often open, close, inactive. Random, not all or none. Neg 40mv is threshold for pacemaking cells/SA node. Ca gates slow opening/predominant channel. K channel closed
What is speed of each cardiac channel?
NA-fast and slow, Ca- ALWAYS SLOW, K- slow med.
Are sodium channels open or closed during resting membrane potential?
inactive Na channels at rest. BUT 1ST TO OPEN, BC FAST LEAKY
What makes pacemaker quick to reach threshold?
leak of Na due to easy membrane permeability
Resting membrane potential of cardiac cell is -55mv. Pacemaker threshold is -40, slightly more positive/depolarizing, not much of jump btwn
What drives depolarization/ positive membrane action potential?
Fast/slow Na leak and slow Ca influx. Both + ions_then K leak out (opposite of Na)
What is responsilbe for the falling phase of action potential?
K channel opens up fully, Na leaves the cell making cell MORE NEGATIVE again. K concenration HIGH inside cell. K flux resets cell voltage to resting negative potential -55mv
What is responsilbe for the opening phase of action potential?
Sodium and Calcium (T and L channels)
What phase is upstroke d/t opening of voltage gated sodium/calcium channels?
Phase 0
What phase is repolarization d/t inactivation of sodium/calcium channels and opening of potassium channels?
Phase 3
What phase is resting, d/t slow leak of sodium into cell, moves that membrane potential back toward its threshold?
Phase 4
What mainly drives cell from resting to threshold threshold- theory hyperpolarization?
Slow leak of Na into cell
At what voltage does K channel open?
After depolarization and plateau. HIGHer voltage, 0-10mv, as Na, Ca gates become inactive
Why are conduction cells needed?
chambers that contain the cells are electrically insulated via cardiac skeleton
What does the cardiac skeleton protect?
SA node signal is blocked from getting to ventricle_ATRIOVentricular NODE completes conduction
Describe signal pathway
SA node- R and L atria_AV node_Bundle of His_L/R bundle branch_purkinje_ventricles
What is the delay in the AV node?
Time it take for SA node to accumulate enough signal to reach pacemake cells in AV node threshold. Provide filling time for ventricles.**
What are conduction times and bpm for each node?
- SA- AV- 0.03, 60-100, 2. Passage through AV node-0.12, 40-55pbm. 3. Purkinje- 25-40. Total 0.16 to ventricle
What is difference in contracting cells?
Phase 0- fast Sodium channel causes fast/sharp slope. NOT autorhymic. Phase 4 flat
What is the plateu phase 1-2?
Na stops, Ca slow open, K stops
What is MC sinus rythmn?
72bpm, higher than 60 bc SNS dominate our Basal HR. Low or High is ANS activation
What happens if the SA node is dysfunctional?
AV node picks up, but 40-55bpm. Rate slower
What does NSR mean?
Normal sinus atrial rhythm. 60-100bpm, intact SA node. Normal rate originating from SA node
P-wave present mean NSR
What does SA node fire signify?
P-wave Atrial contraction. Atrial depolarization.
What signifis AV node is intact?
QRS spike, depoloariztion of ventricles. Ventricular contractions. Q dips-AP_ rises to R+platue sustain contracion
What on EKG gives info on repolariztion?
repolarization/falling phase= ALL Q-T interval
What does EKG provide?
Info on the conduction system of heart.
What is normal change in rate in very short periods of time, related to changes in thoracic pressure when we breathe?
Respiratory sinus arrhythmia- gaps btwn beats, auscultate well
What is sawtooth pattern / no p-wave?
Conductin d/o Atrial Flutter- self stimulatin, reentry circuit. NO p-wave. Flutter waves. AV node fires_ Goes down to ventricle_reenter atrium. Double tap
What is bag of worm appearce on EKG, no p-wave?
A. Fib- Wall of chamber not contracting consistently, random pattern. Less consistent rythm vs A. flutter.
What is normal EKG for a period of time, and then onset of an atrial tachycardia, and you lose these P waves?
paroxysmal atrial tachycardia.
What is NSR, then next beat is absence of a discernable P wave?
premature atrial contractions- Premature= waveform abnormal
What is signs of AV node dysfunctin?
AV Blocks _1st deg-LONG PR= long time of SA node to stimulate AV for Ventric depolorization _2nd deg- multiple p wave close intermittently _3rd deg. no consistent relationship between P and QRS complex. Close or far P wave, 1+P wave b4 QRS. Few QRS, rate slow
What occurs when ventrical fire on it’s own, even with proper conduction?
Premature ventricular contractions- waveform abnormal. Spike is WIDE
What are wide spikes at high rate?
Ventricual tacyhcardia
What are bag of worm, larger worms, inconsistent waveforms?
Ventricular fibrilation
