C-1a Flashcards
CARDIAC CYCLE - ELECTRICAL
Cardiac conduction system
Consists of:
Theory:
Movement of action potentials:
Consists of specialized cardiac cells
- can GENERATE and CONDUCT action potentials ( impulses) by themselves - they are NOT neurons.
Theory: any area of cardiac cells in the heart can perform these functions > seen in arrhythmias
Movement of action potentials: progresses along a SPECIFIC PATHWAY.
: allows heart chambers to contract in a SPECIFIC SEQUENCE- necessary for proper function.
Components of cardiac conduction system Sinoatrial Node: Location: What it's made of: It's responsibility:
Sinoatrial node: located in the upper ( superior lateral)part of the atrium. Referred to as the hearts pacemaker- collection of cells.
- specialized cardiac cells that spontaneously generate action potentials- NO STIMULATION from the nervous system
- activity of generating AP’s is rhythmic
- time between APs is same
- one AP stimulates the next AP, the trigger for the next is always the previous one
Cardiac conduction system
Atrial cardiac cells- how they work?
APs from the SA node
Spread throughout both the right and left atria simultaneously b/c connected through intercalated discs
Causes both atria to contract together
Cardiac conduction system
Atria are separated from the ventricles by;
Fibrous connective tissue hat is used to support valves does not conduct APs
EXCEPT: at an opening in the connective tissue - located in the inferior portion of the inter atrial septum.
This is the location of the AV node ( atrial ventricular)
Cardiac conduction system
AV node; what does it do?
Specialized CONDUCTING cardiac cells
- conduct APs SLOWER than the cells in the SA node
- slow down impulses, before getting to the ventricles
- allows the atria to FINISH CONTRACting, before the VENTRICLES contraction.
Cardiac conduction system
When an AP leaves the AV node :
The sequence that follows.
Continues through more specialized conducting tissues- DERIVED from MODIFIED myocardial cells
- AV node - inferior aspect of interstitial septum
- Atrioventricular bundle ( bundle of HISS) / superior aspect of interventricular septum
- Rt & Lt bundle branches- travel along interventricular septum in their respective sides
- Perkinjie fibers/ within ventricle walls
- Ventricular cardiac cells- intercalated discs
Cardiac conduction system
Once the AP has reached the Bundle of HISS
The IMPULSE VELOCITY begins to INCREASE, continues to INCREASE all the way through purkinjie fibers
- Impulse velocities: SA node thru atria 1m/sec
- AV node .03-.05m/sec (20x slower than SA)
- bundle of hiss toPurkinjie fibers 5.0m/sec (100x faster than AV)
- Because of this rapid increase in velocity thru ventricles - ventricular contraction begins only .1-.2 sec after the contraction of the atria
- Just enough time for VENTRICLE FILLING
Cardiac cycle electrical
ECG
ECG picks up change in polarity
- electrical activity of the heart can be detected and recorded thru the skin.
Review: during action potentials the cells internal environment changes 1) neg to pos 2) pos back to neg- this is the same whether it’s a NEURON or CARDIAC cell.
ECG waveforms represent ANY change in polarity for specific area whether - -> +. Or +- ->-
ECG during one complete cycle
What does the P, QRS, T wave stand for
Heart has 4 periods of polarity change
- Atrial contraction - to + / atrial systole
- Atrial relaxation + to - / atrial diastole
- Ventricular contraction - to +/ ventricular systole
- Ventricular relaxation + to - / ventricular diastole
P wave- atrial contraction (atrial depolar)
QRS- ventricular contraction (ventricle depolar)
T wave- ventricular relaxation ( ventricle repolarization)
Atrial diastole missing (2nd waveform) so close together the QRS covers up - amount of ventricle muscle far greater than that of atria
Cardiac cycle rhythm
Refers to SPAcing or TIMING of successive cardiac cycles (beats) - how far apart they are.
Sinus rhythm - is regular normal , Rythm ORIGINATES from SA node - should be at regular intervals.
CARDIAC CYCLE - ELECTRICAL
Cardiac muscular tissue review
Cardiac tissue is special because:
- have intercalated discs
> hear are gap junctions in cardiac tissue
> allow action potential that cause a contraction to pass from cell to cell without a nerve connection
» allows: atria to contract as single unit & ventricles to contract as a single unit - contractions are self activated : heartbeats without any external signal or stimulus
- does NOT need connection to the nervous system to cause contractions*
