Lab 7 ECG

atrial contraction

blood into ventricles

ventricle contraction

blood to vessels

auto rhythmic cells generate

action potentials

cardiomyocytes contract

by squeezing and no input from the nervous system

Cardiac action potential channels are

leakier

Cardiac RMP

-90 mv

cardiac AP step on depolarization is when

Na inflow

cardiac AP step 2 is plateau when

K outflow and Ca inflow

Cardiac AP step 3 repolarization

K+ outflow

Ca rushes in during

the beginning of repolariation

Cardiac AP have NO

relative refractory period

P wave

atrial depolarization

QRS complex

Ventricular depolarization

T wave

ventricular Repolarization

electrical axis

net direction of electrical activity that changes moment to moment

Electrical circuitry

SA → AV→bundle branches→purkinje fibers

electrocardiogram measures

electrical activity of the heart

Multiple leads allow for

measurements at different angles of the heart

cardiac axis

net direction of electrical activity over an entire heart beat

cardiac axis is typically between

-30 and 90 degress

Pulse waves reflect

ejection of blood, delayed from ventricle contraction due to the travel time through the arteries

Triangle top line is lead

I

triangle left side is

Lead II

triangle right side is

Lead III

acute myocardial infraction looks at what interval

ST

Lead II is closest to

normal cardiac axis vectors

vectors have

magnitude, direction, obey parallelogram rule, no component vector at right angles

toward positive electrode =

positive deflection

away from positive electrode

negative deflection

Normal

Lead I is up (+)
aVF is up (+)
Lead II is up (+)

Left axis deviation

lead I is up (+)

aVF is down (-)

lead II is down (-)

indeterminate

Lead I down (-)

aVF is down (-)

right axis deflection

Lead I is down (-)

aVF is up (+)

12 lead ECG =

10 electrodes