electrical properties of the heart

permeability changes in a membrane

what causes an action potential?

negative inside, K+ inside, Na+ outside

resting membrane potential

Na+ rushing in

depolarization is caused by

ca2+ channels slowly opening and letting calcium in

plateau phase is caused by

k+ channels slowly opening and k+ coming back rushing out of the cell

repolarization is caused by

about 250 ms (the whole contraction

how long is the cardiac action potential including the refractory period?

to contract, hold, and relax—prevent tetanic contractions

why is the cardiac action potential have a long refractory period?

the tension building is related to the ca2+ influx

why is tension in the heart muscle increasing during the plateau phase of the cardiac action potential?

why do we need ca2+ for contraction?

it acts as a signal to initiate the interaction between actin and myosin filaments within the muscle fiber—ca2+ binds to troponin-binds with tropomyosin-moves myosin head, gets more force

Sinoatrial (SA) Node

found in the upper right atrium of the heart, causes atrial contraction, “pacemaker of the heart”

Atrioventricular (AV) Node

found next to the tricuspid valve, receives stimulation from atria and send it to the ventricles, delays the electrical impulse by one second to make sure atria are empty

Atrioventricular (AV) Bundle

found superior to the interventricular septum, is the connection between the ventricles & carries the signal to both sides— splits into 2 branches

Purkinje FIbers

found all throughout the ventricles and papillary muscles, contracts the ventricles and papillary muscle (has the fastest depolarization rate x100 than others)

autorhythmic cells & opening of Na+ channels and closing of K+ channels

hyperpolarization caused by &leads to

autorhythmic cells

found in the SA & AV nodes, set the pace of heart contractions— AP begins on its own (these are non-contractile cells)

after depolarization, once threshold is hit (-40mV)

when do ca2+ channels open?

it depolarizes faster than the others

what makes the SA node the “pacemaker” of the heart?

EKG/ECG

how do we measure electrical activity in the heart?

voltage difference between 2 locations

what does an ECG measure?

to detect abnormal heart rhythms and risks for heart attack

what do we use an ECG for?

when the ventricular pressure exceeds the aortic pressure

what causes the aortic valve to open?

when ventricular pressure becomes less than aortic pressure

what causes the aortic valve to close?

the “lub” sound is caused by the AV valves napping shut

what causes s1 sound of the heart?

the “dub” sound is caused by the SL valves snapping shut

what causes s2 sound of the heart?

valve abnormalities

what causes abnormal heart sounds?