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Flashcards in Heart Deck (11)
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Heart contracted



Heart relaxed


Heart Sounds

1st sound “Lub”
- close AV valves
- begin systole

2nd sound “Dub”
- close SL valves
- begin diastole


Blood pressure

Systole / diastole

Pressure in arteries when heart is contracted

Over /

Pressure in arteries when heart is relaxed


What is blood pressure directly proportional to

Cardiac output
- stroke volume x heart rate

Peripheral Resistance


Peripheral resistance

The force exerted by blood in the vessels

- vessels constrict = decrease in diameter, decrease in flow, increase resistance and increase blood pressure

- vessels dilated = increase in diameter, increase in flow, decrease resistance and decrease blood pressure


Cardiac muscle cells action potential

Uses electrical instead of chemical stimulation

Spontaneous depolarization because of pacemaker cells

Voltage gated sodium channels open when you reach the threshold and sodium rushes into the cell, then they become inactive and K becomes more active and leaves the cell but quickly after calcium comes into play

Voltage Calcium channels open and calcium goes into the cell and you plateu until the calcium channels close


Why does calcium channels open right after in the hearts action potential

Extends the absolute refractory period
- cardiac cells cannot achieve tetany like skeletal muscle cells can

Tetanic contraction
- maximum muscle contraction and holdd


Autorythmic cells

Starts off the action potential signal

-40 is our resting

Have sodium leak channels; allows there to constantly be a leak in the channels to allow sodium to go into the cell

Once you reach threshold slow voltage gated calcium channels open and increase the membrane potential until you close the ca gated channels and open potassium channels and then continue continue


Cardiac conduction system

SA node
- leaky sodium channels
- starts it off

AV node
- slows the heart rate down

Bundle branches

Purkinje fibres
- have gap junctions to make the cells contract


Three reasons for the conduction system

The atrial muscle cells and ventricular muscle cells are not electrically connected (no gap junctions)

AV nodes delays impulse allowing atria contract first then the ventricles

Impulse travels to the bottom of the heart first before entering ventricular muscles allowing ventricles to contract from the bottom to the top