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Flashcards in 12-lead ch.2 Deck (21):

Where are actin and myosin molecules located in relation to the cell?

Outside edges edges of the barrel wall of the cells


Explain what cell barrels are made of including myofibrils and sheets.

The outside barrels are fused to form long bands called myofibrils. The bands are held together with connective tissue that make up the sheets. The sheets are covered in extra cellular fluid.


What are the positive and negative ions in cells?

Positive ions are: sodium, potassium and calcium. Chloride is the negative ion.


Which ions are intra and extra-cellular? What charges do each carry?

Potassium is generally inside the cell while sodium has a higher concentration outside the cell making it mor positive. Calcium also is on the outside of the cell generally making it even more positive outside the cell.


Why do cells need a sodium-potassium pump?

Ions naturally want to cancel themselves out so the natural tendency is for sodium to enter the cell and potassium to leak out. So the pump is necessary to keep them on their proper sides of the cell.


How many ions can the pump shift?

The pump can push out 3 sodium ions and bring in two potassium ions at a time.


What is normal resting electrical potential?

-70 to -90mV


Which phase of action potential is slowly increasing the cell's electrical potential?

Phase 4


When the cell becomes so positively charged that a new set of channels open this is called______, ________.

Threshold potential


What channels are opening at threshold potential?

The fast sodium channels


The most common ion outside the cell is____ and the rapid increase inside the cell causes action potential to fire; this is phase___.

Sodium. Phase 0


The point where the cell is not polarized or negatively charged is______.



The initial slowdown phase is when some negatively charged chloride ions enter and inflow of sodium slows.

Phase 1.


Two channels that open in phase 2 are_____ and ____ ____ channels.

Calcium and slow sodium channels.


Which phase is the plateau phase?

Phase 2


Why/How is the cell maintained in a depolarized state in phase 2?

Calcium channels open. Calcium is a double positive ion where the calcium and influx of sodium help to maintain the depolarized state


How is calcium essential to the actin/myosin work?

Calcium is a key to activate a clamp of proteins which are troponin and tropomyosin. This clamp brings together the actin and myosin. Without calcium, the "teeth" wouldn't come close enough to cause a reaction.


How does it relate to action potential in the cell? (calcium)

Calcium helps to maintain contraction for a longer period of time. The more calcium the faster the clamp and longer the contraction.


Rapid repolarization occurs in phase _____ during which ______ channels open and allow ______ into the cell.

3, potassium, potassium


At which phase do Na-K ATPase pumps move sodium out and potassium in?

Phase 3


What is the sequence that myocytes reach threshold potential at?

SA node, AV node, His Bundle, Purkinje fibers, and ventricular myocytes