Ventricular Ap Flashcards

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1
Q

Which 2 major ions are in highest concentration outside

A

Na and ca (ca inside but in sr)

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2
Q

What is phase 4 (start and end of ap)

A

Rmp at -80mv

Cell is polarised

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3
Q

What is the major channel in phase 4 rmp

A

Na/k ATPase

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4
Q

What is phase 0

A

Depolarisation via fast acting Na channels eg scn5a

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5
Q

What happens to allow Na in through fast acting Na channels

A

Electrical impulse from neighbour myocytes causes conformational change

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6
Q

What happens at around +40mv

A

Fast acting Na channels rapidly close via conformational change (h gate active)

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7
Q

What is phase 1

A

Early repolarisation

Transient outward current flow

via fast opening k channels (ones that encode ikr)

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8
Q

Is transient outward current flow in early repolarisation down conc gradient

A

Yes

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9
Q

Why does repolarisation stops fast after phase 1

A

Plateau phase phase 2 starts when ca enter cell

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10
Q

What type of ca channel allows entrance into cell in phase 2 plateau

A

L type (long type)

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11
Q

What does ca enterance allow

A

Excitation contraction coupling

Ca induced ca release via Ryanodine receptors on sr

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12
Q

Which phase is unique to ventricular heart muscle and why

A

Phase 2, ca not needed for others bc eg san cells don’t contract

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13
Q

Which channels causes uptake of ca back into sr

A

Ca ATPase

Serca channel

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14
Q

Other than serca, what else removes ca for heart relaxation (diastole)

A

Ncx

3 Na move in , 1 ca moves out via energy from Na gradient

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15
Q

What is phase 3

A

Rapid repolarisation

L type channel closes

Slow acting k channels open eg kcnq1
K leaves cell

(Shortly after restored by Na/k pump)!

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16
Q

How is san cell ap different

A

No phase 1 or 2 (just phase 0 dep and 3 rep)

Uses ca for depolarisation mainly

Has an unstable rmp

17
Q

What is diff about the rmp in san compared to ventricular myocytes

A

Not stable, it gradually diminishes to reach threshold

Usually less negative eg -70

18
Q

What is the name of the unstable rmp

A

Pacemaker potential

19
Q

What is the unstable pacemaker potential reason called

A

Funny current - opening of Na or k channels to get it closer to threshold

20
Q

What allows pacemaker to reach threshold

A

SNS release of nadr which makes it less negative

PNS allows k permeability so it becomes more repolarised= bradycardia

21
Q

Which 2 arrhythmias are normal to have eg through exercise or rest

A

Sinus tachycardia and bradycardia

Heart rate slows through san but conduction is normal through heart

22
Q

What is sinus tachycardia and bradycardia influenced by in san

A

The Ans

23
Q

What are the 3 causes of arrhythmia

A

Abnormal impulse formation (eg early or late repolarisation or depolarisation)

Enhanced automaticity - increased SNS activity causes extra heart beats

Re entry mechanisms - current through abnormal pathways