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CV exam 1 wk 1 > ion channels > Flashcards

Flashcards in ion channels Deck (29):
1

electrical activity of the heart

1. Varies between Regions
2. Generates repetitive firing in pacemaker regions
3. Propagates within myocardium and via specialized conductive pathways
4. Trigger for contraction
5. Can Malfunction (AV block, Arrhythmias)
6. Measured via EKG (aka ECG)

2

Heart rate controlled by:

pacemaker cells in the sinoatrial node (SA node)

3

SA nodal cells fire

intrinsically at ~100/min. Rate modulated by ANS.

4

SA nodal cell rate is modulated by

ANS

5

Parasympathetic tone effect on rate?

slows rate to 60-80/min.

6

atrioventricular node (AV node) cell activity?

spontaneous activity.
but fire at lower frequency than SA nodal cells

7

AV cells are normally driven by?
This is called?

action potentials originating in the SA node (overdrive suppression).

8

Under abnormal circumstances, AV cells can?

take over initiation of the heartbeat, becoming ectopic pacemakers

9

Pumping of the heart depends upon propagation of the

action potential from the SA node to other regions.

10

where does SA node propagation occur?

both within the myocardium and via specialized conducting pathways.

11

cell to cell propagation occurs via

gap junctions

12

The direction of propagation is controlled by

gap junction position and by connective tissue “insulation” (e.g., between the atria and ventricles).

13

where is the only place where action potentials can propagate from the SA node to the ventricles?

The atrioventricular node (AV node)

14

Cardiac APs categories

fast and slow.
They vary by region

15

slow regions

1. SA node
2. AV node

16

fast regions

1. atrial muscle (R and L)
2. ventricular muscle (R and L)

17

ion channel: direction of current flow depends on

1. membrane potential (Vm)
2. ion gradient (Nernst Potential, Eion)

18

If Vm

into cell

19

If Vm>Eion, current flows

out of cell

20

Current flowing into cell will cause

depolarization

21

Current flowing out of cell will cause

hyperpolarization

22

Ena is

+58

23

Eca is

+124

24

Ek is

-90

25

Sodium current

1. (INa) – (NaV1.5)
2. Voltage-dependent inactivation

26

Calcium currents:

1. ICa-L
2. ICa-T

27

ICa-L

1. L-type current;
2. dihydropyridine receptor,
3. DHPR (CaV1.2, CaV1.3)
4. High Voltage Activated (HVA)
5. Both voltage- and calcium-dependent inactivation

28

ICa-T

1. T-type current
2. (CaV3.1, CaV3.2)
3. Low-Voltage Activated (LVA)
4. Voltage-dependent Inactivation

29

Time-dependent potassium currents

1. IKto
2. IKr
3. IKs