C-Electrical Activity of the Heart Flashcards Preview

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Flashcards in C-Electrical Activity of the Heart Deck (25):
1

Heart rate controlled by pacemaker cells in the SA node. SA nodal cells fire intrinsically at ___________. Rate modulated by ANS.

~100/min.

Parasympathetic tone slows rate to 60-80/min.

2

These cells are normally driven by action potentials originating in the SA node (overdrive suppression).

atrioventricular node (AV node)

3

ectopic pacemakers

Abnormal circumstances--> AV node (or others, especially in damaged myocardium) can take over initiation of the heartbeat,

4

Cell-to-cell propagation of the action potential from the SA node to other regions occurs via _______

gap junctions

5

The _______________, is the only place where action potentials can propagate from the SA node to the ventricles

atrioventricular node (AV node)

6

From the AV node, additional conducting pathways propagate the action potential to the left and right ___________

ventricles

7

Cardiac Action Potentials vary between regions and are categorized as ___________

“fast” or “slow”

arise from different regions of the heart

8

a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory.

Action potential

9

Nernst Potential, Eion
ENa---> +58
ECa---> +124
EK---> ______

-90

10

Current flowing into cell causes depolarization
Current flowing out of cell causes ______

hyperpolarization

11

Direction of current flow depends on __________ (Vm) and ion gradient (Nernst Potential, Eion)

membrane potential

12

Nernst Potential, Eion
ENa---> _____
ECa---> +124
EK---> -90

+58

13

Current flowing into cell causes _______
Current flowing out of cell causes hyperpolarization

depolarization

14

Direction of current flow depends on membrane potential (Vm) and _______

ion gradient (Nernst Potential, Eion)

15

Cardiac sodium channels- Ion gate is _______ at rest/hyperpolarized

Closed

16

Inactivation vs deactivation ion gate

deactivation- activation gate is closed (activation gate)

inactivation- Inactivation gate is plugging channel

different processes

17

The properties of calcium channels are mainly determined by the________

principle (CaV) subunit

L type- high volt
T type- low volt

18

Ca Channel-Calcium currents:
High Voltage Activated (HVA)
Both voltage- and calcium-dependent inactivation

ICa-L, L-type current

19

Ca Channel-Calcium currents:
Low-Voltage Activated (LVA)
Voltage-dependent Inactivation

ICa-T, T-type current

20

IKs (KvLQT1 tetramer + minK) mutations can cause

long QT

21

IK1 (Kir tetramer) functions to

lowers rate of pacemaker

22

______ is an “anti-target” tested in preclinical evaluation of new drugs

HERG

HERG produces IKr
Reducing IKr can result in arrhythmias

23

Because _____ (tetramer of HERG) is important for repolarization of both fast and slow cardiac action potentials, altered HERG function can disrupt normal cardiac electrical activity, leading to arrhythmias.

IKr

24

HERG channels are blocked by a wide variety of_______

structurally unrelated compounds

25

You _____ want to block HERG

DO NOT

all drugs must be tested with HERG to avoid arrhythmias