ion channels 2

Question 1

IKto

Answer 1

1. – (Kv4.3 tetramer + KChiP2)

2. voltage-dependent inactivation

Question 2

IKr

Answer 2

1. (HERG tetramer + miRP1)

2. “rapid” delayed rectifier

Question 3

IKs

Answer 3

1. (KvLQT1 tetramer + minK)

2. “slow” delayed rectifier

Question 4

Time-dependent cation current

Answer 4

1. If (or Ih)
2. (HCN tetramer)
3. Evoked by hyperpolarization
4. Na+ & K+ permeable
5. Erev ~ -30 mV

Question 5

Inward Rectifier potassium currents

Answer 5

1. IK1

2. IKACh

Question 6

IK1

Answer 6

(Kir tetramer)

Question 7

IKACh

Answer 7

1. (GIRK tetramer)
2. Increased by activation of muscarinic receptors
3. slows pacemaking

Question 8

Pacemaker Depol.

Answer 8

1. Turning on of If
2. Activation of ICa-T
3. Deact. of IKr & IKs

Question 9

HERG is an

Answer 9

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

Question 10

HERG produces

Answer 10

Ikr

Question 11

HERG is important for

Answer 11

duration of slow and fast APs

Question 12

Reducing Ikr can cause

Answer 12

arrhythmias

Question 13

HERG is blocked by

Answer 13

diverse compounds

Question 14

in the heart, electrical activity functions to

Answer 14

1. Generates repetitive firing in specialized, “pacemaker” regions
2. Propagates within the myocardium and via specialized conductive pathways
3. Serves as a trigger for contraction of the myocardium

Question 15

The cardiac action potential is the trigger for an

Answer 15

increase in the intracellular concentration of calcium ions, which, in turn, causes contraction of the myocardium.

Question 16

pacemaker cells

Answer 16

initiate cardiac AP

slowly depolarize to threshold in the absence of extrinsic input

Question 17

The rate at which a normal heart beats is controlled by

Answer 17

pacemaker cells in the sinoatrial node (SA node).

Question 18

The SA node is a

Answer 18

1. cluster of small (7 μm diameter), round and spindle-shaped cells that contain few myofilaments.
2. automaticity
3. rhythmicity

Question 19

automaticity

Answer 19

cells are spontaneously active

Question 20

rhythmicity

Answer 20

will fire action potentials at a frequency of about 100/min

Question 21

The SA node is innervated by

Answer 21

both sympathetic and parasympathetic axons.

Ongoing activity in the parasympathetic axons (parasympathetic tone) typically slows the rate at which cells in the SA node fire to 60-80 action potentials/min.

Question 22

overdrive suppression

Answer 22

an action potential will spread to them from the SA node before they reach threshold on their own

Question 23

ectopic pacemaker

Answer 23

Under abnormal circumstances these cells (or others, especially cells in damaged regions of the myocardium) can take over initiation of the heartbeat

Question 24

Because heart rate is controlled by electrical activity of the SA node, the propagation of this activity to other regions of the heart has to occur such that

Answer 24

the two atria contract and relax in a coordinated fashion, that two ventricles contract and relax in a coordinated fashion, and that ventricular contraction occurs during atrial relaxation (and vice versa).

Question 25

High Voltage activated (HVA) types

Answer 25

1. L type

2. neuronal

Question 26

L type channels include

Answer 26

CaV1.1, CaV1.2, CaV1.3, CaV1.4

Question 27

Neuronal channels include

Answer 27

CaV2.1, CaV2.2, CaV2.3

Question 28

Low voltage activated (LVA) types

Answer 28

T type, which includes: Cav3.1, 3.2, 3.3

Question 29

L-type calcium channels containing CaV1.2 are predominant in

Answer 29

ventricular and atrial myocardium and cells of the SA and AV nodes and conductive pathways.

Question 30

SA nodal cells also express

Answer 30

L-type channels containing CaV1.3.