Heller Ch. 2

Question 1

What is the RMP of calcium?

Answer 1

+100mV (more in interstitial fluid)

Question 2

What is the RMP of sodium?

Answer 2

+70mV (more in interstitial fluid)

Question 3

What is the RMP of potassium?

Answer 3

-90mV (more in intracellular fluid)

Question 4

What does movement of ions across a membrane cause?

Answer 4

A charged membrane…cations move out leaving behind negative proteins

Question 5

Phase 0 of Fast Response Action Potentials?

Answer 5

Sodium permeability rapidly goes UP–>

a sudden DEpolarization

Question 6

Phase 1 of FRAP?

Answer 6

Sodium permeability rapidly goes DOWN and
Potassium permeability goes DOWN–>
a slight REpolarization

Question 7

Phase 2 of FRAP?

Answer 7

Calcium permeability goes UP
Sodium permeability slightly UP and
Potassium permeability stays LOW–>
a PLATEAU

Question 8

Phase 3 of FRAP?

Answer 8

Potassium permeability goes UP
Calcium permeability goes DOWN and
Sodium permeability goes DOWN–>
a REpolarization (Phase 4)

Question 9

Pacemaker potential cells (Slow-Response Action Potential)?

Answer 9

Unstable membranes

Question 10

Net movement in SRAP cells before AP?

Answer 10

Potassium goes DOWN while
Calcium (major) and Sodium (minor) go UP–>
an eventual DEpolarization (action potential)

Question 11

How is conduction velocity modified?

Answer 11

Connexin proteins in gap junctions

Question 12

Parasympathetic actions through the vagus nerve (ACh):

Answer 12

An initial hyperpolarization of the RMP

Slows the rate of spontaneous depolarization of the RMP

Question 13

How does ACh achieve parasympathetic effects?

Answer 13

ACh interacts with muscarinic receptors–>activates Gi
Increases potassium permeability (K[ACh] channels)
Suppresses adenylate cyclase–>decreased cAMP–>reduces inward-going pacemaker current by sodium (i[f] current)

Question 14

Sympathetic actions (NE):

Answer 14

Increases inward currents carried by both sodium (i[f] current) and calcium during the diastolic interval–>increases rate of diastolic depolarization

Question 15

How does NE achieve sympathetic effects?

Answer 15

NE interacts with beta1-adrenergic receptors–> activates Gs
Increases adenylate cyclase–> increases cAMP–> increases open-state probability of the pacemaker sodium current channel (i[f] current)

Question 16

Define chronotropic:

Answer 16

Heart rate

Question 17

Define dromotropic:

Answer 17

Conduction velocity

Question 18

Digitalis:

Answer 18

Inhibits sodium/potassium pump–>decreased sodium gradient–>non-functional sodium/calcium exchanger–>increased contraction strength/length

Question 19

Ryanodine:

Answer 19

Blocks the calcium induced calcium channel

Question 20

Caffeine:

Answer 20

Activates the calcium induced calcium channel

Question 21

Contractility:

Answer 21

Force at a given length

Question 22

Inotropic:

Answer 22

Change in contractility

Question 23

Tension in ventricle?

Answer 23

T = intraventricular pressure x internal radius

Question 24

Potassium channel (inward rectifier)
i[K1]

Answer 24

Maintains high K+ permeability during phase 4
Decay contributes to diastolic depolarization
Suppression during phases 0-2 contribute to plateau

Question 25

``` Sodium channel (fast) i[Na] ```

Answer 25

Accounts for phase 0 | Inactivation may contribute to phase 1

Question 26

``` Potassium channel (transient outward) i[TO] ```

Answer 26

Contributes to phase 1

Question 27

``` Calcium channel (slow inward, L channels) i[Ca] ```

Answer 27

Primarily responsible for phase 2 Inactivation may contribute to phase 3 Is enhanced by sympathetic stimulation and beta-adrenergic agents

Question 28

``` Potassium channel (delayed rectifier) i[K] ```

Answer 28

Causes phase 3 | May be enhanced by increased intracellular Ca++

Question 29

``` Potassium channel (ATP-sensitive) i[KATP] ```

Answer 29

Increases K+ permeability when ATP is low

Question 30

``` Potassium channel (ACh-activated) i[KACh] ```

Answer 30

Responsible for effects of vagal stimulation Decreases diastolic depolarization and HR Hyperpolarizes RMP Shortens phase 2

Question 31

``` Sodium channel (pacemaker current) i[f] ```

Answer 31

Contributes to the diastolic depolarization Enhanced by sympathetic stimulation and beta-adrenergic agents Suppressed by vagal stimulation