Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

085. Cardiopulmonary Exam 2 > 1. Cardiac Action Potentials > Flashcards

1. Cardiac Action Potentials Flashcards

1
Q

What is the general path for the conduction system of the heart?

A
  1. Sinoatrial Node (pacemaker)
  2. Atrioventricular Node
  3. Bundle of His (common bundle)
  4. Right bundle branch & left bundle branch
  5. Purkinje fibers/subendocardial
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is important to remember about the purkinje fibers?

A

They are larger in diameter than myocytes surrounding them, mean they have a much faster AP than the AV/SA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Unlike nerves/skeletal M and smooth muscle, the conduction occurs directly between _________ in the cardiac muscle.

A

cardiac myocytes (gap junctions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is phase 0?

A

depolarization, inwards Na+ current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is phase 1?

A

Initial repolarization, inward Na+ current ceases but outward K+ is present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is phase 2?

A

Plateau, then inwards Ca+ current and slowed outward K+ current. K+ becomes less than at rest during phase 2 due to a special class of voltage dependent channels that close during depolarization and open a predetermined time follow closure. These opening plus Ca2+ closing causes phase 2 to end.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is phase 3 during the action potential of V/A and purkinje system?

A

repolarization, restoration of outward K+ current and cessation of inwards Ca2+ current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is phase 4?

A

resting membrane potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Regarding the conduction system of the heart, what areas of the heart receive action potentials before others?

A

Endocardium of ventricles receive AP before the epicardium, and right ventricle epicardium before left ventricle epicardium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the order of conduction velocity, from highest to lowest of the heart?

A

Purkinje fibers (atrial pathway)> atrial and ventricular muscle > Av node (slow!!! will see pause)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the delay or pause in the AV allow?

A

Allows the atria to empty into ventricles before they contract, allowing maximal volume in the heart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What phase of the sinoatrial node is the determinant of the heart rate?

A

The rate of phase 4 depolarization of the SA node!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Na+(m) is activated when membrane potential crosses threshold, opening channels and contributing to phase 0 and 1, doing what?

A

very fast generation of depolarization then automatically closes allowing partial repolarization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

K+ (a) or IKTO is activated when the cell depolarizes, and will open channels and close quick allowing?

A

very rapid partial repolarization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Ca2+ (L type) is activated when the cell depolarizes, and will open channels during phase 2.. doing?

A

slow to open and remains open for a determined amount of time and closes causing phase 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

K+ (b - Kinward/rectifier) is activated when the cell depolarizes and close channels during phase 2, allowing?

A

–slow to close and remains closed for a determined amount of time then opens and helps with phase 3 (balances phase 2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

K+ (c) remains open all the time, helping with phase 4, meaning it is?

A

a leak channel which maintains resting potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Na+ (f/funny) is activated when SA or AV node repolarizes, opening channels during phase 4 and?

A

causes slow depolarization during the resting phase

19
Q

In the SA node, RMP gradually depolarizes spontaneously until it reaches threshold and then will fire, although slower than other regions. This feature is why the SA node is considered?

A

The intrinsic, spontaneous depolarization makes the SA node the PACEMAKER due to its automaticity

RHYTHMICITY

20
Q

What allows phase 4 to occur in the pacemaker of the heart?

A

Phase 4 is due to opening of the funny voltage gated Na+ channels that open when membrane is repolarized

21
Q

What is important to remember about phase 4 in the AV node?

A

Its depolariation is SLOWER than SA node, it doesnt reach threshold until SA node triggers it

22
Q

What causes Phase 0 in the SA/AV nodes?

A

(action potential) Opening of the slow Ca2+ channels and closing of special K+(b) channels… balancing act between Ca2+ in and modulating K+ out

23
Q

K+ b channels help modulate the heart rhythm. What are they sensistive to and what does that mean?

A

Sensitive to acetylcholine meaning there is a parasympathetic effect

24
Q

What causes phaes 3 in the SA/AV nodes? (**there are no phase 1/2 d/t scarcity of Na+(m) channels)

A

Repolarization: Closing of Ca2+ gates and opening of special gates K+(b)

25
Q

the bundle of his and purkinje fibers remain polarized. If not stimulated for a period of time what will they begin to do?

A

spontaneously depolarize during phase 4.

**rate of bundle/purkinje fibers is slower than AV node

26
Q

The equilibrium potential is lower for fast tissues/fibers (-90). Phase 4 is the resting potential and is sustained by what channels?

A

high K+ (c) conductance

27
Q

What occurs in phase 0 of fast tissues/fibers?

A

Rapid upstroke (depolarization) caused by crossing threshold and voltage gated Na+ channels (m) opening (AP is generated)

28
Q

What occurs in phase 1 of fast tissues/fibers?

A

Small repolarization cause by inactivation gates in Na+ (m) channels closing and K+(a) channels opening

29
Q

What occurs in phase 2/plateau in tissues/fibers and functionally what does this do?

A

Plateau: Slow opening of Ca2+ channels and closing of K+(b) channels

Functionally prolongs contraction and is fundamentally different than observed in skeletal muscle

30
Q

What occurs during phase 3 in tissues/fibers?

A

Complete repolarization caused by Ca2+ channels closing and K+(b) channels opening

31
Q

Conduction velocity usually relates to phase 0, how and what is the velocity related to?

A

The more rapid phase 0 occurs, (faster conduction velocity) the steeper the phase is.
It is related to the differences in the speed of either Na+ or Ca2+ channels

32
Q

AV node damage delays conduction of the heart called AV block. What can happen if the purkinje fibers are damaged?

A

Disrupts the natural conduction and contraction of ventricles (arrhythmias)

33
Q

Refractory period is when electrolyte gates have not ‘reset’ sufficiently to allow a second AP to be generate and is important to help prevent arrythmias, and are longer in cardiac cells than neurons. What occurs during absolute and relative refractory periods (ARP RRP)?

A

ARP: no depolarization
RRP: AP can be generated but will have an abnormal conduction

34
Q

What is a supranormal period? (SNP)

A

cell is more exictable than normal

plays roles in arrythmias

35
Q

What effect changes the rate of depolarization of SA node and therefore the heart rate HR?
What does a positive or negative effect cause?

A

Chronotropic effect

If there is a positive chronotropic effect, there will be a faster heart rate, if negative then slower heart rate

36
Q

What effect changes the speed of conduction (velocity) in the heart?

A

Dromotropic (increase in dromotropic = increase in conduction velocity)

37
Q

What is the difference between inotropic and lusitropic effects on action potentials in the heart?

A

Inotropic effect changes the strength of muscular contraction
Lusitropic effect changes the rate of muscular relaxation

38
Q

A parasympathetic stimulus is carried by the vagus nerve to the SA and AV node but not really to ventricular myocytes. What neurotrasmitter and receptor is used for parasympathetic signaling?

A

Acetylcholine and muscarinic M2/M3

Reduces kinase activity to slow down HR

39
Q

What do negative chronotropic effects cause? (2)

A

Decrease HR by Slowed opening of Na+(f) channels during phase 4
Hyperpolarization by increasing outward K+ current via K+-Ach channel

40
Q

What do negative dromotropic effects cause? (2)

A

decrease conduction velocity by :
Reduced Ca2+ inward current
Increased outward K+ current via K+-Ach

41
Q

A sympathetic stimulus goes to SA/AV nodes AND into myocytes via which neurotransmitter and receptor?

A

Via norepinephrine and muscarinic-B1-adrenergic receptors

42
Q

What do positive chronotropic effects casue? (2)

A

Increase in heart rate by increased opening of Na+ (f) channels during phase 4 and increased inward Ca2+ current

43
Q

What do positive dromotropic effects cause? (1)

A

increase conduction velocity (and HR) by increased Ca2+ inward current during phase 2

44
Q

What are the differences between atropine and propranolol?

A

Atropine is a muscarinic receptor antagonist and increases HR
Propranolol is a B adrenergic antagonist and decreases HR

085. Cardiopulmonary Exam 2 (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions