Brainscape's Knowledge GenomeTM

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


See full index

Cardiology > Origin and conduction of cardia impulse > Flashcards

Origin and conduction of cardia impulse Flashcards

1
Q

How is the heart controlled?

A

The heart is electrically controlled by signals generated within the heart

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

What is the term to describe the heart and its ability to pump in the absence of external stimuli?

A

Autorhythmicity

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

Where in the heart does the excitation normally originate?

A

The Sino-Atrial (SA) node (the pacemakers)

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

Where is the SA node located?

A

In the upper right atrium close to where the SVC enters the right atrium

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

What is the function of the SA node (in a general sense)? and what term is given to this?

A

Sets the pace for the entire heart.

Termed sinus rhythm

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

What do cells in the SA node not have?

A

A RMP

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

What kind of potential does the SA exhibit?

A

Spontaneous pacemaker potential (slow depolarisation of MP to a threshold)

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

What does the pacemaker potential do?

A

Takes the MP to a threshold to generate an AP in the SA nodal cells

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

Describe the basic ionic flux for the spontaneous pacemaker potential

A

Decrease in K+ efflux
Na+ and K+ influx (Funny current)
Transient Ca++ influx (via T-type Ca++ Ch’s)

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

What happens when the threshold has been reached for a pacemaker action potential?

A

The rising phase - activation of L-type Calcium channels resulting in an influx of calcium.

The falling phase - is cause by the inactivation of L-type calcium channels and activation of potassium channels (efflux of potassium)

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

What type of calcium channels are involved in spontaneous pacemaker potential?

A

T-Type channels - transient calcium influx

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

What type of calcium channels are involved in the pacemaker action potential?

A

L-Type Calcium channels

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

Summarise the SA node cell action potential

A
  1. Decrease in K+ efflux
  2. Funny current influx (Na+ and K+ influx)
  3. Transient Ca2+ influx (T-Type Calcium channels)

All of the above is spontaneous until the pacemaker action potential threshold has been reached. Then:
L-type calcium channels open allowing an influx of calcium (depolarisation) and re-polarisation and is K+ efflux

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

Anatomically, describe the pathway of excitation within the heart.

A

Begins at the SA node (cell-cell conduction) - AV node - Bundle of the His - purkinje fibres - ventricle mass cells

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

What cell feature allow for the excitation to be spread from the SA node to the ventricles?

A

From the SA node - AV node through both atria to the ventricles via gap junctions which all for a cell to cell current flow.

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

Where is the AV node located?

A

At the base of the right atrium, above the junction of the atria and the ventricles

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

Do the AV node cells have a fast or slow conductivity?

A

SLOW conduction velocity

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

How does excitation pass from the SA to AV node?

A

Cell-cell junctions via gap junctions

Some inter-nodal pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why is the conduction delayed within the AV node?

A

To allow for atrial systole (contraction) which precedes ventricular systole

20
Q

From the AV node how is the excitation conducted to the ventricles?

A

Via the Bundle of His and Purkinje fibres (Right and left branches)

21
Q

Is the conduction from AV node to the ventricles slow or rapid?

A

Rapid

22
Q

What is TMP (transmembrane potential) of a pacemaker action potential

A

-60mV

23
Q

What is the RMP in atrial and ventricular myocytes (contractile cardiac cells)?

A

-90mV (different from the pacemaker cells) and it remains here until the cell is excited

24
Q

What ion influx causes the depolarisation rising phase of the contractile cardiac muscle cells?

A

Na+ (fast influx)

25
Q

What MP does the rising phase in cardiac contractile AP reach?

A

+20mV

26
Q

What is phase 0?

A

Phase 0 is the rising phase of contractile cardiac muscle cells to +20mV due to a rapid influx of Na+ ions.

27
Q

How many phases are there in Ventricular muscle action potential and describe which ion (and associated flux direction) at each phase

A

5 - Phase 0, 1, 2 ,3 and 4.
Phase 0 - is the influx of Na+ ions
Phase 1 - is the opening of K+ channels and the transient efflux of K+ ions
Phase 2 - Ca2+ influx
Phase 3 - Closure of the Ca2+ channels and K+ efflux
Phase 4 - RMP

28
Q

Describe the plateau phase (around phase 2 of the AP) of the ventricular action potential

A

Where the AP is maintained after the peak of the AP - unique to cardiac muscle cells

29
Q

What ion causes the plateau phase of the Ventricular contractile cardiac AP?

A

The influx of Ca2+ ions through L-type Ca2+ ion channels

30
Q

What happens during the falling phase of a ventricular muscle action potential?

A

K+ channels open

Ca2+ are inactivated

31
Q

What changes the heart rate?

A

Done so by the autonomic nervous system

Sympathetic stimulation increases the heart rate
Parasympathetic stimulation decreases the heart rate

32
Q

Which nerve gives the parasympathetic supply the heart? (Under normal resting conditions)

A

The Vagus - cranial nerve X - slows the intrinsic HR from ~ 100bpm to a normal resting HR of ~ 70 bpm

33
Q

What is a normal resting HR (in BPM)

A

60-100

34
Q

Bradycardia

A

less than 60 BPM

35
Q

Tachycardia

A

More than 100 BPM

36
Q

Parasympathetic supply to the heart is to the ______ and ________ (2)

A

SA and AV node

37
Q

Parasympathetic - What does vagal stimulation do?

A

Slows the heart rate and increases the AV node delay

38
Q

What is the parasympathetic NT? And to which receptors do they act upon?

A

ACh

Muscarinic M2 receptors

39
Q

Parasympathetic: Name a competitive inhibitor of ACh & when it’s used

A

Atropine - severe cases of bradycardia to speed up the heart

40
Q

What are the effects of vagal stimulation on pacemaker potentials?

A

Cell hyperpolarises - takes longer to reach threshold
The slope of the pacemaker potential decreases
frequency of the AP increases
NEGATIVE CHRONOTROPIC EFFECT (decreases the heart rate)

41
Q

Sympathetic supply to the heart is to the ______, ______ and ________ (3)

A

SA node, AV node and myocardium

42
Q

What does cardiac sympathetic stimulation do to the heart rate and AV node?

A

Increases HR
Decreases AV nodal delay
increases the force of contraction

43
Q

Sympathetic: What is the NT and which receptors does it act upon?

A

NA - B1 adrenoreceptors

44
Q

NA on pacemaker cells:

A

Slope of pacemaker potential increases
pacemaker potential reaches threshold quicker
frequency of AP’s increase (+ chronotropic effect)

45
Q

What is positive chronotropic effect?

A

Increase in heart rate

46
Q

What does an ECG record?

A

The depolarisation and re-polarisation cycle of cardiac muscle. This is obtained from the skin surface.

47
Q

How many standard limb leads are there?

A

3:
Lead I: Right Arm to Left Arm
Lead II: Right Arm to Left Leg
Lead III: Left Arm to Left leg

Cardiology (2 decks)

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