M2-C5-L17 --> Electrical Conduction Of Heart Ii

Front 1

EXTRACELLULAR POTASSIUM (K+)

- compare [K+] outside vs inside

- K+ is responsible for what & why?

Back 1

- Inside (135 mM) > Outside (4 mM)

- Membrane Potential (Vm)

- Because K+ is highly membrane permeable

Front 2

EXTRACELLULAR POTASSIUM (K+)

- if the ATP around cardiomyocyte is decreased, what happens to external K+?

- what pathologic event might decrease the ATP surrounding Cardiomyocyte?

Back 2

- Goes UP

- Myocardial Infarction

Front 3

EXTRACELLULAR POTASSIUM (K+)

- A Myocardial Infarction will do what to K+ levels?

Back 3

- External K+ goes up

(increase external K+ availability)

Front 4

EXTRACELLULAR POTASSIUM (K+)

- Increasing extracellular K+ will have what effect on Vm?

- above will cause what conversion?

Back 4

- Increases the Vm
(towards more positive)

- Converts Fast Response cells to Slow response cells

Front 5

EXTRACELLULAR POTASSIUM (K+)

- Increasing extracellular K+ will have what effect on the Overshoot?

Back 5

- Decrease overshoot.

Front 6

EXTRACELLULAR POTASSIUM (K+)

- Increasing Extracellular K+ will do what to the Vm?

- Increasing Extracellular K+ will do what to the graphical representation of cardiomyocyte AP.

Back 6

- Increase Vm
(towards more positive)

- Converts Fast response curve to Slow response curve

Front 7

NORMAL HEART CONDUCTION

- The slowest conduction seen where? x2
(give values)

Back 7

SA node
( < 0.01 m/s)

AV node
( 0.02 to 0.05 m/s)

Front 8

NORMAL HEART CONDUCTION

- The fastest conduction seen where? x2
(give values)

Back 8

- Bundle Branches
- Purkinje network

(Both are 2.0 to 4.0 m/s)

Front 9

NORMAL HEART CONDUCTION

- what 2 things are important for pacemaker activity?

Back 9

- SA node

- AV node

Front 10

NORMAL HEART CONDUCTION

Rate of Pacemaker Discharge for:

- SA node

- AV bundle

- Purkinje fibers

Back 10

- 60 to 100 discharges / min

- 40 to 55 discharges / min

- 25 to 40 discharges / min

Front 11

NATURAL HEART EXCITATION

- define Automaticity

- define Rhythmycity

Back 11

- heart can initiate its own beat
(pacemaker)

- regularity of such pacemaker activity

Front 12

NATURAL HEART EXCITATION

- SA node undergoes spontaneous "what?"

Back 12

- "Diastolic Depolarization"

Front 13

NATURAL HEART EXCITATION

- what are the 3 phases of SA node?

Back 13

- 4
(resting Vm that's not flat)

- 0
(upstroke)
- 3
(repolarization)

Front 14

NATURAL HEART EXCITATION

T/F : upon depolarizing, the SA node will come back to a flat profile.

Back 14

False

(goes back to a profile where it is gradually raising itself back up again)

Front 15

NATURAL HEART EXCITATION

- what is the reason behind the continuous spontaneous depolarization, as well as the return to a non-flat profile?

Back 15

- SA Node cells have intrinsic "LEAKINESS" to Sodium

Front 16

NATURAL HEART EXCITATION

- SA Node threshold?

- channel associated with the "Leakiness" in SA node cells?

Back 16

- 55 mV

Na+ IF channels

Front 17

SINOATRIAL NODE

- contains what type of cells? x2

Back 17

- Pacemaker cells

- Conducting cells

Front 18

SINOATRIAL NODE

- factors influencing Pacemaker cell discharge? x4

Back 18

(DART)

- Depolarization rate in Phase 4
- Autonomic effects
- Resting potential
- Threshold potential

Front 19

SA NODE: AUTONOMIC EFFECTS

- Sympathetic NT type?

- Sympathetic effects? x2

Back 19

- Catecholamines

- Heart rate increases
- Slope of Pacemaker Potential increases

Front 20

SA NODE: AUTONOMIC EFFECTS

- Parasympathetic NT?

- Parasympathetic effects? x3

Back 20

- Acetylcholine

- Heart rate decrease
- Slope of pacemaker potential decrease
- Hyperpolarize pacemaker cell membrane

Front 21

SA NODE: AUTONOMIC EFFECTS

- what is the INTRINSIC heart rate?

- what is the NORMAL heart rate?

Back 21

100 to 120 / min

72 / min

Front 22

SA NODE: AUTONOMIC EFFECTS

- which ANS part has Tonic activity?

Back 22

- Parasympathetic

Front 23

SA NODE: AUTONOMIC EFFECTS

- Parasympathetic system will slow the HR to?

- by doing what?

Back 23

60 to 80 / min

by maintaining a state of open K+ channels

Front 24

SA NODE: AUTONOMIC EFFECTS

- Parasympathetic effects in opening K+ channels, will cause what physiological effect?

Back 24

- Hyperpolarization

Front 25

SA NODE: AUTONOMIC EFFECTS

- Hyperpolarization is caused by which ANS part?

- Hyperpolarization causes what 2 physiological effects?

Back 25

- Parasympathetic

Decrease
- Rate of Diastolic Depolarization
- Conduction Velocity

Front 26

SA NODE: AUTONOMIC EFFECTS

- what is the INTRINSIC heart rate?

- what is the NORMAL heart rate?

Back 26

- 100 to 120 / min

- 72 / min

Front 27

SA NODE: AUTONOMIC EFFECTS

- which ANS part has Tonic Activity?

Back 27

- Parasympathetic

Front 28

SA NODE: AUTONOMIC EFFECTS

- Parasympathetic slows heart to what levels?

- does so by what mechanism?

Back 28

- slows to 60 to 80 / min

- maintaining OPEN K+ channels

Front 29

SA NODE: AUTONOMIC EFFECTS

- which ANS part is responsible for the mechanism of opening and open maintenance of K+ channels?

- Open K+ channels lead to what physiological event?

Back 29

- PS

- Hyperpolarization

Front 30

SA NODE: AUTONOMIC EFFECTS

- Hyperpolarization caused by which ANS part?

- Hyperpolarization does what 2 physiological effects?

Back 30

- PS

Decreases:
- Diastolic Depolarization Rate
- Conduction Velocity

Front 31

SA NODE: AUTONOMIC EFFECTS

- Assuming no change in Threshold, how does the Sympathetic drugs increase the rate Pacemaker cell discharge?

Back 31

- Increases the slope @ Phase 4

(reaches threshold faster)

Front 32

SA NODE: AUTONOMIC EFFECTS

- Assuming no change in Threshold, how does the Parasympathetic drugs decrease the rate Pacemaker cell discharge?

Back 32

- Decreases the slope @ Phase 4

(slower to reach threshold)

Front 33

SA NODE: AUTONOMIC EFFECTS

- How would a Parasympathetic drug (such as a membrane stabilizer) effect Threshold?

Back 33

- Increases Threshold

(thus takes longer to reach threshold)

Front 34

AUTOMATICITY : IONIC BASIS

- ionic currents affect what polarization?

Back 34

- Phase 4 SLOW Depolarization

Front 35

AUTOMATICITY : IONIC BASIS

- what 3 ionic currents are involved in Slow Phase 4 Depolarization?

Back 35

- Inward Na+ currents

- Slow Inward Ca2+ & Na+ currents

- Outward K currents

Front 36

AUTOMATICITY : IONIC BASIS

- Inward Na+ currents are induced by?

- Inward Na+ currents have what effect on cell?

Back 36

- Hyperpolarization

- Depolarizes cell

Front 37

AUTOMATICITY : IONIC BASIS

- Slow Inward Ca2+ & Na+ currents are induced by?

- Slow Inward Ca2+ & Na+ currents have what effect on cell?

Back 37

- Vm = -55 mV

- Depolarize cell

Front 38

AUTOMATICITY : IONIC BASIS

- Outward K+ currents has what effect on cell?

- BUT......

Back 38

- Opposes Progressive Depolarization

- current decays steadily during Phase 4, thus its opposition to depolarization also gradually decreases

Front 39

AUTOMATICITY : IONIC BASIS

- Outward K+ current decays during what Phase?

- such decay leads to?

Back 39

- Phase 4

- corresponding Decrease in its Opposition to Depolarization

Front 40

AUTOMATICITY : IONIC BASIS

- what ionic current is responsible for triggering the AP?

Back 40

- Slow Inward Na+ current

Front 41

AUTOMATICITY : IONIC BASIS

- Diastolic Depolarization occurs @?

- Outward leaking of Potassium causes the cell's inside to have what polarity?

Back 41

- SA Node

- more Electronegative

Front 42

AUTOMATICITY : IONIC BASIS

- what effect does Ca2+ ion have on Pacemaker function?

Back 42

- Modulates SA Node Pacemaker F(x)

Front 43

CALCIUM & CONDUCTANCE

- if the external concentration of Ca2+ was decreased, what effect would it have?

- how would his affect the heart? x2

Back 43

- Decreases the Amplitude of AP

- Decreases HR
- Decreases contractility force

Front 44

CALCIUM & CONDUCTANCE

- can you actually change the Ca2+ environment of the cardiomyocytes?

Back 44

No

Front 45

CALCIUM & CONDUCTANCE

- what drug can mimic the effects of decreasing the extracellular levels of Ca2+

- what is the drugs mechanism?

Back 45

- Nifedipine

- Calcium Channel Blocker
(on the transmembrane of SA node cell)

Front 46

CALCIUM & CONDUCTANCE

- application of Nifedipine does what to the heart physiology? x2

Back 46

- Decrease the AP amplitude

- Decrease the rate of AP

Front 47

IMPULSE PROPAGATION IN HEART

- impulse propagation in atria via what structures? x4

Back 47

- Anterior InterAtrial Myocardial Band

- Anterior Internodal tracts
- Middle Internodal tracts
- Posterior Internodal tracts

Front 48

IMPULSE PROPAGATION IN HEART

- Bachman's bundle is what?

Back 48

- Anterior InterAtrial Myocardial Band

Front 49

ATRIOVENTRICULAR CONDUCTION

- what are the only Normal paths for conduction from Atria to Ventricles? x2

Back 49

- AV node

- Bundle of His

Front 50

ATRIOVENTRICULAR CONDUCTION

- what are the 3 functional regions of the AV node?

Back 50

1.) A-N region
(atrial-node)

2.) N region
(nodal)

3.) N-H region
(nodal to His)

Front 51

WOLF PARKINSON WHITE SYNDROME

- acquired or congenital?

Back 51

- Congenital Defect

Front 52

WOLF PARKINSON WHITE SYNDROME

- due to what anatomical structure?

Back 52

- Extra conduction pathway between Atria & Ventricles

Front 53

WOLF PARKINSON WHITE SYNDROME

- extra AV conduction pathway results in what physical event?

- thus leading to what pathological condition?

Back 53

- Early Ventricular Contraction

- Arrhythmias

Front 54

PURKINJE FIBERS

- conducts what property to what location?

Back 54

- Cardiac Impulses

to
- Ventricular Endocardium

Front 55

PURKINJE FIBERS

- discuss size

- discuss velocity

Back 55

- Large fibers

- Very Rapid Conduction Velocity

Front 56

PURKINJE FIBERS

- associated with what cells?

- graphical representation would show what? x2

Back 56

- Ventricular Myocytes

- Long Plateau Phase
- Long Refractory Period

Front 57

CARDIAC SYNCYTIUM

- once the signal is initiated in the ventricular myocardium, sequential signals will spread from monocyte to monocyte via what process?

- above process done thru what anatomical structure?

Back 57

- Cardiac Syncytium

- Intercalated discs

Front 58

CARDIAC SYNCYTIUM

T/F : both atrial myocytes and ventricle myocytes are linked to others of its kind by intercalated discs.

Back 58

True

(linked to others of its own kind, but not to each other - separated electrically)

Front 59

ECTOPIC PACEMAKERS

- what are they?

Back 59

- Regions (Foci) of heart that initiate beats under special conditions

Front 60

ECTOPIC PACEMAKERS

- Ectopic foci may become pacemakers when? x3

Back 60

- when Rhythmicity is ENHANCED

- when Rhythmicity of Higher Pacemakers is Depressed

- with a BLOCKADE of Conduction pathways between Higher Centers & Ectopic Foci

Front 61

ELECTROCARDIOGRAM

- define a segment

Back 61

- straight line BETWEEN waves

Front 62

ELECTROCARDIOGRAM

- define an interval

Back 62

- Wave PLUS a Segment

Front 63

ELECTROCARDIOGRAM

- duration of a normal PR interval?

Back 63

0.12 to 0.20 milliseconds

Front 64

ELECTROCARDIOGRAM

- ST segment begins from?

- ST segment ends @?

Back 64

- End of Ventricular Depolarization
(QRS complex)

- Start of Ventricular Repolarization
(T-wave)

Front 65

ELECTROCARDIOGRAM

- QT interval represents?

- QT takes up what % of each cardiac cycle?

Back 65

- Ventricular Cycle

- 40% of each cardiac cycle

Front 66

ELECTROCARDIOGRAM

- P wave has a normal amplitude of?

Back 66

0.25 mV

(2.5 mm)

Front 67

ELECTROCARDIOGRAM

- P wave has a normal duration of?

Back 67

0.04 to 0.12 milliseconds

Front 68

ELECTROCARDIOGRAM

- what follows a P wave?

Back 68

- AV node conduction pause

Front 69

ELECTROCARDIOGRAM

- List all the anatomical structures involved in Ventricular Depolarization. x7

Back 69

- Bundle of His

- Left Bundle Branch
- Right Bundle Branch

- Septal Purkinje fibers
- Posterior Purkinje fibers
- Anterior Purkinje fibers
- Terminal Purkinje fibers

Front 70

ELECTROCARDIOGRAM

- normal QRS duration?

Back 70

0.06 to 0.12 milliseconds

Front 71

ELECTROCARDIOGRAM

- normal height of T wave?

Back 71

- 1/3 to 2/3 that of corresponding R wave

Front 72

ELECTROCARDIOGRAM

- U wave is seen when?

- U wave represents what? x2

Back 72

- after the T-wave

Repolarization of :
- Papillary Muscles
- Purkinje fibers

Front 73

ELECTROCARDIOGRAM

- what is only seen on 50% of the ECG's?

Back 73

- Septal Repolarization

(U-wave?)