9/1 Electrochemistry of the heart

Question 1

what are the waves of the normal heart EKG

Answer 1

P,R,Q,S,T

Question 2

what is the normal activation sequence of the heart?

Answer 2

SA node — Atria — AV node — His bundle — bundle branches — Purkinje fibers — ventricles.

Question 3

what are the two types of cells in anormal heart

Answer 3

working cells and the specialized cells

Question 4

working cardiac cells

Answer 4

contract and impart energy and import a stroke volume

Question 5

what are the specialized cells in the heart:

Answer 5

SA, AV, His, BB, Perkinje fibers

Question 6

job of Specialized cells in the heart

Answer 6

to initiate the electrical signal and to propigate that electrical signal through the cell.

Question 7

what is the SA node

Answer 7

the node of speical cells on top of the right atrium that is the dominant pace-maker of the heart.

Question 8

How could the signal get to the rest of the heart form the SA node

Answer 8

the AV node in the bottom of the Right atrium into the ventricle. The only path from the atrium to the ventricle.

Question 9

why delay the activation of the ventricle

Answer 9

to time the distole/systole correct

Question 10

what is the path from the RA to the RV/LV electricly

Answer 10

SA node, then AV node, then His bundle then bundle branches then purkinje fibers

Question 11

where is the electrical signal slow or rapid in the heart?

Answer 11

slow in the SA to AV node, and fast everywhere else

Question 12

what is automaticity

Answer 12

the ability to fire spontaniousley

Question 13

what cardio cells have automaticity?

Answer 13

the Specialized cells: SA, AV, His, BB, Purkinje fibers

Question 14

what are the phases of cardiac action potentials?

Answer 14

phase 0: upstroke, rapid dpolarization; Phase 1: rapid repolarization following the peak; Phase 2: the plateau; Phase 3: rapid repolarizatio following the plateau; Phase 4: period between the maximum negativity (diastolic potential) and the upstroke of the next action potential.

Question 15

how do the activation sequence of cardiac specialization cells look different than working cells?

Answer 15

the specialization cells depolarize during phase four of the cycle, leading to spontaneous APs and pacemaker activity

Question 16

what is the dominant pace maker of the heart?

Answer 16

the SA node

Question 17

what property of the SA node make it a pace maker

Answer 17

phase four of the activation sequence is shortest among the specialized cells.

Question 18

describe the sequence of electrical activation in the heart.

Answer 18

P2

Question 19

how does the sypathetic nervous system or epinepherin/neuroepinephrin change the activation of the SA node

Answer 19

it increases the rate of depolarization

Question 20

how does a lower pacemaker represent a safety mechanism

Answer 20

the lower pacemaker has a lower fate of spontaneous firing, that will take over the rate if the SA node doesn’t fire

Question 21

what is less than 60 beats per minute in heart

Answer 21

bradycardia

Question 22

what is greater HR than 100

Answer 22

tachycardia

Question 23

where does the electrical activity recorded on the skin come form in the heart

Answer 23

the depolarization of the atrium (P); the depolariztion of the ventricle (QRS) the repolariztion of the ventricle (T)

Question 24

what is the p wave

Answer 24

depolarization of the atrium

Question 25

what is the q, R, S wave

Answer 25

depolarization of the ventricle

Question 26

what is the T wave

Answer 26

the repolarization of the ventricle cells

Question 27

what are the two big parts of info in an EKG

Answer 27

how long does it take to get to different parts of the heart. How does the signal move through the heart (vector direction)

Question 28

what does the width of the P and QRS wave tell us

Answer 28

the atrial and ventricale cells take time to depolarize, and wider peak is a longer delay

Question 29

where does the activation sequence fit into the ECG signal and what are the common intervals of the ECG?

Answer 29

P1

Question 30

why do we have a space between the P and QRS? (P-R interval)

Answer 30

the activation of the AV node

Question 31

what would the time interval between P and QRS tell us

Answer 31

the conduction through the AV node is properly timed

Question 32

what woud the S-T segment tell us

Answer 32

reflect action potential duration. elevation or depression frequently occurs during acute myocardial infarction.

Question 33

what would the Q-T interval tell us

Answer 33

action potential duration, where a block of potasium flux to depolarize the AP would lead to a long Q-T syndrome!

Question 34

what if we block Na channels in heart cells

Answer 34

prolong QRS duration since the QRS duration reflects the action potential propagation through the ventricles.

Question 35

what would highper cholemia do to the ECG

Answer 35

slow the action potential duration and get long long Q-T syndrome!

Question 36

whould would bundle branch block, ventricular hypertrophy, and severe hyperkalemia lead to?

Answer 36

prolonged QRS duration due to a longer time to electrically activate the ventricles.

Question 37

what is the basis of the electrical dipole that is measured by the ECG

Answer 37

dipoles form in the cells due to cells of different Vm and therefore different membrane potentials being near another; and these will then sum together to give an average dipole as the difference in potential propagates.

Question 38

wwhat is the direction of the dipole

Answer 38

towards the resting cells or towards the positive extracellular potential.

Question 39

what is the dipole once all of the cells are depolarized

Answer 39

ZERO!!! there is only a dipole when cells of different external membrane potential are in close proxcimony.

Question 40

when do you get an EKG signal

Answer 40

when the depolarization wave moves through the cell so that some of the cell is depolarized and some is not. This difference in polarization in the cell makes the dipole whose magnitude is measured by the ECG

Question 41

what if the dipole signal is in the same direction as your leads are oreinted, or in the opposite, or half way between?

Answer 41

maximum signal; minumum signal; Isoelectric signal

Question 42

as the cell depolarizes and is half way depolarized what is the EKG signal doing

Answer 42

the signal is at its peak