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259 - physiology > lecture 3: guyton chapter 11 > Flashcards

lecture 3: guyton chapter 11 Flashcards

1
Q

what 2 types of nervous systems act on the pacemaker activity

A

sympathetic and parasymphathetic

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2
Q

explain 3 ways which the parasympathetic nervous system can affect pacemaker activity

A

1) slower depolarization (less sodium entering cells, slower HR)

2) lower resting membrane potential (more energy needed to reach threshold)
=longer=slower HR

3) more positive threshold
longer to reacher=slower HR

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3
Q

true or false: ventricular cells have leaky sodium which allows them to have inherent excitatory abilities

A

false, no leaky

need exact energy for thresholf

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4
Q

explain phase 0 of ventricular AP

A

depolarizing impulse activates fast NA+ channels and inactivates K+ channels.

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5
Q

explain phase 1 of ventricular Ap

A

Transient opening of K+ channels and Na+ channels begin to close
(k+ starts to excite the cell)

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6
Q

explain phase 2 of ventricular AP

A

Ca2+ channels are open, the key difference between nerve AP.

balance between the influx of calcium and the efflux of K

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7
Q

what is the key difference between ventricular AP and muscle AP

A

calcium channels are open for a period of time while K+ channel are also open

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8
Q

explain phase 3 of AP ventricular

A

repolarization, Ca2+ inactivate and K+ channels open.

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9
Q

explain phase 4 of the ventricular AP

A

resting membrane potential near the K+ equilibrium potential.
(few leaky channels)

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10
Q

the resting potential of the heart is near the K+ equi, the Ca2+ or the NA+ equilibrium

A

k+

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11
Q

where is AP generated

A

SA node

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12
Q

why is AP generated in SA node

A

leaky cells

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13
Q

explain the steps or conduction in the heart

A

1) AP initiated in SA node
2) AP travels through atrial cells (they get depolarized easily through syncytium)
3) Signal gets collected at AV node and gets slowed down because of less gap junctions
4) signal passes through a bundle of His to the ventricles
5) moves through Purkinje fibers to the apex of the heart
6) signal moves inside to outside and upwards to facilitate the emptying during contraction

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14
Q

why and how the signal slowed down at the AV node

A

to allow the atrium to contract before the ventricles (max filling)
they have fewer gap junctions

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15
Q

why is the signal collected at the bundle of His

A

only place where the signal can travel through the fibrous membrane between atrium to ventricle

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16
Q

what device is used to record the depolar and repolar wave

A

voltmeter

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17
Q

if the depolarization wave moves towards the positive node, what type of reading on the volt meter

A

positive

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18
Q

if the repolarization wave moves towards the positive node, what type of reading on the volt meter

A

negative

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19
Q

the depolar and repolar waves move from the BLANK electrode to the BLANK electrode

A

negative to positive

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20
Q

true or false: when the cardiomyocyte is either completely depolarized or repolarized there is no potential recorded

A

true

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21
Q

the mean vector through a partially depolarised heart goes towards where

A

down towards the apex of the heart

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22
Q

what records the signal (negative or positive)

A

positive node

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23
Q

what does bipolar lead mean

A

ECG is recorded from 2 electrodes on the body

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24
Q

explain where lead 1 is placed

A

The negative terminal of the electrocardiogram is connected to the right arm, and the positive terminal is connected to the left arm.

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25
Q

explain where lead 2 is placed

A

The negative terminal of the electrocardiogram is connected to the right arm, and the positive terminal is connected to the left leg.

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26
Q

explain where lead 3 is placed

A

The negative terminal of the electrocardiogram is connected to the left arm, and the positive terminal is connected to the left leg

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27
Q

what does einthoven’s law state

A

that the electrical potential of any limb equals the sum of the other two (+ and - signs of leads must be observed).

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28
Q

lead 1+ lead BLANK= lead BLANK

A

led 1 + lead 3 = lead 2

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29
Q

the amplitude of the R wave is recorded highest at what lead

A

the lead that is facing closest to the apex of the heart

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30
Q

what augments unipolar limb leads are used

A

aVR aVL and AVF

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31
Q

where is the electrode for AVR

A

For aVR the + electrode is the right arm, and the – electrode is the left arm + left leg;

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32
Q

where is electrode for aVL

A

aVL + electrode is left arm

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33
Q

where is electrode for aVF

A

positive electrode on left foot

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34
Q

how many chest leads are there

A

6

v1-v6

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35
Q

are chest leads unipolar or bipolar

A

unipolar

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36
Q

true or false: chest leads are placed around the heart

A

true

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37
Q

chest leads give readings in the plane BLANK to the limb leads

A

perpendicular plane

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38
Q

what is another name for chest leads

A

precordial leads

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39
Q

what are chest leads very sensitive to

A

very sensitive to electrical potential changes

underneath the electrode.

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40
Q

for a 12 lead ECG how many beats are needed to make an interpretation

A

1 beat

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41
Q

true or false: each lead for an 12 lead ECG has 2 positive electrodes

A

false, only 1

42
Q

which electrode acts like the camera

A

positive

43
Q

where is the view from in an ECG

A

View is from the positive electrode towards the negative electrode.

44
Q

what is the portion of the left ventricle that each lead “sees” determined by

A

by the location of the positive electrode

45
Q

true or false: no matter where you place the electrodes, you will get the same viewpoint

A

false. Different placements of the electrodes will yield different viewpoints.

46
Q

what leads look at an inferior view of the heart wall and how do they look

A

leads II, III and aVF

from the left leg up

47
Q

which leads get a view of the posterior heart wall

A

leads V1 and V2

48
Q

which leads give a view of the lateral heart wall (for high lateral)and how do they look

A

leads I and AVL

looks from the left arm towards the heart

49
Q

which leads give a view of the lateral heart wall (low lateral or apical view) and how do they look

A

leads V5 and V6

looks from left lateral chest towards heart

50
Q

which leads give view of entire lateral heart wall and how do they look

A

leads I, aVL, V5 and V6

look at liateral wall from two diff perceptions

51
Q

which leads give a view of anterior heart wall and how do they look

A

leads v3 and v4

from left anterior chestt

52
Q

which leads give a view of septal heart wall and how do they look

A

leads v1 and v2

look along sternal borders

53
Q

true or false: you should get different HR when using different leads

A

false, always same HR

54
Q

what does the p wave represent

A

Represents positive and negative deflections of atrial contraction and relaxation
=atrial depolarization

55
Q

what is the PR intervant

A

Distance between the P wave and the R wave. Should be consistent
=delay of the contraction from atrium to ventricles

56
Q

what does an inconsistent PR interval mean

A

problem with AV node (not slowing the signal down properly)

57
Q

what does the QRS complex represent

A

the ventricle depolarization

58
Q

what is the Q R and S waves

A

Q wave: First negative deflection
Normal in I, aVL, V1, V6
Significant or pathologic if one box wide and/or 1/3 the height of the R wave

R Wave: First positive deflection

S Wave: Next negative deflection

59
Q

what is the ST segment

A

essentially isoelectric (slopes gently upwards)

60
Q

what is the J point and what does it give info on

A

the point at which the ST Segment takes off from the QRS complex

gives info on heart function

61
Q

what type of wave is the t wave (de or repol)

A

repolarization

62
Q

explain the t wave (in terms of sings)

A

Upright always in leads I, II, V2-V6. aVR is always negative. Leads III, aVL, aVF, and V1 can be positive or negative

63
Q

what is the Uwave

A

Seen best in V3, the same polarity as T wave, represents the last part of ventricular repolarization, and can be a sign of hypokalemia

64
Q

what is hypokalemia

A

lack of k+ in the body

65
Q

what is the QT interval

A

one complete ventricular cycle

66
Q

what 4 structures can ECG not show the activity of

A

SA node
AV node
Bundle of his (and branches)
purkinje network

67
Q

what is the P wave a small bump in comparison to the QRS wave

A

The P wave or atrial depolarization is a small bump because the walls of the atria are thinner than the walls of the ventricle, therefore, the total amount of electrical activity is smaller than the QRS wave.

68
Q

what do the individual squares of the ECG represent

A

measure time and amplitude.

69
Q

3 squares ventricle is what amplitude

A

0.3 mv

70
Q

each square of ECG is how many seconds

A

0.04 sec

71
Q

what do ECGS diagnose

A

Cardiac arrhythmias
Heart rate
Axis deviations
Chamber enlargement
Conduction abnormalities

72
Q

What determines the amplitude of the waves in an ECG

A

the mass of the cells (ex: atrial thinner than ventricles so faster)

73
Q

what is the 1st step when interpreting ECG

A

evaluate the P wave

74
Q

what does the P wave indicate on ECG

A

if atrial rhythm is normal

75
Q

what are the 3 questions to ask about P waves

A

Are all the P waves occurring at regular intervals?
Do all the P waves have the same appearance on the ECG?
Are the P waves visible at all?

76
Q

true or false: P wav es occur at reg intervals during normal sinus rhythm

A

true

77
Q

what is the 2nd step when interpreting ECG

A

determine whether the ventricles are activated from inside or from another location.
This can be done by looking at the duration (time) of the QRS complex.

78
Q

what is the duration of a normal QRS complex

A

0.04-0.06

79
Q

what does a QRS compelx of longer than 0.06 seconds indicate

A

waves have left normal pathways (conduction tissues) and occur within ventricular myocardium.

80
Q

what is a longer QRS called and what does it cause

A

Ventricular Complex and causes the QRS complex to have a wide and bizarre appearance on the ECG

81
Q

what is the 3rd step when analyzing ECG

A

define the relationship between the P wave and the QRS complex.

82
Q

what does the relationship between the P wave and the QRS complex determine

A

This determines whether the atria and ventricles are working in sync!

83
Q

what are you looking for in terms of the relationship between P wave and QRS

A

You must control whether the P wave is always, never or sometimes associated with the QRS complex.
Does the P wave always come before the QRS complex?

84
Q

what is the 4th step when analyzing the ECG

A

look for anything abnormal.
Arrhythmias
Escaped beats
Or anything else that does not resemble the classical PQRST complex.

85
Q

what are different waves of calculated HR

A

Count the R waves registering within 6 seconds and
multiply by 10. (quick, but inaccurate method)

R-R interval = 0.83 sec
Heart rate = (60 sec)/(0.83 sec) = 72 beats/min min beat

86
Q

what is respitory sinus arrythmia

A

Looks the same as the normal heart sinus rhythm, except that the heart rate is variable because it corresponds with respiration.

87
Q

as a patient inhales, the heart rate BLANKS

A

increases

88
Q

as a patient exhales, the HR blank

A

decreases

89
Q

why does a wandering pacemaker (P wave) happen

A

This happens when the P waves have varied conformation, spacing and size within the same lead.
The pacemaker site may shift locations within the sinoatrial node, causing the vectors to shift slightly.

90
Q

what is a wandering pacemaker a sign of

A

arrythmias

91
Q

what are the 3 common artifact types

A

Sixty-cycle interference
Muscle tremors
Wandering Baseline

92
Q

what is sixty cycle interference

A

This is an electrical interference pattern that occurs when the electrical equipment is not properly grounded
Looks like continuous electrical stimulations on readout.

93
Q

how can you fix sixty cycle interference

A

Make sure the power cord is grounded, clips are contacting skin, clips are clean and securely attached to the cable, pull plugs on nearby equipment, turn off fluorescent lights, make sure cables are not touching one another, and that no one else is touching cables.

94
Q

what are muscle tremors

A

These look like rapid and random movements of the baseline.

95
Q

how to fix muscle tremors

A

calm them
place hand on them for calm
stop talking

96
Q

true or false: muscle tremors on ECG can be caused by talking

A

true

use of muscles

97
Q

what is a wandering baseline caused by

A

caused by the moving chest when the patient breathe.

98
Q

how to fix wandering baseline

A

make sure the patient holds his/her breath for 20-30 seconds to get a quick reading

99
Q

true or false: Avr , AVl and AVF are new leads

A

false, by using the limb leads and computers you can manipulate for different angles

100
Q

why is it called augmented unipolar limb leads

A

because 1 lead is ground while the other is the electrode

101
Q

signal comes from BLANK TO BLANK

but view is from opposite

A

signal is from negative to positive

view is from psotive to neg

259 - physiology (21 decks)

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