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

lecture 3: guyton chapter 11 Flashcards

(101 cards)

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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
explain where lead 2 is placed
The negative terminal of the electrocardiogram is connected to the right arm, and the positive terminal is connected to the left leg.
26
explain where lead 3 is placed
The negative terminal of the electrocardiogram is connected to the left arm, and the positive terminal is connected to the left leg
27
what does einthoven's law state
that the electrical potential of any limb equals the sum of the other two (+ and - signs of leads must be observed).
28
lead 1+ lead BLANK= lead BLANK
led 1 + lead 3 = lead 2
29
the amplitude of the R wave is recorded highest at what lead
the lead that is facing closest to the apex of the heart
30
what augments unipolar limb leads are used
aVR aVL and AVF
31
where is the electrode for AVR
For aVR the + electrode is the right arm, and the – electrode is the left arm + left leg;
32
where is electrode for aVL
aVL + electrode is left arm
33
where is electrode for aVF
positive electrode on left foot
34
how many chest leads are there
6 | v1-v6
35
are chest leads unipolar or bipolar
unipolar
36
true or false: chest leads are placed around the heart
true
37
chest leads give readings in the plane BLANK to the limb leads
perpendicular plane
38
what is another name for chest leads
precordial leads
39
what are chest leads very sensitive to
very sensitive to electrical potential changes | underneath the electrode.
40
for a 12 lead ECG how many beats are needed to make an interpretation
1 beat
41
true or false: each lead for an 12 lead ECG has 2 positive electrodes
false, only 1
42
which electrode acts like the camera
positive
43
where is the view from in an ECG
View is from the positive electrode towards the negative electrode.
44
what is the portion of the left ventricle that each lead "sees" determined by
by the location of the positive electrode
45
true or false: no matter where you place the electrodes, you will get the same viewpoint
false. Different placements of the electrodes will yield different viewpoints.
46
what leads look at an inferior view of the heart wall and how do they look
leads II, III and aVF | from the left leg up
47
which leads get a view of the posterior heart wall
leads V1 and V2
48
which leads give a view of the lateral heart wall (for high lateral)and how do they look
leads I and AVL | looks from the left arm towards the heart
49
which leads give a view of the lateral heart wall (low lateral or apical view) and how do they look
leads V5 and V6 | looks from left lateral chest towards heart
50
which leads give view of entire lateral heart wall and how do they look
leads I, aVL, V5 and V6 | look at liateral wall from two diff perceptions
51
which leads give a view of anterior heart wall and how do they look
leads v3 and v4 | from left anterior chestt
52
which leads give a view of septal heart wall and how do they look
leads v1 and v2 look along sternal borders
53
true or false: you should get different HR when using different leads
false, always same HR
54
what does the p wave represent
Represents positive and negative deflections of atrial contraction and relaxation =atrial depolarization
55
what is the PR intervant
Distance between the P wave and the R wave. Should be consistent =delay of the contraction from atrium to ventricles
56
what does an inconsistent PR interval mean
problem with AV node (not slowing the signal down properly)
57
what does the QRS complex represent
the ventricle depolarization
58
what is the Q R and S waves
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
what is the ST segment
essentially isoelectric (slopes gently upwards)
60
what is the J point and what does it give info on
the point at which the ST Segment takes off from the QRS complex gives info on heart function
61
what type of wave is the t wave (de or repol)
repolarization
62
explain the t wave (in terms of sings)
Upright always in leads I, II, V2-V6. aVR is always negative. Leads III, aVL, aVF, and V1 can be positive or negative
63
what is the Uwave
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
what is hypokalemia
lack of k+ in the body
65
what is the QT interval
one complete ventricular cycle
66
what 4 structures can ECG not show the activity of
SA node AV node Bundle of his (and branches) purkinje network
67
what is the P wave a small bump in comparison to the QRS wave
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
what do the individual squares of the ECG represent
measure time and amplitude.
69
3 squares ventricle is what amplitude
0.3 mv
70
each square of ECG is how many seconds
0.04 sec
71
what do ECGS diagnose
Cardiac arrhythmias Heart rate Axis deviations Chamber enlargement Conduction abnormalities
72
What determines the amplitude of the waves in an ECG
the mass of the cells (ex: atrial thinner than ventricles so faster)
73
what is the 1st step when interpreting ECG
evaluate the P wave
74
what does the P wave indicate on ECG
if atrial rhythm is normal
75
what are the 3 questions to ask about P waves
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
true or false: P wav es occur at reg intervals during normal sinus rhythm
true
77
what is the 2nd step when interpreting ECG
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
what is the duration of a normal QRS complex
0.04-0.06
79
what does a QRS compelx of longer than 0.06 seconds indicate
waves have left normal pathways (conduction tissues) and occur within ventricular myocardium.
80
what is a longer QRS called and what does it cause
Ventricular Complex and causes the QRS complex to have a wide and bizarre appearance on the ECG
81
what is the 3rd step when analyzing ECG
define the relationship between the P wave and the QRS complex.
82
what does the relationship between the P wave and the QRS complex determine
This determines whether the atria and ventricles are working in sync!
83
what are you looking for in terms of the relationship between P wave and QRS
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
what is the 4th step when analyzing the ECG
look for anything abnormal. Arrhythmias Escaped beats Or anything else that does not resemble the classical PQRST complex.
85
what are different waves of calculated HR
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
what is respitory sinus arrythmia
Looks the same as the normal heart sinus rhythm, except that the heart rate is variable because it corresponds with respiration.
87
as a patient inhales, the heart rate BLANKS
increases
88
as a patient exhales, the HR blank
decreases
89
why does a wandering pacemaker (P wave) happen
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
what is a wandering pacemaker a sign of
arrythmias
91
what are the 3 common artifact types
Sixty-cycle interference Muscle tremors Wandering Baseline
92
what is sixty cycle interference
This is an electrical interference pattern that occurs when the electrical equipment is not properly grounded Looks like continuous electrical stimulations on readout.
93
how can you fix sixty cycle interference
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
what are muscle tremors
These look like rapid and random movements of the baseline.
95
how to fix muscle tremors
calm them place hand on them for calm stop talking
96
true or false: muscle tremors on ECG can be caused by talking
true | use of muscles
97
what is a wandering baseline caused by
caused by the moving chest when the patient breathe.
98
how to fix wandering baseline
make sure the patient holds his/her breath for 20-30 seconds to get a quick reading
99
true or false: Avr , AVl and AVF are new leads
false, by using the limb leads and computers you can manipulate for different angles
100
why is it called augmented unipolar limb leads
because 1 lead is ground while the other is the electrode
101
signal comes from BLANK TO BLANK | but view is from opposite
signal is from negative to positive | view is from psotive to neg

259 - physiology (21 decks)

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