Brainscape's Knowledge GenomeTM

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


See full index

cardiovascular physiology > Electro -cardio Gram (ECG) > Flashcards

Electro -cardio Gram (ECG) Flashcards

1
Q

what is an** ECG**?

A
  • electrocardiography is the process of producing an electrocardiogram - a recording of the hearts electrical activity
  • involves a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

in what direction does a current flow?

A

from positive to negative

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

Describe the current flow and the electrode with the deflection

A
  • current flowing towards an electrode gives a positive deflection
  • currenr flowing away from an electrode gives a negative deflection
  • current flowing at right angles to an electrode gives no deflection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe how the electrical activity in the heart spreads from the SA node

A
  • the initiation of the heart beat begins with the pacemaker activity of the SA node
  • it then spreads across the heart from the right atrium (where SA node is) to the left atrium before passing to the ventricles
  • It passes to the ventricles via the AV node, bundle of His and its left and right branches.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what can the ECG be useful to discover?

A
  • abnormal electrical activity of the heart & abnormal function
  • example : cardiac arrhythmias (heartbeat is too fast or too slow)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is an electrical potential generated?

ie what charges are involved

A
  • Myocytes of one part of the heart must be at their normal resting potential while others are in a depolarised state
  • since the myocytes are electrically connected and the heart muscle is a syncytium (acts in sync), current will flow between these 2 regions ( & this current can be detected by ECG)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what determines the deflection direction in an ECG recording?

A
  • the nature of the chemical event - ie depolarisation or repolarisation
  • its direction of travel - in relation to the positive electrode
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does each electrode placement of the ECG measure?

A
  • detects the average current flowing towards or away from it at any time
  • electrodes placed in different locations will have different views of the electrical current
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the** waves** in a typical ECG recording? what do these waves correspond to?

A
  • P wave
  • Q wave
  • R wave
  • S wave
  • T wave

These waves correspond to specific cardiac events

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

What cardiac event is represented by the P wave?

A
  • As the atria depolarise, the extracellular current flows between the depolarised regions of the atria and the rest of the heart
  • this wave is a small positive deflection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what cardiac event is represented by the Q wave?

A
  • after a brief delay at the AV node, the septum depolarises and the current flows from left to right
  • small negative deflection - current flows away from V5 & V6 (eg’s of the unipolar leads)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what cardiac event is represented by the** R wave**?

A
  • depolarisation of the ventricular walls
  • current flows towards V3-V6 and therefore a large positive wave is recorded
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what cardiac event is represented by the S wave?

A
  • as the depolarisation passes up the ventricular walls toward the atria, the current flows away from V2-V3 and therefore a ** large negative wave is recorded.**
  • NB - by the end of the S wave, the ventricles are fully depolarised and there is no current flow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What cardiac event is represented by the T wave?

A
  • the last myocytes to depolarise are also the first to repolarise
  • hence the T wave is in an upward direction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is the ECG actually recorded?

A
  • It is recorded by placing electrodes at different points of the body and measuring voltage differences between them with an electronic amplifier (generates the graph)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what do the electrodes detect?

A

they detect a small portion of the current flow during depolarisation and repolarisation

17
Q

What are ECG leads?

A
  • information from a number of electrode placements
18
Q

Describe the 2 types of ECG leads

A

1.** Bipolar -** record the voltage between electrodes placed on** both wrists and the left ankle **
2. Unipolar - record the voltage between a single electrode placed on the body surface and an electrode that is maintained at zero potential

19
Q

What are the 3 standard bipolar leads?

A
  • **limb leads **
  • limb lead I, II & III
20
Q

Describe limb lead I

A
  • the** positive terminal of the amplifier is connected to the left arm and the negative terminal to the right arm**
  • with this placement - the amplifer records the component of wave excitation that is moving along this axis between the left and right sides of heart
21
Q

Describe the** limb lead II**

A
  • the** right arm is the negative terminal and the left leg is the positive terminal **
  • the component of the wave of excitation is moving from the **right upper portion of the heart to the tip of the ventricles **
22
Q

Describe the limb lead III

A
  • the** left leg is the positive terminal and the left arm is the negative terminal**
  • this lead records the component of the wave of excitation spreading along an axis **between the left atrium and the tip of the ventricles **
23
Q

What are the 2 types of unipolar leads used in electrocardiography?

A
  1. chest
  2. augmented limb leads
24
Q

What is used when an ECG is recorded using the unpolar chest leads?

A
  • a reference electrode is produced by joining the 3 limb leads while exploring electrode records along specific points on the chest
  • the exploring electrode is placed in 1 in 6 positions - leads V1-V6
25
Q

what do the chest leads provide information about?

A
  • the current flow in the transverse plane
26
Q

what are the 3 augmented unipolar leads?

A
  • aVr
  • aVl
  • aVf
27
Q

describe the difference between the frontal and transverse plane in terms of information activity of the heart

A
  • the three limb leads and augmented limb leads each provide information about the activity of the heart viewed from a specific point on the frontal (vertical) plane
  • each of the** 6 chest leads** (V1-6) provide information about the activity of the heart from a specific point in the transverse plane

cardiovascular physiology (23 decks)

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