Lecture 10 (Electrodiagram, Mechanisms of Disease)

Question 1

What’s an Electrocardiogram (ECG)?

Answer 1

Graphic record of the heart’s electrical activity, its conduction of impulses (APs)
A record of electrical events that precede the contractions of the heart

Question 2

What is a normal ECG composed of?

Answer 2

• P wave
• QRS complex
• T wave
  Measurements of the intervals between P, QRS and T waves can provide information about the rate of conduction of an AP through the heart

Question 3

Describe the P wave

Answer 3

Lasts 0.08s
Results from the movement of the depolarization wave from the SA node through the atria
The atria contracts

Question 4

Describe the QRS complex

Answer 4

Results from ventricular depolarization & atrial repolarization
Precedes ventricular contraction
Complicated shape because the paths of the depolarization waves through the ventricular walls change continuously

Question 5

Describe the T wave

Answer 5

Caused by ventricular repolarization
Repolarization is slower than depolarization
T wave is more spread out and has lower amplitude than the QRS wave

Question 6

Explain Heart Block

Answer 6

AV node block→impulses are blocked from getting through to ventricular myocardium. Ventricules contract at much slower rate. Large interval between P wave and R peak

Question 7

Explain Tachycardia

Answer 7

Very rapid heart rhythm (more100)
Normal after exercise & stress response
Abnormal can result from improper autonomic control of the heart, blood loss, shock, the action of drugs and toxins, fever

Question 8

Explain Bradycardia

Answer 8

Slow heart rhythm
Normal during sleep/ for athletes
Abnormal can result from improper nervous control of the heart or from a damaged SA node

Question 9

Explain Sinus Dysrhythmia

Answer 9

Variation in heart rate during the breathing cycle
The heart rate increases during inspiration & decreases during expiration.
Causes not clear
Common in young ppl & does not require treatment

Question 10

Explain Premature Contractions

Answer 10

Contractions that occur before the next expected contraction in a series of cardiac cycles.
Occur with lack of sleep, too much caffeine or nicotine, alcohol or heart damage

Question 11

Define Fibrillation. What are the 2 types?

Answer 11

Condition in which cardiac muscle fibers contract out of step with each other.
Atrial fibrillation & Ventricular fibrillation

Question 12

What’s the difference between Atrial fibrillation and Ventricular fibrillation

Answer 12

Atrial fibrillation: Occurs in mitral stenosis, rheumatic heart disease, and infarction of the atrial myocardium

Ventricular fibrillation: Immediately life threatening situation in which the lack of ventricular pumping suddenly stops the flow of blood to vital tissues
Treated by defibrillation