Cardiovascular physiology part 2

Question 1

What does the PR interval measure?

Answer 1

PR interval shows the duration of impulse from the SA node to the ventricles.
If there is a delay it is usually due to AV node.

Question 2

What does the QT interval measure?

Answer 2

electrical activity in ventricles.

Question 3

What does the RR interval measure?

Answer 3

this is used for heart rate, therefore the duration should be equal to cardiac length.

Question 4

What are the advantages of using an ECG?

Answer 4

• simple
• non-invasive
• painless
• measures a number of irregularities in the heart.

Question 5

What are the clinical uses of an ECG?

Answer 5

• drug effects
• chamber enlargements
• disturbances in electrolytes and rhythm
• anatomical orientation

Question 6

What are some examples of ECG changes in the case of arrhythmia?

Answer 6

• may not have a p wave
• p wave may not be followed by QRS wave
• abnormal p - wave
  prolonged PR interval.

Question 7

What is cardiac arrhythmias?

Answer 7

Abnormailites in normal heart rate which could be due to:
Cardiac block and this can happen in any breed of dog and even in cats or
ectopic pacemaker.

Question 8

What are the different stages of AV block and describe them.

Answer 8

1st degree:
slow conduction of AV node and there is prolonged PR interval.
2nd degree:
two types = mobitz type I and type II
Mobitz type I = PR intervals increase gradually until AV node fails.
Mobitz type II = PR is constant but some P waves are not followed by QRS. this means the ECG is flat until the third P wave comes at expected time.
3rd degree:
complete conduction block where there is no AV node impulse. atrium and ventricles are in complete isolation and will therefore beat at own intrinsic rate.

Question 9

What causes ectopic pacemaker cardiac arrhymia?

Answer 9

this could be caused by certain toxins, electrolyte imbalance and ischemia

Question 10

What is atrial fibrillation?

Answer 10

continous AP’s throughout the atria which is common in horses, elderly animals and large breed dogs.

Question 11

What is ventriculat fibrillation?

Answer 11

continous random AP’s throughout the ventricles which is seen in boxers, bull dogs and german shepards.

Question 12

How is atrial fibrillation presented?

Answer 12

irregular RR interval with no detectable P waves. this is well tolerated but blood pools in parts of the atria which causes complications.

Question 13

How is ventricular fibrillation presented?

Answer 13

there is electrical choas with random voltage fluctuations and no coordinated ventricular contraction.
this is an emergency.

Question 14

Describe systole and diastole.

Answer 14

systole is the period of contraction/ejection and diastole is the period of relaxation.

Question 15

How many systoles and diastoles are there in the cardiac cycle?

Answer 15

there is one of each.

Question 16

What are the factors involved in wigger’s diagram?

Answer 16

p wave = rise in atrial pressure
QRS complex = rise in ventricle pressure
T wave = decrease in ventricular pressure

Question 17

In Wigger’s diagram what are the 4 phases?

Answer 17

phase 1: ventricular filling phase
phase 2a: isovolumetric contraction phase, steep rise in pressure as both ventricles remain closed (no change in volume)
phase 2b: ejection phase, left ventricle pressure is higher than aortic pressure and aortic valves open (volume is reduced)
phase 3: isovolumetric relaxation phase where there is a steep drop in ventricle pressure and valves remain close (no change in volume)

Question 18

What is arterial pulse?

Answer 18

pressure along the arteries when blood is forced into aorta during systole.

Question 19

How many heart sounds are recorded during a cardiac cycle?

Answer 19

4 heart sounds.

Question 20

What causes heart sounds?

Answer 20

vibrations from the closure of the valves.

Question 21

What heart sounds are heard in different animals?

Answer 21

first and second are in small animals and the third and fourth are heard in large animals.

Question 22

Describe S1.

Answer 22

closure of AV valves it is the LUB sound.

Question 23

Describe S2.

Answer 23

closure of semilunar valves which is the DUB sound.

Question 24

What are heart murmurs?

Answer 24

abnormal heart sounds which occur when heart flows through leaky valves and if there is a valvular defect which could be caused by bacteria or blood born parasites.

Question 25

What does the parasympathetic nerve system supply?

Answer 25

SA node (right vagus), AV node (left vagus), bundle of his and a few to atrial and ventricular muscles.

Question 26

What does the sympathetic nervous system supply?

Answer 26

SA node, AV node, bundle of his and both the atrial and ventricular muscles.

Question 27

What happens during parasympathetic stimulation?

Answer 27

• decrease in heart rate
• increased AV nodal delay
• decreased atrial convertibility
• vagus works by releasing Ach which act on M2 receptors in the heart.

Question 28

What are the effects of sympathetic stimulation?

Answer 28

• increase in heart rate (chronotrophic effects)
• increased force of contractibility (intotrophic) and relaxation (lusitrophic)
• increased cardiac velocity of cardiac impulse (dromotropic)
• heart has B1 and B2 receptors which respond adrenaline