Lab 8 electrocardiography and cardiovascular sounds I

Question 1

what is the PR interval and what does it correspond to?

Answer 1

beginning of P wave to beginning of QRS

corresponds to time taken for excitation wave to spread from SA node to initial spread through the ventricular muscle

Question 2

what is the PR segment and what does it correspond to?

Answer 2

it is from the end of the P wave to the beginning of the first deflection away from baseline of QRS complex. It is when the excitation wave spreads through the bundle of His and Bundle branches

Question 3

what is the QRS complex and what does it represent?

Answer 3

the Q wave is the first negative deflection away, R is the first positive deflection; S is the negative deflection after a negative Q and or a positive R. The duration of the QRS measures the time for ventricular depolarization

Question 4

what is the Q-T interval and what does it represent?q

Answer 4

it is the interval from the beginning of the QRS to the end of the T wave. It measures the duration of ventricular depolarization and repolarization. it approximates ventricular contraction.

Question 5

what is the S-T segment?

Answer 5

the time from the end of the QRS to the beginning of the T wave. it is a plateau period of ventricular action potential and is normally isoelectric or only slightly displaced from 0mV.

Question 6

what are bipolar leads?

Answer 6

when both electrodes are close enough to the heart to be influenced by it

Question 7

what is Lead I?

Answer 7

records potential difference between the left forelimb (+) and the right forelimb (-)

Question 8

what is lead II?

Answer 8

records potential difference between the left hindlimb (+) and the right forelimb (-)

Question 9

what is lead III?

Answer 9

it records the potential difference between the left hindlimb (+) and the left forelimb (-)

Question 10

what are unipolar leads?

Answer 10

leads that measure potentials between an exploring electrode close to the potential source and a distant reference electrode or a neutralizing reference electrode

Question 11

what are precordal (chest) unipolar leads?

Answer 11

the unipolar exploring lead is placed at various points from V1-V10 over the thorax. The reference is the central terminal of Wilson

Question 12

what is the central terminal of Wilson?

Answer 12

it is where the limb electrodes (left, right forelimbs and right forelimbs) are connected to a single point throug 5000 ohm resistors which serves as a reference or electrical zero

Question 13

what are augmented unipolar leads?

Answer 13

they use the standard electrode placements with one electrode serving as the exploring electrode and the remaining two combined as the reference.

Question 14

what is aVR?

Answer 14

the right forelimb is the (+) and the left forelimb and left hind limbs are references

Question 15

what is aVL?

Answer 15

the left forelimb is (+) and the left hindlimb and right forelimb are reference

Question 16

what is aVF?

Answer 16

the left hindlimb is (+) and the left and right forelimbs are reference

Question 17

what is percussion?

Answer 17

the elicitation of sounds from parts of the body by tapping with the fingers or an instrument

Question 18

what is auscultation?

Answer 18

it is the detection and study of sounds produced by the body

Question 19

what is sound?

Answer 19

a mechanical wave creating vibrations or waves in the air or other medium, which, upon reaching the ear, are perceived as sounds

Question 20

what are tones?

Answer 20

they are distinct from noises; they are sounds produced by regular oscillations causing a series of waves, vibrating at a uniform rate

Question 21

what is intensity?

Answer 21

the loudness of the sound; depends upon the amplitude of the vibrations produced

Question 22

what is pitch?

Answer 22

the perception by the ear of vibrations produced in a given period of time or the frequency

Question 23

what are transients?

Answer 23

cardiovascular sounds of short duration; may be normal or abnormal

Question 24

what are murmurs?

Answer 24

sounds of longer duration than transients; frequently reflect abnormal function

Question 25

how many (normal) heart sounds are there?

Answer 25

4

Question 26

what is the first heart sound?

Answer 26

it occurs at the end of atrial contraction and at the onset of ventricular contraction, usually just following the QRS complex of the ECG. It is related to the closing of the atrio-ventricular valves

Question 27

what is the second heart sound?

Answer 27

it begins near the end of the T wave; it coincides with the closing of the aortic and pulmonic semilunar vales at hte beginning of ventricular relaxation

Question 28

what is the third heart sound?

Answer 28

it is a low frequency sound during diastole that corresponds to the rapid inflow of blood into the ventricle

Question 29

what is the fourth heart sound?

Answer 29

produced by atrial systole