5.2 EKG

Question 2

What is an ECG?

Answer 2

ECG & EKG = same

• composite of all APs generated by nodal and contracile cells at given time
• waves: deflections above or below baseline
• Segments: sections of baseline between 2 waves
  intervals: combination of waves & segments

*ECG is NOT an action potential -> looking at all electrical activity from all heart parts @ same time

Question 3

what are the different deflections in an ECG

Answer 3

Question 4

What does the P-R interval represent?

Answer 4

0. 16s
   - start of atrial excitation to start of ventricular excitation

*sometimes called P-Q interval, but Q wave is often hard to find so finding P-R interval is easier

Question 5

what is the S-T segment

Answer 5

0. 08s
   - AP of ventricular myocytes are in plateaus phase

(ventricles depolarize)

*all muscles are contracting here

Question 6

describe teh QT interval

Answer 6

• start of ventricular depolarization to end of ventricular repolarization

Question 11

Answer 11

P wave

• atrial depolarization, initated by SA node

*stops at atria -> doesnt spread to ventricles

Question 12

Answer 12

With atrial depolarization complete, impulse is

delayed at AV node

Question 14

Answer 14

ventricular depolarization

• begins at apex, causes QRS complex
• atrial repolarizaiton occurs

Question 15

Answer 15

ventricular depolarization is complete

*moment where all ventricular muscles are contracting

Question 16

Answer 16

ventricular repolarization begins at apex, causing the T wave

Question 17

Answer 17

ventricular repolarization is complete

• after T wave the ventricles are fully relaxed

Question 18

Answer 18

junctional rhythm

• Sa node is non functional so P waves are absent
• av node paces heart at 90-60 bpm

* P wave caused by Sa node that causes atrial depolarization

Question 19

Answer 19

• second degree heart block
• AV node fails to conduct some SA node impulses
• As result there are more P waves than QRS

Question 20

what is systole

what is diastole

Answer 20

systole = contraciton (1/3 of time)

diastole = relaxation (2/3 of time)

Question 21

what is the first phase of the cardiac cycle

Answer 21

ventricular filing

(mid to late diastole)

• AV valves open; semilunar vales are closed
• 80% of blood passively flows into ventricles
• Atrial systole occurs, delivering remaining 20%
• end diastolive volume: volume fo blood in each ventircle at end of ventricular diastole

Question 22

what is end diastolic volume

Answer 22

happens at end of venricular filling

volume of blood in each ventricle at end of ventricular diastole

Question 23

describe the second phase of the cardiac cycle

Answer 23

• ventricular systole
• atria relax (atrialdiastole); venticles begin to contract
• INC venticular pressure results in closing of AV valves (dec in vol so inc P)
• Isovolumetirc contraction phase: all valves are closed
• Ejection phase: ventricular pressure > pressure in large arteries; semilunar values open

*end systolic volume

Question 24

describe end systolic volume

Answer 24

volume of blood remaining in each ventricle at end of ventricular systole

Question 25

describe the 3rd pahse of the caridac cycle

Answer 25

isovolumetirc relaxation

• occurs in early diastole
• > ventricles relax
• > backflow of blood in aorta & pulmonary trunk closes SL valves & causes dicrotic notch

*breif rise in aortic pressure

Question 26

describe the sounds of the heart

Answer 26

• two sounds associated with closing of heart vlaves
• 1st:
  
  • Av valves closing
  • beginning of ventricualr systole
  • “lub”
• 2nd
  
  • occurs when SL vlaves close
  • beginning of ventricular diastole
  • “dub”

Question 27

what is a heart murmer

Answer 27

abnormal heart sounds, most often indicative of value probelms

Question 28

Question 29