Exam 3: Heart Part 2: Arrhythmias

Question 1

what sets the normal sinus rhythm

Answer 1

SA node

Question 2

arrhythmia or dysrhythmia

Answer 2

disruption in normal rhythm

Question 3

P wave

Answer 3

atrial depolarization

SA node firing, start to get waves across atria

Question 4

PR interval

Answer 4

depolarization of atria completed, now delay bc reached the AV node, ventricles filling

Question 5

QRS complex

Answer 5

ventricular contraction - down bundle branches to the purkinje fibers

Question 6

ST interval

Answer 6

completion of contraction of ventricles

Question 7

T wav

Answer 7

ventricular repolarization

Question 8

bradycardia

Answer 8

below 60bpm

Question 9

tachycardia

Answer 9

above 100bpm

Question 10

when does a heart block occur

Answer 10

when conductive tissue has been impaired

when communication between SA node and AV node is “blocked”

Question 11

first degree heart block

Answer 11

still communicating from SA to AV node

lengthened PR interval - so a delay but still getting overdrive suppression

Question 12

second degree heart block

Answer 12

each P wave does not result in a QRS can be 2:1 or 3:1

drop a QRS - indicative of at least 2nd degree heart block

Question 13

third degree heart block

Answer 13

complete block
no communication between SA and AV node
AV node set its own pacemaker (ectopic pacemaker)
distance between p waves regular and QRS but would not coordinate with eachother and heart would not fill and pump properly

Question 14

atrial flutter

Answer 14

SA node gets irritable, atria going very fast in contractions
sawtooth pattern
problem with filling

up to 350 bpm

Question 15

ventricular flutter

Answer 15

ventricles cannot contract

up to 450 bpm

Question 16

atrial fibrillation

Answer 16

can lead to ventricular fibrillation
irritability in the muscle: many ectopic sites working at once - get no pattern
see QRS but cannot respond to activity in atria

Question 17

ventricular fibrillation

Answer 17

no pattern at all

need to look into defibrillation to reset heart so SA node can resume overdrive suppression

Question 18

things that can cause irritability

Answer 18

inc epinephrine
inc sympathetic stimulation
drugs: caffeine, cocaine, amphetamines, excess digitalis
some toxins
hyperthyroidism
inc stretch of heart muscle
hypoxia - if blood flow impaired to heart get irritable

Question 19

cardiac output

Answer 19

amount of blood ejected from heart per minute

CO = SV x HR

Question 20

stroke volume

Answer 20

volume of blood ejected from ventricle per contraction

SV = EDV-ESV

Question 21

heart rate

Answer 21

contractions per minute

Question 22

EDV

Answer 22

end diastolic volume

amount of blood in ventricle at end of filling

Question 23

ESV

Answer 23

end systolic volume

amount of blood left in ventricle after contracting

Question 24

ejection fraction

Answer 24

EF = SV/EDV

normal range = 55-75%

Question 25

preload

Answer 25

how much venous return comes back into heart , how it fills and stretches

Question 26

afterload

Answer 26

ability of heart to contract, force it gives, resistance needed by heart
if lots of resistance, higher afterload - ex: hardening of arteries

Question 27

frank-starling law

Answer 27

the contraction force of the heart increases as EDV increases
the inc force is due to inc stretching during filling
this allows blood flow to keep up with needs of tissues and organs

bigger preload, stronger the contraction should be

Question 28

factors affecting venous return

Answer 28

muscle contraction - activity
body position - gravity
venous compliance

Question 29

the SV will only increase if the afterload…

Answer 29

remains constant