The heart

Question 1

3 physical recordings on ECG

Answer 1

lead I - right arm to left arm

lead II - right arm to left leg

lead III - left arm to left leg

Question 2

what controls the heart rhythm?

Answer 2

SAN

Question 3

normal heart rate

Answer 3

60-100 bpm

Question 4

which nerve is stimulated for heart rate?

Answer 4

vagus nerve (parasympathetic)

Question 5

which neurotransmitter does the vagus nerve release?

Answer 5

acetylcholine

Question 6

do we all have normal HR?

Answer 6

no - physiological arrhythmias

due to fluctuation of vagus nerve with breathing

Question 7

P wave

Answer 7

depolarisation of atria

Question 8

QRS complex

Answer 8

depolarisation of ventricles

Question 9

T wave

Answer 9

re-polarisation of ventricles

Question 10

ST segment

Answer 10

ventricular plateau

Question 11

PR interval

Answer 11

atrial depolarisation & AV delay

Question 12

QT interval

Answer 12

ventricular depolarisation & re-polarisation

Question 13

2 types of action potential of the heart?

Answer 13

pacemaker AP

cardiac AP

Question 14

pacemaker AP

Answer 14

slow depolarisation followed by repolarisation

(no true baseline)

Question 15

cardiac AP

Answer 15

[characterised by fast upstroke]

Phase 0 - rapid depolarisation
Phase 1 - rapid re-polarisation
Phase 2 - plateau
Phase 3 - re-polarisation
Phase 4 - stable baseline

Question 16

cardiac AP - ions

Answer 16

Phase 0 - rapid Na+ influx (= depolarisation)

Phase 1 - K+ efflux (= re-polarisation

Phase 2 - Ca2+ influx via L-type voltage gated Ca2+ channels

Phase 3 - K+ efflux

Question 17

absolute refractory period

Answer 17

when 2nd AP generation is not possible

Question 18

relative refractory period

Answer 18

when 2nd AP generation is possible

Question 19

pacemaker AP - ions

Answer 19

Na+ influx (generates depolarisation)

Ca2+ influx followed by K+ efflux

Question 20

funny current

Answer 20

mixed Na+ - K+ channel that activates @ hyper polarisation directly by increased cAMP conc.

controls HR

Question 21

effect on depolarisation if there’s an increase in sympathetic stimulation

Answer 21

increase in magnitude of funny current

speeds up depolarisation

larger current = less time required to reach threshold = increase in HR

smaller current = more time to reach threshold = reduced frequency of AP

Question 22

how are arrhythmias classified?

Answer 22

1.By effect on HR - bradycardia vs tachycardia

2. By effect on heart rhythm - regular vs irregular
3. By site of origin in heart - supraventricular (SAN, atria, AVN) vs ventricular (Bundle of His, Purkinje fibres and ventricles)
4. By type of QRS complex - narrow vs broad

Question 23

signs and symptoms of arrhythmias

Answer 23

palpitations

shortness of breath

chest pains

dizziness and feeling faint

blackouts/syncope

cardiac arrest

Question 24

physiological causes of bradycardia

Answer 24

increased vagal tone

trained athletes

Question 25

extrinsic/non-cardiac causes of bradycardia

Answer 25

hypothyroidism

severe hyperkalaemia or hypo/hypercalcaemia

anti-arrhythmic or anti-hypertensive drugs

Question 26

intrinsic causes of bradycardia

Answer 26

sick sinus syndrome

atrioventricular blockade / heart block

Question 27

sick sinus syndrome

Answer 27

malfunction of SAN

[on ECG]
1. sinus pause
2. sinus arrest (pause > 3s)
3. bradycardia-tachycardia syndrome

Question 28

treatment for sick sinus syndrome

Answer 28

implantable transcutaneous pacemaker

Question 29

1st degree AV block

Answer 29

slower AV conduction

Question 30

2nd degree AV block

Answer 30

missed beats to ventricle

Question 31

3rd degree AV block

Answer 31

= complete block

no conduction to ventricle

P waves + QRS = completely random/separated

Question 32

drugs used to treat AV block

Answer 32

atropine and isoprenaline

Question 33

long term solutions to AV block

Answer 33

implantable transcutaneous pacemaker (TCP)