heart

Question 1

Absolute refractory period

Answer 1

during action potential, another AP cannot be stimulated

Explained by Na channel state, is inactive for a period of time
open -> a function of time -> inactive -> a function of voltage -> closed (when membrane potential reaches -90mV)

Question 2

muscle twitch

Answer 2

same duration as AP, can’t be summated

Question 3

pacemaker cells

Answer 3

found in sinoatrial node of heart (insert PIC of action potential)
AKA SA node cells

• Slow depolarization, due to Na coming in
• Upstroke due to Ca2+ opening (ca channels open slower, less steep)
• Self induced action potential (cell processes do it on its own)

Determine heart rate

Question 4

Gap junctions

Answer 4

connects cells in the heart

Question 5

conseq of incr slope on pace maker heart rate

Answer 5

faster heart rate

Question 6

Sympathetic nervous innervation

Answer 6

noradrenaline acts on pacemaker cells (b1 receptors
OR adrenaline coming from adrenal gland
- Incr slope of pacemaker pot (phase 4 slope) -> incr HR

Question 7

parasympathetic nervous innervation

Answer 7

aCh acts on pacemaker cells (muscurinic m2 receptors)
- decr slope of pacemaker depolarization (phase 4 slope) -> decr HR

***make table w neurotransmitters

Question 8

AP pathway

Answer 8

Starts in SA node (60-100 bpm)
AV node (40-50 bpm when taken out, when stimulated by SA node cells it synchronizes), atria contraction

Bundle of His
left + right bundle branches
purkinje fubers, ventricles contract after

Question 9

Regular heart rate

Answer 9

60-100 bpm

Question 10

paper speed for ecg

Answer 10

25mm/sec

Question 11

sinus arrhythmia

Answer 11

faster HR at inspiration, slower at expiration

Question 12

Paul’s ecg

Answer 12

no p waves
irregular, no pattern
rate: varies between 80 and 120

Question 13

paroxysmal atrial fibrillation

Answer 13

atrial depolarization + repolarization are disorganized due to alcohol
- AV node receiving random APs