CardioVascular Physiology 2

Question 1

Myocyte AP length

Answer 1

• longer to prevent summation
• heart relaxes at the end of the twitch to allow the heart to fill with blood
• 200 ms

Question 2

Cardiac Muscle Fibre Refractory Period

Answer 2

• refractory period lasts as long as the entire muscle twitch which prevents tetanus

Question 3

Pacemaker AP’s

Answer 3

1) Calcium Channels - mediate depolarization
2) Slower K Channels - mediate repolarization
3) HCN Channels - mediate pacemaker cells
- conduct Na/K leads to depolarization

Question 4

SA Node initiation

Answer 4

AP’s rhythemically initiated in the SA Node cells set the pace of the heart

Question 5

Electrocardiogram Waves

Answer 5

P-Wave = atrial depolarization
QRS = atrial repolarization & ventricle depolarization
T-Wave = ventricular repolarization

Question 6

Tachycardia

Answer 6

fast heart rate

Question 7

Bradycardia

Answer 7

slow heart rate

Question 8

Atrial Fibrillation

Answer 8

heart still functions as a pump

Question 9

Ventricular Fibrillation

Answer 9

heart does not function as a pump

Question 10

SA Node Function

Answer 10

sets the pace of the heartbeat

Question 11

AV Node function

Answer 11

1. directs electrical signals
2. delays the transmission of AP’s
3. can act as the pacemaker under certain conditions

Question 12

how do action potentials turn into a contraction

Answer 12

as AP’s pass across tissues, myocytes are depolarized causing a contraction from ventricles up, from apex to base

Question 13

Electrical Movement

Answer 13

1. SA Node
2. AV Node
3. AV Bundle (bundle of his)
4. Bundle Branches
5. Purkinje Fibres