Week 9- The heart (Cardio week 1)

Question 1

What are the non-contractile cardiac cells that automatically depolarize?

Answer 1

Nodal cells (modified cardiac monocytes)

Question 2

What is the RMP of nodal cells

Answer 2

No resting membrane potential- automatically depolarize

Question 3

What fibers are the connection between the atria and ventricles

Answer 3

Bundle of HIS

Question 4

What is the pacemaker of the heart

Answer 4

SA node

Question 5

What causes atrial contraction

Answer 5

SA node

Question 6

What causes a slight pause (.1 second) for filling time?

Answer 6

AV node

Question 7

Why is the SA node the pacemaker and not the AV node?

Answer 7

SA depolarizes faster than AV node

Question 8

What causes the AV node to increase the pause vs decrease the pause?

Answer 8

Pause is increased by AcH (slower heartrate), Decreased by catecholamines (faster heart rate)

Question 9

What is the fastest conduction rate in the heart

Answer 9

purkinje fibers (100x faster than the rest of the heart)

Question 10

What part of the heart conduction contracts ventricles and papillary muscles

Answer 10

Purkinje fibers

Question 11

How long is the cardiac action potential including the refractor period

Answer 11

250-300 ms

Question 12

Effect of SNS activity on auto rythmic potentials

Answer 12

Increase slope of depolarization line (Increase Na and Ca influx)

Question 13

Effect of PNS activity in auto rythmic potential

Answer 13

Change slope (decrease) Increase hyperpolarization (get more -)
Mechanism: Open more K channels, decrease Na and Ca influx

Question 14

What is the EF

Answer 14

(SV/EDV ) * 100

Question 15

What is SV

Answer 15

EDV-ESV

Question 16

What is CO

Answer 16

HRxSV

Question 17

What is afterload and what is a measure of it

Answer 17

pressure required to open aortic valve, measured by MAP

Question 18

What is preload? How is it measured?

Answer 18

Stretch on L ventrical before contraction (measured with EDV)