Cardiovascular Physiology 2

Question 1

2 Types of Cardiac Muscle cells

Answer 1

1. CONTRACTILE CELLS
   - ~99% of cells
   - Do mechanical work of pumping
2. AUTORHYTHMIC CELLS
   - initiate and conduct AP

Question 2

Autorhythmicity

Answer 2

• beating rhythm BECAUSE of AP it generates itself

there is pace maker cells that initiate the heart

Question 3

Autorhythmic Cells

Answer 3

• pacemaker cells

- cause a contraction

Question 4

Pacemaker Potential

Answer 4

• slow rise in membrane potential (before AP in SA Node)

- rise in membrane potential BEFORE threshold

Question 5

Depolarization

Answer 5

Influx of Na+

Question 6

Repolarization

Answer 6

Efflux of K+

Question 7

Ca++ T-type

Answer 7

• Transient channel (sometimes open/closed)
• happens before threshold
• during slow depolarization

Question 8

Ca++ L-type

Answer 8

Channel OPEN:

• threshold is reached
• rapid depolarization

Channel CLOSED:

• reaches AP, channel closes
• K+ comes in to “rectify”
• closes at repolarization

Question 9

what causes rapid depolarization in pacemakers?

Answer 9

Calcium (L-type)

Question 10

Myocardial Contractile Cells AP

Answer 10

1. Resting
2. Depolarization (Na+ in)
3. Plateau (Na+ stops, Ca2+ in, fast K+ close)
4. Repolarization (Ca2+ close, K+ slow open)
5. Resting

Question 11

Refractory Periods

pacemaker vs. myocaridal

Answer 11

Pacemakers – NO REFRACTORY
(bc constantly depolarizing)

Myocardial – REFRACTORY (long)

• long AP means long refractory period
• allows for relaxation and diastolic filling

Question 12

Sympathetic System AP

Answer 12

• no resting membrane potential
• hyperpolarization does not go as low as parasympathetic
• fight or flight - you want quick AP

Question 13

Parasympathetic System AP

Answer 13

• no resting membrane potential

- hyperpolarization is lower

Question 14

What sets the pace for the rest of the heart?

Answer 14

SA Node