Cardiovascular Physiology

Question 1

Electrical impulse

Answer 1

-triggers contraction of cardiac muscle cells is intrinsic –> stimulation from the nervous system not required

Question 2

Intrinsic conduction system

Answer 2

1. conducting cells: initiate and distribute and action potential
2. nodes: clusters of conducting cells that initiate action potential
3. has an unstable resting potential (Na+ constantly leaks in)
4. gradual depolarization (prepotential develops)
5. at threshold: opening of voltage gated Ca++ channels , Ca++ rushes in from ECF –> spontaneous AP!

Question 3

AP in the conducting cell

Answer 3

1. Na+ enters through Na+ leak channels
2. Cell develops prepotential
3. voltage gated Ca++ channels open at threshold
4. Ca++ influx causes nodal cells to depolarize (AP!)
5. Ca++ channels close, voltage-gated K+ channels open
6. K+ efflux causes repolarization

Question 4

How are APs spread along conduncting pathways?

Answer 4

-through gap junctions at intercalated discs

Question 5

What are APs initiated by?

Answer 5

-the pacemaker (SA node) and transmitted via other conducting cells to heart muscle

Question 6

How often does the SA node depolarize?

Answer 6

-100 times/min

Question 7

Walk me through the conducting pathway

Answer 7

1. SA node
2. AV node
3. AV bundle
4. Right and left bundle branches
5. Purkinje fibers