Rhythmical Excitation of the Heart

Question 1

where does conduction through the heart begin?

Answer 1

SA node

Question 2

at what time is the signal at the SA node?

Answer 2

.00 sec

Question 3

where does the signal travel from the SA node?

Answer 3

through internodal pathway to AV node

Question 4

at what time does the signal arrive at the AV node?

Answer 4

.03 sec

Question 5

where does the signal travel from the AV node?

Answer 5

AV septa (beginning of Bundle of His)

Question 6

at what time does the signal reach the AV septa?

Answer 6

.12 sec

Question 7

at what time does the signal arrive at the AV bundle of His?

Answer 7

.16 sec

Question 8

where does the signal travel from the AV bundle?

Answer 8

bundle branches in interventricular septum

Question 9

where does the signal travel from the AV bundle branches?

Answer 9

Purkinje fibers (apex of heart -> up to base)

Question 10

at what time does the signal end in the left side of the heart?

Answer 10

.22 sec

Question 11

at what time does the signal end in the right side of the heart?

Answer 11

.21 sec

Question 12

where are the SA and AV nodes and internodal pathways located?

Answer 12

posterior wall of right atrium

Question 13

at what point is the conduction rate the slowest?

Answer 13

between AV node and AV bundle of his

Question 14

can conduction travel backwards?

Answer 14

no

Question 15

name the self-excitatory components of the heart

Answer 15

SA node
AV node
Purkinje Fibers

Question 16

which self-excitatory component of the heart discharges at the fastest rate?

Answer 16

SA node

Question 17

which self-excitatory component of the heart has the highest rate of conductance?

Answer 17

Purkinje fibers

Question 18

which self-excitatory component of the heart is responsible for sinus rhythm and is also known as the ‘pacemaker’ of the heart?

Answer 18

SA node

Question 19

what is the rhythm of the SA node?

Answer 19

60-80bpm

Question 20

what is the rhythm of the AV node?

Answer 20

40-60bpm

Question 21

what is the rhythm of the purkinje fibers?

Answer 21

15-40bpm

Question 22

what has the slowest rate of conduction of the cardiac AP?

Answer 22

AV bundle of His

Question 23

what is responsible for the drifting RMP in the nodes?

Answer 23

leaky Na+ channels

Question 24

what happens in the nodes when threshold is reached?

Answer 24

slow Ca++ channels open (in)

Question 25

what causes the beginning of repolarization in the nodes?

Answer 25

K+ channels open (out)

Question 26

what is the threshold for S-A discharge?

Answer 26

-40mV

Question 27

the strength and contraction of cardiac muscle depends on…

Answer 27

amount of Ca++ surrounding cardiac myocytes