Cardiac electrophysiology

Question 1

what regulates the movement of blood bw the two chambers of the heart?

Answer 1

atrioventricular valve (AV valve)

Question 2

the atrial wall contains what compared to the ventricular wall? why is that?

Answer 2

less cardiac muscle tissue; the atria do not need to produce as much force as the ventricles

Question 3

where does the right half of the heart collect blood from and where does it pump it?

Answer 3

collects from the systemic circuit and pumps into the pulmonary circuit

Question 4

where does the left half of the heart collect blood from and where does it pump it?

Answer 4

collects from pulmonary circuit and pumps it into the systemic circuit

Question 5

which ventricle contains more cardiac muscle tissue? why is that?

Answer 5

left ventricle; bc more pressure must be produced to drive blood thru systemic circuit

Question 6

how are all cardiac muscle cells linked? Where are they located? what does this allow?

Answer 6

electrical synapses; intercalated discs; fast, synchronized responses

Question 7

cardiac muscle tissue is _________________

Answer 7

autorhythmic

Question 8

what are the two types of cardiac muscle cells?

Answer 8

contractile and conducting cells

Question 9

what do contractile cells do?

Answer 9

generate the force that pumps blood; not autorhythmic

Question 10

what do conducting cells do?

Answer 10

do not generate force. they generate action potentials and rapidly propagate them thru the muscle tissue

Question 11

in what two groups are conducting cells found in? where are the groups found?

Answer 11

sinoatrial node (SA node) and atrioventricular node (AV node) ; both found in the right atrium

Question 12

how are most conduction cells organized? what links the SA node to the AV node?

Answer 12

bundles/ tracts; atrial internodal tracts

Question 13

Where does the AV node propagate action potentials? (2 places)

Answer 13

into the ventricles or to the bundle of His

Question 14

where else are the action potentials propagated to after the bundle of His?

Answer 14

from bundle of His to the bundle branches and the Purkinje fibers

Question 15

Propagation of an action potential from the SA node to all other parts of cardiac muscle tissue takes how long at resting heart rate?

Answer 15

220 msec

Question 16

is propagation slower or faster between conducting cells? is this in all conducting cells?

Answer 16

faster; no the two nodes are 50-100 times slower

Question 17

why are the nodes slower than the rest of the contractile cells?

Answer 17

slow conduction thru AV node allows the atria to contract before the ventricles

Question 18

what kind of resting potential do cells in the SA node have? what happens to it once it completes an action potential and what is it called?

Answer 18

not stable; begins a slow depolarization = pacemaker potential

Question 19

the pacemaker potential is produced by what two types of ion channels?

Answer 19

f-type and t-type channels

Question 20

when do f and t-type channels open and close?

Answer 20

both open during pacemaker potential and close when the membrane potential reaches threshold again

Question 21

non-specific cation channels that primarily allow sodium ions to cross the membrane. open @ end of an action potential, inward movement of Na+ depolarizes the membrane

Answer 21

F-type channels

Question 22

open as the membrane potential nears threshold, allowing Ca+ to move inward, further depolarizing the membrane

Answer 22

t-type channels

Question 23

what happens to SA action potential at threshold?

Answer 23

L-type Ca+ channels open

Question 24

what are L-type calcium ion channels?

Answer 24

voltage-gated channels that open gradually, allowing prolonged inward movement of Ca+

Question 25

when do the L-type channels begin to close?

Answer 25

at the same time as voltage-gated K+ ion channels begin to open.

Question 26

what do K+ ion channels allow?

Answer 26

the outward movement of K+; repolarizes the membrane