Electrophysiology

Question 1

cardiac muscle features

Answer 1

intercalated disks
gap junctions
striated
involuntary

Question 2

most superfical layer of the heart, it’s the visceral layer of the serous pericardium

Answer 2

epicardium

Question 3

this is the middle layer of the heart, it’s composed of cardiac muscle and is the layer that contracts. It contains gap junctions.

Answer 3

myocardium

Question 4

this is the inner layer of the heart which is continuous with the lining of the blood vessels

Answer 4

endocardium

Question 5

true or false- every heart cell contracts with every beat of the heart

Answer 5

true

Question 6

can the heart replace its muscle cells?

Answer 6

yes, but it is very limited
only about 1% per year

Question 7

this is a small group of cells that depolarize spontaneously and the AP spreads through gap junctions in intercalated discs

Answer 7

conducting/ pacemaker cells

Question 8

list the order of the pacemaker activation sequence

Answer 8

SA node
AV node
Bundle of His
Left and right branches
Purkinje fibers

Question 9

SA node firing rate

Answer 9

70-80

Question 10

AV node firing rate

Answer 10

40-60

Question 11

Bundle of His firing rate

Answer 11

30-40

Question 12

Purkinje fiber firing rate

Answer 12

15-20

Question 13

are cardiac AP shorter or longer than skeletal or neuronal?

Answer 13

longer

Question 14

nodal cells have _____ which means they spontaneously generate APs

Answer 14

Automaticity

Question 15

explain 3 nodal depolarization events

Answer 15

1- slow Na+ through funny channels
2- T-type Ca2+ channels open
3- L-type Ca2+ channels open–> rapid depolarization

Question 16

explain nodal repolarization

Answer 16

Ca2+ channels close
K+ channels open and K+ rushes out leading to repolarization

Question 17

what is Bachmann’s bundle?

Answer 17

atrial projections for intratrial communication

Question 18

what is the only path to the ventricles from the SA node?

Answer 18

internodal tracts to the AV node

Question 19

which node has a pause?

Answer 19

AV node

Question 20

Why does the AV node pause?

Answer 20

to allow the atria to empty

Question 21

what is the purpose of a long refractory period in the heart?

Answer 21

allows all activated muscle fibers to stay contracted for a set period of time

Question 22

this type of refractory period is more excitable than normal which makes it easier to fire another AP

Answer 22

supranormal refractory period

Question 23

explain the events that occur in heart muscle contraction phase 0- upstroke

Answer 23

Na+ rushing IN

Question 24

explain the events that occur in heart muscle contraction phase 1- initial repolarization

Answer 24

Na+ channels close and K+ channels open
K+ rushes out

Question 25

explain the events that occur in heart muscle contraction phase 2- plateau

Answer 25

L-type Ca2+ channels open Ca2+ in= K+ out

Question 26

explain the events that occur in heart muscle contraction phase 3- repolarization

Answer 26

Ca2+ channels close K+ channels remain open and K+ rushes out hyperpolarization occurs K+ channels close

Question 27

explain the events that occur in heart muscle contraction phase 4- resting membrane potentials

Answer 27

inward and outward currents are equal Na+ and Ca2+ IN= K+ OUT

Question 28

what type of Ca+ channels do Ca2+ channel blockers inhibit?

Answer 28

L-type leads to a lengthened refractory period

Question 29

how is Ca2+ removed from cardiac muscle?

Answer 29

NCX- Na/Ca2+ exchanger SERCA- sarcoplasmic/endoplasmic Ca2+ ATPase

Question 30

is sympathetic or PS innervation a positive chronotrope

Answer 30

sympathetic

Question 31

is sympathetic or PS innervation a negative chronotrope?

Answer 31

PS

Question 32

is sympathetic or PS innervation a positive ionotrope?

Answer 32

sympathetic

Question 33

is sympathetic or PS a negative ionotrope?

Answer 33

PS

Question 34

this term refers to conduction velocity through the heart (how fast the signal moves through the heart)

Answer 34

dromotropic effects

Question 35

what does the sympathetic NS release on the heart and to what receptor type?

Answer 35

NE--> beta adrenergic on nodes, atria, and ventricles

Question 36

what does the PS NS release on the heart and to what receptor type?

Answer 36

ACh--> muscarinic receptors on nodes and atria

Question 37

how does ACh act as a negative chromotrope at SA and AV nodes?

Answer 37

decreases rate of depolarization by: opens K+ channels--> K+ leaves slows Ca2+ entry through T- channels

Question 38

how does ACh have negative ionotropic effects in atrial myocytes?

Answer 38

decreases available Ca2+ in plateau phase increases K+ out- shortens plateau phase

Question 39

how does NE have positive chronotropic effects at the SA and AV nodes?

Answer 39

increases speed of depolarization increases rate the Na+ and Ca2+ flow in increases conductance of funny and T-type channels

Question 40

how does epinephrine have positive ionotropic effects at beta1 receptors on atrial and ventricular myocardial cells?

Answer 40

increases Ca2+ channel permeability faster uptake of Ca2+ by Ca2+ ATPase--> faster relaxation and more Ca2+ for next contraction (phospholambin)

Question 41

how do beta blockers block ionotropic effects of the sympathetic NS?

Answer 41

blocks release of epinephrine from adrenal gland

Question 42

increased HR can also increase ______ by increasing overall Ca2+ influx

Answer 42

contractility

Question 43

what is an ECG?

Answer 43

composite of electrical activity *not a single AP *note node depolarization

Question 44

what is the p wave?

Answer 44

atrial depolarization

Question 45

what is the QRS complex?

Answer 45

ventricular depolarization

Question 46

what is the T wave?

Answer 46

ventricular repolarization

Question 47

when does atrial repolarization occur on an ECG?

Answer 47

QRS complex

Question 48

this is a group of positive ionotropic agents used to treat heart failure and includes digoxin

Answer 48

glycosides

Question 49

how does digoxin work?

Answer 49

inhibits Na/K ATPase - less Na+ outside the cell means less to be used to pump Ca2+ out via NCX pumps and more Ca2+ stays in the cell more intracellular Ca2+= stronger contraction