Electric Activity of the Heart

Question 1

Which node spreads the impulse from R Atrium to Left atrium?

Answer 1

Sino-atrial node

Question 2

What is the electrical connection between the atrium and ventricle?

Answer 2

AV node

Question 3

What ions are found outside the cell?

Answer 3

Na and Ca

Question 4

Which ion is found in the cell?

Answer 4

K

Question 5

Describe the 3 states a channel can be in

Answer 5

• open
• closed
• inactivated

Question 6

Compare the % of specialized cardiac muscle cells

Answer 6

1% autorhythmic and 99% contractile cells in the heart

Question 7

T/F: Autorhythmic cells can generate action potentials spontaneously

Answer 7

True, they can contract without any outside signal

Question 8

What is the term when the signal for contraction is originating within the heart itself?

Answer 8

Myogenic

Question 9

What is another term for the autorhythmic cells?

Answer 9

Pacemaker cells

Question 10

What makes up the conduction system?

Answer 10

Specialized myocytes: SA node, AV node, His-Purkinje fibers

Question 11

What is the role of the conduction system?

Answer 11

Initiate and coordinate HB

Question 12

From where does the contraction travel?

Answer 12

Apex to base

Question 13

From where does the impulse travel?

Answer 13

Base to apex

Question 14

Where is the SA node located?

Answer 14

Right atrium, at junction between cranial vena cava and atrium

Question 15

What is the role of the SA node?

Answer 15

normal pacemaker and initiate the impulse

Question 16

Atrial depolarization distributes how?

Answer 16

right to left; top to bottom

Question 17

Where is the AV node located?

Answer 17

Base of the Interventricular septum

Question 18

What is the role of the AV node?

Answer 18

Only conduction pathway between atria and ventricles

Question 19

Why is the impulse slowed down in the AV node?

Answer 19

To allow for the atria to contract before the ventricles

Question 20

If the atrium is beating too fast, what does the AV node do?

Answer 20

Limit the number of impulses conducted to the ventricles

Question 21

What structure conducts the impulse from AV node to apex of the heart?

Answer 21

Bundle of His

Question 22

The right bundle branch is isolated from what before the cardiac apex?

Answer 22

Myocytes

Question 23

Which bundle has connections with the myocytes in the interventricular septum?

Answer 23

Left bundle

Question 24

Which structure propagates the impulse to the ventricular myocytes?

Answer 24

Purkinje fibers

Question 25

Which node sets the amount of times the heart will beat?

Answer 25

SA node

Question 26

What can affect the rate of depolarization?

Answer 26

Autonomic (parasympathetic or sympathetic)

Question 27

T/F: the Purkinje fibers can take over impulse generation if the SA and AV node fail

Answer 27

True

Question 28

What is the electrical connection in the intercalated disks called?

Answer 28

Gap junction

Question 29

Describe the specialized assembling of the conduction systems cells that allow for faster conduction

Answer 29

Wider and contain more gap junctions

Question 30

How is the electrical impulse in the heart propagated?

Answer 30

In the form of an action potential

Question 31

T/F Autorhythmic cells have a "flatline"

Answer 31

False, always generating electrical impulses

Question 32

At rest, the cell is _____________ (electrical description)

Answer 32

polarized

Question 33

During depolarization (phase 0), Which channels are open?

Answer 33

Sodium only

Question 34

When Na channels are inactivated, which channels open?

Answer 34

K channels

Question 35

In the plateau phase, what 2 channels are open?

Answer 35

Ca and K

Question 36

In the repolarization phase, what is the channel that is closed while K keeps flowing out of the cell?

Answer 36

Ca

Question 37

What restores equilibrium at the end of repolarization?

Answer 37

Na/K ATPase pump

Question 38

If you inhibit the Ca ATPase pump, what happens to the muscle contraction?

Answer 38

Strengthens it

Question 39

The time between the beginning and end of an action potential is:

Answer 39

Refractory period

Question 40

Why does the refractory period occur?

Answer 40

Because Na channels are inactivated "blocked"

Question 41

List a role of the refractory period

Answer 41

- prevent repetitive cardiac contractions

Question 42

What are the 2 types of refractory period?

Answer 42

Absolute and Relative

Question 43

During which refractory period is an action potential possible if there is a high enough energy stimulus?

Answer 43

Relative

Question 44

Depolarization = _________ Influx Rapid Repolarization= ___________ Efflux Plateau= __________ Influx Repolarization= Potassium ___________

Answer 44

- Sodium - Potassium - Calcium - Efflux

Question 45

T/F autorhythmic cells have stable resting membrane potential

Answer 45

False, they have a pacemaker potential

Question 46

What is the cause of the instability of membrane potentials in autorhythmic cells?

Answer 46

Channels are both permeable to Na and K, which leads to Ca channel opening

Question 47

In an autorhythmic action potential, which channels open in depolarization?

Answer 47

long-lasting Ca channels

Question 48

T/F the pacemaker cells has a plateau phase

Answer 48

False

Question 49

What type of receptor is associated with the sympathetic nerves?

Answer 49

Beta 1 and 2

Question 50

What will a vagal (parasymp) tone do to HR?

Answer 50

Slows it by decreasing firing of sinus node

Question 51

How does the adrenergic tone increase HR?

Answer 51

Increase firing (rate of depolarization)

Question 52

T/F: The sympathetic nervous system can influence cardiomyocytes

Answer 52

True

Question 53

List some NT associated with Adrenergic tone

Answer 53

Epinephrine Norepinephrine Dobutamine

Question 54

Describe the excitation contraction coupling

Answer 54

Delay between stimulus and contraction

Question 55

Where does Ca bind to stimulate the contraction of the myocyte

Answer 55

Myofilament

Question 56

What can you do to make the heart not contract as strongly?

Answer 56

Block Ca

Question 57

Cardiac contraction depends on what?

Answer 57

Calcium entering the cell

Question 58

List some sources of intracellular calcium

Answer 58

- Extracellular Ca through voltage-gated channels - released from Sr through Ca Induced Calcium release

Question 59

How does dobutamine work as a sympathomimetic drug?

Answer 59

Increases intracellular calcium with ca reuptake from SR