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603 Physiology > Cardio 3 > Flashcards

Cardio 3 Flashcards

1
Q

sarcomere

A

structural and functional subunitof cardiac muscle

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2
Q

Functional syncitium

A

cardiac muscle fibers connect at intercalated disks which contain gap jxns that allow AP to go through all cells

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3
Q

Are the atria electrically isolated from the ventricles?

A

yes

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4
Q

Dominant pacemaker in the heart

A

Sinoatrial (SA) node

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5
Q

Are gap junctions fast or slow?

A

slow

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6
Q

Bachmann’s Bundle

A

runs from SA node to left atrium

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7
Q

Where do the three internodal tracts start and end?

A

Starts at the SA (sinoatrial) and ends at AV (atrioventricular)

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8
Q

What are the three pacemakers of the heart?

A
  1. SA node
  2. AV node
  3. Bundle of His
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9
Q

Consequence of a damaged His bundle?

A

depolarization from the atrium to the ventricle could not occur

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10
Q

Specialized conduction pathways of the ventricle (4)

A
  1. Bundle of His
  2. Right bundle branch
  3. Left bundle branch
  4. Purkinje fibers
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11
Q

Purkinje fibers

A

continuations of the depolarization of the bundle branches

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12
Q

Category A animals

A

Purkinje fibers run on the endocardial surface
ex: dogs, cats, humans

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13
Q

Category B animals

A

Distance from endocardial to epicardial surface is too far, so the Purkinje fibers expand and branch into the myocardium
ex: horses, ruminants, swine, whales

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14
Q

Which node is bigger - SA or AV?

A

AV

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15
Q

What category animals is an ECG most useful in?

A

Category A

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16
Q

4 Major Cations

A

Sodium, calcium, potassium, magnesium

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17
Q

3 Types of Ion Channels

A
  1. Voltage Gated
  2. Ligand Gated
  3. Stretch Activated
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18
Q

What ion channel is potassium most involved in?

A

ligand-gated (and there’s a gazillion of them)

19
Q

What factors affect ionic curreents in myocardial cells?

A

number of open channels
current through each channel
probability of each channel being open

20
Q

Which type of cells have the longest action potential duration: nerve, cardiac, or skeletal muscle?

A

Cardiac

21
Q

Resting cell membrance potential in myocardial cells

A

dependent on the sodium-potassium pump (which depends on ATP which depends on oxygen delivery)

negative

22
Q

Why is the AP of cardiac cells longer?

A

Calcium moving into the cell

23
Q

Label where each phase occurs
0 1 2 3 4

A
24
Q

Phase 0

A

Opening of sodium channels

25
Q

Phase 1

A

inactivation of sodium channnels and activation of potassium channels

26
Q

Phase 2

A

Calcium channels open (balanced by outward flow of potassium)

27
Q

Phase 3

A

Repolarization, the closure of calcium and potassium channels

28
Q

Phase 4

A

resting membrane potential

29
Q

Action potential

A

rapid change in transmembrane potential (depolarization) followed by rturn to resting membrane potential (repolarization)

30
Q

Match the cation permeability to the graph.
Calcium. Potassium. Sodium.

A
  1. Potassium
  2. Sodium
  3. Calcium
31
Q

3 Main Pacemaker Cells IN ORDER

A
  1. SA node (fastest)
  2. AV node
  3. Bundle of His and Purkinje fibers
32
Q

Fast response APs in Cardiac Cells

A

Atrial and ventricular myocytes (contractile cells, lots ofactin and myosin)

33
Q

Size of SA node in cells?

A

approximately 150

34
Q

Why do ventricular myocytes have slightly longer APs than atrial myocytes?

A

Ventricular cells need to generate more pressure with more contractile work so need more calcium

35
Q

What phase sets the heart rate?

A

Phase 4

36
Q

What type of cells have a significant slope to their phase 4?

A

Slow APs, like SA and AV nodes

37
Q

Acetylcholine effect on heart rate

A

decreases heart rate

(lengthens interval between APs)

38
Q

Norepinephrine effect on heart rate

A

increases heart rate

(shortens interval between APs)

39
Q

Which increases heart rate - sympathetic or parasympathetic response?

A

Sympathtic (fight or flight)

(this is how your body has control over heart rate)

40
Q

Effective Refractory Period (ERP)

A

Start of action potential until the myocyte can conduct another action potential (b/n phases 0 and up to 3), but would need a much larger voltage

41
Q

Relative Refractory Period (RRP)

A

time during which an action potential could occur but depolarization varies (b/n phases 3 and 4)

42
Q

Why does all myocardial tisse have long relative refractory periods?

A

Cardiac cells need rest between contractions, to get nutrients delivered and waste products removed (prevents tetany)

43
Q

Flow of Excitation/APs in the Heart

A

SA node –> internodal fibers –> AV node atrial excitation –> bundle of His –> bundle branches –> Purkinje fibers –> ventricles ventricular excitation

44
Q

Explain some differences you see here.

A

SA node has the steepest slope to Phase 4 since it is the fastest of the pacemaker cells
Atrial cells have shorter peaks because they’re not contractile myocytes that need lots of calcium
Look at the time it takes for the whole heart to be depolarized

603 Physiology (22 decks)

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