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CRRAB 1 > Nordgren Week 1 > Flashcards

Nordgren Week 1 Flashcards

1
Q

used to coordinate and appropriately time the contractile activity

A

electrical stimulus

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2
Q

develop tension in, as well as shorten and relax the muscle cells

A

mechanical activity

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3
Q

How do cardiac muscle APs differ from skeletal APs and promote synchronous rhythmic excitation of the heart?

A
  1. self-generating 2. conducted directly from cell to cell 3. long duration (long refractory period)
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4
Q

What prevents summation and tetanus in cardiac muscle that you see in skeletal muscle?

A

long duration and long refractory period

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5
Q

what creates an electrical potential?

A

separation of electrical charges across a membrane

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6
Q

What changes the electrical potential of a cell membrane?

A

flow of current through the cell membrane

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7
Q

When is transmembrane voltage stable?

A

when there is no net current

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8
Q

What are the two interstitial fluid ions?

A

Na and Ca

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9
Q

What is the intracellular fluid ion?

A

K

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10
Q

What is the potassium equilibrium potential?

A

-90mV

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11
Q

electrical charge is very soluble or insoluble in lipids?

A

insoluble and so must pass through lipid bilayer via transmembrane protein structures

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12
Q

Name 3 transmembrane protein structures

A

ion channels, ion exchangers, ion pumps

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13
Q

What are the three states of ion channels?

A

open, closed, inactivated

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14
Q

what does it mean when said ‘high permeability to sodium’

A

many of the Na ion channels are open

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15
Q

What responds quickly to membrane depolarization QUICKLY by opening?

A

activation gates

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16
Q

What responds to membrane depolarization SLOWLY by closing; limits the time a channel can remain open, despite continued stimulation; NOT in all channels?

A

inactivation gates

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17
Q

What type of cardiac muscle has action potentials similar to those of neurons and skeletal muscle?

A

myocardial contractile cells

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18
Q

What type of cardiac muscle generates action potentials spontaneously due to unstable membrane potential?

A

myocardial autorhythmic or pacemaker cells

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19
Q

What type of cardiac cell has a rapid depolarization with large overshoot (+mV), rapid reversal of overshoot, long plateau, re, repolarization to a stable, high (-mV) resting membrane potential?

A

Contractile cells

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20
Q

What type of cardiac cell has slower initial depolarization, lower amplitude overshoot, shorter and less stable plateau, repolarization to unstable slowly depolarizing ‘resting’ membrane potential

A

Pacemaker cells

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21
Q

What is the main differences in AP between the contractile and the pacemaker cells in phase 0?

A

contractile cells: mediated by Na

pacemaker cells: Ca

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22
Q

What is the main differences in AP between the contractile and the pacemaker cells in phase 1 and 2?

A

absent in pacemaker cells

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23
Q

What is the main differences in AP between the contractile and the pacemaker cells in phase 3?

A

none

24
Q

What is the main differences in AP between the contractile and the pacemaker cells in phase 4?

A

resting versus pacemaker potential

25
Q

specialized adherens junction structure that connects ends of two adjacent cells

A

intercalated disks

26
Q

Name 3 types of adhering junctions that make up intercalated discs

A
  1. fascia adherens 2. macula adherens (aka desmosomes) 3. gap junctions
27
Q

anchoring sites for actin, connect to the closest sarcomere

A

fascia adherens

28
Q

join cells together by binding intermediate filaments

A

macula adherens (aka desmosomes)

29
Q

channels formed of proteins called connexin permit passage of ions between cells, thus allowing the spread of action potentials

A

gap junctions

30
Q

What ensures the transmission of force from one muscle cell to the next?

A

firm mechanical attachments: fascia adherens and macula adherens (desmosomes)

31
Q

What facilitates the transmission of electrical impulse from cell to cell?

A

low-resistance electrical connections: channels formed of proteins called connexin in structures called gap junctions

32
Q

What largely determines the speed at which action potentials travel between cells?

A

the number of gap junctions in the intercalated discs; more=faster

33
Q

Which has more gap junctions: AV node or the SA node and atrial myocardium?

A

AV node has fewer gap junctions

34
Q

What is the rate of action potential conduction of the SA node, atrial tissue?

A

1 m/sec

35
Q

What is the rate of action potential conduction of the AV node?

A

0.05 m/sec

36
Q

What is the rate of action potential conduction of the ventricular tissue?

A

0.3-0.5 m/sec

37
Q

What is the rate of action potential conduction of bundle of His, Purkinje?

A

4 m/sec

38
Q

What does an electrocardiogram measure?

A

record of how the voltage between two points on the body surface changes with time as a result of the electrical events of the cardiac cycle

39
Q

Where do fibers from the sympathetic nervous system and parasympathetic nervous system terminate to increase or decrease the automaticity of pacemaker cell firing from the intrinsic level?

A

cells in SA node

40
Q

What is released by the cardiac parasympathetic fibers via vagus nerves?

A

acetylcholine

41
Q

How does acetylcholine affect the permeability of resting membrane K?

A

increases permeability

42
Q

How does acetylcholine affect diastolic funny current through HCN channels?

A

decreases diastolic

43
Q

Net effect of parasympathetic nervous system

A

slow heart rate via prolonging time to depolarization, slows rate of spontaneous depolarization and causes initial hyperpolarization of resting membrane potential

44
Q

Net effect of sympathetic cardiac fibers? how?

A

speeds heart rate via release of norepinephrine to increase diastolic inward currents through HCN channels

45
Q

Define preload

A

the passive/resting tension placed on cardiac muscle cells before contraction (a function of the volume and pressure at the end of diastole)

46
Q

What 4 things increase the preload?

A

hypervolemia, regurgitation of cardiac valves and heart failure

47
Q

Define afterload

A

the active tension placed on cardiac muscle cells during contraction (a function of the resistance the left ventricle must overcome to circulate blood)

48
Q

What 2 things increase afterload?

A

hypertension and vasoconstriction

49
Q

What does active tension depend on?

A

active tension developed during isometric contraction depends on the muscle length at which contraction occurs (which is linked to the resting tension)

50
Q

What type of contraction has the same load but the length changes?

A

isotonic contraction

51
Q

What influences the amount of tension the muscle can develop and the amount of shortening the muscle can achieve?

A

ionotrope

52
Q

a positive ionotrope that increases afterloaded shortening; increases isometric tension

A

norepinephrine

53
Q

What do the length-tension relationships of cardiac muscle fibers in the ventricular wall determine?

A

the volume and pressure tensions in the chamber

54
Q

What leads to an increase in the length of the cardiac muscle cells?

A

an increase in ventricular volume causes an increase in ventricular circumference and therefore an increase in ventricular circumference

55
Q

What leads to an increase in intraventricular pressure?

A

an increase in tension (at any volume) of individual cells in the wall

56
Q

as ventricular volume decreases what happens to total force?

A

lesser total force is needed by the muscle cells in the ventricular walls to produce any given intraventricular pressure

57
Q

what does the TOTAL ventricular wall tension (T) depend on?

A

intraventricular pressure (P) and the internal ventricular radius (r); T=Pxr

CRRAB 1 (9 decks)

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