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VMP814 Physiology/Microanatomy 1 > Lecture 24 10/18/23 > Flashcards

Lecture 24 10/18/23 Flashcards

1
Q

What does it mean for cardiomyocytes to be excitable?

A

an electrochemical gradient is maintained across their cell membranes

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2
Q

What is the stimulation of cardiomyocytes?

A

momentary reversal of trans-membrane potential (an action potential)

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3
Q

What are the characteristics of the action potential?

A

-initiates excitation-reaction coupling
-stimulus for myocardial shortening

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4
Q

What determines membrane potential?

A

conductance of ions (Na+, K+, Ca2+)

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5
Q

What are the two electrophysiologically distinct populations of cells?

A

-specialized conduction cells
-working cardiomyocytes

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6
Q

What are the characteristics of specialized conduction cells?

A

-depolarize spontaneously
-exhibit automacity

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7
Q

What is the role of working cardiomyocytes?

A

responsible for contraction

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8
Q

When do working cardiomyocytes get excited?

A

when there is an action potential to stimulate them

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9
Q

How does the AV node give rise to perkinje fibers?

A

-AV node gives rise to common bundle/His
-common bundle splits into bundle branches
-bundle branches give rise to perkinje fibers

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10
Q

Which structures have cells that exhibit normal automaticity?

A

-SA node
-AV node
-His/purkinje system

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11
Q

What is the role of the fibrous skeleton?

A

to electrically isolate the atria and ventricles

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12
Q

Why is it important for the atria and ventricles to be electrically separated?

A

allows for the atria and ventricles to depolarize separately

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13
Q

What is unique about the AV bundle?

A

it penetrates the fibrous skeleton

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14
Q

What is the role of gap junctions?

A

rapid diffusion of ions between cells

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15
Q

What things contribute to the negative resting membrane potential of the cell?

A

-Na/K pump
-Donnan effect
-selective permeability of membrane to K, but not Na (K leaks)

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16
Q

What type of current is associated with potassium?

A

outward current

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17
Q

What are the two types of channels for potassium and their functions?

A

-voltage gated: repolarization
-inward rectifier: maintain resting membrane potential

18
Q

What type of current is associated with sodium?

A

inward current

19
Q

What are sodium channels responsible for?

A

depolarization

20
Q

What type of current is associated with calcium?

A

inward current

21
Q

What are the two types of Ca channels?

A

-L type “slow” channels
-T type channels

22
Q

What happens during the 0 phase?

A

Na+ in and depolarization

23
Q

What happens during the 2 phase?

A

Ca2+ in and plateau

24
Q

What happens during the 3 phase?

A

K+ out and repolarization

25
Q

When do the refractory periods occur?

A

during repolarization

26
Q

What is an absolute refractory period?

A

when the cell cannot be re-stimulated

27
Q

What is a relative refractory period?

A

when the cell can be re-stimulated only by a strong stimulus; causes a less robust AP

28
Q

Which ion is associated with depolarization of atrial/ventricular cells?

A

sodium

29
Q

Which ion is associated with depolarization of nodal cells?

A

calcium

30
Q

Which type of cells do not spontaneously depolarize?

A

atrial/ventricular cells

31
Q

Which type of cells do spontaneously depolarize?

A

nodal cells

32
Q

Why is the SA node the dominant pacemaker?

A

most rapid inherent rate of discharge of the conduction system

33
Q

What is overdrive suppression?

A

when depolarization occurs at a rate that exceeds inherent rate, spontaneous depolarization is inhibited

34
Q

Why is overdrive suppression important?

A

it prevents competition of automatic tissues

35
Q

What are the mechanisms of spontaneous depolarization?

A

-deactivation of K+ channels
-influx of Na+
-influx of Ca+

36
Q

How does the sympathetic nervous system impact spontaneous depolarization and heart rate?

A

increases rate

37
Q

How does the parasympathetic nervous system impact spontaneous depolarization and heart rate?

A

decreases rate

38
Q

What are the characteristics of sympathetic cardiac innervation?

A

-diffuse distribution
-norepinephrine is main transmitter

39
Q

What are the characteristics of parasympathetic cardiac innervation?

A

-vagal innervation of conduction system
-acetylcholine is main transmitter

40
Q

Why is it important that APs in cardiac cells have a greater duration than in nerve cells?

A

prevents development of physiologic tetanus

VMP814 Physiology/Microanatomy 1 (46 decks)

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