Physio Ch 10 Flashcards

1
Q

Under normal conditions, atria contract ___ ahead of ventricles

A

1/6 of a second

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2
Q

conduct impulses from the sinus node to the atrioventricular (A-V) node

A

internodal pathways

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3
Q

conducts impulses from the atria into the ventricles

A

A-V bundle

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4
Q

conduct the cardiac impulses to all parts of the ventricles

A

right and left bundle branches of Purkinje fibers

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5
Q

where impulses from the atria are delayed
before passing into the ventricles

A

AV node

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6
Q

a small, flattened, ellipsoid strip of specialized cardiac muscle

A

SA node

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7
Q

Located superior posterolateral wall of right atrium below and slightly lateral to the opening of the superior vena cava

A

SA node

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8
Q

a process that can cause automatic rhythmical discharge and contraction

A

self-excitation

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9
Q

resting membrane potential of the sinus nodal fiber between discharges

A

-55 to -60 mV

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10
Q

RMP of ventricular muscle fiber

A

-85 to -90

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11
Q

Why does SA node have lesser RMP or negativity?

A

Due to cell membrane’s natural leak to sodium and calcium ions (positive ions go inside the fibers)

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12
Q

What are the 3 types of membrane ion channels present in the cardiac muscle?

A

(1) fast sodium channels
(2) slow sodium-calcium channels
(3) potassium channels

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13
Q

Which channel is responsible for the rapid upstroke spike of the action potential observed in ventricular muscle

A

fast sodium channels

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14
Q

Which channel is responsible for the plateau of the ventricular action potential

A

slow sodium-calcium channel

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15
Q

Responsible for returning the cell membrane’s potential to its resting level

A

potassium channels

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16
Q

resting potential of SA fibers gradually rises and becomes less negative between each ___ ?

A

2 heartbeats

17
Q

threshold voltage of SA fibers

A

-40 mV

18
Q

What is responsible for sinus nodal fibers self-excitation?

A

Inherent leakiness to sodium and calcium ions

19
Q

What are the 2 events that cause the sinus nodal fibers not remain depolarized all the time, despite its leakiness to sodium and calcium?

A
  1. Sodium-calcium channels become inactivated within 100-150 secs after opening
  2. Many potassium channels open
20
Q

Briefly summarize the process of self-excitation to re-excitation process of SA fibers.

A
  1. self-excitation to cause the action
    potential
  2. recovery from the action potential
  3. hyperpolarization after the action potential is over
  4. drift of the “resting” potential to threshold
  5. re-excitation to elicit another cycle
21
Q

small bands of atrial fibers that passes through the anterior walls of the atria
to the left atrium

A

Anterior interatrial band

22
Q

What delays the transmission of conduction of the atria to the ventricles?

A

A-V node and adjacent conductive fibers

23
Q

located in the posterior wall of the right
atrium immediately behind the tricuspid valve

A

A-V node

24
Q

What causes the slow conduction in the transitional, nodal, and penetrating A-V bundle fibers?

A

diminished gap junctions

25
Q

transmit action potentials at a velocity of 1.5 to 4.0m/sec

A

Purkinje fibers

26
Q

What allows rapid transmission of action potentials by Purkinje fibers?

A

High permeability of gap junctions at the intercalated discs

27
Q

acts as an insulator to prevent passage of
the cardiac impulse between atrial and ventricular muscle through any other route besides forward conduction through the A-V bundle itself

A

continuous fibrous barrier

28
Q

discharge at an intrinsic rhythmical rate
of 40 to 60 times per minute when not stimulated from outside source

A

A-V nodal fibers

29
Q

Why does the sinus node rather than the A-V
node or the Purkinje fibers control the heart’s rhythmicity?

A

Discharge rate of the sinus node is considerably faster than the natural self-excitatory discharge rate of either the A-V node or the Purkinje fibers.

30
Q

its rate of rhythmical discharge is faster than
that of any other part of the heart

A

SA node

31
Q

What is an ectopic pacemaker?

A

A pacemaker elsewhere than the sinus node

32
Q

responsible for abnormal sequence of contraction of the different parts of the heart and can cause significant debility of heart pumping

A

ectopic pacemaker

33
Q

delayed pickup of the heartbeat due to A-V block

A

Stroke-Adams syndrome

34
Q

What are the 2 major effects of acetylcholine released on the vagal endings to the heart?

A
  1. Decreases rate of rhythm of the sinus node
  2. Decreases the excitability of the A-V junctional fibers between the atrial musculature and the A-V node
35
Q

It is when vagi stops or block the transmission of cardiac impulse from atria to ventricles, but some areas of Purkinje fibers develops a rhythm of its own and causes ventricular contraction

A

Ventricular escape

36
Q

Effect of Sympathetic Stimulation on Cardiac Rhythm and Conduction (3)

A
  1. Increases the rate of sinus nodal discharge
  2. Increases the rate of conduction and level of excitability
  3. Increases the force of contractions of all the cardiac musculature
37
Q

hormone released by sympathetic nerves to increase the overall activity of the heart

A

norepinephrine