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Physiology - MV > Lecture 7 & 8 & 9 & 10 (part) Heart Rhythm > Flashcards

Lecture 7 & 8 & 9 & 10 (part) Heart Rhythm Flashcards

0
Q

______ fibers connect directly to atrial fibers.

A

SA

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1
Q

• Therefore, there is a______sec delay from the initial origin of the signal until onset of ventricular contraction? and # seconds from End of Q to T?

A

.16 sec The Q-T interval ≈ 0.35 sec.

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2
Q

Slow conduction is caused mainly by diminished numbers of ______________ along pathway resulting in an increase in the resistance to conduction.

A

gap junctions

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3
Q

What is the threshold potential for the SA node?

A

-40 mV

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4
Q

Why are atrial nodal action potentials, & repolarization slower to develop?

A

•Fast sodium channels are already inactivated (blocked) and only slow sodium-calcium channels can open.

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5
Q

Large numbers of __________ channels open at the time the sodium-calcium channels become inactivated. •Nodal cells become ____________.

A

potassium repolarized

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6
Q

•Ventricular fiber resting potential?

A

-85 to -90 mV

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7
Q

•Action potentials originating in the SA node generate a “_________”rhythm.

A

sinus

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8
Q

•Action potentials that originate anywhere other than the SA node are said to be from an __________ focus or pacemaker.

A

ectopic

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9
Q

Which of the five cardiac phases are not represented in the sinus nodal Action potential that you see in a ventricular or skeletal muscle fiber ?

A

1 & 2 do not appear

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10
Q

The _____________ nerve is Distributed mainly to the SA and AV nodes, and is parasympathetic or sympathetic?

A

Vagus Parasympathetic

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11
Q

The neurotransmitter for the parasympathetic system is?

A

Acetylcholine

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12
Q

Can potentials flow from the atria to the ventricles?

A

No

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13
Q

_________ Gates close when membrane potential is less negative than_______?

A

Inactivation -55

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14
Q

•An ECG measures _________ potential; it is not the same as the potential recorded from an axon when recording the transmembrane potential.

A

extracellular

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15
Q

Current flows between regions of different

A

membrane potentials

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16
Q

the atrial musculature and ventricular musculature are __________ isolated.

A

electrically

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17
Q

The ____wave appears at the beginning of the potential, and the _____wave appears at the end of the

A

QRS T

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18
Q

• No potential is recorded when the ventricle is: _______or_________.

A

Completely polarized or Completely depolarized

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19
Q

QRS complex represents phase _____ ofthe action potential

A

0

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20
Q

The T wave representsphase ___ or repolarization of ventricular muscle

A

3

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21
Q

When taking EKGs, which lead is attached to both arms? 1, 2, or 3? Which lead Looks at heart from upper right to lower left? What is the degree for Lead III?

A

Lead 1 Lead 2 120 degrees

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22
Q

Ventricles begin contraction, in the ___________ ___________?

A

Interventrical septum

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23
Q

whos law states? •If the electrical potentials of any two of the three bipolar limb ECG leads are known at any given instant, the third can be determined by summing the first two. a. Hovenbach’s b. Einthoven’s c. Bachhoven’s d. Nenthoven’s

A

b

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24
Q

Normally, in the ventricles, current flows from _____to _____ primarily in the direction from the base of the heart toward the apex for most of the heart cycle until the very end. Therefore the electrode nearer the base will be _______ and the electrode nearer the apex will be ________.

A

negative to positive negative positive

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25
Q

•The summated vector of the generated potential at a particular instant is called the ______________ mean vector.

A

instantaneous

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26
Q

•The average direction of the vector during spread of the depolarization wave through the ventricles results in the apex of the heart remaining ________ with respect to the base of the heart.

A

positive

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27
Q

TQ - This depolarization vector,(QRS vector) is about ____ degrees in relation to the zero reference point. •This is the mean electrical _____ of the heart.

A

+59 axis

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28
Q

• Atrial depolarization begins in the ____ node and ECG is normally _____ in all three leads.

A

sinus positive

29
Q

The sinus node area is the first part to become _________. Atrial ____-wave is almost always obscured by QRS wave.

A

repolarized T

30
Q

Some Abnormal ventricular conditions that cause axis deviation are?

A

• Change in position of heart in the chest • Hypertrophy of one ventricle • Bundle branch block • Fluid in pericardium • Pulmonary emphysema

31
Q

TQ - What is the reference point for analyzing current of injury?

A

J point= The zero reference potential of ECG. occurs at the very end of the QRS wave and is the point at which all parts of the ventricle, including the injured areas, have become depolarized.

32
Q

Tachycardia Is defined as how many beats per min? Bradycardia?

A

> 100 < 60

33
Q

loss of blood flow to an area is called?

A

ischemia

34
Q

dropped beats begin at which degree of AV block?

A

2nd

35
Q

Premature Contractions are mostly due to __________ contractions?

A

ectopic

36
Q

You have have sudden reoccurances of tachycardia called ___________ Tachycaradia

A

Paroxysmal

37
Q

Fibrillation is the twitching of individual muscle fibers in the atria or ventricles.Is this twitching usually slow or fast?

A

slow

38
Q

•Fibrillation occurs as a result of ________ movements.

A

circus (circular)

39
Q

What are the Three different conditions that cause the impulse to travel around the circle within the heart?

THESE three reasons typically happen because..

A

• Circle pathway is too long.

    • Usually occurs because of the blockage of the Purkinje 
       system, ischemia, or high potassium levels.
  • Conduction velocity slows down.

• Refractory period becomes greatly shortened.

    * May occur in response to drugs such as epinephrine.
    * May occur after repetitive electrical stimulation.
40
Q

What is Stokes-Adams
syndrome

A

After a complete block occurs, patients will often faint due to
lack of blood to the brain until the ventricles escape.

41
Q

What is ventricular escape

A

Resumption of the ventricular beat (= ventricular escape) may
be due to parts of the Purkinje system acting as an ectopic
pacemaker.

42
Q

electrical alternans refers to?

A

Partial Intraventricular Block (you see different sized QRS complexes)

43
Q

Premature contractions are the result of ectopic foci caused by (3)

A
  • Local ischemic areas
  • Calcified plaques
  • Irritation of the conduction system or node
44
Q

define: Paroxysmal Tachycaradia

A

Heart becomes rapid in paroxysms:
• Paroxysm begins suddenly and lasts for a few seconds,
minutes, hours, or longer
• Paroxysm ends suddenly
• Pacemaker of the heart instantly shifts back to the sinus
node.

45
Q

Atrial Fibrillation are caused by:

A

• Enlargement of the atria (i.e., due to valve lesions)
• Inadequate emptying of the ventricles causing blood to back up into
the atria

46
Q

____ % of blood volume is in the systemic circulation. Where is it mostly located?

A

84%, veins (64%)

47
Q

Velocity of blood flow (V) is ________ proportional to
vascular cross-sectional area (A). (F = volume of blood
flow)

A

inversely, V=F/A

48
Q

Where is blood flow the slowest? Think highest cross sectional area.

A

Capillaries

49
Q

Rate of blood flow to tissues is primarily determined by?

A

• Rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the
tissue need.

• In each tissue, microvessels monitor tissue needs.
•O2, other nutrients, CO2 accumulation, tissue waste
product accumulation:

50
Q

• Arterial pressure regulation is generally _________
of either local blood flow control or cardiac output
control.

A

independent

• If arterial pressure falls below 100 mm Hg, nervous
reflexes:
• Increase force of heart pumping.
• Constrict large venous reservoirs.
• Generally constrict most of the arterials throughout the
body.
• Kidneys may later play important role in pressure control.

51
Q

Equation for calculating flow through a vessel?

A

F= (P2-P1)/R

52
Q

Laminar blood flow means?

A

streamline flow:
• Blood flows at a steady rate.
• Blood vessel is long and smooth.
• Blood flows in streamlines (layers).

53
Q

Why does turbulence occur?

A

Turbulent flow:
• Occurs:
• When flow is too great
• When blood passes an obstruction within the vessel
• When blood has to make a sharp turn
• When blood passes over a rough surface

• Blood flows with greater resistance when eddy currents
occur.

54
Q

Turbulent flow occurs ________ proportion to the density of the blood and _______ proportion to viscosity

A

direct, inverse

55
Q

Equation for calculating Laminar Flow

A

Re = (v · d · ρ)/η

• Re = Reynolds number = measure of the tendency for
turbulence to occur
• v = mean velocity of blood flow in cm/sec
• d = vessel diameter in cm
• ρ = density (normally only slightly > 1)
• η = viscosity (in poise) (blood viscosity normally = 1/30 poise)

56
Q

If Rate of blood flow through the entire circulatory system = cardiac output = 100 ml/sec.

AND

Pressure difference from systemic arteries to systemic veins = 100 mm Hg

What is the RESISTANCE?

A
  • Resistance of entire systemic circulation:
  • = 100/100 = 1 PRU
57
Q

If Rate of blood flow through the entire circulatory system = cardiac output = 100 ml/sec.

and Mean pulmonary arterial pressure: averages 16 mm Hg

and Mean left atrial pressure averages 2 mm Hg

What is the Resistance?

A

= 14/100 = 0.14 PRU

58
Q

Define Conductance

A

Conductance is the measure of blood flow through a
vessel for a given pressure difference.

It is the exact reciprocal of resistance

59
Q

Conductance equation = Poiseuilles law = _______

A

F = πΔPr4/8ηl

  • F = rate of blood flow
  • ΔP = pressure difference between ends of vessel
  • r = radius of vessel
  • l = vessel length
  • η = blood viscosity
60
Q

Arterioles, capillaries, venules, and veins are arranged in ________. (parallel or series)

A

series

BUT

Blood vessels branch extensively to form parallel circuits that
supply blood to the many organs and tissues of the body

Total conductance for vessels arranged in parallel is the sum
of the conductance of each parallel pathway

61
Q

examples of circulations arranged in parallel:

A
  • Circulations arranged in parallel:
  • Brain
  • Kidney
  • Muscle
  • Gastrointestinal
  • Skin
  • Coronary circulation
62
Q

The viscosity of blood is higher than water due to:

A

Red blood cells (hematocrit)

63
Q

Review and discuss figure 14-13

A
64
Q

Vascular distensibility =

A

Increase in volume/(Increase in pressure X Original volume)

65
Q

Which is more distensible, arteries or veins?

A

• Veins are about 8 times more distensible than arteries.

• Pulmonary artery distensibilities are about 6 times that of
systemic arteries.

66
Q

Vascular compliance (capacitance) =

A

Increase in volume/Increase in pressure

OR

Compliance is equal to distensibility X volume.
• VD = Vinc/(Pinc x Vorig)
• VD x Vorig = Vinc/Pinc = Compliance

67
Q

Vascular compliance = _____quantity of blood that can be stored in a
given portion of the circulatory system

Elastance is…..________

A

total

Elastance is a measure of the tendency of a hollow
viscus to recoil toward its original dimensions upon
removal of a distending or collapsing force.

68
Q

Explain why:

When the arterial system contains 700 ml of blood, the mean
arterial pressure is 100 mm Hg. But when the arterial system
contains 400 ml of blood, the mean arterial pressure is 0 mm
Hg

A

high elasticity?

69
Q

explain why:

The venous system contains a volume of blood ranging from
2000 to 3500 ml. Removing several hundred ml from the
normal venous volume only changes venous pressure 3 to 5
mm Hg.

A

High compliance?

Review figure 15-1

Physiology - MV (9 decks)

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