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Physiology I > 1.4 The heart as a pump 43-58 > Flashcards

1.4 The heart as a pump 43-58 Flashcards

1
Q

Cardiac muscle tissue is composed of what kind of muscle cells:

A

Striated

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2
Q

How are striated heart muscles cells anchored at their ends?

A

Intercalated discs

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3
Q

Why is the syncytium of cardiac muscle important?

A

Allows rapid coordinated contraction/action potential from cell to cell (slowly)

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4
Q

The heart is a demanding tissue that requires:

A

Extensive capillary density within endomysium to deliver steady supply of O2

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5
Q

Ischemia

A

Reduction in O2

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6
Q

With would happen without syncytium?

A

Cell won’t maintain polarized state, will reach action potential and fire out of sequence

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7
Q

A non-regenerating tissue with cells that are capable of hypertrophy (add new myofibrils) when worked hard

A

Cardiac muscle

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8
Q

Responsive to chronic stresses

A

Cardiac muscle Ie. Pressure and/or volume loading

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9
Q

Cells that abandoned much of their myofibrillar apparatus for rapid impulse conduction/propagation:

A

Purkinje cells

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10
Q

What is Purkinje’s system?

A

Network of Purkinje fibers that carry cardiac impulse from AV node to ventricles of the heart and causes them to contract. Acts as a wiring to get depolarization stimulus everywhere at the right time (as opposed to the normally slower paced propagation between cells due to intercalated disks.)

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11
Q

The action potential of cardiac, contrite cells is very _____ and has 3 basic phases:

A

Long

  1. Depolarization
  2. Plateau
  3. Repolarization
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12
Q

Rapid influx of Na+ as voltage gates then open Ca2+ channels

A

Depolarization

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13
Q

Contraction happens at this phase:

A

Plateau AKA absolute refractory period (ARP)

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14
Q

The phase when the cell is resistant to stimulation, cytosolic Ca2+ rises and induces SER release of Ca2+ reserves

A

Plateau / absolute refractory period

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15
Q

This phase consists of a variable sensitivity period known as relative refractory period

A

Repolarization

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16
Q

When K+ is relocated to the interior, as at rest

A

Repolarization

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17
Q

The end of the relative refractory period (RRP) has a period of

A

Supranormal excitability period (SNP)

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18
Q

Where stimulation easily causes another depolarization and contraction

A

Supranormal excitability period (SNP)

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19
Q

As a cell is _____ during relaxation, it tends to produce a stronger contraction in the next cycle

A

Lengthened

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20
Q

Action potentials are ____ depending upon the particular cardiac muscle cell examined (form, duration, timing)

A

Variable

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21
Q

Nodal tissue tends to be ___ to depolarize but ___ to repolarize.

A

Slow; quick

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22
Q

Spontaneous action potentials are called

A

Auto-rhythmicity

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23
Q

In auto-rhythmicity, membranes are:

A

Leaky to inward movement of ions

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24
Q

Are nerves needed in auto-rhythmicity?

A

No. Though may modulate action

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25
Q

Cardiac muscle cells are complexly covered with

A

Receptors

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26
Q

What renders cardiac cells sensitive to some hormones and neurotransmitters from the autonomic nervous system?

A

Receptors

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27
Q

What two broad category receptors are on the cardiac muscle?

A

Adrenergic receptors

Cholinergic receptors

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28
Q

Receptors that bind adrenergic agonists such as sympathetic neurotransmitter norepinephrine and circulating hormone epinephrine

A

Adrenergic

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29
Q

What Adrenergic receptor is sensitive to norepinephrine and released from the axons of sympathetic fibers?

A

β1 receptors

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30
Q

What receptor increases excitability, strength and rate of contraction by hypo-polarizing the plasma membrane of the cell through G-protein signaling?

A

Adrenergic receptors (primarily β1 receptors)

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31
Q

Adrenergic receptors bind to

A

Norepinephrine and epinephrine

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32
Q

What receptor works by decreasing excitability, strength and rate fo contraction by tending to hyperpolarize the membranes (through G-protein signalin)

A

Cholinergic receptors

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33
Q

How does cholinergic receptors work

A

Ach “muscarinic” receptors sensitive to acetylcholine released from axons of parasympathetic fibers

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34
Q

Describe the flow of blood through the heart starting with the IVC/SVC

A

Right atrium —> Right ventricle —> Pulmonary trunk, arteries —> lungs —> pulmonary veins —> Left atrium —> left ventricle —> ascending aorta, etc.

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35
Q

Name the valves that prevent retrograde (backwards) flow of the blood

A

Atrioventricular (AV) valves

Tricuspid and Bicuspid/Mitral valves

Semilunar valves: aortic and pulmonic

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36
Q

Both the left and right ventricles must pump the ____ amount of blood per unit time.

A

Same

37
Q

The systemic circulation is ______ while the pulmonary circulation is ______

A

Large; small

38
Q

Contraction and ejection of blood

A

Systole

39
Q

Relaxation and filing of blood

A

Diastole

40
Q

The full action of the heart per beat is usually presented as a classic, integrated, display of all relevant activity of the heart and is known as

A

Cardiac cycle

41
Q

In the cardiac cycle, atrial pressure supplies

A

additional filling to the ventricles (not important for us)

42
Q

In the cardiac cycle, the heart sounds are called

A

phonocardiogram, clinically important

43
Q

In the cardiac cycle, the thing that gets it all going

A

electrocardiogram (ECG)

44
Q

In the cardiac cycle, the “bottom line” product of contraction

A

ventricular volume

45
Q

In the cardiac cycle, the arterial blood pressure (left side output)

A

aortic pressure

46
Q

In the cardiac cycle, the source of most initial ∆P

A

ventricular pressure

47
Q

Memorize Wiggers diagram (sketch it out)

A

check your work

48
Q

25% of ventricular filling is done by _____. The other 75% is done by:

A

atrial systole (at rest)

blood pouring straight from great veins through atria into ventricles.

49
Q

Ventricular diastole subphases:

A
  1. isovolumetric relaxation
  2. rapid inflow (75% passive filling)
  3. diastasis
  4. atrial systole (25% active filling)
50
Q

Ventricular systole subphases:

A
  1. isovolumetric contraction
  2. ejection
51
Q

end-diastolic volume (EDV) = the volume at end of diastole

A

~130 ml

52
Q

end-systolic volume (ESV) = volume end of systole

A

~60 ml

53
Q

stroke volume (SV) equation

A

SV = EDV - ESV

54
Q

average stroke volume

A

~70 ml

55
Q

a useful indicator of heart performance

A

ejection fraction

56
Q

ejection fraction equation

A

SV/EDV

57
Q

an event occurring in early systole during which the ventricles contract with no corresponding volume change

A

period of isovolumetric contraction (AKA isovolumic or isometric)

58
Q

once ventricular pressure exceeds aortic pressure, then aortic valve opens and the ____ begins

A

period of ejection

59
Q

systolic pressure (systolic BP) should be

A

~120 mm Hg

60
Q

diastolic pressure (diastolic BP) should be

A

~80 mm Hg

61
Q

a secondary upstroke in the descending part of a pulse tracing corresponding to the transient increase in aortic pressure upon closure of the aortic valve

A

dicrotic notch

62
Q

2 principle heart sounds, S1 is described as the:

A

LUB

63
Q

2 principle heart sounds, S2 is described as the:

A

DUB

64
Q

S1 is the closure of __________ while S2 is the closure of ___________

A

AV valves; semilunar valves

65
Q

What is the valvular abnormality due to difficulty pushing blood through aortic valve. Loud and strong murmur during LEFT ventricular ejection heard throughout systole that is sometimes be felt as a “thrill.”

A

aortic stenosis

66
Q

What is the valvular abnormality that is regurgitation, when the valve fails to prevent backflow into the left ventricle. Often heard as a “blowing” murmur or higher pitch swishing sound through diastole.

A

aortic insufficiency

67
Q

What is the valvular abnormality that is due to difficulty pushing blood through mitral valve? Creates a weak/low-pitched murmur sound heard in the 2nd half of diastole but especially the later aspect (atrial systole)

A

mitral stenosis

68
Q

What is the valvular abnormality that is regurgitation, occurring when the valve allows blood back into the left atrium? Creates a blowing, swishing murmur heard throughout systole.

A

mitral insufficiency

69
Q

All valvular abnormalities due to stenosis or insufficiency usually _________ the net stroke volume

A

reduce

70
Q

extra strain due to stenosis, the cardiac muscle will usually

A

hypertrophy

71
Q

serious overload on the heart leads to chamber ___

A

dilation

72
Q

cardiac output for resting adult is about

A

5000 ml/min

73
Q

name the 2 basic mechanisms to regulate cardiac output

A

intrinsic autoregulation (self-regulated)

reflex / extrinsic control (nervous)

74
Q

The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant

A

law of the heart

AKA frank-starlin mechanism

75
Q

law of the heart is sometimes stated simply as _____ in venous return leads to _____ in cardiac output

A

an increase; an increase

76
Q

peripheral factors, which affect returning blood flow, are more important than

A

cardiac factors

77
Q

blood pressure does/does not normally affect cardiac output

A

does not

78
Q

sympathetic innervation include numerous nerves from

A

spinal sympathetic chain

79
Q

parasympathetic innervation includes

A

2 vagus cranial nerves

80
Q

conduction speed

A

dromotropic effect

81
Q

rate of contraction

A

chronotropic effect

82
Q

strength of contraction

A

inotropic effect

83
Q

What serves as landing site for neurotransmitter norepinephrine from sympathetic innervation on the heart? (also epinephrine from adrenal glands)

A

β1 adrenergic receptors

84
Q

How do β1 adrenergic receptors affect dromotopism, chronotropism and inotropism?

A

positive (by opening Na+ and Ca2+ channels)

85
Q

a heart rate greater than or equal to 100 bpm is perfectly normal in many situations but not at rest

A

tachycardia

86
Q

some cardiac myocytes respond to this parasympathetic neurotransmitter ____ because it displays receptors for it

A

acetylcholine

87
Q

how does acetylcholine affect dromotropism (conduction speed), chronotropism (rate of contraction), inotropism (strength of contraction)?

A

makes them negative

88
Q

a heart rate less than or equal to 60 bpm is sometimes perfectly normal, sometimes abnormal

A

bradycardia

89
Q

reflex control is

A

rapid and anticipatory

Physiology I (15 decks)

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