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Medsci 142 > Cardiovascular System Part 2 > Flashcards

Cardiovascular System Part 2 Flashcards

1
Q

Cardiac output

A

Total blood flow, the volume of blood that circulates through the blood vessels each minute

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2
Q

Cardiac output equation

A

CO = heart rate x stroke volume

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3
Q

How the cardiac output becomes distributes into circulatory routes that serve various body tissues depends on two more factors:

A

1) The pressure difference that drives the blood flow through a tissue
2) the resistance to blood flow in specific blood vessels

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4
Q

Frank-Starling law of the heart

A

The law states that the stroke volume of the left ventricle will increase as the left ventricular volume increases due to myocyte stretch cause a more forceful systolic contraction

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5
Q

Preload

A

The amount of sarcomere stretch experienced by cardiac muscle cells, called cardiomyocytes, at the end of the ventricular filling during diastole

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6
Q

Contractility

A

The inherent strength and vigor of the heart, contraction during systole.
According to Starling’s law, the heart will eject a greater stroke volume at greater filling pressures.

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7
Q

Afterload

A

The pressure against which the heart must work to eject blood during systole (systolic pressure). The lower the afterload, the more blood the heart will eject with each contraction.

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8
Q

Stroke volume =

A

End diastolic volume - end systolic volume

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9
Q

Average stroke volume at rest:

A

70ml -> amount of blood being pumped out per cardiac cycle

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10
Q

Stroke volume is regulated by:

A

Preload, contractility, and afterload

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11
Q

Cardiac reserve

A

Is the heart’s ability to increase cardiac output to meet the metabolic requirements during exercise

The difference between resting level and max we can achieve

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12
Q

Contractility (Inotropy)

A

Contractility is important for the balance between the left and right sides of the heart

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13
Q

Positive inotropy agents:

A

Increase forcefulness of a contraction (Ca2+)

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14
Q

Negative inotropy agents:

A

Reduce forcefulness of contraction (K+)

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15
Q

In blood plasma, key components that drive contractility are:

A

Na+, Ca2+, and K+

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16
Q

Factors that affect inotropy (contractility) of the heart include:

A

Heart rate
afterload
sympathetic activation
parasympathetic activation

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17
Q

At very high rates, stroke volume is _______, this can result in a ________ of cardiac output.

A

Decreased

Decrease

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18
Q

Increasing heart rate ______ ventricular filling time.
The heart compensates by being more efficient at relaxation.
Stroke volume is ______
_______ cardiac output and efficiency of contraction.

A

reduces
decreased
decreases

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19
Q

Ejection fraction: pumping efficiency usually between __-__%

A

60-70%

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20
Q

Ejection fraction goes ___ with high BP/hypertension (140/90mmHG), extra _____, can lead to heart failure.

A

down

afterload

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21
Q

What does the heart’s conducting system consist of?

A

Cardiac muscle cells and conducting fibers that are specialized for initiating impulses and conducting them rapidly through the heart.

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22
Q

The sequence of contraction:

A

1) The SA node signals the atria to contract
2) The signal travels to the AV node, through the bundle of His, down the bundle branches, and through the Purkinje fibers
3) Causing the ventricles to contract

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23
Q

The AP will be fired when the _______ reaches about ___mV (the threshold)

A

depolarisation

-55

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24
Q

ECG: P-wave

A

depolarisation of atrial contractile fibers produces P-wave

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25
Q

ECG: QRS complex

A

the onset of ventricular depolarisation

depolarisation of ventricular contractile fibers produces QRS complex

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26
Q

ECG: T wave

A

ventricular repolarisation

repolarization of ventricular contractile fibers produces T wave

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27
Q

ECG

A

A summation of the action/electrical potentials

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28
Q

ECG: After P-wave

A

atrial systole (contraction)

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29
Q

ECG: S-T segment

A

Ventricular systole (contraction)

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30
Q

ECG: After T wave

A

Ventricular diastole (relaxation)

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31
Q

Parasympathetic system on the heart

A
  • affects the heart via the vagus nerves
  • if reduced increases heart rate
  • relaxation, slows the heart
  • can change heart rate very quickly
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32
Q

Sympathetic system on the heart

A
  • increase in the rate of spontaneous SA node depolarisation
  • affects the heart via cardiac accelerator nerves
  • sympathetic nerves run down the spinal cord and to the heart
  • increases heart rate
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33
Q

chronotropic:

A

the heart rate

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34
Q

contractility/inotropy:

A

The force of energy of heart muscular contraction

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35
Q

Vagus nerve

A

Innervates the SA node to slow the rate of spontaneous depolarization, decreasing heart rate. It does not have any fibers that innervate and relax cardiac myocytes

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36
Q

Sympathetic nerves

A

Innervate both the SA node (accelerating spontaneous depolarization and therefore heart rate) and the cardiac myocytes (increasing contractility and stroke volume)

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37
Q

Time length of cardiac AP

A

300ms

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38
Q

Time for nerve AP

A

1-2ms

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39
Q

Phases of cardiac action potential

A

1) Rapid depolarization
2) Early repolarization
3) Plateau
4) Repolarization
5) Restoration of the resting membrane potential

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40
Q

Rapid depolarization:

A

Na+ channels open in the cell membranes -> rapid influx of Na+ ions into the cell
The membrane potential changes from -90mV - 30mV within 1-2ms

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41
Q

Early repolarization:

A

Na+ channels closed -> membraine potential stops esculating -> some K+ channels are activates -> produces small outward possitive current

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42
Q

Plateau:

A
  • Inward and outward currents are equal
  • producing constant MP at 0mV
  • Inward current due to influx of Ca2+
  • Balances by the outward current due to small efflux of K+
  • This phase lasts 200ms
43
Q

Repolarization:

A
  • K+ flows down a concentration gradient and out of cell -> decreasing the MP towards a resting value of -90mV
  • Slower than depolarisation
44
Q

Restoration of resting membrane potential:

A
  • Inward and outward currents are balanced
  • MP sits at -90mV till the next wave of depolarisation
  • Na+/K+ATPase is important in resetting concentration gradients across the cell.
45
Q

Nervous system regulation of heart rate originates in the cardiovascular center of the _____ ______

A

medulla oblongata

46
Q

____ input is a major stimulus that accounts for the rapid rise in heart rate at the onset of physical activity

A

Proprioceptor

47
Q

Hormones from the _____ ______ and the _____ gland can increase heart rate

A

adrenal medulla

thyroid gland

48
Q

Blood pressure

A

the pressure of circulating blood against vessel walls

49
Q

Blood colloid osmotic pressure

A

a form of osmotic pressure induced by the proteins in the blood which draws fluid into the bloodstream

50
Q

Total peripheral resistance

A

the amount of force affecting resistance to blood flow throughout the circulatory system

51
Q

Capillary exchange

A

exchange of material between blood and capillary tissue

52
Q

Blood hydrostatic pressure

A

the pressure that water in blood plasma exerts on the vessel walls. Drives filtration into the interstitial fluid

53
Q

Interstitial fluid osmotic pressure

A

A form of pressure which is produced in the interstitial spaces and draws fluid out of the bloodstream

54
Q

Interstitial fluid hydrostatic pressure

A

the oppositional force which “pushes” fluid from the interstitial spaces back in the capillaries

55
Q

Hypertension:

A

High blood pressure

56
Q

Bradycardia:

A

Slow heart rate

57
Q

Tachycardia:

A

fast heart rate

58
Q

Baroreceptors:

A

Sensors detect blood pressue

59
Q

Poiseuille’s law:

A

flow is related to factors such as viscosity and the radius of a vessel

60
Q

Angiotensin II:

A

A peptide that produces vasoconstriction

61
Q

Hemorrhage:

A

loss of blood from a broken blood vessel

62
Q

Starling’s law:

A

the force of contraction is related to how much stretch occurs

63
Q

If a patient suddenly loses 15% of his blood volume and there was no adequate compensation, the end-diastolic volume would _____ and preload would _____. As a result, stroke volume would also _____

A

decrease
decrease
decrease

64
Q

Name the law that described the relationship between end-diastolic volume and stroke volume:

A

Frank-Starling’s law

65
Q

Decrease in blood volume leads to _____ in blood pressure

A

decrease

66
Q

Pressure is sensed by the baroreceptors in the:

A

carotid sinus and aortic arch

67
Q

In response to a decrease in arterial pressure, sympathetic nerve activity to the heart would increase (resulting in an increase in heart rate) and parasympathetic nerve activity to the heart would ___.

The sympathetic nerve would also _____ contractility of the cardiac myocytes.

A

decrease

increase

68
Q

What does increased sympathetic activity due to peripheral resistance?

The resulting increase in the frequency of sympathetic nerve activity causes _______ (of smooth muscle fibers) in systemic blood vessels. This reduces the ____ of the lumen of the vessel, _______ resistance to blood flow, _____ total peripheral resistance

A

increases it

vasoconstriction
radius
increasing
increasing

69
Q

Is there direct vagal (parasympathetic) innervation of the blood vessels?

A

No, the reduction in parasympathetic activity would increase the heart rate.
There is no direct parasympathetic nervous input to the blood vessels, total peripheral resistance is controlled by sympathetic nerve activity, as well as hormones and local metabolites.

70
Q

If cardiac output falls by 20% but means arterial pressure remains constant, what must have happened?

A

TPR compensated:

  • mean arterial pressure is a product of cardiac output and TPR, MAP = CO x TPR
  • if MAP is constant, but CO is reduced by 20%, then TPR must have increased to compensate
  • this is achieved by sympathetic stimulation of the smooth muscles of smaller arteries and arterioles, reducing their diameter and therefore, increasing their resistance.
71
Q

A patient presents to the hospital with a heart rate of 37 beats per minute and a BP of 100/50mmHG. What is their condition?

A

Bradycardiac, hypotensive

  • typically bradycardia is defined as HR < 50bpm and typically hypotension is defined as BP less than ideal pressure of 100/80mmHg
  • these values can be normal for a young fit person
72
Q

Fluid exits the capillaries because capillary hydrostatic pressure is _____ than blood colloidal osmotic pressure

A

greater

- remember that hydrostatic pressures force fluid out, which osmotic pressure pills back in

73
Q

On what side of the capillary does reabsorption occur?

A

Venous

- Fluid re-enters capillary because the capillary hydrostatic pressure is less than the blood colloidal osmotic pressure

74
Q

You stand up suddenly and feel faint for a few seconds. What would occur to restore homeostasis?

A

Decreased blood pressure -> decreased firing of baroreceptors -> increased cardiac output and vasoconstriction -> homeostasis restored

75
Q

Arterioles are the major resistance vessels due to a big ____ in pressure

A

decrease

76
Q

The opposition to blood flow due to friction between blood and the walls of blood vessels

A

vascular resistance

77
Q

Vascular resistance is determined by three factors:

A
  • Size (diameter) of lumen
  • Blood viscosity
  • Total blood vessel length
78
Q

Stenosis

A

The abnormal narrowing of a passage in the body

79
Q

Input to cardiovascular center from sensory receptors comes from:

A
  • propioreceptors
  • chemoreceptors
  • barorecptors
80
Q

Which sensory receptors monitor blood chemistry (blood acidity H+, CO2, and O2)

A

Chemoreceptors

81
Q

____ arterial blood pressure during diastole leads to ___ afterload which leads to semilunar valves opening sooner when the blood pressure in the aorta and pulmonary artery is lower which leads to ____ stroke volume and therefore, ___ cardiac output.

A

decreased
decreased
increased
increased

82
Q

Chemicals such as ___ or ____ hormones in the blood lead to a moderate increase in extracellular ___ which leads to increased ___ ___ and therefore, increased cardiac output

A

catecholamine
thyroid
Ca2+
heart rate

83
Q

____ sympathetic stimulation and ____ parasympathetic stimulation leads to increased ___ ___

A

Increased
decreased
heart rate

84
Q

In an ECG, a larger P wave could signal ___ ___

A

Atrial hypertophy

85
Q

In an ECG, a very large R could signal ____ ___

A

ventricular hypertrophy

86
Q

Cardiac accelerator nerves (sympathetic nervous system) affect which two things

A

Heart rate and stroke volume

87
Q

The vagus nerve (parasympathetic NS) only affects ____ ____

A

heart rate

88
Q

What is it called when vasomotor nerves (sympathetic) cause blood vessels to constrict?

A

vasoconstriction

89
Q

The sympathetic nervous system ____ contractility, thus cause an ______ in stroke volume

A

increase

increase

90
Q

The term that describes a change in HR

A

Chronotrophy

91
Q

The term that describes a change in contractility

A

Inotropy

92
Q

Blood distribution in the cardiovascular system:

  • Pulmonary vessels _%
  • Heart _%
  • Systemic arteries and arterioles _%
  • Systemic capillaries _%
  • Systemic veins and venules (blood reservoirs) _%
A
  • Pulmonary vessels 9%
  • Heart 7%
  • Systemic arteries and arterioles 13%
  • Systemic capillaries 7%
  • Systemic veins and venules (blood reservoirs) 64%
93
Q

Mean arterial pressure

A

The average blood pressure in the arteries, roughly 1/3 between the systolic and diastolic blood pressures

diastolic BP + 1/3(systolic BP - diastolic BP)

94
Q

Systolic blood pressure

A

the highest pressure attained in arteries during systole

95
Q

Diastolic blood pressure

A

The lowest arterial pressure during diastole

96
Q

Blood hydrostatic pressure at the arterial end is:

A

35 mmHg

97
Q

Blood hydrostatic pressure at the venous end is:

A

16 mmHg

98
Q

Blood colloid osmotic pressure at the arterial end is:

A

26 mmHg

99
Q

Blood colloid osmotic pressure at the venous end is:

A

26 mmHg

100
Q

Net filtration at the arterial end of capillaries is ___ per day

A

20 litres

101
Q

Net reabsorption at the venous end of capillaries is ___ per day

A

17 liters

102
Q

What are the pressures promoting filtration?

A

BHP

IFOP

103
Q

What are the pressures promoting reabsorption

A

BCOP

IFHP

Medsci 142 (9 decks)

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