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Physiology 2nd Midterm > Circulatory System 2 > Flashcards

Circulatory System 2 Flashcards

1
Q

What is cardiac output

A

Volume of blood pumped per minute by each ventricle

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2
Q

What is heart rate

A

Number of heart beats (cardiac cycle) per minute

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3
Q

What is stroke volume

A

Volume of blood pumped per beat (per cardiac cycle) by each ventricle

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4
Q

How to calculate cardiac output CO

A

Heart rate x stroke volume

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5
Q

What is the average resting cardiac rate (heart rate)

A

70 beat/min

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6
Q

What is the average stroke volume

A

70-80 ml/beat

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7
Q

An average person with an average HR and SV would have an CO of ….?

A

HR = 70 beat/min
SV = 70 ml/beat

So…⁣⁣⁣⁣⁣ CO = HR x SV = 70 x 70 = 4900 ml/min or about 5 L/min

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8
Q

Unit of heart rate

A

Beat/min

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9
Q

Unit of stroke volume

A

ml/beat

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10
Q

Unit of cardiac output

A

ml/min

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11
Q

How many liters of blood does an average human have ?

A

5L of total body blood

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12
Q

For a person with 5L of blood and a CO of 5 L/min , this means that ….

A

The WHOLE total volume is circulated once around the body

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13
Q

What controls heart rate

A

Sympathetic and parasympathetic divisions of ANS

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14
Q

In the absence of any neural effects, does the heart stop beating?

A

No

The heart is still automatically controlled by the rate at which SA node fires action potential

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15
Q

How does sympatheitc activity increase heart rate ?

A
  1. increases the steepness of pacemaker potential
  2. threshold is reached sooner
  3. increases the rate of SA node firing

= increases heart rate

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16
Q

How does parasympathetic activity reduce heart rate

A
  1. Reduces the steepness of pacemaker potential
  2. Threshold is reached later
  3. Reduces rate of SA node firing

= decreases heart rate

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17
Q

What happens to cardiac output if heart rate increases ?

A

Increases

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18
Q

What controls stroke volume SV

A
  1. EDV (preload)
  2. Total peripheral resistance TPR (afterload)
  3. Contractility (inotropy)
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19
Q

What is EDV (preload)

A

Volume of blood in ventricles at the end of diastole

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20
Q

How does preload (EDV) affect SV

A

The more the ventricles are filled with blood during diastole, the greater EDV, and therefore the greater stroke volume



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21
Q

How does afterload (total peripheral resistance) affect stroke volume SV?

A

The greater the resistance to blood flow in the arteries, such as when there is vasoconstriction, the lower the stroke volume

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22
Q

What is total peripheral resistance TPR (afterload)

A

The resistance to blood flow offered by all the systemic vasculature, excluding the pulmonary vasculature

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23
Q

How does inotropy (contractility) affect stroke volume ?

A

The greater the inotropy, the greater the stroke volume

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24
Q

What is contractility (inotropy)

A

The intrinsic ability of the myocardium to contract independently of changes in preload or afterload

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25
Q

What is the relationship between SV and EDV (preload) and what is that relationship called

A

SV is directly proportional to EDV ; therefore if EDV increases, SV will increase too.

This is called Frank-Starling Law of the heart

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26
Q

What is Frank-Starling Law of the heart

A

Increased EDV stretches the myocardium, resulting in a more forceful contraction, therefore higher SV and CO

( high EDV = high SV = high CO)

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27
Q

The greater the volume of blood we start with (EDV), the greater the ejected volume

What law is this

A

Frank-starling law of the heart

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28
Q

How to calculate SV

A

SV= EDV - ESV

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29
Q

What is ejection fraction EF

A

The percentage of blood ejected by the ventricle each time it contracts

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30
Q

How to calculate ejection fraction EF

A

EF = SV/EDV x 100

Or

EF = (EDV-ESV)/EDV x 100

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31
Q

What happens to ejection fraction EF if EDV increases

A

Increases

High EDV = High SV = High EF = High CO

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32
Q

Normal EF is between ___% - ____%

A

50% to 70%

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33
Q

Calculate the EF of an individual if his ESV = 80 ml and EDV = 120 ml

A

EF = (EDV -ESV) / EDV x 100
EF = (120-80)/120 x 100
= 33%

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34
Q

EDV is controlled by factors that affect the ____________.

A

Venous return VR

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35
Q

What is venous return VR

A

The rate at which venous blood enters the right atrium

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36
Q

How does venous return affect EDV and SV and CO

A

The more venous blood returning to the heart, the higher the EDV and thus the higher the SV and CO

(High VR = High EDV = High SV = High EF = High CO)

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37
Q

What are some special mechanisms that INCREASE venous return VR

A
  1. Skeletal muscle pump
  2. Respiratory pump
  3. Venoconstriction
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38
Q

How does skeletal muscle pump increase venous return VR

A

NORMALLY, The low venous pressure is insufficient to push blood towards the heart, especially from the lower limbs

HOWEVER, Contraction of skeletal muscles of the lower limb such as during exercise, compresses the deep veins which facilitates venous blood flow to the heart. 

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39
Q

Venous blood flow from the lower limbs to large abdominal veins is facilitated by ________________. HOWEVER, movement of venous blood from abdominal to thoracic veins is aided by an additional mechanism which is _______________.

A

Skeletal muscle pump
Breathing

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40
Q

How does respiratory pump increase VR?

A

During inspiration,
Intra-thoracic pressure : reduced
Abdominal pressure: increased

  • this pressure difference INCREASES the venous return by increasing the flow of venous blood from the abdominal viscera to the heart and lungs
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41
Q

How does venoconstriction increase venous return VR

A

Sympathetic activity increases VR by stimulating smooth muscle contraction in the venous walls:
- reducing their compliance and distensibility (⬇️C)
- increasing their pressure (⬆️P)

Venoconstriction increases VR by causing:
- lumen becomes more rounded (less surface area)
- decreases resistance
- increase venous return

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42
Q

Summary of factors that affect VR and EDV

A
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43
Q

TPR is mainly determine by the __________.

A

Arterioles

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44
Q

How does TPR reduce stroke volume ?

A

A greater TPR increases the afterload (arterial pressure) , thus reducing SV
(Unless there is compensation by increased inotropy)

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45
Q

True or false
The degree of constriction and relaxation of arterioles markedly affects TPR

A

True

46
Q

Explain the effect or arteriolar vasoconstriction on blood pressure

A
  • INCREASES the pressure upstream (arterial pressure)
  • DECREASES the pressure downstream (capillary and venous pressure)
47
Q

How does inotropy affect SV

A

The greater the inotropy, the greater the SV

48
Q

Inotropy depends on ___________________.

A

Cytosolic calcium (Ca2+)

49
Q

As the cytosolic calcium increases, what happens to inotropy

A

Increases

50
Q

Agents that increase contractility are called ____________________. While agents that decrease contractility are called ________________.

A

Positive inotropes
Negative inotropes

51
Q

What two things have a positive inotropic effect on the myocardium (increase contractility)

A

Stimulation of sympathetic nervous system
Circulating catecholamines

52
Q

What two things have a negative inotropic effect MOSTLY ON THE ATRIA (decrease contractility)

A

Stimulation of parasympathetic nervous system
Acetylcholine

53
Q

Quick summary revision

A

Notice that:
Heart rate
Preload
Afterload
Contractility

ALL affect cardiac output

54
Q

Veins contain ____% to ____% of the blood volume in the body

A

60% to 70%

55
Q

Which blood vessels are called capacitance vessels

A

Veins

56
Q

Which blood vessels are called resistance vessels

A

Arteries

57
Q

why are veins called capacitance vessels ?

A
  • bigger lumen
  • more distensible
58
Q

Why are arteries called resistance vessels ?

A
  • smaller lumen
  • less distensible
59
Q

Why are veins more distensible

A

Due to thinner, less muscular walls that contain less elastic tissue

60
Q

Why are arteries less distensible

A

Due to thicker, highly muscular walls that contain more elastic tissue

61
Q

Velocity of the blood flow is related to two things

A

-Total cross-sectional area of blood vessel (diameter)
- blood flow

62
Q

How to calculate velocity of blood flow

A

V = F/A

F - blood flow
A - cross-sectional area

63
Q

What’s the advantage of the low velocity of blood flow through the capillaries

A

To allow enough time for gas, nutrients, and waste exchange

64
Q

Understand this fact:

A

👍🏻

65
Q

Arterial blood pressure depends on:

A
  1. Stroke volume SV
  2. Heart Rate HR
  3. Total Peripheral Resistance TPR
66
Q

How does stroke volume affect arterial blood pressure

A

The greater the stroke volume, the greater the blood pressure

67
Q

How does heart rate affect arterial blood pressure

A

The greater the heart rate, the greater the blood pressure

68
Q

How does total peripheral resistance affect arterial blood pressure

A

Vasoconstriction of the arteries increases peripheral resistance which increases the blood pressure

69
Q

Physics law for flow

A

F = ΔP/R

ΔP - pressure difference
R - resistance
F - blood flow

70
Q

What is the relationship between blood flow and pressure difference

A

Directly proportional

71
Q

What is the relationship between blood flow and resistance

A

Inversely proportional

72
Q

Physics law for resistance

A
73
Q

Relationship between resistance and viscosity of blood

A

Directly proportional

74
Q

Relationship between resistance and length of the vessel

A

Directly proportional

75
Q

Relationship between resistance and radius of the vessel

A

Inversely proportional to the 4TH power of the radius of the vessel !

76
Q

We can combine these 2 formulas to give us a single formula which is

A
77
Q

Understand this

A

As you can see in (b) …⁣⁣⁣⁣⁣
When we doubled the size of the radius (2x),
The resistance reduced (1/16 of original resistance)
= blood flow increasing 16x

When we halved the radius (1/2),
The resistance increased (16x the original resistance)
= blood flow is reduced (1/16 of original flow)

78
Q

Understand this

A
  • Mean pressure is highest in aorta and large arteries
  • mean pressure decreases progressively as blood flows from the arteries to the artieroles to the capillaries to the veins and back to the heart
  • LARGEST PRESSURE DROP OCCURS IN THE ARTERIOLES !!
79
Q

Why does the largest pressure drop occur in the arterioles

A

Due to their high resistance to flow

80
Q

A sudden change in blood pressure will be sensed by the ______________.

A

Baroreceptors

81
Q

where are baroreceptors located

A

Arch of aorta AND the carotid sinuses

82
Q

What happens if baroreceptors detect an increase in blood pressure

A
  • The parasympathetic system will be activated
  • The sympathetic activity will decline

to restore blood pressure to normal level

83
Q

What happens if baroreceptors detect a decrease in blood pressure

A
  • The sympathetic system will be activated
  • The parasympathetic activity will decline

to restore blood pressure to normal level

84
Q

How is blood pressure regulated by the baroreceptor reflex

A

By regulation of:
- HR
- SV
- TPR

85
Q

Understand this (read picture)

A

Note:

This reflex is a SHORT-term mechanism for BP regulation

The opposite will take place if BP was high

86
Q

How to calculate arterial blood pressure

A

Hint: we already know that the factors that affect arterial blood pressure are : SV, HR, and TPR

87
Q

An increase in ______, ______, or _______ will increase MAP

A

SV
HR
TPR

(Unless there is a compensation via a decrease in another factor )

88
Q

Blood pressure is usually measured by __________________.

A

Sphygmomanometer

89
Q

Unit of blood pressure

A

mmHg

90
Q

How is blood pressure represented

A

BP = systolic BP / diastolic BP

91
Q

Normal blood pressure is around :

A

120/80 mmHg

92
Q

Explain how sphygmomanometer works

A
  1. Cuff pressure is increased to a value higher than systolic pressure SP (ex: 140 mmHg) to constrict the brachial artery closed and stop blood flow (NO SOUNDS)
  2. Cuff pressure is then reduced slowly. The reading at the FIRST turbulent sound is the SYSTOLIC pressure
  3. Cuff pressure is reduced even lower (< DP) , until NO SOUND is heard, which is DIASTOLIC pressure . (Laminar blood flow)
93
Q

When the cup pressure is between SP and DP, blood flow stops at each diastole and resumes with every systole. The turbulent blood flow through the partially constricted artery at each soul produces sounds called ___________________.

A

Korotkoff sounds

94
Q

What is pulse pressure ? calculation

A

Is the difference between the systolic pressure SP and diastolic pressure DP

PP = SP - DP

95
Q

SP = 120 mmHg
DP = 80m mmHg

What is pulse pressure ?

A

PP = SP - DP = 120 - 80 = 40 mmHg

96
Q

We know MAP = CO x TPR
But how can you just approximate MAP?

A

By adding 1/3 of PP to the diastolic pressure
So…⁣⁣⁣⁣⁣
MAP = DP + 1/3PP

97
Q

DP = 80 mmHg
PP = 40 mmHg

Estimate MAP

A

MAP = 80 + (1/3 x 40) = 93 mmHg

98
Q

What is hypertension

A

Consistently high blood pressure

99
Q

What is secondary hypertension

A

Hypertension that is caused by failure of another organ

100
Q

What is essential or primary hypertension

A

Hypertension which is not related to any other organ

101
Q

Two types of hypertension

A

Primary hypertension and secondary hypertension

102
Q

What is elevated hypertension ?

A

SP = 120-129
DP = less than 80

103
Q

What is stage 1 hypertension ?

A

SP = 130 - 139
DP = 80 - 89

104
Q

What is stage 2 hypertension ?

A

SP = 140 or higher
DP = 90 or higher

105
Q

What is hypertensive crisis?

A

SP = higher than 180
DP = higher than 120

106
Q

Which type of hypertension accounts for 95% of cases

A

Primary hypertension

107
Q

Essential (primary) hypertension might be due to:

A
  • increased renin secretion
  • increased sympathetic activity
  • increases salt intake
108
Q

True or false
Essential hypertension is multifactorial and doesn’t have one distinct cause

A

True

109
Q

True or false
Hypertension is a silent killer

A

True

110
Q

Hypertension may lead to complications such as:

A
  • vascular damage
  • organ failure
  • congestive heart failure
  • stroke (cerebral blood vessel damage)
111
Q

Hypertension treatment includes:

A

Lifestyle changes + medication

Physiology 2nd Midterm (7 decks)

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