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Biology (S2) > Blood and Gas Exchanage ppt > Flashcards

Blood and Gas Exchanage ppt Flashcards

1
Q

What are the 3 histologic layers of blood vessels?

A
  • Tunica: intima
  • Tunica media
  • Tunica adventitia
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2
Q

Describe the structure of arteries

A

Large diameter, thick muscular walls (thick Tunica media)

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3
Q

When do arteries stretch and recoil?

A

Stretch during ventricular ejection & recoil during diastole

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4
Q

What do arteries act as?

A

Pressure reservoirs

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5
Q

What happens to the arterial blood pressure and pulse during the cardiac cycle?

A

It fluctuates

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6
Q

What causes the stiffness of arteries? **

A
  • Age
  • Atherosclerosis
  • Rise in arterial BP
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7
Q

Describe the structure of veins

A

Thin walled, larger lumen than arteries, thin tunica media

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8
Q

What structure in veins prevents backflow?

A

Valves

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9
Q

How is blood flow mostly achieved in veins?

A

By the contraction of surrounding musculature or respiratory movements

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10
Q

What do veins function as?

A

Major blood reservoir

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11
Q

What are the 4 main descriptive measures of arterial pressure?

A
  • Systolic pressure (highest during one cycle)
  • Diastolic pressure (lowest during one cycle)
  • Pulse pressure (systolic pressure – diastolic pressure)
  • Mean arterial pressure (diastolic pressure = 1/3 pulse pressure
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12
Q

Name the 4 palpable pulses in the upper body

A
  1. Temporal
  2. Cartoid - side of neck
  3. Brachial - inner biceps
  4. Radial - inner wrist under thumb line
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13
Q

Name the 4 palpable pulses in the lower body

A
  1. Femoral - near pelvic bone
  2. Popliteal - behind knee
  3. Anterior & Posterior tibialis - lower limb
  4. Dorsal Pedis - over instep of foot
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14
Q

How does blood pressure change with age?

A

Systolic blood pressure rises throughout life
Diastolic blood pressure rises until the 6th decade and then becomes constant.

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15
Q

Is blood pressure higher in men or women?

A

Blood pressure is generally higher in men

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16
Q

What factors are associated with raised blood pressure?

A

-Dietary fats and salt
- Obesity
- Physical inactivity
- Psychological stress
- Excess alcohol intake.

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17
Q

What is the conventional unit for measuring blood pressure?

A

Millimeters of mercury (mmHg)

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18
Q

How is blood pressure typically expressed?

A

systolic pressure / diastolic pressure
Normal value is around 120 / 80

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19
Q

What is the mean arterial pressure?

A

The average pressure in the arteries over a cardiac cycle
Typically around 93 mmHg

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20
Q

What is the normal blood pressure range?

A

Systolic - less than 120
Diastolic - less than 80

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21
Q

What is the elevated blood pressure range?

A

Systolic - 120-129
Diastolic - Less than 80

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22
Q

What is the stage 1 high blood pressure range?

A

Systolic - 130-139
OR
Diastolic - 80-89

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23
Q

What is the stage 2 high blood pressure range?

A

Systolic - 140+
OR
Diastolic - 90+

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24
Q

Hypertensive crisis is when….?

A

Systolic - 180+
AND/OR
Diastolic - 120+

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25
Q

What are the principles of gas exchange?

A

Gas molecules move randomly, but in a net direction from regions of high concentration to regions of low concentration

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26
Q

What is partial pressure?

A

The pressure exerted by a specific gas in a mixture of gases, expressed as a percentage of the total pressure

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27
Q

What is the atmospheric pressure and composition of air?

A

Atmospheric pressure = 760mmHg
Dry air is composed of 79% nitrogen, 21% oxygen, and 0.04% carbon dioxide

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28
Q

How is partial pressure of a gas calculated?

A

By multiplying the percentage of the gas in the mixture by the total pressure of the mixture
Eg. partial pressure of oxygen (PO2) in air is 0.21 x 760 mmHg = 159.5 mmHg

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29
Q

What happens to air as it enters the respiratory tract?

A

Air is humidified>Oxygen diffuses from alveoli into blood>CO2 diffuses from blood into alveoli
This air is then partially replaced by the next inspiration

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30
Q

What is the partial pressure of oxygen and CO2 in air?

A

PO2 = 159mmHg
PCO2 = 0.3mmHg

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31
Q

What is the partial pressure of oxygen and CO2 in the alveolar air?

A

PO2 = 104mmHg
PCO2 = 40mmHg
O2 diffuses into blood until it has PO2 of 104mmHg
Blood has PCO2 of 45mmHg so CO2 diffuses into alveoli

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32
Q

What is the partial pressure of oxygen and CO2 in the oxygenated blood in the left atrium?

A

PO2 = 95mmHg
PCO2 = 40mmHg

Slight loss of PO2 from alveoli to end the of pulmonary vein - pulmonary vein receives some deoxygenated blood from bronchial veins

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33
Q

What is the partial pressure of oxygen and CO2 in systemic tissue cells?

A

PO2 = 40mmHg
PCO2 = 45mmHg

CO2 diffuses into the capillaries that have a PCO2 of 40mmHg

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34
Q

What is the partial pressure of oxygen and CO2 in the deoxygenated blood in the right atrium?

A

PO2 = 40mmHg
PCO2 = 45mmHg

(same as in tissue cells)

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35
Q

What percentage of blood is plasma and formed elements?

A

Plasma = 46-63%
Formed Elements = 37-54%

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36
Q

What makes up formed elements of blood and in what percentage?

A

Platelets + white blood cells = 0.1%
Red blood cells = 99.9%

37
Q

What are the 5 types of white blood cells are what are their percentage quantities?

A

Neutrophils = 50-70%
Lymphocytes = 20-30%
Monocytes = 2-8%
Eosinophils = 2-4%
Basophils = <1%

38
Q

What is the lifespan of an erythrocyte?

A

120 days in men and 110 days in women.

39
Q

How many erythrocytes are destroyed every second?

A

About 2.5 million or 1/10000% of the total 25 trillion erythrocytes are destroyed every second.

40
Q

Where does erythropoiesis occur and how long does it take?

A

In the bone marrow and takes about 4 days.

41
Q

How does low PO2 stimulate erythropoiesis?

A

By increasing the formation of the glycoprotein erythropoietin in the kidneys
This induces the bone marrow to make more erythrocytes

42
Q

What is the ratio of erythrocytes to white blood cells?

A

There are 700 times more Erythrocytes, than white blood cells.

43
Q

What property allows erythrocytes to exchange quickly with surrounding plasma?

A

A large volume to surface ratio

44
Q

How do erythrocytes pass through narrow capillaries?

A

They form stacks and bend/flex
This allows them to pass through capillaries as narrow as 4 um

45
Q

What is haemoglobin made up of?

A

4 polypeptides (called globins) which each bind one heme molecule

46
Q

What is the colour of each heme molecule and what does it bind to?

A

Red
Binds to 1 iron molecule - this then binds with oxygen

47
Q

What does adult haemoglobin consist of?

A

2 alpha chains, and 2 beta chains

48
Q

What is oxygen rich haemoglobin called?

A

Oxyhaemoglobin

49
Q

What is oxygen-deficient haemoglobin called?

A

Deoxyhaemoglobin

50
Q

What percentage of oxygen in the blood is carried by haemoglobin?

A

97%

51
Q

How is the remaining 3% of oxygen carried in the blood?

A

It is carried in solution in the blood plasma

52
Q

What type of binding does O2 have with haemoglobin?

A

Reversible

53
Q

Where does O2 bind to haemoglobin?

A

In the lungs

54
Q

Where does O2 dissociate from haemoglobin?

A

In the tissue

55
Q

What describes the relationship between O2 and haemoglobin?

A

The oxygen dissociation curve

56
Q

At what PO2 is haemoglobin in erythrocytes nearly 100% saturated with oxygen?

A

PO2 of 80 mm Hg and above
thus the blood in the alveolar capillaries is saturated

57
Q

At what PO2 is haemoglobin 75% saturated?

A

40mmHg
About 25% of O2 carried by erythrocytes can dissociate into the interstitial fluid

58
Q

When, and at what PO2, does haemoglobin give up 75% of its O2?

A

During moderate exercise when interstitial fluid in skeletal muscle can drop to 15 mm Hg

59
Q

What is the Haldane response?

A

The decline in haemoglobin’s affinity for O2 with increasing CO2 concentrations

60
Q

How is carbonic acid formed?

A

CO2 combining with water

61
Q

What does carbonic acid dissociates into?

A

H ions and bicarbonate ions
This further decreases the affinity of haemoglobin for O2

62
Q

What is the Bohr effect?

A

The shift in the oxygen dissociation curve to the right
Caused by a decrease in pH and an increase in CO2 concentration
Leads to a greater PO2 being required to saturate haemoglobin

63
Q

How does increased temperature affect the oxygen dissociation curve?

A

It shifts the oxygen dissociation curve to the right

64
Q

What effect does the accumulation of lactic acid have on the oxygen dissociation curve?

A

It shifts the oxygen dissociation curve to the right

65
Q

In what conditions can haemoglobin release around 95% of its bound O2?

A

In heavy exercise - CO2 and lactic acid accumulates, temperature increases

Opposite in lungs

66
Q

How is lactic acid important in the cardiovascular system?

A

It is transported to the heart and used by the cardiomyocytes to generate ATP

67
Q

What 3 major tasks does physical exercise impose on the cardiovascular system?

A
  1. Increase pulmonary blood flow - along with gas exchange and ventilation
  2. Increase blood flow through the working muscles
  3. Maintain a stable blood pressure
68
Q

What is the most important respiratory adjustment to exercise?

A

Ventilation-perfusion matching

69
Q

What is Ventilation-perfusion matching?

A

Matching the increase in pulmonary blood flow with an increase in alveolar ventilation

70
Q

How is ventilation-perfusion matching achieved?

A

By increasing both the rate and depth of breathing

71
Q

Cardiac Output (CO) equation?

A

Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)

72
Q

How much can O2 consumption increase during exercise?

A

About 13 times its resting level

73
Q

How is a 13-fold increase in O2 absorption by the pulmonary circulation is typically achieved?

A

a 1.5X increase in Stroke Volume
a 3X increase in Heart Rate
a 3X increase in Arteriovenous O2 difference

74
Q

How does heart rate increase with work rate in adults and what is the maximum?

A

Rises Linearly
Maximum of 180-200bpm

75
Q

What 2 factors increase heart rate and O2 uptake?

A
  • Decreased vagal (parasympathetic) inhibition
  • Increased sympathetic stimulation of the pacemaker cells in the sinoatrial node
76
Q

How is an increase in stroke volume achieved?

A

-Increased filling pressure (which increases ventricular EDV)
- Increased ventricular contractility (which increases ejection fraction and decreases ventricular ESV)

77
Q

What compromises ventricular end diastolic volume?

A

Reduced ventricular filling at higher work loads

78
Q

How does cardiac output increase with O2 consumption?

A

In a virtually linear relationship

79
Q

How does rest cardiac output change during exercise in an untrained adult?

A

From around 5 L.min-1 at rest to a maximum of 20-25 L.min-1 (a 4-5 fold increase)

80
Q

What is the initial anticipatory respiratory response to exercise?

A

Inhalation and breath holding

81
Q

What does the Initial anticipatory response do?

A

Forces more blood from the lungs back to the heart This increases heart stroke volume

82
Q

What does increased PCO2 do to blood pH, and what detects change??

A

Decreases
Detected by chemoreceptive area in the medulla oblongata

83
Q

What follows detection of pH change by the chemoreceptive area?

A

Increased respiratory rate
Increased tidal volume

84
Q

What is respiratory rate in exercise measured as?

A

The ventilatory equivalent for oxygen (Ve/Vo2) - ratio between minute ventilation arte and oxygen consumption

85
Q

What is the (Ve/Vo2) maintained at in a normal health individual?

A

25 up up to about 55% the maximum O2 consuption (Vo2 max)

86
Q

When does the minute ventilation start to increase disproportionately during exercise?

A

When O2 consumption (Vo2) exceeds 2.5L/min

Ve can increase from 25 to 35-40 during maximal exercise (oxygen uptake efficiency from lungs can almost half)

87
Q

What is the point at which there is a disproportionate increase in ventilation called?

A

Ventilatory threshold (VT)

88
Q

What buffers the onset of blood lactate accumulation (OBLA) and increased lactic acid during exercise?

A

A reaction with sodium bicarbonate
Lactate + NaHCO3 —–> Na lactate + H2CO3 ——> H20+ CO2

89
Q
A

Biology (S2) (7 decks)

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