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HUBS192 2022 > lecture 19 - gas transport & respiration > Flashcards

lecture 19 - gas transport & respiration Flashcards

1
Q

What are the 2 forms in which oxygen is transported in the blood?

A

Dissolved, and bound to haemoglobin in red blood cells

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2
Q

Why does oxygen dissolve poorly in the blood?

A

It has low solubility at physiological partial pressure

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3
Q

What is the equation for haemoglobin and oxygen binding?

A

O2 + Hb ⇌ HbO2

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4
Q

What is the shape of a haemoglobin-oxygen saturation curve?

A

Sigmoidal

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5
Q

What does an oxygen-haemoglobin saturation curve show?

A

oxyhemoglobin (% saturation) vs PO2(mmHg)

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6
Q

What is the advantage of the upper flat part of a oxygen-haemoglobin saturation curve?

A

Moderate changes in PO2 around the normal value in the lungs (~100mmHg) have only small effects of the %saturation, and therefore the amount of oxygen carried by the arterial blood

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7
Q

What is the advantage of the steep part of a oxygen-haemoglobin saturation curve?

A

helps in the unloading of O2 to the tissues

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8
Q

What is the Bohr effect?

A

Haemoglobin has a lower affinity for oxygen when there is an increase in the partial pressure of CO2 and/or a decrease in blood pH

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9
Q

If the binding affinity of oxygen decreases, what direction does the oxygen-haemoglobin saturation curve shift?

A

Rightwards - higher PO2 is needed to achieve greater saturation

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10
Q

What factors affect oxygen affinity to Hb?

A

Temperature, PCO2, pH, BPG levels

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11
Q

What is the affect of high temperature on oxygen affinity to Hb?

A

Reduced affinity

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12
Q

What is the effect of BPG on oxygen binding/affinity to Hb?

A

Decreases affinity, causes rightward shift of saturation curve

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13
Q

How does exercise affect the affinity of oxygen and Hb?

A

Causes plasma pH to drop and temperature to rise, causing right ward shift

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14
Q

What are the 3 forms in which CO2 is transported in the blood?

A

dissolved in plasma, as bicarbonate, combined with protein as carbamino compounds (The latter two are within RBCs)

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15
Q

What percentage of CO2 is in the plasma and in RBCs?

A

7% in plasma, 93% diffuses into RBCs

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16
Q

In what form is CO2 bind to haemoglobin?

A

HbCO2 - carbaminohaemoglobin

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17
Q

How is carbon dioxide converted to bicarbonate ions in the blood?

A

Carbonic anhydrase enzymes convert CO2 + H2O to carbonic acid, which then dissociates into hydrogen ions and bicarbonate ions

18
Q

What enzyme converts CO2 to carbonic acid in RBCs?

A

Carbonic anhydrase

19
Q

What is the equation for the conversion of CO2 to carbonic acid and then bicarbonate ions?

A

CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-

20
Q

What is the chemical formula for the bicarbonate ion?

A

HCO3-

21
Q

What happens to the H+ ions in RBCs that are the product of the dissociation of carbonic acid from CO2?

A

They bind to haemoglobin to form HbH+

22
Q

What is the product of H+ ions binding to haemoglobin?

A

HbH+

23
Q

What happens to the bicarbonate ions (HCO3-) in RBCs that are the product of the dissociation of carbonic acid from CO2?

A

They move into the plasma in exchange for chloride ions in a process called chloride shift

24
Q

What is chloride shift?

A

When bicarbonate ions move into the plasma from RBCs in exchange for Cl- ions

25
Q

What is the role of the respiratory rhythmicity centres?

A

Generate cycles of contraction and relaxation in the diaphragm, establishing normal pace of respiration. Modify activity in response to chemical and pressure signals

26
Q

What are the 3 key respiratory rhythmicity centres?

A

Inspiratory centre of the dorsal respiratory group (DRG), ventral respiratory group (VRG), Pre-Bötzinger complex

27
Q

Where are the key respiratory rhythmicity centres located?

A

The medulla oblongata, in the brain stem

28
Q

What is the function of the inspiratory centre of the dorsal respiratory group (DRG)?

A

signals to diaphragm & external intercostals muscles - the essential inspiratory muscles

29
Q

What is the function of the ventral respiratory group?

A

Inspiratory centres signal to accessory inspiratory muscles, expiratory centres signal to accessory expiratory muscles

30
Q

What is the function of the Pre-Bötzinger complex?

A

Acts as a ‘pulse generator’ (similar to the SA node) to establish the pace/rate of respiration

31
Q

What is the efferent signal from the medulla in respiratory control?

A

Contraction signals to the respiratory muscles

32
Q

What is the afferent signal to the medulla in respiratory control?

A

sensory information from receptors

33
Q

What are the types of sensors that provide afferent input to the medulla from sensory control?

A

chemoreceptors, lung stretch receptors, baroreceptors, protective reflexes

34
Q

Where are (respiratory) central chemoreceptors located?

A

In the medulla

35
Q

What are (respiratory) central chemoreceptors sensitive to?

A

PCO2, but not to PO2 of blood

36
Q

How do (respiratory) central chemoreceptors detect PCO2?

A

When CO2 diffuses out of the cerebral capillaries, it changes the pH of cerebrospinal fluid. Central chemoreceptors can detect this pH change.

37
Q

Where are (respiratory) peripheral chemoreceptors located?

A

In the carotid and aortic bodies

38
Q

What are (respiratory) peripheral chemoreceptors sensitive to?

A

PO2, little response to PCO2

39
Q

What are the most rapidly responding type of respiratory chemoreceptor?

A

Peripheral chemoreceptors

40
Q

What is the function of lung stretch receptors?

A

As the lungs inflate or deflate, they send afferent input to the brain to ensure that the lungs do not stretch too much or too little.

41
Q

How are protective reflexes involved in respiratory control?

A

Receptors detects irritation from dust and other foreign particles and feedback to the brain stem that can send an efferent signal to trigger a sneeze or cough

HUBS192 2022 (38 decks)

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