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142 . Human Cardiorespiratory System > Control of Respiration and Gas Exchange > Flashcards

Control of Respiration and Gas Exchange Flashcards

1
Q

What factors affect gas exchange?

A

Partial pressure difference
Distance of diffusion
Solubility of gas
Surface area

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2
Q

When is gas exchange used?

A 
Ventilation
External respiration
Transport
Internal respiration
Cellular respiration
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3
Q

Each Red Blood Cell contains 250 million haemoglobin molecules, describe the structure of haemoglobin:

A

4 polypeptide chains, 2 alpha and 2 beta

Each chain contains an Iron (Fe2+) core

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4
Q

How many oxygen molecules can one haemoglobin hold?

A

Each Iron (Fe2+) can bind with one oxygen molecule, therefore, the max number of oxygens that one haemoglobin can hold is 4

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5
Q

If a Red Blood Cell contains 250 million haemoglobin molecules, how many oxygen molecules can it bind to when fully saturated?

A

1 billion as each haemoglobin can have 4

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6
Q

What happens to oxygen when all RBC’s are fully saturated?

A

It dissolves into the water in the plasma

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7
Q

What is meant by a saturated haemoglobin molecule?

A

When a haemoglobin molecule has oxygen bound at all 4 polypeptides

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8
Q

What is the equation for the oxygen content in the blood?

A

O2 bound to Hb + O2 dissolved in plasma

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9
Q

What is the equation for oxygen saturation?

A

O2 content / O2 capacity x100

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10
Q

What is meant by a partially saturated haemoglobin molecule?

A

When a haemoglobin molecule has oxygen bound at some but not all polypeptides

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11
Q

What is association and where does it take place?

A

The process where haemoglobin binds with O2, this occurs at the lungs

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12
Q

How does haemoglobin allow association and dissociation with O2?

A

It changes shape under different conditions

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13
Q

Explain what is shown in the first part of the oxygen dissociation curve:

A

There is a shallow gradient, meaning when partial pressure of O2 is low, Hb saturation is low. This means the haemoglobin has low affinity and it is hard for the first O2 to bind

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14
Q

Explain what is shown in the second part of the oxygen dissociation curve:

A

There is a steep gradient as the binding of the first O2 molecule changes the shape of haemoglobin to increase the affinity, allowing more O2 to bind

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15
Q

What happens to the haemoglobin when the first O2 binds?

A

The proteins structure is changed which allows more oxygen molecules to bind

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16
Q

What happens to the haemoglobin when the third O2 binds?

A

There are now less available spaces for O2 to bind and affinity is lowered

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17
Q

What are the axis labelled on the Oxygen Dissociation Curve?

A 
X = Saturation of Hb with O2 (%)
Y = Partial pressure of O2 (mmHg)
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18
Q

Explain what is shown in the third part of the oxygen dissociation curve:

A

There is a shallow gradient, after the third O2 binds, there are now less available spaces for O2 to bind and affinity is lowered

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19
Q

What happens to Hb when the dissociation curve shifts left?

A

Haemoglobin has a higher affinity for oxygen, association is easier and dissociation is harder

20
Q

Explain what happens to the oxygen dissociation curve during exercise, and think about why this happens:

A

There is a greater requirement for ATP.
Causing more respiration.
Leads to increased temperature and decreased blood pH as a result of carbonic acid.
Curve shifts right to allow easier dissociation and more O2 to muscles.

21
Q

What conditions would cause a shift of the oxygen dissociation curve to the left?

A

Decreased body temp
Increased pH of blood
Decreased CO2 produced

22
Q

What happens to Hb when the dissociation curve shifts right?

A

Haemoglobin has a lower affinity for oxygen, dissociation is easier and association is harder

23
Q

What conditions would cause a shift of the oxygen dissociation curve to the right?

A

Increased body temp
Decreased pH of blood
Increased CO2 produced

24
Q

What is the Bohr shift?

A

The shift of the oxygen dissociation curve to the right meaning oxygen dissociates at the tissues more easily.

25
Q

The Bohr shift is the movement of the curve which way?

A

Right, causing easier dissociation at tissues

26
Q

What are the three ways CO2 is transported in the blood?

A

Dissolved in the plasma - 10%
Carbamine compounds - 30%
Bicarbonate ions - 60%

27
Q

Explain how CO2 is carried in plasma:

A

It is dissolved into the plasma of the blood, it is 20x more soluble than O2 in the plasma so can be carried easily

28
Q

Explain how CO2 is carried in carbamine compounds:

A

CO2 interacts with the terminal amine group on proteins to form carbamine compounds

29
Q

Explain how CO2 is carried in bicarbonate ions:

A

CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-
Reaction catalysed by carbonic anhydrase
HCO3- diffuses down conc^ gradient in exchange for Cl- (chloride shift)

30
Q

What is the chloride shift?

A

The exchange of HCO3- (bicarbonate) down a conc^ gradient for Cl- (chloride)

31
Q

Where are respiratory control centres (RCC)located?

A

In the brainstem

32
Q

Carbon dioxide needs to be excreted as it impacts pH, what is the optimal pH for cellular function?

A

7.35 - 7.45

33
Q

What is the function of respiratory control centres (RCC)?

A

Generation and control of breathing (basic inspiration and expiration)

34
Q

Explain the Respiratory Feedback Mechanism:

A

RCC in brain generates impulse, sent to effector muscles (dia / inter / abd), sensors detect and send impulses to RCC, loop continues

35
Q

What are the 4 main respiratory control centres?

A 
Inspiratory centre (found in medulla)
Expiratory centre (found in medulla)
Pneumotaxic centre (found in pons)
Apneustic centre (found in pons)
36
Q

What are the 2 groups of respiratory neurones?

A

Ventral respiratory group (VRG)

Dorsal respiratory group (DRG)

37
Q

What is the function of the Ventral respiratory group (VRG)?

A

Controls voluntary forced expiration
Increases the force of inspiration
Regulates rhythm of inspiration and expiration

38
Q

What is the function of the Dorsal respiratory group (DRG)?

A

Controls inspiratory movements and timing

39
Q

What is the function of the Pneumotaxic centre?

A

Sends inhibitory impulses to inspiratory centre

Fine tunes respiratory frequency

40
Q

What is the function of the Apneustic centre?

A

Sends stimulating pulses to inspiratory centre

Activates and prolongs long deep breaths

41
Q

What is are higher brain centres?

A

They have the ability to over-ride central control over breathing, such as when singing or holding breath

42
Q

What are the different types of respiratory system sensors?

A 
Chemoreceptors (peripheral and central)
Mechanoreceptors
Irritant receptors
Juxta-capillary receptors
Proprioceptors
43
Q

What is the function of chemoreceptors

A

Constantly sample arterial blood and feedback to the respiratory control centres about the pH of the blood

44
Q

What are peripheral chemoreceptors responsible for detecting?

A

Arterial hypoxemia, if PpO2 is less than 8Kpa

45
Q

Where are peripheral chemoreceptors located?

A

Aortic arch

Carotid body

46
Q

Where are central chemoreceptors located?

A

Ventral surface of the medulla, at the blood/brain barrier

142 . Human Cardiorespiratory System (8 decks)

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