Gas Transport

Question 1

Carbon dioxide:

Is produced as _______ product from cells after cellular respiration.
It then flows down its partial, pressure gradient into the _______.

10% CO2 in blood is transported as simply dissolved carbon dioxide. Most CO2 enters ______.

30% CO2 in blood binds to haemoglobin at the globin, a site away from oxygen-binding site forming ____________.

Other CO2 reacts with water to form ______ ______ which dissociate into hydrogen ions and bicarbonate, catalysed by carbonic anhydrase → takes place in RBCs

Answer 1

waste
blood
RBCs
Carbaminohaemoglobin
carbonic acid

Question 2

Some released hydrogen ions bind with ________, helping to buffer the reduction in pH associated with conversion to acid.

The released bicarbonate ions move into plasma in exchange for chloride → ______ shift

____ % of total CO2 in blood is transported in the form of bicarbonate ions

Answer 2

haemoglobin
chloride
60%

Question 3

What is the Haldane effect?

Answer 3

When CO2 deoxygenated blood reaches lungs, high amounts of O2 will kick the CO2 off the haemoglobin and replace it, binding to haemoglobin.

Question 4

In arterial blood, much less _____ is bound to haemoglobin because more oxygen is bound to haemoglobin.

Answer 4

CO2

Question 5

Oxygen
Amount of oxygen dissolved in blood is _____ proportional to the partial pressure of oxygen
in the blood

Oxygen is very insoluble unlike _____ ______

Oxygen in solution: 3 mL of oxygen can be carried per litre (1.5%)→ if we had to rely on this rate, our body would have to pump 180 L /min which is not viable therefore we need another mechanism to help carry the _______ Oxygen

Haemoglobin (respiratory protein) helps to transport oxygen

197mL O2/L of blood is transported by haemoglobin (98.5%)

Haemoglobin increases the amount of oxygen blood can carry by ___ times.

Haemoglobin takes oxygen out of solution so that more oxygen can dissolve in solution

Addition of _______ allows more oxygen to be carried in the blood while the partial pressures being the same.

Answer 5

directly
Carbon dioxide
insoluble
65 times.
haemoglobin

Question 6

What is Haemoglobin?

Answer 6

(Hb) 4 subunits → 2 alpha + 2 betas

4 Iron containing heme groups, where oxygen binds to iron located at the centre of the heme.

4 polypeptides = globin

Each molecule of haemoglobin can carry 4 molecules of oxygen

Each RBC can carry 250 million haemoglobins
5 million RBCs per drop of blood
∴ Haemoglobin effectively transports large quantities of oxygen

Question 7

Deoxyhaemoglobin (Hb) + 4 O2 →

Answer 7

Oxyhaemoglobin (HbO2)

Question 8

Cooperativity:

Answer 8

each time a single oxygen binds to haemoglobin, it changes the shape to make the haemoglobin more acceptable to the oxygens.

Question 9

Percent haemoglobin saturation →

Answer 9

→ to determine how much oxygen a person’s blood is
carrying

Question 10

Pulsometer →

Answer 10

→ tries to determine colour of arterial blood (red = more oxygen, purple = less oxygen)

Question 11

Fraction of al Hb in the form of oxyhaemoglobin (HbO2)
Oxygen saturation =

Answer 11

Oxygen saturation =

[HbO2] / [HbO2][Hb] x 100

Question 12

Denominator is the Oxygen carrying capacity of blood
Normal values:
Arterial = __________
Venous = __________

Answer 12

95% to 100%
70% to 75%

Question 13

Right shift in dissociation curve:

Answer 13

• means that we have less oxygen bound to haemoglobin so that more oxygen can be delivered to the tissues
• decreased affinity
• give up O2 more readily

Factors effecting right shift:
- Increase in temp as tissues get warmer, so that more oxygen is delivered to tissues (during exercise)
- Increase in partial pressure of CO2, higher level of cellular respiration so that more oxygen is delivered to metabolising cells
- Increase in H+ ions (as CO2 combines with water) , decrease in pH
- Bohr effect: increase in CO2 and decrease in pH which increases O2 delivery to cells
- Increase in 2,3-DPG

Question 14

Left shift in dissociation curve:

Answer 14

• Means that we have more oxygen bound to haemoglobin so that less oxygen is delivered to tissues
• Higher haemoglobin saturation
• Increased affinity
• Retain O2

Factors effecting left shift:
- Decrease in temperature
- Decrease in partial pressure of CO2
- Decrease in 2,3-DPG
- Decrease in H+ ions, increase in pH

Question 15

2,3-DPG = (3)

Answer 15

2,3 diphosphoglycerate binds to haemoglobin

Results in conformational; change, squeezing oxygen out of place, making it more available for tissues

Reduces haemoglobin’s affinity for oxygen

Question 16

What is Foetal haemoglobin? (2)

Answer 16

• Has higher affinity for O2 than adult Hb because of decreased sensitivity to 2,3 DPG
• Left shift in dissociation curve

Foetal haemoglobin has a higher affinity for oxygen so that when mother gives off oxygen, foetus is able to pick it up and use for bodily function and growth.

Question 17

______ control of respiration
_______ feedback loop

Answer 17

Conscious
Negative

Question 18

Peripheral chemoreceptors, location and function:

Answer 18

Location: aortic and carotid arteries/bodies
Function: monitor O2 CO2 and pH of blood

Question 19

Peripheral chemoreceptors, location and function:

Answer 19

Location: aortic and carotid arteries/bodies
Function: monitor O2 CO2 and pH of blood

Question 20

Central chemoreceptors, location and function:

Answer 20

Location: medulla oblongata in brain
Function: monitor pH (CO2) of cerebrospinal fluid (CSF)

Question 21

In the brain, you have capillaries that contain blood as well as fluid in brain and _____ column called Cerebrospinal fluid. A blood brain barrier is very restrictive of what it allows into the CSF. CO2 can pass through barrier and reacts with water in CSF, forming ______ _____ which then dissociates into bicarbonates and hydrogen ions. Central chemoreceptors in the ____ _______ in the brain stem are sensitive to the hydrogen ions and hence the ___ of the CSF.

Answer 21

spinal
carbonic acid
medulla oblongata
pH

Question 22

What is Respiratory centre input?

Answer 22

Peripheral and Central chemoreceptors give an input to the respiratory centre in the medulla and pons.

Question 23

Peripheral chemoreceptors:
detect:
effect:

Answer 23

Detect: O2 decreases, CO2 increases, H+ increases, decrease in pH

Effect: Have positive influence on respiratory centre, to increase respiratory functions in order to increase O2 and decrease CO2

Question 24

Central chemoreceptors:
detect:
effect:

Answer 24

Detect: CO2 increases, H+ increase, decrease in pH

Effect: Have positive influence on respiratory centre, to increase respiratory functions in order to decrease CO2 and breathe faster

Question 25

Stretch receptors:
Effect:

Answer 25

In bronchi, bronchioles
Sensitive to over inflation
Herring-Breuer inflation reflex → prevents lungs from over-inflation
Effect: inhibitory influence on respiratory centre, to stop breathing in so that air can be breathed out

Question 26

Irritant receptors:

Answer 26

To expel any irritants that have been breathed in
Defensive respiratory reflex

Question 27

Receptors in muscles + joints:

Answer 27

Increase/stimulate respiratory system in order to increase breathing rate before we even begin to exercise and start running out of oxygen

Question 28

Other receptors:

Answer 28

Pain, emotional stimuli → acts through hypothalamus
Can be stimulatory or inhibitory
Can cause:
- Hyperventilation: when scared or nervous

Question 29

What are Higher brain centres?

Answer 29

Conscious brain within cerebral cortex, allows for voluntary control of breathing → holding breath while diving → if you keep holding your breathe, you will pass out so that other receptors can take over. Can have stimulatory or inhibitory effect.

Question 30

Central controller:

________respiratory centre sends neural impulses to the respiratory muscles

Diaphragm is stimulated by _______ nerve
(hiccup – misfiring of phrenic nerve causing diaphragm to contract)

Neural impulses are sent to ______ muscles as well

Answer 30

Medullary
phrenic
intercostal

Question 31

What controls regular breathing?

Answer 31

Control of regular breathing – involuntary – is controlled by Pre-Bot zinger complex → stimulates inspiratory motor neurons

Question 32

How do inspiratory motor neurons start?

Answer 32

These inspiratory motor neurons send action potentials to the diaphragm and intercostal for 2 seconds

• diaphragm contracts + flattens
• intercostal muscles contract + increase chest cavity volume allowing for negative pressure breathing

Question 33

How do the inspiratory motor neurons stop?

Answer 33

The inspiratory motor neurons then stops sending neural impulse for 3 seconds
- diaphragm relaxes and moves up in chest cavity
- intercostal muscles relax + decrease chest cavity volume allowing for increasing in pressure, forcing air out of lungs

Question 34

No muscular contraction for normal expiration →

Answer 34

passive process relying on elastic recoil of lungs

Question 35

The central chemoreceptors contribute about 70% to the increase in ________ whereas peripheral chemoreceptors only contribute about 30%. Shows that changes in CO2 levels has a far more impact on
ventilation that changes in O2 as _______ chemoreceptors work on O2 changes whereas central chemoreceptors work on CO2 changes.

Answer 35

ventilation
peripheral

Question 36

How does CO2 and O2 sensitivity differ?

Answer 36

Question 37

Why is CO2 the driving force in causing huge changes in ventilation?

Answer 37

If we think about the haemoglobin saturation to partial pressure of oxygen curve, we see that even though pressure of oxygen in arterial blood is lowering, there is still enough haemoglobinsaturated with oxygen. It is only when we drop to a partial pressure of 40 to 60 mmHg, haemoglobin starts releasing oxygen, respiratory centre is then stimulated due to low partial pressure of oxygen.