Session 12 - Gas Transportation

Question 1

Blood transports what?

Answer 1

The blood transports gases between the lungs and body tissues.

Question 2

In each 100 ml of oxygenated blood- what’s the percentage carried with haemoglobin?

Answer 2

• 98.5% is carried with haemoglobin (Hb) inside red blood cells as oxyhaemoglobin (HbO2).
• The haeme portion of Hb contains 4 atoms of iron, each capable of combining with one molecule of oxygen

• 1.5% of the O2 is dissolved in the plasma – Oxygen does not dissolve easily in water
– Only the dissolved O2 can diffuse into tissues

Question 3

Factors affecting O2 binding to and dissociation from haemoglobin?

Answer 3

• Oxygen Partial Pressure
• Acidity (pH)
• carbon dioxide partial pressure • Temperature
• 2,3-bisphosphoglycerate (BPG) • Foetal haemoglobin

Question 4

What is the most important factor that determines how much oxygen combines with haemoglobin?

And define in regards to pulmonary capillaries and tissue capillaries

Answer 4

Oxygen Partial Pressure

The greater the PO2, the more oxygen will combine with haemoglobin, until all the available haemoglobin molecules are saturated.

When there is a greaterPO2- it will drive the binding as it passes through the lungs in the pulomnary capillaries.

Therefore: In pulmonary capillaries:PO2 is high because we have just breathed it in, a lot of O2 binds to haemoglobin and transported to systemic circulation to be carreid out of the lungs.

In tissue capillaries: PO2 in the blood as it gets to the tissues is lower, therefore haemoglobin lets go of its oxygen (dissociation) and the dissolved O2 is unloaded via diffusion into tissue cells.

Question 5

Explain the oxygen-haemoglobin dissocitation curve and the relationship between haemoglobin saturation and PO2

Answer 5

As PO2 increases, more O2 combines with haemoglobin.

oPO2 of 60-100 mmHg: Hb is 90% or more saturated ( going through the lungs)

oPO2 of 40 mmHg: Hb is 75% saturated

oPO2 of 20 mmHg: Hb is 35% saturated

•Large amounts of O2 is released in contracting muscles.

When exercising, contracting muscles where the PO2 of the blood is 20 mmHg - 35% of haemoglobin is saturated - the other 65% of the oxygen has been distributed to the working tissues/muscles

Question 6

Acidity (pH) affects haemoglobin saturation. Explain this

Answer 6

Look at the diagram - 30 Po2 is used as an example where a low blood pH, normal blood pH and high blood pH takes place. Although the partial oxygen is the same (30) the acidity affects the percent of saturation.

At a lower pH ( low blood pH) at the same amount of Po2 ( 30) the haemoglobin will give off more oxygen when the acidity increases

O2 dissociates more readily from haemoglobin when acidity increases ( low blood pH)

Question 7

The increase of CO2 affects the saturation of haemoglobin how?

Answer 7

CO2 can also bind to haemoglobin, and as PCO2 rises, haemoglobin releases O2 more readily. This is good as the carbon dioxide is the signal that we are tissues are meatabolically active and we need to give our tissues more oxygen.

It drives the dissociation of oxygen off haemoglobin therfore giving the tissues more oxygen

Question 8

When we exercise what happens to pH, CO2 and temperature

Answer 8

pH drops, CO2 goes up and temperature goes up - this causes greater dissociation of oxygen from haemoglobin to supply metabolically active tissues and contracting muscles with oxygen

Question 9

How does 2,3-biphosphoglycerate (BPG) affect haemoglobin saturation ?

Answer 9

2,3-biphosphoglycerate (BPG): A substance formed in red blood cells during glycolysis.

oThe greater the level of BPG, the more oxygen is released from haemoglobin. Drives changes in the properties of haemoglobin to give off more oxygen

oHigher formation of BPG caused by Certain hormones:

–Thyroxine

–Human growth hormone

–Epinephrine

–Norepinephrine

–Testosterone

•In people living at higher altitudes.

Question 10

Carbon dioxide transport - how is CO2 carried in the blood ?

Answer 10

• Dissolved CO2 (7%)
• Carbaminohaemoglobin (23%)

– combined with the globin part of Hb molecule ( the protein part - oxygen is carried on the haem portion bound to ion)

• Bicarbonate ions (70%)
– CO2 + H2O combine to form carbonic acid that dissociates into H+ and a bicarbonate ion

Question 11

Respiratory Center

Answer 11

Respiratory Center:

Controls respiration

Found in the medulla oblongata and pons of the mid brain

Located bilaterally in the reticular formation of the brain stem

Question 12

What are the three areas of respiratory center ?

Answer 12

• Medullary rhythmicity area: in Medulla oblongata
• Pneumotaxic area: in Pons
• Apneustic area: in Pons

Question 13

Where is the Respiratory Center located?

Three areas of the Respiratory Center?

Answer 13

Found in the medulla oblongata and pons of the mid brain

Three areas of respiratory center:

Medullary rhythmicity area: in Medulla oblongata

Pneumotaxic area: in Pons

Apneustic area: in Pons

Question 14

Function of the Medullary Rhythmicity Area ?

Answer 14

Controls the basic rhythm of respiration: Inspiration for 2 seconds, expiration for 3 seconds

Inspiratory area: Excites autorhythmic neurons for 2 seconds then inactive

Expiratory area: Inactive during most quiet breathing, only active during high ventilation rates

Question 15

Control of respiration:

Pneumotaxic Area is found where and function?

Answer 15

Coordinates the transition between inspiration and expiration.

oLocatedin Upper Pons

• Shorten the duration of inhalation: Transmits inhibitory impulses to the inspiratory area
• When the pneumotaxic area is more active, breathing rate is more rapid
• (increases breathing rate).

Question 16

Control of respiration:

Apneustic Area - location and function

Answer 16

o Coordinates the transition between inspiration and expiration.

o Locatedin Lower Pons

o Prolong the duration of inhalation: Sends stimulatory impulses to the inspiratory area result in a long, deep inhalation.

o When the pneumotaxic area is active, it overrides signals from the apneustic area.

Question 17

Regulation of respiratory center:

Cortical regulation - function and location

Answer 17

• Voluntarily alter breathing patterns - control our respiration rate. e.g we can choose to hold our breath, breathe faster etc..

Central chemoreceptors:

 Respond to changes in H+ or PCO2

 Located in or near medulla

Peripheral chemoreceptors:

 Respond to changes in H +, PO2 or PCO2

Located in Aortic body - in wall of aorta

Question 18

Regulation of respiration negative feedbackc control

Answer 18

Negative feedback control: Regulation of breathing in response to changes in blood PCO2, PO2, and pH (H+)