Biol121 Week 8 Lecture 3 Gas Exchange

Front 1

What is the difference between external respiration and internal respiration?

Back 1

External respiration: Exchange of O2 and CO2 with the environment

Internal respiration: Uptake of O2 andremoval of CO2from individual cells

Front 2

What does gas exchange occur between & though?

Back 2

Between blood and alveolar air.

Through/across the respiratory membrane (simple squamous epith of alveolar & simple sqam eptih of capillary).

Front 3

What is gas exchange dependent on?

Back 3

-Partial pressures of the gases

-Diffusion of molecules between air and blood

Front 4

What is partial pressure?

What is the symbol?

Back 4

• Partial pressure (P) = contribution of each gas to total pressure of a mixture of 2 or moregases

Hint 4

girls and boys speaking at once - like the P of O2 and CO2, but together: partial pressure.

Front 5

What is Dalton's law of partial pressure?

Back 5

• In a mixture of 2 or more gases, individual concentration decides partial pressure
• Total pressure = sum of the partial pressures
• Each gas behaves as though the other wasn'tthere

Hint 5

3 parts

Front 6

What is the most common gas in the air? Amount?

Back 6

Nitrogen. 597mmHg

Front 7

What is the total atmospheric pressure?

Back 7

A combo of all the partial pressures.

760mmHg

Front 8

What is Henry's law of partial pressure?

Back 8

• When gas under pressure comes in contact with liquid

• Gas dissolves in liquid until equilibrium is reached – Amount of a gas in solution is proportional topartial pressure of that gas

Hint 8

2 things

remember coke cans.

increase solubility by increasing pressure.

Front 9

What does Henry's law of partial pressure depend upon?

Back 9

• Dependent on solubility of that gas in thatparticular liquid

Hint 9

increased solubility can be achieved by increasing pressure aka coke cans with CO2 inside

when you open the can, the co2 escapes because pressure is down

Front 10

How does gas exchange occur?

Back 10

Via passive transport

Hint 10

diffusion

Front 11

How does gas move?

Back 11

From high pressure to low pressure.

Front 12

What is the partial pressure of O2 and CO2 in the alveoli?

Back 12

O2 (lots): 100mmHg

C02 (less): 40mmHg

Front 13

What is the partial pressure of O2 and C02 in all tissue cells?

Back 13

CO2 (high - must remove it): 45mmHg

O2 (low-needs more): 40mmHG

Front 14

The external respiration diagram of pressures.

List what is happening, at least the pressures in each part.

Back 14

Hint 14

Alveoli pressure: PO2 100, PCO2 40

Pulmonary cap b4 diffusion: P02 40, PCO2 45

Pulmonary cap after diffusion: PO2 100, PC02 40

Front 15

External respiration in summary. List the steps (6).

Back 15

• Gas exchange at the lung•Blood (in capillaries) arrives from body full ofCO2; empty of O2
• So, it drops off CO2; picks up O2
• And leaves full of O2, empty of CO2
• O2 flows from alveoli into blood
• CO2 flows from blood to alveoli (and toexhaled air)

Hint 15

6 steps

Front 16

Internal respiration diagram.

List the partial pressures.

Back 16

Hint 16

• Start of systemic capilalry: P02 95, PC02 40
• Tissues: P02 40, PCO2 45
• After diffusion/end of systemic capillary: P02 40, PC02 45

Front 17

Basic figures for these graphs:

What is a high for 02?

What is low for 02?

What is a high for C02?

What is less for C02?

Back 17

High O2: 100

Low 02: 40

High CO2: 45

Low CO2: 40

Front 18

Internal respiration summary.

List the steps.

Back 18

• Gas exchange at the tissues
• Blood delivers O2; and picks up waste (CO2)
• So it arrives full of O2 , empty of CO2
• And leaves full of CO2, empty of O2
• O2 flows from blood into tissues
• CO2 flows from tissues to blood and back to lungs to continue the process

Hint 18

6 steps

Front 19

Why is gas exchange efficient?

List the (5) reasons.

Back 19

• There are big differences in partial pressures (e.g. O2 100 to 40) aka gas WANTS to move on the gradient
• Distances 4 exchange are short (alveoli to capillaries - simple squamous)
• O2 & CO2 are lipid soluble (they can cross into cells easily)
• Total surface area is large
• Blood flow and airflow are coordinated

Hint 19

Diffusion distance can be disturbed by mucous and disease like pneumonia

Front 20

What is gas transport?

Back 20

Gas pickup and delivery within the cardiovascular system.

Hint 20

NOT in the respiratory system

Front 21

Why can't we transport O2 or CO2 in the plasma?

Back 21

Because O2 and CO2 are LIPID soluble and do not absorb well in water

Front 22

What do RBC (erythrocytes) do in blood transport?

Back 22

Remove 02 from air and CO2 from from plasma

Transport 02 to, and CO2 from, peripheral tissues

Hint 22

2 things

Front 23

What is haemoglobin made of?

Back 23

1 x globin protein (1 co2)

4 x haem rings (4 o2)

Hint 23

O2 LOVES haem rings!

C02 LOVES co2!

Front 24

What is haemoglobin called when it has all its oxygen sites full?

1/2?

Back 24

100% saturated

&

the new molecule is called oxyhemoglobin

50% saturation (only 2 sites occupied)

Front 25

Where is haemoglobin located?

Back 25

In the RBC / Erythrocytes

Millions (280mil) per RBC

Front 26

How is haemogloblin transported? %

Back 26

1.5% in plasma

98.5% in RBCs

Front 27

How is CO2 transported?

Back 27

7% in plasma

23% in amino groups

70% carried as bicarbonate ions in plasma

Front 28

How is CO2 generated in the body?

Back 28

As a product of aerobic respiration in the cells.

Front 29

What is meant by 02 affinity?

Back 29

How much love there is b/w O2 and haemoglobin.

How tightly they are binding.

Front 30

How does o2 partial pressure and Hb saturation relate?

Back 30

As o2 partial pressure increases (100mmhg) so does Hb saturation.

Front 31

If the pH is less, what happens to o2 saturation and affinity?

Back 31

Both decrease.

e.g. more co2 means lower ph/more acidic = o2 disassociates.

Front 32

What happens in the tissues when it comes to O2 saturation decreasing?

Back 32

o2 saturation decreases

PCO2 increases

Pco2 increase means lower PH & more acidity aka less o2 affinity

o2 disassociation increases

o2 affinity decreases

Front 33

What happens with a lower pH in the blood/tissues in terms of o2 affinity?

Back 33

o2 has less affinity with haemoglobin with a lower pH/more acidity.

Front 34

What happens when temperature increases for oxyhemoglobin?

Back 34

for e.g. in running

Oxygen and haemoglobin will split so oxygen can head to the muscles

Hint 34

Allows hB to ration oxygen use

Front 35

How is pH decreased in the tissues?

Back 35

With increased pCo2 made by the tissues.

pCo2 makes pH drop as it divides into hydrogen ions.

Front 36

What do hydrogen ions do to pH?

Back 36

Lower it/make it more acidic.

Front 37

How do gas concentrations effect breathing?

Back 37

• Respiration controlled by low PO2 or high PCO2
• Stimulus to breathe once PCO2 > 40 mm Hg
• Hypercapnia = high levels of CO2– Acidosis cured by hyperventilation
• Hypocapnia = Low levels of CO2 – PCO2 < 40 mm Hg– No breathing until level reaches PCO2 ≥ 40 mm Hg
  

Front 38

What is the effect the pH has on haemoglobin affinity?

Back 38

• CO2 diffuses into RBC
• Carbonic anhydrase, catalysesreaction with H2O Produces carbonic acid (H2CO3)
• Dissociates into hydrogen ion (H+) and bicarbonate ion
• CO2 + H20 ↔ H2CO3 ↔ H+ + HCO3-
• Hydrogen ions diffuse out of RBC, lowering pH
• So blood pH is dependent on CO2 levels in blood
• At low pH, less o2 affinity for Hb
  

Front 39

What does low pH allow for?

Back 39

Less o2 affinity with haemoglobin aka more o2 freed up for other tissues/needs

Front 40

How does the brain know to increase the breathing rate?

Back 40

high pco2

Front 41

How is acidosis caused?

Back 41

High pco2

therefore high hydrogen

therefore lower ph

Front 42

Where is respiration rhythm dictated?

Back 42

The Rhythmicity in the medulla oblongata

Front 43

What centres exist in the rhythmicity?

How do they fire?

Back 43

This inspiratory centre. fires for 2 seconds, rests for 3.

The expiratory centre. only involved in forced expiration.

Front 44

Where is the Pneumotaxic centre? What does it do? Why?

Back 44

• In the Pons.
• Inhibits inspiratory centre and promotes expiration
• Prevents lungs overfilling and speeds up rate

Front 45

What two centres modify the respiration rhythm?

Back 45

The Pneumotaxic centre.

The Apneustic centre.

Front 46

What does the Apneustic centre do and where is it?

Back 46

• Pons
• Prolongs inspiration when pneumotaxic centre isinactive
• for deep breathing

Front 47

What gives us voluntary control over respiration? What is it limited by?

Back 47

• Cerebral cortext
• Protective (poison gases) and voluntary
• Limited by rising co2 levels
• cannot hold breath forever!

Front 48

What is the inflation reflex? How does it work? What does it stop?

Back 48

• Receptors sensitive to stretch in lungs
• Over-stretching inhibits apneustic area
• Stops inspiration
  

Front 49

What is the chemoreceptor reflex?

Back 49

Peripheral chemoreceptors (carotid artery andaortic arch) & Central chemoreceptors (CSF in medulla)

Affected by changes in: – PCO2 – PO2– H+ / stimulate receptors