lecture 13,14-

Question 1

The functions of the mamallian respiratory system ?

Answer 1

1. Provides O2 to blood and eliminate CO2 from blood
2. regulates blood H+ conc
3. Forms speech sounds
4. defends against inhaled microbes
5. Traps & dissolves blood clots arising from systemic veins

highly branched airways=alveoli->site of gas exchange

Question 2

What are the 2 circuits that are in circulatory system ?

Answer 2

1. Pulmonary circulation:right ventricle->lungs->left atrium
2. Systemic Circulation:left ventricle ->peripheral organs & tissues->right atrium
   delivery of nutrients & O2 to tissues& removal of CO2

BC suspended in plasma

Question 3

Where are RBC produced ?

Answer 3

prod in red bone marrow -destroyed in spleen & liver
-hormone : erythopoietin
formation requires iron,folic acid,vitamin B12

Question 4

What is anaemia ?

Answer 4

decrease in the ability of blood to carry O2
1. A decrease in total no of RBC
2. lower conc of Hb per RBC
3. or combo of both
4. bone marrow failure
5.

ron storage in body: 50% (of total body iron)
is in haemoglobin, 25% in other haem/heme-
containing proteins (e.g. cytochromes) in
cells, and 25% in liver as ferritin (protein

Question 5

RBC and the transport of respiratory gases ?

Answer 5

blood within pulmonary capillaries seperated from air
by thin barrier
Total alveolar SA is huge–>rapid exchange of large quantities of O2 & CO2 by diffusion

Question 6

Blood transport of respiratory gases ?

Answer 6

Vertebrates use haemoglobin in RBCs; high concentration
of haemoglobin (in mammalian blood) allows each volume
of blood to carry 50-60x more O2..!

Question 7

Haemoglobin the respiratory pigment ?

Answer 7

Quaternary structure
composed of more than 1 polypeptide chain together
Vertebrate Hb has 4 polpeptide globin subunits
2 a,2b subunits
each heme= 1 Fe2+ atom reversibly bind to1 O2

Question 8

What is Hb positive cooperativity ?

Answer 8

ability to combine with O2 depends on PO2
High PO2 –>can carry 4 O2 max
Low PO2 –>some O2 is released from Hb
displayed by hB binding dissociation curve
Sigmodial :low PO2 ,only 1 subunitbinds to 1 O2–>conformational change ->altering quaternary structure–>increasing affinity of other subunits
easier for 2nd O2 to bind

Question 9

some extra info on Hb and CO ?

Answer 9

combine with other ligands -H+,CO2
allosteric ligands/modulators
CO binds with 240 fold higher affinity than O2 competing with the latter–>preventing O2 being transported -toxic /deadly at high conc
Total amount of O2 trnasported by blood Hb

Question 10

What is normal partial pressure of gas in air and body ?

Answer 10

Alveolar PO2 is lower than atmosphere PO2 because of net diffusion of alveolar O2 into lung capillaries
Alveolar Po2 and PCO2 determine the sytemic arterial PO2 , PCO2

Question 11

Hb abilty for loading & unloading O2 ?

Answer 11

High PO2 in lungs vs Low PO2 in venous blood–>Hb binds (loads O2)
Low PO2 in tissues cappilaries vs High PO2 in arterial blood
Loading:oxygenation of Hb
Unloading :deoxygenation

Question 12

How does Hb load O2 in the lungs ?

Answer 12

Plasma & RBC enetering (venous blood) have PO2 of 40mmHg
O2 diffuses into blood–>RBC

O2 binds Hb removing O2 from dissolved solution –> lowers the plasma PO2
thuis gradient is maintained unitl Hb is 100% saturated
Exiting blood :100mmHg

O2 bound to Hb does not contribute directly
to blood PO2; only dissolved O2 does

Question 13

What is Hbs loading plateau O2 ?

Answer 13

loading plate provides protection
If alveolar PO2 falls to 60 mmHg

even a moderate limitation of lung
function still allows for significant Hb saturation!

Question 14

Hb:O2 unloading in tissues ?

Answer 14

Plasma and RBC entering tissue capillaries =PO2 -100 mmHg
O2 unloaded into blood-then diffuses into tissue/cells
plasma PO2 falls-only 25% O2 is unloaded
exiting blood PO2 -40mHg

Question 15

O2 unloading in general ?

Answer 15

cells still can get more O2 whenever they increase activity
Exercising muscle -consumes more O2 –>lowering intracellular & interstitial PO2 –>increasing blood-to-cell ratio
-increased rate of O2 diffusion from blood into cells=decrease in RBC PO2 casues additional unloading
if tissue PO2 fall below 40mmHg-reserve O2 released

Question 16

Myoglobin and properties ?

Answer 16

muscle cells -own O2 binding aka myoglobin
found in skeletal & cardiac muscles
consists of 1 polypeptide chain with 1 heme
can bind to 1 O2 with very high affinity
1. facilitates diffusion of O2 in muscle cell
2. provides O2 reserve

Question 17

Myoglobin as a reserve of O2 how does it work ?

Answer 17

during exercise=high metabolic demand & interruptions in supply of O2 :
tissue PO2 drops and Hb cant supply more O2 -myoglobin then release its bound to O2
Myoglobin abindant in muscles of diving muscles

During vigorous exercise, blood PO2 is lower than at rest → blood passes through lungs
faster:↓ time of gas exchange

Question 18

Human Hb vs Human Mb O2 eqm curves ?

Answer 18

Myo=hyperbolic O2 eqm curve contains 1O2 binding sites per molecules ->no coperativity

Question 19

Is Hbs affinity for O2 variable ?

Answer 19

yes its dependent on
1. CHemical composition of Hb
2. presence of 2,3-bisphosphoglyceric acid
3. pH,CO2,H+
4. Temperature

Question 20

What is the chemical composition of Hb ?

Answer 20

Fetal Hb:8 weeks after conception consists of 2 a,2y globin subunits
higher affinity for O2 than adult Hb
Adult Hb :consists of 2a2b globin subunits

Question 21

How does living at higher altitiudes affect Hb ?

Answer 21

Llamas-live at >5000 metres above seaw level
higher affinity for O2 than fetal/adult Hb
Hb becomes saturated at much lower PO2

Question 22

Llama vs Human ?

Answer 22

Llama
* Hb with high affinity for O2
* binding curve shifted to left
* saturated occurs at lower PO2 values
* tissues can operate at lower PO2
Human
* Hb never 100% saturated due to low environmental PO2
* binding curve shifted to right
* More O2 is unloaded in tissues

Question 23

What does the presence of 2,3-bisphosphoglyceric acid do ?

Answer 23

reversibly bind to Hb –>alosteric conformational change
–>reduces Hb affinity for O2

High levels of 2,3-DPG in mature RBCs as they
rely on glycolysis (there are no mitochondria):
↑ [2,3-DPG] enhances O2 unloading.

Question 24

What is the Bohr effect ?

Answer 24

O2 affintiy decreases as pH decreases so curve shifts to right.

Question 25

What effect does CO2 have on binding to globins ?

Answer 25

CO2 bind to globin causing allosteric conformational change -->reduces Hb affinity for O2-->increased O2 unloading in tissues

Question 26

How does temp effect O2 affinity ?

Answer 26

an increase = decrease in O2 affinity shifts their O2 binding curves to the right ## Footnote O2 affinity of Hb is (often) inversely dependent on the temperature.

Question 27

How does the blood transport CO2 ?

Answer 27

3 modes of transport of CO2 1. 5-10% dissolved in physical solution-plasma -cytosol of RBC 2. 20-30% reversibly bound to A groups on Hb not containing O2 :carbaminohaemoglobin 3. 60-70% converted =bicarbonate ions in cappilarie endothlial cells and primarily in RBC

Question 28

What is the blood transport of CO2 :as HCO3- ?

Answer 28

A-rate limiting step * catalysed by carbonic anhydrase * in capillary endothelium & primarily RBC * prod carbonic acid * B-Rapid dissociation * no enzyme involved * dissociates into proton (H+) and bicarbonate ions * HCO3-=transported into plasma in exchanhe for CL-=chloride shift

Question 29

The transport of CO2 in blood ?

Answer 29

RBC membrane transporter exchanges for 1 bicarbonate ion for 1 chloride -chloride shift=maintaining electroneutrailty deoxyhaemoglobin =higher affinity for H+ so it binds most of H+-->only small amount of free H+ in plasma ## Footnote CO2 is highly soluble; readily diffuses through cell membranes

Question 30

The transport of CO2 to the lungs ?

Answer 30

reversed reaction Venous blood PCO2 >alveolar PCO2 =net CO2 diffusion into lungs -->drives reaction above the right HHb releases H+, picks up O2 → the H+ reacts with HCO3- → enzymatic conversion to H2CO3 → dissociates: CO2 into alveoli

Question 31

What are the mechnics of breathing ?

Answer 31

Visceral pleura covers lungs pleural layers are seperated/filled by intrapleural fluid -->intrapleural pressure changes cause the lungsglide over thoracic wall during breathing

Question 32

How does the control of breathing respiration work ?

Answer 32

breathing = autonomic rythmical process of inhalation follwed bty expiration -Diaphragm and intercostal muscles contrct in respons to efferent activity from phrenic and interocostle nerves asic respiratory rythm is generated in brainstem -meulla oblangata -involes 2 groups of neurons :dorsal,ventral respiratory system reflexes -can influence breathing pattern

Question 33

What are the nerve patterns invloved in breathig ?

Answer 33

neurons medulla establish the respiratory rythm this info is transmitted by descending motor neurons

Question 34

How is breathing regulated ?

Answer 34

lack of O2 stimulates hyperoxia stimulating respiration but strongest one is increase in CO2 (hypercapnia) ## Footnote he body uses this feedback info (from chemoreceptors) to then match the breathing rate to the metabolic demand(s)

Question 35

What are peripheral cheoreceptors ?

Answer 35

include carotid & aortic bodies: carotid bodies have predominant roles in responding to changes in PO2 of arterial blood afferents of CB increase AP charges as PaO2 falls below 50-60mmHg ## Footnote In humans, the carotid bodies are/contain the only receptors/sensors able to elicit a ventilatory response to hypoxia.