Respiratory sys P2.

Question 1

Why are central chemoreceptors sensitive to changing levels of PCO2?

Answer 1

Bc sensitive to pH changes; caused when Hi PCO2 diffuses through blood-brain barrier and dissolve in CSF => H+ = lowers pH (bc no buffers in CSF). When stimiulated = increase resp. rate

Question 2

Where are central chemoreceptors located? What chemical factors do they monitor?

Answer 2

Third ventricle of the brain w/in brainstem. Monitor increase PCO2 (bc lead to decrease in pH in CSF)

Question 3

Where are peripheral chemoreceptors located? What chemical factors do they monitor?

Answer 3

Carotid and aortic bodies in major arteries. Monitor to [H+] in blood (due to increase in PCO2 or formation of lactic acid during exercise)

Question 4

What’s the role of the Pontine respiratory centre (PRG)?

Answer 4

limits inspiration and facilitate expiration: sends inhibitory impulses to inspiratory area => stop inspiration (b4 lung becomes too full), & sends stimulatory sig. => “inspiratory drive”

Question 5

What’s the role of the Medullary rhythmicity centre (MRC)?

Answer 5

For basic rhythm of breathing

1. Dorsal respiratory group: active during inspiration (phrenic nerve -> diaphram; intercostal nerve -> intercostal muscles)
2. Ventral respiratory group: only active during heavy breathing to establish rhythm (pacemaker)

Question 6

Describe normal control of respiration?

Answer 6

• respiratory muscles = changes volume thoracic cavity
• Inspiring: external intercostal muscles & diaphragm contract
• expiring: elastic recoil & surface tension forces in alveoli

Question 7

Explain how chloride shift works at tissues and lungs

Answer 7

Tissues: CO2 diffuses in blood -> RBC -> carbonic anhydrase convert CO2 -> H2CO3 -> H+ & HCO3- ->HCO3- leaves RBC & replaced w/ Cl- (in plasma)
Lungs: reverse process

Question 8

How is CO2 transported in the blood?

Answer 8

• 70% HCO3- in plasma
• 23% carbaminihaemoglobin
• 7% dissolved in plasma

Question 9

What is the Bohr effect?

Answer 9

H+ bind to Hb. Decrease in pH = decrease O2 in the Hb

Question 10

What factors facilitate O2 unloading @ tissues?

Answer 10

Partial pressure gradient. PO2 = 95 (@capillary) -> =20 (@cells)

Question 11

How does % saturation of Hb relate to mls O2 per 100 ml blood?

Answer 11

1. @ rest: 75% O2 left in Hb & 25%/ 5ml released in tiss.
2. Exercise: 73% O2 left in Hb & 27%/ 15ml released in tiss.

Question 12

Give e.g of a restrictive & obstructive problem

Answer 12

Restrictive: Pneumonia, obesity
Obstructive: Asthma, emphysema, cystic fibrosis

Question 13

Pulmonary artery: origin, blood type, function

Answer 13

a. R ventricle via pulmonary trunk
b. deoxygenated
c. Deox. blood from RV to lungs => oxy.

Question 14

Bronchial artery: origin, blood type, function

Answer 14

a. Aorta
b. oxy
c. provide O2 to lung tiss.

Question 15

Name the 2 types of cells in alveolar epithelial layer & function of each

Answer 15

Type I pneumocyte: gas exchange

Type II pneumocyte: secrete surfactant

Question 16

Function of surfactant

Answer 16

decrease water tension

Question 17

How does surfactant aid in expiration

Answer 17

prevent alveolar collapse

Question 18

Whats the cell on the alveolar surface - removes dust, debri & bacteria?

Answer 18

Alveolar macrophage (dust cells)

Question 19

Function of small alveolar pores connecting adjacent alveoli

Answer 19

equalise pressure b/w alveoli

Question 20

Binding protein in muscle (like Hb)

Answer 20

myoglobin

Question 21

Why CO is poisonous

Answer 21

competes and displaces O2 (O2 can’t bind to Hb)