lecture 19 - gas transport and respiratory control

Question 1

what are the two forms that oxygen is carried in

Answer 1

dissolved O2 and bound to haemoglobin in red blood cells

Question 2

why is haemoglobin needed

Answer 2

because oxygen dissolves poorly, due to its low solubility at physiological partial pressure

Question 3

what does the binding of oxygen and haemoglobin depend on

Answer 3

PO2

Question 4

what are the steps of haemoglobin and oxygen binding in terms of partial pressure

Answer 4

1. oxygen moves from the alveoli into the pulmonary capilary
2. then is absorbed by haemoglobin
3. this reduces the partial pressure in capillary
4. partial pressure gradient is created from alveoli to capillary
5. so more oxygen will move from the alveoli to capillary

Question 5

what are the three forms that carbon dioxide is transported in

Answer 5

dissolved in the plasma (20 times more soluble than O2)
as bicarbonate
combined with proteins as carbonamino compounds

Question 6

what is the enzyme that catalyses the reaction between CO2 and water

Answer 6

carbonic anhydrase

Question 7

what does the reaction between CO2 and water form and what does it dissociate into

Answer 7

carbonic acid which then immediately dissociates into H+ and bicarbonate

Question 8

what form is the majority of CO2 carried in

Answer 8

in the form of bicarbonate

Question 9

what are the products of metabolism

Answer 9

• increased CO2
• increases acidity or H+
• and in working tissues increased temperature

Question 10

what happens to the haemoglobin binding curve when there is increased affinity for oxygen

Answer 10

curve shifts to the left = as haemoglobin wants to hold onto oxygen more tightly

Question 11

what happens to the haemoglobin binding curve when there is decreased affinity for oxygen

Answer 11

curve shifts to the right = as haemoglobin doesn’t hold oxygen as tightly

Question 12

where are the central chemoreceptors located

Answer 12

in the medulla

Question 13

what are the central chemoreceptors sensitive to

Answer 13

PCO2

Question 14

what do central chemoreceptors respond to

Answer 14

pH change

Question 15

what changes the pH of the cerebrospinal fluid

Answer 15

when CO2 diffuses out of the cerebral capillaries

Question 16

how do chemoreceptors respond to changes in pH

Answer 16

respiratory centre increasing breathing rate

Question 17

where are peripheral chemoreceptors located

Answer 17

in the carotid and aortic bodies

Question 18

what do peripheral chemoreceptors respond to

Answer 18

mainly changes in arterial PO2 and limited response to changes in PCO2

Question 19

what is sent from the stretch receptors as the lungs inflate or deflate

Answer 19

they send afferent input

Question 20

after receiving afferent input from the stretch receptors what does the brain do

Answer 20

the brain sends efferent output preventing them from stretching to far either way