Gas Exchange and Transport

Question 1

what is hypoxia?

Answer 1

decreased O2, from impaired diffusion or improper transport

Question 2

what is hypercapnia?

Answer 2

excess CO2

Question 3

1

Answer 3

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Question 4

2

Answer 4

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Question 5

2

Answer 5

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Question 6

sensors which prevent hypoxia and hypercapnia?

Answer 6

O2 sensor (needed for ATP production); CO2 (CNS depressant, acid precursor); pH (protein denaturation)

Question 7

what are the two causes of low alv Po2 assuming perfusion is constant?

Answer 7

1. Inspired air has low O2 content (high elevation = low Po2); 2. Alveolar ventilation–hypoventilation decrease rate and depth of breathing= increased airway resistance; or decreased lung compliance, CNS respiratory control issue

Question 8

how can rate of diffusion be impaired?

Answer 8

low conc gradient, reduced SA, and reduced barrier permability

Question 9

what affects the movement of gas from air to liquid?

Answer 9

1. The pressure gradient of the gas
2. Solubility of gas in liquid
3. Temperature-relatively constant

Question 10

what is mass flow?

Answer 10

movement of a substance per minute = O2 transport = CO x O2 conc

Question 11

what is mass balance?

Answer 11

any substance in the body must remain constant

Question 12

mass flow and balance together?

Answer 12

= Fick eq’n; CO x (Arterial [O2] - Venous [O2]) = QO2

Question 13

Arterial conc of O2 under resting conditions?

Answer 13

200 mL O2/ L blood

Question 14

Venous conc of O2 under conditions?

Answer 14

150 mL O2/ L blood

Question 15

how does pH affect % sat of Hb?

Answer 15

the lower the pH, the more H to change the conformation of Hb–>less O2 binds–>more O2 for active tissues

Question 16

what is the bohr effect?

Answer 16

shift in Hb saturation curve as a result of pH or CO2 change

Question 17

how does CO2 affect Hb saturation?

Answer 17

increase aerobic metabolism results in increase CO2 production–>increases Pco2 in the blood->CO2 binds Hb & competes wtih oxygen, and is also converted to HCO3- + H

Question 18

how does temperature affect Hb saturation?

Answer 18

active muscles produce heat–>heat causes conf change of Hb, leading to decrease affinity for O2–>more O2 dropped off at very active muscles

Question 19

how does 2,3-BPG affect Hb saturation?

Answer 19

by-product of glycolysis–chronic hypoxia increases 2,3 BPG (RBCs release ATP during hypoxia), or ascending to igher altitudes increases 23BPG–> competes with Oxygen, decreases Hb’s affinity for O2

Question 20

what are the factors that affect % sat of Hb?

Answer 20

temp, pH, PCO2, and 2,3 BPG conc

Question 21

waht affects the total number of binding sites?

Answer 21

Hb content per RBC x # of RBCs

Question 22

what affects O2 bound to Hb?

Answer 22

% sat x total number of binding sites

Question 23

what is total artieral O2 content determined by?

Answer 23

PO2 of plasma (oxygen dissolved in plasma) and O2 bound to Hb

Question 24

what is PO2 of plasma determined by?

Answer 24

composition of inspired air, alveolar ventilation, oxygen diffusion between blood and alveoli, and adequate perfusion to alveoli

Question 25

what is alveolar ventilation controlled by?

Answer 25

rate and depth of breathing; airway resistance; lung compliance;

Question 26

what is oxygen diffusion between alveoli and blood determined by

Answer 26

surface area and diffusion distance

Question 27

what is diffusion distance influenced by?

Answer 27

membrane thickness and amount of interstitial fluid

Question 28

why is it important to remove CO2 from the body?

Answer 28

1. excess CO2 can cause acidosis-->low pH disrupts H-bonds and causes denaturing of proteins; 2. high amounts can cause CNS depression-->leads to confusion, coma, and maybe death

Question 29

how much CO2 can be dissolved in plasma, usually?

Answer 29

7% of the CO2

Question 30

how else is CO2 carried in the blood?

Answer 30

23% binds to Hb--> carbaminoHb; 70% is converted to HCO3 (bicarbonate) + H

Question 31

what is the purpose to convert CO2 to HCO3?

Answer 31

1. Provides an additional means of CO2 transport from cells to the lungs 2. HCO3- is available to act as a buffer for metabolic acids, stabilizing body’s pH

Question 32

what ensures equil is not reach from the conversion f CO2 to HCO3 + H?

Answer 32

removal of HCO3 from RBC via chloride exchanger, and binding excess H by Hb

Question 33

what is the current model for control of respiration?

Answer 33

1. Respiratory neurons in the medulla control inspiratory and expiratory muscles 2. Neurons in the pons integrate sensory information and interact with medullary neurons to influence ventilation 3. Rhythmic pattern of breathing arises from a neural network with spontaneously discharging neurons 4. Ventilation is continuously modulated by various chemo and mechano receptor-linked reflexes and by higher brain centers.

Question 34

what groups are involved in medulla-mediated respiration?

Answer 34

the nucleus tractus solitaris which contains the dorsal respiratory group of neurons; the pontine resp group; the ventral resp group

Question 35

how does the NTS/DRG function?

Answer 35

the nucleus tractus solitaris in the medulla contains the dorsal respiratory group of neurons-->mainly control inspiratory muscles via phrenic nerve and intercostal nerve during quiet respiration; the NTS receives input from the peripheral mechano and chemoreceptors;

Question 36

how does the PRG function in respiration

Answer 36

the pontine resp group provides tonic (always active) input to the DRG to help the medullary networks create a smooth resp rhythm (not essential for resp itself, but essential for smoothness)

Question 37

how does the VRG function in respiration?

Answer 37

``` has a few areas with different functions: • Pre-botzinger complex: contain pacemaker neurons that may ini8ate respira8on • control muscles of active inspira8on and expiration, remain quiet otherwise • outputs that keep upper airways open (tongue, larynx, pharynx), Some8mes outputs slow down too much while asleep: sleep apnea, snoring. ```

Question 38

what are the peripheral chemoreceptors, and what do they monitor?

Answer 38

aortic and carotid bodies (main sensors), sense changes in artieral PO2, PCO2, and H-->adjust ventilation rates accordingly; NOT always active

Question 39

where are central chemoreceptors located?

Answer 39

medulla

Question 40

how do central chemoreceptors function?

Answer 40

always active-->continuously providing input to resp control centre; mainly respond to changes in CO2-->CO2 in cerebrospinal fluid converts to HCO3 + H, and the central chemo receptors also sense the increase in H; H activates ASIC (acid-sensing ion channels) in neurons and transmit APs to resp control centre

Question 41

what ae the protective reflexes that guard the lungs from damage?

Answer 41

1. irritant receptors--respond to inhaled particles or noxious gases; – Send input into the CNS, parasympathetic outputs then respond by causing bronchoconstriction – Leads to rapid shallow breathing and turbulent airflow to deposit irritant in mucosa 2. stretch receptors--in lungs, prevent lung over-inflation--> Hering-Breuer inflation reflex

Question 42

how can receptors in muscles and joints affect respiration?

Answer 42

will anticipate physical exertion-->start increasing vent rates before any chemical changes have occurred in the blood