Bio307 - Test #3 - Chapter 18 (Gas Exchange)

Hypoxia

oxygen deficiency causing a very strong drive to correct the deficiency

hypercapnia

the physical condition of having the presence of an abnormally high level of carbon dioxide in the circulating blood

hypocapnia

a state in which the level of carbon dioxide in the blood is lower than normal; can result from deep or rapid breathing

erythrocyte

aka RBC

hemoglobin

a hemoprotein composed of globin and heme that gives red blood cells their characteristic color, carries oxygen

oxygenated

supplied, treated, enriched with oxygen

deoxygenated

lacking oxygen

affinity (of hemoglobin for O2)

oxyhemoglobin saturation curve

Hemoglobin bound to oxygen

Resting Cell: 75% Saturation

saturated (with respect to hemoglobin)

hemoglobin has adequate oxygen content

Transport of Gases

O2 and CO2 move only by simple diffusion in the body

CO2 can be turned into Bicarbonate (HCO3) to be transported

How do different factors affect the diffusion of O2 and CO2

Emphysema - destroyed alveoli means less surface area for gas exchange
Fibrotic Lung Disease - thick alveolar membrane slows gas exchange
Pulmonary Edema - Fluid in interstitial space increases diffusion distance
Asthma - Increased airway resistance decreases alveolar ventilation

Physical Factors:
- pH
- Temperature
- P(CO2)
- 2,3-BPG

Lung Compliance (lung expandability)
Lung airway resistance
Rate/Depth of breathing
Surface Area (surfactant effect)
Diffusion distance (affected by barrier thickness/fluid amount)

Concentration vs Partial Pressure

Concentration of a molecule dissolved in a water at a certain pressure is the partial pressure of gas in a solution.

Partial pressure of a material depends on the solubility of that gas in that medium

Hemoglobin Purpose + How it Contributes to Ability of Blood to Carry O2

Hemoglobin binds to Oxygen

It increases the ability of blood to carry large amounts of O2

Relationship between tissue's rate of use of O2 and Location on Oxyhemoglobin Saturation Curve

Effect of exercise on O2 delivery

Bohr Effect (what it is? how it happens?)

A shift in the hemoglobin saturation curve that results from a change in pH

as H+ concentrations increase, pH falls, and the affinity of hemoglobin for oxygen decreases

Effect of changes in O2 partial pressure, CO2 partial pressure, pH, temperature on % Saturation of Hemoglobin in that Tissue

^ P(O2): O2 Sat ^
^ P(CO2): O2 Sat v
^ pH = O2 Sat ^
^ temp = O2 Sat v

How is CO2 transported in the blood (% breakdown)

CO2 is more soluble in body fluid than oxygen is

1) 7% dissolved in Blood Plasma
2) 93% diffuses into RBC (of which 23% binds hemoglobin, 70% converted to bicarbonate)

CO2 + H2O -> H+ + HCO3- Equation Significance

Bicarbonate is more soluble than CO2

1) Provides an additional way to transport CO2 from cells to lungs
2) Helps stabilize the body's pH

Runs forward reaction in systemic tissues (lower partial pressure of HCO3 near systemic tissue), runs backwards in lungs (where there is a lower partial pressure of CO2 as it is dispelled)

How Above Equation Affects Breathing Rate, Kidney Reabsorption of Bicarbonate, metabolic rate of blood pH

^ Respiratory Rate to Remove CO2

Blood reabsorbs more bicarbonate, adding it will shift reaction to left to release CO2 to exhale

^ Metabolic rate = higher CO2 release = increase blood pH

Location of Motor Neurons that Control Involuntary Breathing

Medulla + Pons

Pathway by which change in partial pressure of CO2 in the blood leads to change in breathing rate and depth

If the blood has a higher p[CO2] then it wants to diffuse more of it through the alveoli to be exhaled, so breaths will be deeper and more frequent

^ CO2 = stimulation of medullary chemoreceptors + carotid/aortic chemoreceptors (influencing afferent sensory neurons) = targeting medulla/pons to cause inspiration/expiration