gas exchange Flashcards
Explain what happens during inhilation
*external intercostal muscles contract and internal intercostal relax pullling rib up and out
*diaphrams contracts and pulls down
*thoracic cavity volume increases
*pressure in lungs lower than atmospheric
*air moves from atmo to lungs down pressure gradient
Explain what happens during exhalation
*external intercostal muscle relax
*diaphragm moves up and flattens
*thoraric activity decreases
*pressure in lungs increases greater than atmo
*air frrom lungs moves out down conc gradient
Why is it that in exhalation the pressure in the lungs increases greater than the atmospheric pressure?
When thorarcic cavity volume decreases it causes lungs to compress, decreasing volume of lungs, which increases its pressure
Explain gas exchnage in the lungs
*O2 diffuses from alveolar epithilum down concentration gradient to blood supply.
*from alveolar ep to capillary endothilium
How is the alveolar epithilium adapted for gas exchnage
*one cell thick- shorter diffusion path
*good blood supply from surronding capillary endothilium- keeps conc grdaient constant
*folded- high SA
*permeable- allows diffusion of O2
*mosist- gases are able to dissolve
Suggest why exhalation is normally passive at rest
*when exhaling, elastic tissue in lungs and muscles (that were contracted from inhilation) relax, pushing air out with no additional muslce effort.
Suggest how different lung diseases reduce the rate of gas exchange
*thickened alveolar tissue (eg. fibrosis) → increases diffusion distance
● Alveolar wall breakdown → reduces surface area
● Reduce lung elasticity → lungs expand less → reduces concentration gradients of O2 / CO2
How does lungs expanding less reduce the conc gradient of CO2 and O2?
When the lungs expand less, the concentration gradients of oxygen and carbon dioxide across the alveolar membrane are reduced.
*makes it harder for oxygen to enter the blood and for carbon dioxide to leave it
Suggest how different lung diseases affect ventilation
Reduce lung elasticity → lungs expand less
*Reducing volume of air in each breath (tidal volume)
*Reducing maximum volume of air breathed out in one breath (forced vital capacity)
*reduce airflow in & out of lungs (eg. asthma - inflamed bronchi)
* reducing maximum volume of air breathed out in 1 second
*Reduced rate of gas exchange → increased ventilation rate to compensate for reduced oxygen in blood
Suggest why people with lung disease experience fatigue
Cells receive less oxygen → rate of aerobic respiration reduced → less ATP made
Suggest how you can analyse and interpret data to the effects of pollution,
smoking and other risk factors on the incidence of lung disease
*Describe overall trend → eg. positive / negative correlation between risk factor and incidence of disease
● Manipulate data → eg. calculate percentage change
● Interpret standard deviations → overlap suggests differences in means are likely to be due to chance
● Use statistical tests → identify whether difference / correlation is significant or due to chance
○ Correlation coefficient → examining an association between 2 sets of data
○ Student’s t test → comparing means of 2 sets of data
○ Chi-squared test → for categorical data
Suggest how you can evaluate the way in which experimental data led to
statutory restrictions on the sources of risk factors
○ Sample size → large enough to be representative of population?
○ Participant diversity eg. age, sex, ethnicity and health status → representative of population?
○ Control groups → used to enable comparison?
○ Control variables eg. health, previous medications → valid?
○ Duration of study → long enough to show long-term effects?
● Evaluate context → has a broad generalisation been made from a specific set of data?
● Other risk factors that could have affected results
Explain the difference between correlations and causal relationships
Correlation = change in one reflected by a change in another - identified on a scatter diagram
● Causation = change in one causes a change in another
● Correlation does not mean causation → may be other factors involved
Explain how the body surface of a single-celled organism is adapted for gas exchange
● Thin, flat shape and large surface area to volume ratio
● Short diffusion distance to all parts of cell → rapid diffusion eg. of O2 / CO2
Describe the tracheal system of an insect
- Spiracles = pores on surface that can open / close to allow diffusion
- Tracheae = large tubes full of air that allow diffusion
- Tracheoles = smaller branches from tracheae, permeable to allow gas exchange with cells
