Flashcards in Module 3 Deck (25)
Specialised exchange surfaces have...
Increased SA, thin layers, good blood supply, ventilation to maintain diffusion gradient
Important features of the nasal cavity
Large SA with good blood supply, hairy lining which secretes mucus, moist surfaces which increases humidity reducing evaporation
What happens during inspiration?
Diaphragm contracts (flattening)
External intercostal muscles contract
Ribs move up and out
Volume of thorax increases, so pressure decreases
Air moves in
What happens during expiration?
Diaphragm relaxes (domed shape)
External intercostal muscles relax
Ribs move down and in
Volume of thorax decreases, so pressure increases
Air moves out
How do insects increase the level of gaseous exchange?
Mechanical ventilation of the tracheal system- air is actively pumped into the system by muscular pumping of the throax
Collapsible enlarged trachea/air sacs- act as air reservoirs
How are gills in fish adapted to their function?
Tips of adjacent gill filaments overlap (increases resistance, slows down water, more gaseous exchange)
Countercurrent exchange system (steeper concentration gradients are maintained)
Role of elastic fibres
stretch and recoil, providing flexibility
Role of smooth muscle
contract and relaxes, change size of lumen
Role of collagen
provide structural support to maintain shape
Describe what happens as blood flows through arterioles into the capillaries
At the arterial end, the hydrostatic pressure is higher than the oncotic pressure, so fluid is squeezed out of the capillary (tissue fluid.)
At the venous end, oncotic pressure is higher than hydrostatic. So water moves back into the capillary by osmosis.
What does affinity mean?
How easy easier it is to remove oxygen from haemoglobin
What is the Bohr effect?
As partial pressure of CO2 incresaes (higher partial pressure) haemoglobin gives up oxygen more easily
(Curve moves to right)
Describe effects of components of cigarette smoke on the body
binds to haemoglobin / forms carboxyhaemoglobin
Hb has greater affinity for CO
How is CO2 transported?
Carbonic anhydrase catalyses the reversible reaction, breaking down carbonic acid into carbon dioxide and water.
Hydrogen carbonate ions diffuse back into the erythrocytes and react with H+ ions forming more carbonic acid.
When this is broken down again, CO2 diffuses out of the blood into the lungs.
Chloride ions diffuse out of RBC back into plasma down an electrochemical gradient (chloride shift to maintain electrical balance)
Describe the cardiac cycle
Diastole= heart relaxes. Artia and ventricles fill with blood. The volume and pressure increases, pressure in tries is at a minimum
Systole=Atria contract (atrial systole then ventricular systole)Pressure inside the heart increases dramatically and blood is forced out the arteries. At the end, pressure is low in heart but at a maximum in the arteries
heartbeats that are out of normal rhythm
Water molecules evaporate into the air spaces and diffuse into the surroundings out of the stomata
Evidence for the cohesion-tension theory
Changes in tree diameter, if xylem is broken air is drawn in
What is translocation
When organic compounds move from sources to sinks
Describe phloem loading
Symplast=sucrose diffuses through cytoplasm and plasmodesmata
Apoplast=sucrose moves through companion cells and sieve elements by diffusion.
In companion cells sucrose is pumped into the surrounding tissue by actively pumping H+ ions using ATP. The H+ ions return down a concentration gradient via co-transporter protein. Sucrose concentration increases in companion cell.
Describe phloem unloading
Sucrose diffuses from the phloem to the surroundings