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Flashcards in Module 3 Deck (25)
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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

Carbon monoxide;
binds to haemoglobin / forms carboxyhaemoglobin
Hb has greater affinity for CO
Damages cilia
Causes cancer


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



very rapid





Ectopic heartbeat

heartbeats that are out of normal rhythm


Atrial fibrillation

abnormal rhythm


Describe transpiration

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


Evidence of translocation

If the mitochondria in companion cells are poisoned, translocation stops
Advances in microscopy