Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

Always go by what the SNAB book says, CGP's for a different spec.

When a change encourages further changes of the same sort to occur, i.e. when the sodium channels change shape in the action potential, it starts off with a few channels opening, and then lods of channels open

someone tell me about positive feedback mechanism ??!?!?! and its use in thernoregulation after a temeprature limit is crossed ..?!?

someone tell me about positive feedback mechanism ??!?!?! and its use in thernoregulation after a temeprature limit is crossed ..?!?

hey, thanks for uploading your notes!
in your notes it says pr gets converted to pfr at night, i thought pfr gets converted to pr at night as the pr form is more energetically stable, even though pfr is the biologically active one, chemicals tend to revert to their energetically stable form

I'm pretty sure negative feedback occurs in thermoregulation...

can someone go through all the core practicals lol

habitation
obtain a large african snail
place it on a clean, firm surface, leave it for a couple of minutes to let it get use to its surroundings
get a dampened cotton bud, use it to touch the eye stalk
immediately start the stop watch, time how long it takes for the eye stalk to fully extend again
repeat this process 10 times

respiration
essemble a respirometer
place actively respiring organisms on a gauze in the test tube of the respiriometer, also put soda lime
open the tap for one minute then close it, measure the distance travelled by the liquid
repaat this further times
rate of respiration can be found
(sorry, i know it's not a very good explanation)

and i cba to go through the spirometer one now

umm its negative feedback upto a point! once a temp limit si crossed it becomes positive feedback to protect hypothalamus somethign !! thats whats im confused on !

please go through spirometer one!

SNAB book (ann fullik) makes alota mistakes! for e.g. they say that neurotransmitter is released when an action potential is generated in the bipolar cell which is totally wrong.

find a perosn to do experiment on ! lol
put mouthpeice in his mouth and advise him to breathe calmly for a secong just throguh the mouthpirce to acclimatise him to breathing in this situation
-apply a noseclip on him
-fill up the chamber with oxygen
-start the rotating drum on which spirometer trace will be amde.
-calibrate the spirometer trace to read off volume values correctly.
-attach the mouthpeice hose to the chamber and advise the volunteer to breathe in and out calmly for about a minute.
-then advise him to exhale as deeply as possible followed by max inhalation.
-all of this breathing activitiy will be recorded on the trace.
once done, detach the mouthpiese and read off tidal volume and vital capacity form the spirometer trace.

.........
OH YEAH ! also use a soda lime box to remove CO2 from exhaled air. if you do this youll see a gradula decline in the trace!! gradient of this decline will give you the rate of oxygen uptake !

umm its negative feedback upto a point! once a temp limit si crossed it becomes positive feedback to protect hypothalamus somethign !! thats whats im confused on !

How is that wrong? :s