OCR Biology F214 Communication, Homeostasis and Energy Wed 25 Jan 2012

Oh dear, I've barely started revising for this exam. I had a resit for F211 last week and I've (probably wrongly) spent the majority of my time on that. Looks like I've got a week and a half to learn the whole syllabus *sighs*

Exactly the same as me! And I have another exam the day after so I'm struggling for time

Hopefully we'll be able to pull through. I'm really hoping not to have to resit this again in the summer with F114 to do aswell.

I'm struggling with Action Potential/Local Current/Summation/Generator Potential, all that at the moment.

My favourite part ^_^. You need any help on it?

My favourite part ^_^. You need any help on it?

can you describe the negative feedback loop in detail for the hormonal (endocrine) system?

The nervous systems simple as they give us examples from receptor to effector but in hormonal e.g. adrenaline, they just say the adrenal gland releases adrenaline in response to stress.

I'm finding it difficult putting it all together. I think I just need some notes other than the explanation from the textbook, just so I can look at it from another point of view. Usually we have worksheets and photocopies from other books but we've not had any for this.

I hate it when I have a mental block on a topic!

For example, in the book I'm getting confused with the different channels. You've got the sodium/potassium ion channels, voltage gated channels - then it seperately refers to gated channels and I'm not sure if they're refering to the voltage gated ones.

Actually, I think I just need to start reading the whole thing back from the start :X

I can send you my notes on it. they're quite detailed.

That would be very useful if it's not too much hassle. Don't worry if not!

Basically imagine if someone touches you. This is call called a stimulus. A stimulus is an energy change in the surroundings. Another stimulus could be change in temperature or change in light intensity.
On your skin and other parts of your body you have sensory cells called sensory receptors which respond to energy changes in the environment such as change in pressure. They are also called transducer molecules as they convert one form of energy to another. I.e. change in pressure on your skin is converted into electrical energy in the form of a nerve impulse. This is done by receptor cells. The greater the pressure applied (greater the stimulus) the more Na ion channels open in the receptor cells, not in the neurone.

If enough Na ion channels open they will initiate enough generator potentials which will reach the threshold potential and only then are the voltage gated Na ion channels open. These voltage gated Na ion channels only respond to changes in the potential difference across the membrane. If the membrane depolarises due to Na ion channels open due to a stimulus the potential difference across the membrane changes, if it changes enough to reach the threshold potential only then are the voltage gated Na ion channels open on the Dendron of the sensory neurone.

In summary the normal Na ion channels on the receptor molecules open due to a stimulus.
The voltage gated Na ion channels only open if the potential difference across the membrane changes due to Na ions diffusing into the cell from the surrounding tissue fluid via the normal Na ion channels.

ooh never knew there was such a big thread for this exam alone just did a past paper, there was a rather intriguing question on a seal

I know! I did that paper That was quite awkward, I spent like 5 minutes just looking at the drawings to see the differences before I saw 2 and then I just wrote about high lactate tolerance or something for the last mark

Hey!

Yeah there were loads of answers that could've been given weren't there? I'm not too good at doing past papers, I always get bored of writing everything and just end up looking at the answers

Glad to see I'm not the only one like that
Although if the paper is quite tough, I force myself to try to do it first

Heheheh, well I should be going to sleep now, 6 hours of lessons tomorrow (including double biology )