Teevo's superb biology questions

[HERculina]

i created a concept map on the circulatory system. but im not really familiar with concept maps...
anywhoo is this right? 

[shinny]

All the links are correct as far as I can tell. Only minor detail is that not all veins have valves. For example, all the ones in your trunk and the ones in your head don't. It's usually the peripheral ones in your limbs that do. Really don't expect them to test you on this minor detail though.

[HERculina]

kewlios

 ty.
why dont the ones in our head have valves? do they have something else instead?
btw should i avoid writing '...' in concept maps

[shinny]

kewlios

 ty.
why dont the ones in our head have valves? do they have something else instead?
btw should i avoid writing '...' in concept maps

Do it how you want. I've never been a big fan of concept maps so I wouldn't really know. As for the valves, the point of them is to prevent the backflow of blood. So for example, in your legs, the blood is trying to go upwards back to the heart and without valves, the blood would just pool in your legs due to gravity. Instead, each time the muscles in your legs contract, they pump the blood upwards, and in the periods between these contractions, the blood doesn't flow backwards due to gravity. However in your head the blood is trying to go down from your head to your heart (assuming that you generally don't go everywhere upside-down doing handstands and such) so valves aren't necessary.

[HERculina]

ohh yea! i forgot that our heads are in  the opposite direction to our legs. hehe
omg i hope i get that type of q. on the exam cause then i would know how to answer it and sound smart (doubt itll happen though)
more karma for you

[Russ]

Actually for once I'm going to ask a question here: shinny, do you know why the veins of the trunk don't have valves? Not sure if it was mentioned in a lecture at some point, but I'm drawing a blank. Is the respiratory pump enough at that point to draw it back?

[shinny]

Actually for once I'm going to ask a question here: shinny, do you know why the veins of the trunk don't have valves? Not sure if it was mentioned in a lecture at some point, but I'm drawing a blank. Is the respiratory pump enough at that point to draw it back?

Yeh, I assume it's got to do with the respiratory pump. Inspiration causes a decrease in intrathoracic pressure and an increase in intraabdominal pressure so blood is pushed from the IVC to the heart following the pressure gradient. Inverse occurs on expiration. As for between these contractions, there's valves at the entrance to the limbs (subclavian and femoral veins) and to the head (internal jugular vein) so they can't really backflow peripherally.

[Russ]

Yeah sounds reasonable, that's what I was thinking but I wasn't sure if the pressure was sufficient though. Ugh, I'd go check Moore's but it scares me

[shinny]

Given that veins are very low pressure systems themselves, I think the pressure difference created by the thoracic pump is enough to drive it. But yeh, not something I went into any particular detail into.

[HERculina]

i need help with the following questions 

[Milkshake]

8 is Plant B. Just read the transpiration (evaporation/water loss) amount at 20 degrees celcius, and it's the plant with the highest number.
9 is plant C. It's the plant with the largest reduction in water loss from 20 to 35 degrees.
Plant A increases by 0.01.
Plant B increases by 0.10.
Plant C decreases by 0.05.
Plant D stays the same.

[HERculina]

oh kool thanks,
i dont really understand wy you don't take the Surface Area into account though. explaino please

[Milkshake]

I did take the surface area into account, but I saw that a larger surface area didn't correspond with higher water loss - plant C had a higher surface area than plant B, but plant C had a lower water loss :S. So I rejected that.

Instead I looked at the actual water loss values, which the question was directed at.

[HERculina]

oh ya i get it now.
i just checked the answers and although plant B did have greater water lost, it asked for the LEAF. Plant B doesn't look like a leaf so it has to be plant C, the next highest transpiration. WHAT A TRICK QUESTION!

[Russ]

Plant B doesn't look like a leaf so it has to be plant C, the next highest transpiration. WHAT A TRICK QUESTION!

Eh, they're all plants?

Anyway, for the other questions

vein / atrium / ventricle / artery so 16B
lower concentration due to mixing of oxygenated and deoxygenated so 17B
ventricle because it must act as a pump so 18C