Ventricles in the brain.... why?

**Chaos' lil bro Order** · May27-09, 04:32 AM

I am watching a TTC video on the brain and it mentioned that the brain has (as far as I've seen so far) 5 different ventricles (cavities) inside it. I was wondering about why the brain would have spaces in it considering how complex it is, why should it give waste to space? Perhaps later in the video series my question will be answered and I am jumping the gun, but I know several of you here are phd doctors so I was curious if you had a quick answer for a layman like myself.

Thanks

**tiny-tim** · May27-09, 06:32 AM

Hi Chaos' lil bro Order!

I'm just a little goldfish

,

but isn't it surface area that matters, and so the interior of the brain is just there for physical and logistical support, and so holes in it don't matter?

(The brain ventricles seem to be for producing and circulating the cerebrospinal fluid … see http://www.answers.com/topic/cerebro...uid?cat=health and wikpiedia.)

**Chaos' lil bro Order** · May27-09, 04:20 PM

Originally Posted by tiny-tim

Hi Chaos' lil bro Order!

I'm just a little goldfish ,

but isn't it surface area that matters, and so the interior of the brain is just there for physical and logistical support, and so holes in it don't matter?

(The brain ventricles seem to be for producing and circulating the cerebrospinal fluid … see http://www.answers.com/topic/cerebro...uid?cat=health and wikpiedia.)

Thanks Tim, that link is filled with a nice explanation. My simple mind says the ventricles contain the CSF fluid which the brain floats on reducting its weight from 1000g to 50g. Also the CSF buffers the brain from impacting the skull, unless a sudden deceleration occurs, ala car accidents or boxing matches. So in short, the ventricles are channels through which the CSF can flow and the CSF, primarily, protects the brain from injury due to decelerations.

As for your surface area comment. I'm a complete layman in brain studies. My gut tells me that surface area is not all that matters, after all from what I've learned so far, there are several nuclei in the brain (nuclei in this case means areas where specialized neurons clump together to form a functional unit) that are enclosed entirely inside the brain. The Lateral Geniculate Nucleus which takes signals from the optic nerve and passes them onto the cortex, being one. As I said, I'm new to this field of knowledge so any corrections and additions to my comment are welcome and encouraged.

You stupid little goldfish :)

**tiny-tim** · May27-09, 06:11 PM

oooh, I don't think we goldfish have Lateral Geniculate Nuclei …

I think that's more a monkey thing

**atyy** · May27-09, 09:43 PM

Originally Posted by Chaos' lil bro Order

So in short, the ventricles are channels through which the CSF can flow and the CSF, primarily, protects the brain from injury due to decelerations.

That's my guess too.

**Moonbear** · May27-09, 09:47 PM

There are four ventricles in the brain, not five. There are two lateral ventricles, then the third ventricle and the fourth ventricle. That's it for ventricles.

No, surface area is not ALL that matters, but it's not necessarily unimportant either, since it allows for contact with all that CSF and the goodies it carries. As for brain nuclei, there are many, many, many. Nuclei in the brain are specialized clusters of neuronal cell bodies (gray matter). And, tracts are the places where the axons (white matter) travel in big pathways.

CSF does WAY more than just cushion the brain. It carries nutrients to the neurons, carries away wastes, and carries signaling molecules from one part of the brain to another.

**atyy** · May27-09, 09:58 PM

Originally Posted by Moonbear

There are four ventricles in the brain, not five. There are two lateral ventricles, then the third ventricle and the fourth ventricle. That's it for ventricles.

No, surface area is not ALL that matters, but it's not necessarily unimportant either, since it allows for contact with all that CSF and the goodies it carries. As for brain nuclei, there are many, many, many. Nuclei in the brain are specialized clusters of neuronal cell bodies (gray matter). And, tracts are the places where the axons (white matter) travel in big pathways.

CSF does WAY more than just cushion the brain. It carries nutrients to the neurons, carries away wastes, and carries signaling molecules from one part of the brain to another.

yes, of course CSF has other functions. I see I too hastily agreed with a statement that has "primarily" in it. However, my guess related to the volume of the ventricles in the original question. I'm guessing that the main reason for the volume is cushioning - the other major functions of the CSF could be accomplished with less volume.

**Moonbear** · May28-09, 09:45 AM

Originally Posted by atyy

yes, of course CSF has other functions. I see I too hastily agreed with a statement that has "primarily" in it. However, my guess related to the volume of the ventricles in the original question. I'm guessing that the main reason for the volume is cushioning - the other major functions of the CSF could be accomplished with less volume.

There isn't much volume to the ventricles. The lateral ventricles are the largest, and that's more a consequence of the folding patterns of the brain during embryonic development than anything else. The third ventricle, for example, is only about 1-2 mm wide, depending on where you look.

In and around the entire brain, not just the ventricles, it's estimated that there are about 120-150 ml of CSF. Estimates of the volume of the ventricles themselves are around 15-30 ml. The "cushioning" effect of CSF is much more from the volume surrounding the brain, in the subarachnoid space and cisterns, than what's present in the ventricles. Though, the ventricles are where CSF is produced from blood.

**atyy** · May29-09, 01:13 AM

Originally Posted by Moonbear

There isn't much volume to the ventricles. The lateral ventricles are the largest, and that's more a consequence of the folding patterns of the brain during embryonic development than anything else. The third ventricle, for example, is only about 1-2 mm wide, depending on where you look.

In and around the entire brain, not just the ventricles, it's estimated that there are about 120-150 ml of CSF. Estimates of the volume of the ventricles themselves are around 15-30 ml. The "cushioning" effect of CSF is much more from the volume surrounding the brain, in the subarachnoid space and cisterns, than what's present in the ventricles. Though, the ventricles are where CSF is produced from blood.

Would you have numbers how much of the volume (ventricles, or whole brain CSF volume) goes towards cushioning versus biochemical functions like maintaining salt concentration so that the neurons work properly? It seems quite common for the cisterna magna to be drained in physiology experiments, which it seems plausible to me that the biochemical functions only needs a thin layer of CSF around the brain.

**tiny-tim** · May29-09, 03:15 AM

Originally Posted by Moonbear

… No, surface area is not ALL that matters, but it's not necessarily unimportant either, since it allows for contact with all that CSF and the goodies it carries. …

CSF … carries nutrients to the neurons, carries away wastes, and carries signaling molecules from one part of the brain to another.

How do the goodies get to the parts of the brain that aren't on the surface?

**Moonbear** · May29-09, 09:54 PM

Originally Posted by atyy

Would you have numbers how much of the volume (ventricles, or whole brain CSF volume) goes towards cushioning versus biochemical functions like maintaining salt concentration so that the neurons work properly? It seems quite common for the cisterna magna to be drained in physiology experiments, which it seems plausible to me that the biochemical functions only needs a thin layer of CSF around the brain.

I don't think that's even possible. I've collected CSF from the cisterna magna, but never allowed the animals to recover from it (it's too easy to damage the brainstem during the procedure, so usually done as a terminal procedure). It would be similar, though, to doing a spinal tap in terms of the volume of CSF removed. And, many patients will report headaches after a spinal tap. But, there isn't any direct way to answer your question. It's not like the CSF is compartmentalized for different functions. It all flows through the whole system.

Originally Posted by tiny-tim

How do the goodies get to the parts of the brain that aren't on the surface?

Diffusion through the extracellular spaces.

**zoobyshoe** · May30-09, 08:29 AM

Originally Posted by Moonbear

It carries nutrients to the neurons, carries away wastes, and carries signaling molecules from one part of the brain to another.

What are the brain's "wastes" and where are they carried to? Also, could I keep a pet goldfish in one of my ventricles?

**atyy** · May30-09, 10:48 AM

Originally Posted by zoobyshoe

What are the brain's "wastes" and where are they carried to? Also, could I keep a pet goldfish in one of my ventricles?

Can a goldfish live in slightly salty water?

**tiny-tim** · May30-09, 10:59 AM

Originally Posted by atyy

Can a goldfish live in slightly salty water?

actually, it's more the free oxygen content that bothers me

… is there any?

i s'pose i could use scuba equipment

…

but then that sort-of takes away the point of being a goldfish!

**atyy** · May30-09, 12:57 PM

Originally Posted by tiny-tim

actually, it's more the free oxygen content that bothers me … is there any?

i s'pose i could use scuba equipment …

but then that sort-of takes away the point of being a goldfish!

Another guess - the free oxygen should be ok, since brain cells need oxygen! A goldfish can live in tap water (I think

), and brain cells can live in tap water with table salt dissolved in it - if you open up a rat's skull, break the dura, and pour salty tap water on it, the brain will be ok. The snag in this argument is that the oxygen may actually not be from the tap water, but diffusing from the capillaries that richly supply the brain. So to be safe, make sure you swim in a living intact brain!

**atyy** · May30-09, 01:05 PM

Actually, you can even pour oil on the brain. So I guess it's really the capillaries throughout the brain that keeps the thin layer of CSF around all neurons salty and oxygenated. http://jn.physiology.org/cgi/content/full/97/5/3621