Cerebral Pouches? Ventricles?

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Cerebral Pouches? Ventricles?

Postby vivian maxine on August 11th, 2016, 11:58 am 

https://en.wikipedia.org/wiki/Ventricular_system

It is a great article but that is not why I posted it. Please answer my questions.

1. "Cerebral pouches" - which brought up some very strange links - and "cerebral ventricles". Are they the same? Or is the pouch where the tube bends, as I saw in another article?

2. On the Wiki page (above), about 1/3 of the way down, there is an illustration of the CSF flow. In the center there is a sort of pulsing/flashing/beating going on. I assume that is being caused by the movement of the fluid. Is that also what causes the pulse you can feel on your temple just in front of the ear?

3. The CSF flows through the spinal cord. Is this fluid part of the blood or is it separate?

4. Is that enough questions from me for today? :-)
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Re: Cerebral Pouches? Ventricles?

Postby neuro on August 17th, 2016, 5:10 am 

vivian maxine » August 11th, 2016, 4:58 pm wrote:https://en.wikipedia.org/wiki/Ventricular_system

It is a great article but that is not why I posted it. Please answer my questions.

1. "Cerebral pouches" - which brought up some very strange links - and "cerebral ventricles". Are they the same? Or is the pouch where the tube bends, as I saw in another article?

I am not familiar with the term "cerebral pouches". It seems to me as a term related to a site in the neural tube where, during development, cerebral matter develops; it is therefore a temporary structure; but I only saw it cited for some organisms, and I don't know much of comparative anatomy (I know that this is part of my hideous attitude of considering humans much more interesting than animals, but I can't help :°)).

The cerebral ventricles, conversely, are present in the adult brain.

2. On the Wiki page (above), about 1/3 of the way down, there is an illustration of the CSF flow. In the center there is a sort of pulsing/flashing/beating going on. I assume that is being caused by the movement of the fluid. Is that also what causes the pulse you can feel on your temple just in front of the ear?


No. The brain does not possess any sensory innervation (although the hypothalamus does contain receptors for temperature, oxygen, CO2, pH and other chemical substances, to drive body temperature regulation and a number of metabolic functions). What you feel is the pulse of cerebral - meningeal - arteries. Which instead are innervated, with nociceptors as well (nociceptors are free nerve terminals of sensory neurons that generate the sensation of pain; activation of such nociceptors in meningeal arteries gives rise to pulsatile headache, and the paroxysmal hyperactivity of the neurons themselves - located in the trigeminal ganglion - generates migraine).

The image you refer to is misleading, because it is much accelerated. The CSF does flow, but quite slowly. It is filtered from blood at the choroid plexus; its composition is quite similar to plasma (blood minus erythrocytes, i.e. the liquid fraction of blood), except it is much less rich in proteins, and it may contain substances produced by neurons and glial cells (which may be important to diagnose some neurological diseases).
3. The CSF flows through the spinal cord. Is this fluid part of the blood or is it separate?

In general the CSF constitutes a separate compartment. Blood arrives to the brain and spinal cord through arterioles and capillaries (as it is the case for any other tissue), but the capillaries have a slightly different endothelium, in which the cells are tightly connected to each-other. This way, solutes cannot diffuse out of the capillary through the intercellular spaces (fenestrae): they must cross the cells, which is only possible if they are lipophilic or if molecular transport systems exist for them (e.g. transporters for glucose and aminoacids). This feature - combined with further ensheathing of the capillary by pericytes and astrocyte pedicels - creates what is called the "blood-brain-barrier" (BBB). A similar filtration barrier exists at the choroid plexus as well, where the plasma is actively filtered so that water and some solutes can pass into the CSF, other solutes cannot. It is of interest that if inflammation occurs, then the BBB may become permeable, and hydrophilic substances (such as penicillin, for example) can then penetrate the CSF and the brain tissue; also, some proteins, such as immunoglobulins (antibodies) will be able to pass, and lymphocytes will manage in infiltrating between adjacent endothelial cells.

4. Is that enough questions from me for today? :-)

Yes, I'd say so.
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Re: Cerebral Pouches? Ventricles?

Postby vivian maxine on August 17th, 2016, 8:27 am 

Thank you, neuro, for taking all that apart and reassembling it. And thank you for defining 'nociceptors'. This is probably all the learning I can take for one day. :-)
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Re: Cerebral Pouches? Ventricles?

Postby BioWizard on September 23rd, 2016, 7:53 pm 

That was an excellent post by neuro.
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