Reptilian Brain vs Midbrain: Understanding the Differences

[biferi]

Is the Reptilian Brain midbrain the same thing?

I know at the top of the Spinale Cord is a little Ball and this is the Midbrain.
Is this not what they call the Reptilian Brain?

 

[Pythagorean]

Here's the general idea:

The reptilian brain has all the components of "running a smooth engine". It regulates breathing and heart rate based on chemoreception of CO2 and O2 as well as basic motor motions, olfactory, and gustatory that allow the organisms to find, chase/kill, and eat appropriate foods. It can also deposit hormones into the body via the pituitary gland (i.e. adrenaline response).

Limbic system is often referred to as "early mammalian" system. And neocortex is more of a later mammalian thing, becoming a giant part of the brain in species like hominids (including humans), dolphins, and elephants.

 

[biferi]

Thank you for getting back to me but everything you just told me is this not what the Midbrain does?

Are they not the same thing?

 

[Pythagorean]

Ah, sorry, forot that part of the question. Midbrain is defined developmentally and encompasses most of the "reptilian brain". I'm not sure whether brainstem is included in reptilian brain (I included its functionality in my first post). But brainstem wouldn't be midbrain (it would be hindbrain)

 

[Pythagorean]

The more I think about it, "reptilian brain" is probably a very ambiguous phrase. There are definitely similarities between the whole brain of a reptile and the inner structures of our brain, and the evo/devo story (the links between evolution and development) contributes to that view.

But there's two problems with the terminology I think. One is that we didn't evolve from the reptiles of today. Both us and reptiles of today have a common ancestor. The terminology may lead to the former view.

And the other is that it lacks a rigorous definition. It most likely applies to the homology between reptiles and mammals (as defined by our last shared ancestor mentioned above) of some particular set of structures. The basal ganglia was referred to as the "reptilian complex" by MacLean; some aspects of his theory were eventually shown to be wrong. That is, reptiles are now thought to have always had a neocortex-like structure (the dorsal cortex) ... it's just really tiny compared to human cortex.

 

[biferi]

Well let me ask this the top of the Brainstem is the Pons and ontop of this is a Ball type thing and this is the Midbrain right?

 

[Pythagorean]

Yeah, a lot of what I described as reptilian brain would include forebrain and hindbrain as well. The midbrain is very tiny compared to either of them.


Hrm, I stand corrected on my earlier post, apparently midbrain is considered part of the brainstem.