Which one?

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Which one?

Postby Juliedang on June 18th, 2018, 7:17 am 

Handedness is in the spinal cord, not the brain. Whether to use the left hand or right hand is being decided by the fetus before the spinal cord and brain connect - according to this:

https://www.sciencedaily.com/releases/2017/02/170217095904.htm

I thought I once read that the brain grows from the spinal cord. This sounds as though the brain is already developing and then makes a connection to the spinal cord. Right? That is not the gist of the article. Just that the suggestion of one connecting to the other got my curiosity stirring.
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Re: Which one?

Postby Braininvat on June 18th, 2018, 8:59 am 

Hi, Julie. Good question. I am moving it to the biology forum, where it seems to fit best.

Though I have a biology background, morphogenesis is not an area of developmental biology on which I'm well informed. I hope to rouse a member or two who may be more knowledgeable in this area.
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Re: Which one?

Postby BadgerJelly on June 18th, 2018, 11:00 am 

Link?
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Re: On the one hand...

Postby Faradave on June 18th, 2018, 11:16 am 

Julie's link

It's not as if the brain and spinal cord develop separately, then connect. Rather they are different regions of the embryonic neural tube which develop differently. The "connections" referred to are more in the nature of synaptic connections from the motor cortex in the brain to ganglia in the spinal cord, which take their time.

Image

Reflexes can occur before these connections are made and continue to exhibit a degree of independence from the motor cortex throughout life. Thus, your response to a doctor's reflex hammer or withdrawal from a flame can initiate before you even realize it cerebrally (consciously). This involves a loop from end organ to spinal cord and back that is monitored by the brain but does not require initiation by the brain.

Imagine how long it would take a brontosaurus to get a signal from something biting the tip of its tail, all the way to the brain and back. Better if it can start withdrawing via local circuitry with later modifications.
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Re: Which one?

Postby Braininvat on June 18th, 2018, 11:32 am 

Link in OP fixed.

I was going to beat on Faradave's, and perhaps BioWizard's door, until they awoke, but it appears that Faradave managed to get his gang of ganglia, and highly differentiated neural tube, fully activated.

I find it interesting that epigenetic factors seem to be key in asymmetric development, and therefore handedness. I wonder what environmental influences would be at work there - factors like placental vascularization, perhaps? Uterine orientation of twins?
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Re: Which one?

Postby BadgerJelly on June 18th, 2018, 11:33 am 

Thanks. I was wondering what they were talking about because I remembered that the neural, system developed from the “neural tube”, even though I thought it was called “neural lumen” for some reason.

Just googled. i reckon this is what they meant to refer to? I’m rusty, not looked at neurogenesis for ages!
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Re: Right theory?

Postby Faradave on June 18th, 2018, 1:52 pm 

Braininvat wrote:epigenetic factors seem to be key in asymmetric development, and therefore handedness

That's what makes it interesting! One might expect epigenetic influences to be random and evenly biased but it clearly has a familial component and is generally asymmetric.
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