Human body growth in the absence of a brain

  • Thread starter PainterGuy
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  • #1
PainterGuy
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Hi,

Does the brain control the physical growth of a human baby?

I think if, for some unfortunate reason, the brain is absent, the growth would still take place normally but more like a vegetable. I don't think if the brain is absent, one can even blink the eye or move a finger. But the details and data for organ growth such as size and shape, tallness, color, hair color, sex, etc. are present in each cell; in other words each cell has its own 'brain' which tells it how to grow. I think heart and lungs can also work independently of brain because the persons in coma without any brain activity can still pump blood around and breathe. It's possible that in absence of brain the functioning of heart and lungs is not that as smooth and reliable.

I don't think that hypothalamus, pineal gland, and pituitary gland are integral parts of brain so if the brain is absent, the glands could still be there to release the required hormones.

Could you please confirm if I'm thinking along the right lines? Thank you!

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Source: https://upload.wikimedia.org/wikipedia/commons/9/96/Endocrine_central_nervous_en.svg
 

Answers and Replies

  • #3
PainterGuy
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Thank you!

I think you are describing anencephaly: https://www.cdc.gov/ncbddd/birthdefects/anencephaly.html

Yes, though I just made it up, my description was close to 'anencephaly'.

Human growth hormone has be created over and over. It is required for growth.
The glands you mention are derived from nerve tissue - the same as the brain. So I would say 'no', not correct

But those glands are not part of the organ called brain, right? Does this mean that in absence of brain and those glands, human growth or human baby cannot survive? Is survival possible?


Brain death is the complete loss of brain function (including involuntary activity necessary to sustain life).[1][2][3][4] It differs from persistent vegetative state, in which the person is alive and some autonomic functions remain.[5] It is also distinct from an ordinary coma, whether induced medically or caused by injury and/or illness, even if it is very deep, as long as some brain and bodily activity and function remain; and it is also not the same as the condition locked-in syndrome. A differential diagnosis can medically distinguish these differing conditions.
Source: https://en.wikipedia.org/wiki/Brain_death

Is brain needed for the involuntary activity? I believe heart beating and functioning of lungs are involuntary activities. I was under the impression that even when brain is completely dead, one can survive in vegetative state. I knew an elderly person who slipped into coma and later doctors declared that there was no brain activity of any sort, but that person kept on breathing in the vegetative state for some years.
 
  • #4
BillTre
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There are two parts of the pituitary gland, one derived embryologically from neural tissue (posterior pit.), one derived embryologically from an invagination (infolding of a sheet of cells) of the roof of the mouth.

The hypothalamus and pineal are entirely derived embryologically from the nervous system. It controls a lot of pituitary function. They are both considered part of the brain.

The human heart can beat in an unregulated way without innervation (not sure for how long). Some other animals require the brain for a heart beat because that is where the rhythmic driver is.

Breathing (using to lungs) requires innervation to happen. It uses skeletal muscles driven by spinal cord motor neurons. I believe the driver neurons of the motor neurons is in the hindbrain (back part of the brain).

There was a famous case of a headless chicken that was kept alive for 18 months (with special care). The head was cut of with an axe for dinner, but it was not a well done job and the brain stem (including the hindbrain) was not removed, allowing the chicken to survive. It became a side show star.
Screen Shot 2020-12-23 at 5.50.10 PM.png

The brainstem is the most "primitive" part of the brain and includes a lot of functions that would have evolved early in the vertebrates, like control of breathing and heart rate.

The brain also has some indirect control over "involuntary" functions because the autonomic nervous system as well as any other part of the nervous system are connected to the central nervous system which can influence it functioning (such as danger --> increase heart rate).

There are also lots of behaviors considered involuntary which occur within the brain. They are just learned, automated, and then let to run with relatively little conscious control, like bicycle riding.
 
  • #5
PainterGuy
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Thank you!

The case of Mike the Headless Chicken really intrigued me!

The human heart can beat in an unregulated way without innervation (not sure for how long). Some other animals require the brain for a heart beat because that is where the rhythmic driver is.

So, I was wrong. I had thought that human heart can beat and keep its rhythm on its own without any intervention from the brain.

Breathing (using to lungs) requires innervation to happen. It uses skeletal muscles driven by spinal cord motor neurons. I believe the driver neurons of the motor neurons is in the hindbrain (back part of the brain).

Again, I was wrong. I had thought no brain intervention was required.

The brain also has some indirect control over "involuntary" functions because the autonomic nervous system as well as any other part of the nervous system are connected to the central nervous system which can influence it functioning (such as danger --> increase heart rate).

I find it little confusing because I had thought that human brain controlled all the involuntary functions and it does this on its own without any conscious involvement.

By the way, as a layman, now I think of a human brain as an organ responsible for conscious behavior such as decision making, deciding between right and wrong, etc., storing memories, learning, regulating other organs such as heart and lungs, controlling different body such as moving legs, hands, etc. and producing some hormones.
 

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