6 ms·

Title is technically correct (the best kind of correct) but jellies do have a nervous system. Its a net if a few hundred neurons. Here's to hoping this researc

Title is technically correct (the best kind of correct) but jellies do have a nervous system. Its a net if a few hundred neurons. Here's to hoping this research helps is discover why we evolved to sleep.

pstuart 9y ago
Isn't the latest thought that it's to take the brain down for maintenance to flush out debris from processing done during the day? (citation needed)
- ringaroundthetx 9y ago
  its one thought and it answers nothing
  - pstuart 9y ago
    http://www.npr.org/sections/health-shots/2013/10/18/236211811/brains-sweep-themselves-clean-of-toxins-during-sleep http://www.npr.org/sections/health-shots/2013/10/18/23621181...
- amelius 9y ago
  But why didn't our brain evolve to take the debris out while it s working?
  - pstuart 9y ago
    Unqualified anonymous internet answer: it's probably too busy. I believe the brain actually shrinks slightly and channels expand to aid in the flushing. Anectdata: note how when you're really tired you can't think clearly? Also, how (apparently) if one goes without sleep for too long then the brain suffers irreparable damage.
  - deleted 9y ago
    [deleted]
  - Khanthulhu 9y ago
    But what if we evolved sleep before we evolved brains? Might it then have a different benefit and the brain ones came later?
pbhjpbhj 9y ago
The nervous system is mentioned in the OP: >Cassiopea has no brain to speak of — just a diffuse “net” of nerve cells distributed across their small, squishy bodies. These jellyfish barely even behave like animals. Instead of mouths, they suck in food through pores in their tentacles. They also get energy via a symbiotic relationship with tiny photosynthetic organisms that live inside their cells. // From a very cursory glance I can't see how they're differentiating low energy level from lack of "sleep" when they're keeping the jellies "awake". Can that behaviour (resting more the next day) just be explained by low energy reserves, and the jellies needing more time to glean energy from the photosynthesising organisms/cells? Don't plants in winter "sleep" according to their definition; they can wake with a "false spring".

pstuart 9y ago

Isn't the latest thought that it's to take the brain down for maintenance to flush out debris from processing done during the day? (citation needed)

ringaroundthetx 9y ago
its one thought and it answers nothing
- pstuart 9y ago
  http://www.npr.org/sections/health-shots/2013/10/18/236211811/brains-sweep-themselves-clean-of-toxins-during-sleep http://www.npr.org/sections/health-shots/2013/10/18/23621181...
amelius 9y ago
But why didn't our brain evolve to take the debris out while it s working?
- pstuart 9y ago
  Unqualified anonymous internet answer: it's probably too busy. I believe the brain actually shrinks slightly and channels expand to aid in the flushing. Anectdata: note how when you're really tired you can't think clearly? Also, how (apparently) if one goes without sleep for too long then the brain suffers irreparable damage.
- deleted 9y ago
  [deleted]
- Khanthulhu 9y ago
  But what if we evolved sleep before we evolved brains? Might it then have a different benefit and the brain ones came later?

pbhjpbhj 9y ago

The nervous system is mentioned in the OP: >Cassiopea has no brain to speak of — just a diffuse “net” of nerve cells distributed across their small, squishy bodies. These jellyfish barely even behave like animals. Instead of mouths, they suck in food through pores in their tentacles. They also get energy via a symbiotic relationship with tiny photosynthetic organisms that live inside their cells. // From a very cursory glance I can't see how they're differentiating low energy level from lack of "sleep" when they're keeping the jellies "awake". Can that behaviour (resting more the next day) just be explained by low energy reserves, and the jellies needing more time to glean energy from the photosynthesising organisms/cells? Don't plants in winter "sleep" according to their definition; they can wake with a "false spring".