Skip to main content
82 votes

Are there organisms with fewer than 1000 neurons?

Short answer As far as I know, a complete neural map (a connectome) is only available for the roundworm C. elegens, a nematode with only 302 neurons (fig. 1). Fig. 1. C. elegans (left, size: ~1 mm) ...
AliceD's user avatar
  • 52.5k
25 votes

Are there organisms with fewer than 1000 neurons?

The organism you are looking for is the nematode C. elegans, which always has the same number of neurons, 302, and has been fully mapped, see WormWeb or you can chase original publications from there. ...
Jack Aidley's user avatar
  • 6,917
16 votes

Are there organisms with fewer than 1000 neurons?

I believe there are types of water snail with 8 distinct neurons in a ganglia, there's a bit of information here: molluscs.at. The cell bodies of the neurons are massive, visible under a standard ...
Oliver Houston's user avatar
16 votes
Accepted

Why does biomagnification of mercury occur more in large fish?

Bioaccumulation occurs when organisms aren't able to excrete/eliminate/metabolize something as fast as they take it in. The specific circumstance of predators higher on the food chain accumulating ...
Bryan Krause's user avatar
  • 45.9k
9 votes
Accepted

How do our eyes detect light at different frequencies?

Short answer Action potentials generated to different colors are indeed similar throughout the nervous system and do not encode color as such. Instead, the different color- sensitive cells in the ...
AliceD's user avatar
  • 52.5k
8 votes

Are there organisms with fewer than 1000 neurons?

Re: insect brain size Following article has a good summary — in short insects' nervous systems range from 7400 to 850000 neurons: http://blogs.discovermagazine.com/notrocketscience/2011/11/30/how-...
Dima Tisnek's user avatar
5 votes

Do lobsters possess a nervous system to feel pain?

Yes they feel pain, at least in certain areas of their body without a doubt. Research has been done to test whether they feel pain consciously (a signal to the brain that is perceived allows for ...
John's user avatar
  • 14.7k
5 votes

Do lobsters possess a nervous system to feel pain?

To answer if lobsters have a nervous system: YES References: Mapping of serotonin-like immunoreactivity in the lobster nervous system BS Beltz, EA Kravitz Journal of Neuroscience 1 March 1983, 3 (3)...
Antony's user avatar
  • 153
5 votes
Accepted

Are all cone cells connected directly to the brain?

Are all cone cells connected directly to the brain? No. Cones connect to ganglial cells. Let's explore the numbers. Our eyes contain about 6 million cone cells, 90 million rods, and comparative ...
H Walters's user avatar
  • 166
5 votes
Accepted

Why is bacterial meningitis worse than viral meningitis?

One needs to be careful making broad generalizations about meningitis. The term simply refers to inflammation of the meninges (the outer layer surrounding the brain and spinal cord). Meningitis can ...
Harry Vervet's user avatar
  • 2,482
5 votes
Accepted

Is the bipolar neuron of the retina considered a sensory neuron?

In short, yes. Any neuron that is involved in conveying sensory information from the periphery to the CNS is a sensory neuron. So I would consider all of those neurons in the retina sensory. Arguably ...
Oliver Houston's user avatar
4 votes
Accepted

At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'?

First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your ...
anongoodnurse's user avatar
4 votes

Can low temperatures induce a withdrawal reflex?

The withdrawal reflex is a nociceptive flexor reflex and is a spinal reflex intended to protect the body from damaging stimuli. In other words, activation of heat receptors is not the trigger of the ...
AliceD's user avatar
  • 52.5k
4 votes
Accepted

Alcohol consumption and central nervous system

After alcohol intake, the cerebrum related functions like vision and speech is affected first and later on there's problem with the cerebellar functions like balancing and hand-eye coordination. My ...
anongoodnurse's user avatar
4 votes

Seizures and blood pressure

Yes, seizures can affect autonomic function including blood pressure. Such symptoms can even result in death. Note though that not all seizures are the same: there are many different types with many ...
Bryan Krause's user avatar
  • 45.9k
4 votes

Why is the hippocampus considered to be a cortical structure but not the amygdala?

You can't distinguish cortical from deep structures from a picture like the one you reference in Gray's Clinical Neuroanatomy. The hippocampus is a cortical structure because its cell bodies are in ...
De Novo's user avatar
  • 8,791
4 votes

Does the nature of nervous impulses give us a finite number of things we can perceive?

I know we have sensors in the form of hairs that trigger a nervous impulse to the brain when they are stimulated. But as I understand it, each one can only send that on/off binary signal when they ...
Charles E. Grant's user avatar
4 votes
Accepted

What are these two nerves running parallel to the spine called?

From this closeup image, you can see there is more than one nerve on each side that is parallel to the spine. Source: imgur.com First, they are the right and left sympathetic trunk that run from the ...
Jan's user avatar
  • 8,079
4 votes
Accepted

Does ingestion of alcohol with methylphenidate make it act more like dexmethylphenidate?

Does the ingestion of alcohol, when taking (racemic) methylphenidate can actually make it more potent? It is the 2011 study you've mentioned that answers most of the question. In the study, ethanol ...
Jan's user avatar
  • 8,079
3 votes
Accepted

Does GABA help or hinder anxiety?

I wouldn't bother trying to interpret press-release science that doesn't even contain a citation or link to the original research. However, I will try to address some of the other content of your ...
Bryan Krause's user avatar
  • 45.9k
3 votes
Accepted

Photoreceptors and light with mixed frequencies

Yes, current color models assume a linear response in the spectrum. Given a light with mixed spectrum $\Phi(\lambda)$, the response of a cone with spectral sensitivity $\Psi_i(\lambda)$ is a (...
Memming's user avatar
  • 3,090
3 votes

Why is Capsaicin injection not used instead of nerve surgeries for pain?

There is a simple answer to your question: it might cause a massive inflammation-like response and it might also hurt really, really badly. Capsaicin activates heat receptors which are not only ...
AlexDeLarge's user avatar
  • 2,868
3 votes
Accepted

How does (action potential) hyper-polarisation work?

I'll borrow a diagram from another answer to a similar question, but not quite a duplicate (I hope @AliceD won't mind my laziness): Fig. 1. Refractoriness. source: University of British Columbia One ...
Bryan Krause's user avatar
  • 45.9k
3 votes

Does the cranial dura consist of the periosteum? and if not, then is there a mistake in my textbook?

First about the terms: The outer side of the cranial bones is covered by a single layer of periosteum that is specifically called pericranium. The inner side of the cranial bones is covered by dura ...
Jan's user avatar
  • 8,079
3 votes
Accepted

What is the difference between a dermatome and a sensory neurone?

This is just a confusion of English. "Supplied" is a bit of a weird term to use, I agree, due to the direction of information flow, but feel free to substitute in just "connected to&...
Bryan Krause's user avatar
  • 45.9k
2 votes

Differences in the action of Scopolamine and Atropine

It seems that the reason for the different effect of Atropine and Scopolamine on the brain is related to the structural difference between them. From the chemical structures below it is evident that ...
Don_S's user avatar
  • 474
2 votes
Accepted

What is the difference between the neural tube and the dorsal ventral cord?

The terminology can be confusing, and I suspect the question you meant to ask was: what is the difference between the neural tube and dorsal nerve cord? In vertebrates, the neural tube and the dorsal ...
Harry Vervet's user avatar
  • 2,482
2 votes
Accepted

In theory how fast could nerve signals travel if the nerve fibre was perfectly insulated?

For some background on saltatory conduction: https://en.wikipedia.org/wiki/Saltatory_conduction I feel that a "perfectly insulated" neuron couldn't actually allow the signal to travel. Insulation (...
Jory's user avatar
  • 470
2 votes

Why are our muscles limited to 7 Hertz?

The human hand-brain reaction time is normally 100ms minimum - 300ms average, which aligns with the frequency that you talk about. There are different types of muscle movement though, and trembling ...
bandybabboon's user avatar
  • 10.4k

Only top scored, non community-wiki answers of a minimum length are eligible