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) ...
- 51.8k
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. ...
- 6,841
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 ...
- 939
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 ...
- 39.9k
10
votes
Accepted
How long can the brain survive during ongoing cardiac arrest?
From Boron and Boulpaep textbook of Medical Physiology, second edition, p.289:
Because of falling ATP levels in the brain, consciousness is lost within 10 seconds of a blockade in cerebral blood ...
- 3,030
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 ...
- 51.8k
8
votes
Accepted
How are reflexes suppressed?
Short answer
The pain withdrawal reflex can only be suppressed when touching something painful on purpose. Deliberate, conscious contraction of the extensor muscle before reflex initiation can prevent ...
- 51.8k
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-...
- 181
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 ...
- 2,472
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 ...
- 939
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 ...
- 13.8k
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)...
- 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 ...
- 166
4
votes
Accepted
Why are our muscles limited to 7 Hertz?
Our muscles are not limited to 7 hertz.
You provide two examples yourself. I can provide a third: world's fastest clapper: 804 claps in 1 minute (video here), which is an average of 13.4 claps/sec --...
- 28.5k
4
votes
Why are our muscles limited to 7 Hertz?
According to the book, Principles of Animal Locomotion by R. McNeil Alexander, oscillatory movements in animals are limited by an organism's nature in general to minimize metabolic energy costs. The ...
- 826
4
votes
Why we shiver/tremble/shake while performing some work which requires high accuracy?
If you thread needles often - like a dozen times a day for many days - you will eventually be steady as a rock, because practice improves the process (you will also unconsciously maneuver to steady ...
- 24.5k
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 ...
- 51.8k
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 ...
- 24.5k
4
votes
Accepted
Do lobsters possess a nervous system to feel pain?
Before answer, What intuitively seems:
Lobsters structurally contains sense-organs like eye and antennae, and output organs like muscles through which they move. So plausibly these organs should ...
- 2,649
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 ...
- 39.9k
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 ...
- 24.5k
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 ...
- 8,721
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 ...
- 3,131
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 ...
- 8,039
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 ...
- 8,039
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 ...
- 2,878
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 (...
- 3,045
3
votes
Why we shiver/tremble/shake while performing some work which requires high accuracy?
Norepinephrine (noradrenalin) is a neurotransmitter and hormone released by the body in situations which, among other things, require focus. This may (partially) explain the shaking hands when ...
- 16.1k
3
votes
Accepted
How pain can stimulate the vagus nerve
Short answer
Given your comments you are referring to the cause of fainting after being triggered by certain stressors. The reason is a sudden drop in blood pressure due to parasympathetic nervous ...
- 51.8k
3
votes
How long can the brain survive during ongoing cardiac arrest?
If we consider another case, there is blood flow, but no new oxygen is coming into the system, the brain cells may begin to die after about four minutes [1]. However, this depends on the person not ...
- 2,167
Only top scored, non community-wiki answers of a minimum length are eligible