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
62
votes
Do large animals experience a meaningful delay when moving their most distant appendages?
Yes, larger animals do experience larger delays in movement.
There have been studies of size difference vs sensorimotor delays in terrestrial mammals, https://www.ncbi.nlm.nih.gov/pubmed/30158304
...
- 9,113
28
votes
Accepted
Can we taste electrons?
Short answer
Yes, taste sensations can be generated electrically. However, we cannot taste electrons themselves, as taste-receptor proteins on the taste receptor cells are not activated by electrons. ...
- 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
23
votes
Does every person have unique nervous system?
Probably the best way to answer this question is with a counterexample to humans: the nematode worm C. elegans has 302 neurons. Every individual has exactly that number, and each is found in the same ...
- 39.9k
16
votes
Accepted
Is it possible to feel pain in some part of a body, but the pain "feeling" is introduced somewhere else?
Yes, this is pretty common. Examples include
sciatica, pain felt down the back of a leg to the foot, from irritation to components of the sciatic nerve but commonly at the level of the sciatic ...
- 794
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
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
8
votes
Accepted
Does the nervous system have "routers"?
The second model is the one. No tags, flags, or routers, just a 1-to-1 system.
A striking example of this is are the different effects of spinal cord injury, which depend on the place where the ...
- 51.8k
8
votes
Accepted
Relationship between nerves and axons
I will go through your list of questions below:
I wanted to know how similar is our nervous system to [the circulatory system]?
They are very different, but as in every comparison of very complex ...
- 51.8k
7
votes
Accepted
Do hermaphrodites have more nerve fibers in their puendal nerve?
Short answer
The genitals of true intersex individuals are not duplicated. Instead, their external genital features are hybrid structures. In turn, it's not a matter of duplicated neural innervations.
...
- 51.8k
6
votes
How can a brainless Cnidarian hunt and defend itself?
Sea anemones are members of the phylum of Cnidaria. Distinguishing features of this phylum are radial symmetry and the presence of cnidocytes, or stinging cells (like the ones found in jelly fish). ...
- 51.8k
6
votes
Is it possible to feel pain in some part of a body, but the pain "feeling" is introduced somewhere else?
An example of pain evoked by distant sites in the body is referred pain. It's defined as pain perceived at a location other than the site of the painful stimulus. An example is the case of angina ...
- 51.8k
6
votes
Can the dendrites of sensory neurons be a meter long?
Short answer
Axons can be over a meter long, but dendrites are never that long. Distance in the body is covered by axons. The dendritic part of skin receptors is generally considered to be the ...
- 51.8k
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
Is it possible to feel pain in some part of a body, but the pain "feeling" is introduced somewhere else?
Another common medical condition that causes pain elsewhere is the spinal disc herniation. The disc pushes against the nerves in the spinal and causes pain, usually in the leg, foot or arm. https://en....
- 3,657
5
votes
Accepted
What exactly does Curare do to the peripheral nervous system?
Curare is a plant alkaloid originally used as a poison on darts and arrows used in hunting. It is a competitive antagonist for the nicotinic acetylcholine receptor, which is found in the neuromuscular ...
- 8,721
5
votes
Accepted
Are spinal nerves myelinated and unmyelinated at the same time?
Spinal nerves are mixed nerves containing afferent and efferent neurons of various types. Anatomically, they protrude from the spinal column bilaterally at each vertebral level. They contain both ...
- 8,721
4
votes
How many sensory neurons are in the human body?
This is a really interesting question. However, I'm going to try to address the context and update sections of your post rather then attempt to quantify all afferent signals in the nervous system. ...
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
How does the mechanism which controls blood pressure in the brain work?
Blood pressure is sensed in blood vessels by baroreceptors. Baroreceptors are stretch-sensitive nerve fibers located primarily in the aortic arch and carotid sinuses. The baroreceptors send afferent ...
- 51.8k
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
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
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
Why isn't the upper limit of pain lower in humans?
You are assuming that fighting back with a bad wound would be more useful than dropping to the ground. That is not always the case.
Dropping to the ground and ceasing activity is very adaptive in ...
- 24.5k
3
votes
Accepted
Do Schwann cells have Na+/K+ ATPase pump?
Yes. Although utilizing the action potential is not in their function, Schwann cells do have Na/K ATPases. In fact all animal cells do. It contributes to the resting membrane potential in neural ...
- 184
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&...
- 39.9k
2
votes
Accepted
How does motor nerve innervation determine type of muscle fibre?
'Slow' and 'fast' motor neurons differ in their firing patterns. This differentially affects intracellular calcium concentrations and energy usage of the innervated muscle fibers over time, and ...
- 275
2
votes
Is it possible to feel pain in some part of a body, but the pain "feeling" is introduced somewhere else?
Just as an FYI, the answer is emphatically yes. I have two separate areas of my body which exhibit those symptoms. But my answer does not "track" those of others here. They talk about (I would ...
- 29
2
votes
Accepted
Who is organizing the heartbeat and its roles in the body?
The Sinoatrial Node is a ganglion (clump of nerves) attached to the heart, which regulates heartbeat independently from the brain (http://en.wikipedia.org/wiki/Sinoatrial_node).
Heart rate can also ...
- 1,245
Only top scored, non community-wiki answers of a minimum length are eligible