Talk:Neuron
The first sentence of this entry used to read "The basic cells of the nervous systems of metazoan animals, whose job is to transmit and process signals." I took the liberty of changing it, suggesting as it did that the job of metazoan animals is to transmit and process signals. (That's a notion of God that's rather different from any I had previously thought of: suppose that there is a God and that s/he created other beings merely to experience things that s/he can not, and then to report on the experience?)
From the article: "Synapses of nerves may be between two axons, two dendrites or an axon and a dendrite." Do we have any biologists, physiologists, MD or other specialist who can confirm this statement is correct? My understanding of recent reading I have been pursuing has the axon as an emitter and the dendrite as a collector. Recurrent connections would thus require a portion of the neurons in the nerve fiber or neuron cluster to be oriented roughly 180 degrees. In my current understanding, for the organic circuitry to function as the statement above implies would require multiple neurons in complex patterns rather than individual axon-axon or dendrite-dendrite pairs. mirwin 01:14 Aug 24, 2002 (PDT)
- Here is an article that talks about electrical synapses between adjacent dendrites [1]. I think dendro-dendritic chemcal synaptic connections are fairly rare, but here is an article claiming the existence of dendro-dendritic chemical synapses [2]. Chemical synapses between two axons are not unusual; here is a recent article involving such connections [3]. Some of the important work by Eric Kandel on leraning and memory in Aplysia involves axo-axonic sysapses. See the yellow "facilitating interneurons" making axo-axonic synapses onto the sensory neurone in this diagram [4]. 68.109.166.14 04:37, 7 Dec 2004 (UTC)
- It is my understanding that all synapses only occur at the tips of dendrites.
No - I don't think this is true. There can be different kinds of synapses - for example axonal-dendritic are the obvious ones, but there can also be axonal-somatic, possibly somatic-somatic etc. There is no reason why there can't be multiple synapses on a dendrite, axon or soma. There have been quite a few constraints which various researchers have imagined about neurons and their synapses - most have turned out not to be applicable.DaveM
Axons function as a conducting line that may go long distances while dendrites branch from end of the axon or directly from the nerve cell body. Electrochemical signals can only go in one direction for each type of neuron (away from the cell body); in sensory neurons signals are sent from sensory receptors (which are modified neurons), in motor cells a signal propagates from the motor cell neuron to effector cells in muscle. The quoted statement doesn't make sense to me. --mav
I am concerned at the notion that neurotransmitters are hormones - I will have to check up on this. My gut feeling is that this is incorrect. DaveM
- The usual definition for a hormone in human medicine is a substance which is produced in one tissue and carried through the bloodstream to another tissue, where it has its physiological effect. The part that may be getting confused is that some substances (e.g. norepinephrine) are both hormones and neurotransmitters. I think it's probably best not to refer to such substances as hormones when you are discussing them as neurotransmitters. -- Someone else 22:13 Nov 19, 2002 (UTC)
So shall we remove the reference to hormones then? DaveM
- Just did. It didn't add anything anyway<G>. -- Someone else 22:31 Nov 19, 2002 (UTC)
I rearranged things a bit and deleted stuff. The stuff about nerves and the nervous system was up too high given the topic, I thought, and not all of it really germane. Also, I've written long articles on synapses and action potentials, so I felt the paragraphs about those could be pared down. I hope people find these changes agreeable. 168...
100 billions neurons in brains
From WordNet: 1. (1) billion, one million million, 1000000000000 -- ((in Britain) the number that is represented as a one followed by 12 zeros) 2. billion, one thousand million, 1000000000 -- ((in the United States) the number that is represented as a one followed by 9 zeros)
Which billion (US or Britain)?
- I have seen 100 billion, United States. There are a large number of small neurons in the cerebellum, and I have seen 100 billion as an estimate of cerebellar neurons. 68.109.166.14 04:55, 7 Dec 2004 (UTC)
100 trillion connections
Is it certain that there are 100 trillion? Any reference? Multiplying 1000 by 100 billion is not correct, as 100 billion neurons can be connected multiply. It is probably more accurate to say 100 billion to the power of 1000 or something similar involving factorials. I'll try to find a reference...
Neural stem cells
Anyone heard of these?
They are quite a revolutionary discovery, so....I don't see much mention of them in here. I'm looking for information on it as well. Not to mention the neurons' flexibility in rerouting.
- This textbook might be useful for you [5]. Check this out [6]. Human neural stem cells [7]. 68.109.166.14 04:55, 7 Dec 2004 (UTC)
From the article:
- The soma, a relatively fat central cell.
I know v. little about biology, but a neuron is a single cell, is it not. The word 'cell' should be replaced (unless the soma is a seperate cell). SgtThroat 22:51, 19 Dec 2004 (UTC)
- I tried to give a better description of the "soma". I'd rather say "neuronal cell body". It is rather disorienting when you follow the link for soma from the neuron page. Memenen 01:07, 20 Dec 2004 (UTC)
I've fixed this by adding a stub at soma_(biology), but I don't know what to write there - I'm not a biologist - maybe you could add something? SgtThroat 13:13, 21 Dec 2004 (UTC)
Brain cell regeneration?
I've heard a few contradicting statements about whether or not brain cells regenerate over time, so I wondered if anyone would be so kind to give me some clarification on it. Also, if they regenerate - do they regenerate faster than they die, or is the amount of brain cells decreasing all the time? Thanks in advance.
- I think sometimes they can. It depends on the situation. From what I've read, that's a very experimental subject right now. It's also very controversial to try to artificially regernate neurons, because many times the cells used to regenerate neurons are brain stem cells from aborted babies. There is also research to see if hair follicles could be used, which would eliminate the ethical issues. It would be very important if brain cells could regenerate, because so many diseases are a result of destroyed cells that are vital to the brain's existence.
- This is a very new discovery but it is confirmed. It should be added
Nerve Cell Longevity
What is the average longevity of a nerve cell? That's what I was looking for. (I seem to remember it being that nerve cells shouldn't die, and so their life span would be the life of their organism, but if that's so it should be mentioned I think.)