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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) and connectome of C. elegans (right). sources: Utrecht University & Farber (2012) Background Looking at the least complex of animals will be your best bet ...


58

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 That graph is for innate reflexes of a needle to the hind versus a kick-time. Perhaps no one dared to prick a blue whale. Elephant vs shrew, heartbeat of 30 vs ...


28

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. Instead, electrical currents stimulate taste receptors directly by depolarizing the cell membrane, without the need of activation of the proteins that normally ...


25

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. C. elegans is particularly suited for this kind of work because it has a constant number of cells which divide in an entirely predictable order and its neurons ...


16

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 nerve roots angina pectoris, pain from myocardial ischaemia felt in the throat (Latin angina "infection of the throat"), arms, chest etc shoulder tip pain from a ...


16

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 dissecting microscope, so they were popular among early electrophysiologists. I guess there are probably more neurons around the snail, but it's certainly one of ...


8

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-fairy-wasps-cope-with-being-smaller-than-amoebas/ There may be some hope for parasitic insects, e.g. Dicopomorpha echmepterygis where male has neither wings nor ...


8

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 injury occurs. And I quote from the apperalyzed website: Spinal Cord Injury Overview When a person suffers a spinal cord injury, information traveling ...


8

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 systems, there is some overlap. The circulatory system carries fluids, the nervous system electrical signals so they are functionally not alike. However, both ...


6

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). These cells have a mechanical trigger and if activated a subcellular harpoon is fired and paralyzing and painful toxin is injected. A cnidocyte diagram is shown ...


6

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 pectoris (chest pain), caused by myocardial ischemia (decreased oxygen supply to the heart due to a narrowing or complete blockage of the coronary arteries). ...


6

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 receptor part and the receptor part only. The elongated structure leading to the soma, as well as the axonal part to the spinal cord are generally considered to be one ...


6

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. Background Hermaphroditic phenotypes in humans are nowadays preferably described as intersex phenotypes. In humans they come in different flavors, dependent ...


5

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 amacrine and horizontal neurons do not convey information "towards" the CNS, but they are involved in the processing of sensory information, therefore I would ...


5

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.m.wikipedia.org/wiki/Spinal_disc_herniation Sometimes the pain disappears with rest, sometimes surgery is necessary and sometimes the pain partly remains even ...


5

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 junction and autonomic ganglia. We know a lot about this receptor and it's blockade by curare, so most good basic pharmacology textbooks devote a fair amount ...


5

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 myelinated fibers (e.g., A fibers) and unmyelinated fibers (e.g., C fibers). The answer is (c): both myelinated and unmyelinated. Please note that spinal nerves ...


4

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. This is because quantifying those signals would be an exceedingly difficult task. It's not only logistically difficult to measure on an individual level, but to ...


4

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 both hands.) It's not inevitable that all people have involuntary muscle movements with very fine motor skills; it's a matter of ability/practice for most. The ...


4

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 fibers via the glossopharyngeal nerve to the nucleus tractus solitarii in the dorsal medulla in the brainstem. From there, efferent cardiovascular neurons send ...


4

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 base of the skull to the coccyx. Image source: Earthslab.com Additionally, they could be the right and left long thoracic nerve, which innervate the serratus ...


3

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 involved in heat reception (that would cause the pain as TRPV1, the receptor, is strongly activated at temperatures higher than 43 degree Celsius - accordingly, it ...


3

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 networks, with regards to Schwann cells, and prevent differences in osmotic pressure from disrupting the cells. As for your second question, action potentials do ...


3

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 focusing. "The general function of norepinephrine is to mobilize the brain and body for action. Norepinephrine release is lowest during sleep, rises during ...


3

By reasoning, we can make the following distinction: the trigeminal nerve is a cranial nerve. the 2 others are peripheral nerves. Cranial nerves take their origin into their respective nuclei, and bypass the dorsal columns (main spinal tract for sensory information). Peripheral sensory nerves stem from the spinal roots, and from there go up through the ...


3

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 almost any situation involving potentially significant blood loss. Becoming prone or supine prevents loss of consciousness, the most critical aspect of survival. ...


3

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". It seems pretty common to use this word, for example Wikipedia says: A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from ...


2

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 be influenced by hormonal responses produced by the autonomic nervous system. To quote Wikipedia: While heart rhythm is regulated entirely by the sinoatrial ...


2

You are looking for the Trigeminal nerve, the largest nerve in the face. Here it is with its branches. It is both afferent and efferent. Afferent and efferent components of the facial nerve in the bullfrog (Rana catesbeiana) Cranial Nerves Illustrated: Figure V-4 General sensory component of the trigeminal nerve, ophthalmic (V1) division. General sensory ...


2

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 guess) some relatively standard off-site pain actions. In my case, it appears to be more simply the action of (for want of a better term) CrossedNerves. As one ...


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