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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 ...


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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 ...


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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 ...


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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 flow. Irreversible nerve cell injury can occur after only 5 minutes of interrupted blood flow. If conscious is lost within 10 seconds of blockade in cerebral ...


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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 retina are connected to different neurons and these color-specific signals are kept segregated up until the higher visual cortical areas. Background Action ...


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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 the contraction of the flexor muscles once the reflex is started. Background The pain withdrawal reflex arc (Fig. 1) receives input from sensory neurons that ...


7

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 ...


5

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 occur due to a number of causes, most notably viral and bacterial infections, but can also also be due to fungi, parasites, toxins, cancer, etc. There is a vast ...


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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 ...


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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 learned response) or if it is just a reflex response (Nociception), and there is good evidence they actually perceive it especially in the antenna. source Source ...


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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) 585-602 http://umaine.edu/lobsterinstitute/education/life-of-the-american-lobster/anatomy-biology/ Bonus picture:


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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 handfuls of additional photosensitive cells (ipRGC's) that don't play a role in vision. The optic nerve is a bundle of roughly 1 million fibers (perhaps up to ...


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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 are triggered by a very specific level of sound. Your overall question borders on philosophy and the biology of consciousness which is hardly understood at ...


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The accuracy of sensation is actually quite variable depending on the region of our body. Highly innervated areas such as our fingers have a higher degree of accuracy than sparsely innervated areas such as our legs. There is a simple experiment you can do to illustrate this. Close your eyes and then get a friend to lightly and slowly run their finger from ...


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Having just read this article (http://www.ncbi.nlm.nih.gov/books/NBK11164/) there are several advantages/functional reasons that seem apparent and important in having electrical synapses with gap junctions compared to just a very long neuron. a) signals in electrical synapse can be bidirectional. b) electrical synapse synchronize electrical activity among ...


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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 energy capacity, inertial, compliant, and dissipative forces involved in the muscles, tendons, skeleton, and non-actuating load all enter into this cost equation....


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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 withdrawal reflex, it is the activation of pain receptors at high, tissue-damaging temperatures. Extreme cold is also damaging and causes skin lesions akin to ...


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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 second article explains this; read the part about the importance of calcium.) So yes, long before a fetus can feel pain, the heart is beating, because there must ...


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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 be plausibly connected to its controllers, i.e. neurons. The basic histology found in very primitive multicellular animals like Hydra, Planaria to advanced ...


4

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 different causes, and they can affect different parts of the brain. There can also be different effects before, during, and post-seizure. The effects described ...


4

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 question is- why is it so? Why do they appear in that order? It is and it isn't complicated. When you include what each does, it's an interesting question. We ...


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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 the outer layers of the cerebrum. The amygdala is a deep structure because its cell bodies are in nuclei. I'm not sure if your textbook has stained sections, but ...


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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 ...


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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 -- though, you can see his pace changes so at times he's doing more than that. What about a non world-record holding example? I can provide one of those as ...


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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 ...


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In addition to what Spinoral has said, and in response to your comment above, I will add a bit more about the mechanisms. Essentially, in some form or another it's receptive fields all the way up. A brief outline of the anatomy: The cells from the spinal cord are pseudounipolar and have their cell bodies in the dorsal root ganglia in the spinal cord. The ...


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Short answer External stimuli can drive autonomic responses. Background The autonomic nervous system is a visceral sensory and motor system. The viscera are the internal organs. Virtually all visceral reflexes are mediated by local circuits in the brain stem or spinal cord (Fig. 1). It is one of two major subdivisions of the nervous system; the other being ...


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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 system activation (vagus nerve activity). This leads to reduced blood flow to your brain, which results in a brief loss of consciousness (Mayo Clinic). Background ...


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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 the amount of time. Consider free divers and more specifically Tom Sietas. These men and women, in this sport, can go well beyond the 5 minute mark with no ...


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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 ...


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