18

Its not clear that this is true. Working with animals has been a little disconcerting over the past 50-60 years. In the distant past, I think most evolutionary anthropologists and their like bought into the idea that humans were completely uniquely intelligent and spiritual. But the more we try to define human sensibilities apart from other animals, the ...


16

Nice question! I will directly begin with the process through which methamphetamine causes damage to neurons, putting in as much details as are known, and adding appropriate citations wherever required. Methamphetamine (METH) is known to act by increasing concentration of dopamine in brain1. When excess of dopamine is produced, it causes oxidative damage to ...


15

The basis of this question is a common misconception, and unfortunately the accepted answer by @CHM is also based on this common misconception. The misconception is based on the homunculus falacy: the tendency for people to think that the image that lands on the retina is somehow 'assembled' and presented for something (the 'consciousness') to view. This is ...


14

Short answer Yes, brain transplantation is technically possible, but only for short periods of time, and only in experimental settings. Background In terms of a full-brain transplant there has been only one group that have made serious attempts in doing this (according to wikipedia and a literature search on my end). In the 1960's White and colleagues ...


13

It has mainly to do with the embryonic origin of organs, with the heart being a typically left sided organ, it develops sharing some nerves with the left thorax and left arm. There is however high variability, typically among patients but also among coronary vessels. For instance, right coronary stenosis may lead to abdominal pain, whereas left circumflex ...


10

Neurons communicate electrochemically. That is, when a signal arrives to a neuron it fires a series of electrical signals, called action potentials. Action potentials are depolarization events that propagate along the neuronal membrane, down to the neuronal terminal. The terminal of a neuron is (with some exceptions) in contact with another neuron, via a ...


10

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 ...


9

The key to understanding this is to digest the fact that there are two gates blocking a normal sodium channel. These gates are called the activation gate (on the extracellular side) and the inactivation gate on the intracellular side. Both of these together, or any one of these alone, if closed, can block the sodium current from entering the cell. In the ...


8

There is no widely-accepted neurological structure that mediates 'consciousness.' Even if some structures have been shown to be necessary for consciousness, they have not been shown to be sufficient. This is true with anesthetic mechanisms as well -- their ability to paralyze and block pain signals is fairly well-understood, but the mechanism of loss-of-...


8

The brain activity is electric and chemical. The male adult human brain contains about 86 billion neurons (Azevedo et al). There is about 100 trillion connections between them. Solving a puzzle like that is not easy.. what sort of breakthroughs would be necessary to intercept these signals and interpret them as exact thoughts? What you are referring to ...


8

The terms gray and white matter relate to their color in gross specimens (i.e., not microscopic specimens) that have been formalin fixed. Nissl granules describe a microscopic structure, the rough endoplasmic reticulum, and aren't directly related to the color of gross specimens. Here's an example of a frontal cross section from a University of Utah slide ...


7

“Self-induction” in photosensitive epilepsy is a well-described and fascinating phenomenon. Photosensitivity itself is rare, occurring in only ~5% of patients with epilepsy.1 Among this group it has been estimated2 that 25% self-induce epileptiform activity. The most common methods appear to be passing a hand with open fingers repeatedly across the visual ...


7

Often artificial neurons are created with conventions that zero is "rest" and 1 is "threshold". The unit starts at 0, and when it reaches 1 it will send an input to all of its targets and be reset back to 0. This isn't exactly how real biological neurons work, but its a reasonable approximation in some contexts (and can do real world computations). Most of ...


7

Short Answer: "Always" is always a dangerous term in biology. Longer Answer: What does a neuron do if it does not get stimulated/receives no signal for a long time. Will it die ... or try to find new connections that might send signals? What neurons do when they aren't stimulated depends on the neuron and phase of development. Typically, thresholds for ...


6

In terms of cell bodies? Zero. There are autonomic projections from the spinal cord (sympathetic) and vagus nerve (parasympathetic) to the sinoatrial node, the atrioventricular node, and at discrete points in the atria and ventricles.


6

I think that most mature cells do not divide in all tissues. If an organism needs to repair tissues, it uses tissue cell precursors -- stem cells. In case of neurons, these are neuroblasts. Neuroblasts can divide and can repair brains under some circumstances (I don't know under which). There is a cancer grown from neuroblasts, called neuroblastoma. I ...


6

I think this is mostly caused by hyperventilation. The excessive breathing disturbs the balance between CO$_{2}$ and oxygen in our lungs. This will cause respiratory alkalosis (the blood pH, which is normally strictly regulated, gets higher), which can cause dizziness, headaches and fainting. The shift in pH can also disturb the eclectrolyte balance, ...


6

The symptoms of Down syndrome occur due to overexpression of genes present on the duplicated chromosome. If possessing an extra chromosome meant an equivalent change in gene expression, one would expect to observe 50% more protein production for having 3 rather than 2 copies of a chromosome. However, due to complexities in regulation at the level of ...


6

how is one type of neurotransmitter secreted rather than another Most neurons release a single major neurotransmitter. JM97 commented a link about cells releasing more than one, but that is talking about "extra" neurotransmitters are short peptides, different from the major neurotransmitters like glutamate, GABA, acetylcholine, dopamine, norepinephrine, etc ...


6

Neurons are suspended, as you say, in an extracellular matrix. Brain tissues are a little bit more specific. Here I quote a few summaries from literature to answer and give your a perspective on your basic question. In bold I highlight important statements which differentiate the brain's ECM from the ECM found elsewhere in the body. Barros, Franco & ...


5

According to this, in rats it takes about 17 seconds after decapitation for the EEG to become iso-electric. But there is no known correlation between EEG and consciousness. Also at 50-80 seconds after decapitation, EEG being iso-electric, a very slow, late wave appears on the EEG record. The same article concludes that it takes about 3-4 seconds after ...


5

The neurohormones in most mammals include oxytocin and vasopressin, both of which are produced in the hypothalamic region of the brain and secreted into the blood by the neurohypophysis (part of the pituitary gland). A second group of neurohormones, called releasing hormones, also originates in the hypothalamus. The members of this group, however, are ...


5

Short answer People competent in mathematics have been shown to have higher activation of the left angular gyrus according to fMRI. EEG recordings have shown larger activity in the posterior parietal cortex. Background I think you are interested in what makes a good mathematician. A brain imaging study by Grabner et al. (2011). showed that the left anterior ...


5

Polyneuropathy is actually not a very specific term, so the reasons will no doubt vary depending on which specific class you are talking about. That said, here are two reasons that longer neurons are preferentially affected: Some polyneuropathies involve conduction problems that include "failures" where action potentials aren't propagated down the full ...


5

Both L-Dopa and Dopamine are polar molecules and thus hydrophilic. They are solvable in water but not in lipids, so they are not able to cross the Blood-brain barrier on their own. The difference is that L-Dopa has a transport protein (SLC7A5) that allows it to pass through the Blood-brain barrier, whereas dopamine doesn't.


5

what does the "two photon" means? Ordinary confocal microscopy uses single photon of laser light to excite the molecule of fluorescent dye. In two photon microscopy you use two photons, with lower energy, which cannot excite the molecule of dye on their own, but their interference in a specific place leads to summation of their energies and to excitation. ...


4

Strictly stated, Hebb's rule applies only to existing synapses, and not to the formation of new synapses. (This answer applies to biological neurons, not to ANNs). Synapse formation is a topic of active research. During development (and in fact continuously even during adulthood), many synapses are created and destroyed. It is not unreasonable to suspect ...


4

I noticed that a strong background signal in the alpha-wave range was existent at ~10 Hz, but then after a while of doing other things and coming back to it the strong background signal at 10 Hz disappeared but a strong background signal at a smidgen over 8 Hz was present instead. Alpha-waves (7-13 Hz) are related to a dozen of things. Here is an easy first ...


4

Yes, but rarely. Other types of brain cells are much more likely to form tumors. Oligodendrocytes, astrocytes, and more generally glial cells all form tumors with some regularity. Nerve sheaths can also form benign growths. Nerves themselves can even manifest cancerous behavior, even though they are nearly always benign and very slow growing. ...


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