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11

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 ...


10

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 ...


9

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 ...


6

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 ...


6

“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 ...


6

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 ...


4

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 ...


4

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 ...


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. ...


4

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.


4

It is thought that there are no active optical receptors in the brain normally, its possible some effect might show up in the future, it would be minor at best. Shining light into the brain is standard procedure in optogenetics experiments. A subpopulation of neurons is transformed to express an optical receptor to modulate genetic or signalling properties ...


4

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 ...


3

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 ...


3

As you've already mentioned, cells near the primate macula tend to make one to one connections. Due to this lack of convergence they can be somewhat smaller than normal cells (particularly in the size of their dendritic arbors) earning them the moniker "midget" ganglion and bipolar cells (also P cells). By reducing the magnitude of photoreceptor ...


3

A combination of differentiation site, chemical guidance during migration, and signaling cues form a variety of sources. The final step in the generation of an oligodendrocyte is the development of a mature myelinating phenotype, and this is largely regulated by axonal signals. It seems likely that both soluble and cell mediated signals from ...


3

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 a http://en.wikipedia.org/wiki/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 ...


3

I assume with EM you refer to electromagnetic? You are right that the EEG (electroencephalogram) is a tiny signal. When about 50.000 neurons fire simultaneously, it possible to see a change in the measured signal. Typical EEG amplitudes are in the microvolt range. Now, when the EEG is recorded, it is a function of time. You could for example collect data ...


3

Humans and many other organisms have a circadian clock, a biological system that oscillates every 24 hours (but is also sensitive to external stimuli). There are many components to the human circadian clock that are not known. On the molecular level, gene regulation, post-transcriptional and post-translational modification are all implicated. There is also ...


3

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 ...


3

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 ...


2

I've found the answer. The entire brain and spinal cord is bounded by the arachnoid mater, thus both channels would lead into the subarachnoid space, which also circulates the fluid into the spinal cord region. The CSF exits through the arachnoid granulations, which are like valves, found on the dorsal midline, into the superior sagital sinus, where it ...


2

One pathology affecting the vagus nerve is autonomic neuropathy which can be secondary to several causes-one of the most commonly acquired cause is diabetes mellitus. It can manifest with various symptoms such as resting tachycardia (heart beating fast without exercise), exercise intolerance, orthostatic hypotension, constipation, gastroparesis (delayed ...


2

I do not have a source for the following as it was taught to me in neuroanatomy classes, the explanation given for brain freeze is that it is referred pain through the trigeminal nerve. The meninges (the tissue lining the central nervous system) is innervated by the trigeminal nerve in the head. Therefore the pain feels as though it is like a headache from ...


2

I think that most mature cells do not divide in all tissues. If organism need 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 think ...


2

Neurons are tetraploid in pathological situations like Alzheimer disease: Neurons that duplicate their DNA are rarely observed to undergo mitosis, and they remain for long time as tetraploid cells, in accordance with the chronic course of the disease. We have recently shown that cell cycle re-entry and somatic tetraploidization occurs during normal ...


2

I've tried to split this into the answer to three questions: Why does a membrane potential arise at all? Why does it happen to be around -80mV How does the cell use its membrane potential (1) You've indicated that you know this one already, but I'd still like to point a few things out: The NaK pump not only creates a negative resting potential, it also ...


2

Answering the question: "Why is a negative membrane potential important?" I don't think cells have strong feelings about being slightly negative inside its membrane. I'm guessing these are the driving factors: the cell membrane is nonpolar, so charged particles can only pass via transport proteins. This makes ion gradients an easy way to maintain a source ...


2

I think that depends somewhat on how the human dies - in particular on the conditions. If they die in a very cold environment (say at the top of some icy mountain range), they'll freeze and metabolic processes will slow down considerably, and so will cell death. But such hypothermia-based slowing down is a special case. Normally, if your heart stops or you ...


2

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 ...



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