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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 ...


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 ...


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 ...


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. ...


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 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

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

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.


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 ...


2

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 ...


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

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 ...


2

It probably depends on what stage of development the neurons are in and what region of the brain. If there's not branching still going on, then probably not. Hebbian learning is generally considered a concept of neuron connections strengthening (more synapses forming and dendritic spines growing larger) and not the initial formation, particularly in ...


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

It's important to clarify what an EEG machine measures. Electromagnetic waves are photons. An EEG does does not detect radiation. It detects magnetic fields by measuring an electrical current induced in the measuring device by the brain. Electricity is the movement of electrons. Electromagnetic waves are photons of light. Magnetism a force which fills ...


1

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 ...


1

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 ...


1

You might want to read about event related potentials (recorded by EEG) or event related fields (recorder by MEG). The idea is simple: 1) Pick some stimulus, e.g. a person touching the hand of a subject. Pick another stimulus, e.g. the subject seeing a person touching the hand of another subject. Record EEG/MEG. 2) Repeat each condition for at least few ...


1

The sensory and motor components are required (GP and vagus respectively). Similar to the corneal reflex and cranial nerve 5 and 7, if a lesion exists in either the sensory or motor component there will be a defect. In your case, there is no motor innervation on the left due to the lack of the vagus nerve so there is no vagus nerve response.


1

Consciousness is a difficult term to grasp in a short answer, and the question is as interesting as it is challenging. The reticular formation as mentioned by others before me is crucial, as the thalamus is the gateway of information to and from the brain. Therefore, subcortical structures such as the thalamus, when 'shut down', induce unconsciousness. ...



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