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19

Devices that bypass the hair cells in the inner ear and directly stimulate the auditory nerve are called cochlear implants. Cochlear implants are used to treat deafness caused by the loss of hair cells in the cochlea. The hair cells are the sensory cells that convert sound vibrations into electric neural signals (Purves et al., 2001). With state-of-the-art ...


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As @AliceD mentioned, cochlear implant is one of the earliest achievements of neural engineering. However, there are orders of magnitude more inner hair cells (IHC) and even more auditory nerve fibers (AN) in human cochlear than the current cochlear implants offer electrodes. If you are interested in a more detailed model of IHC to AN signal transmission, ...


5

Feelings of pleasure and reward are transient in nature. Similarly, the dopamine release in the reward centers (the limbic structures) is transient, namely in the order of seconds (Rebec et al., 1997). One way to chronically elevate dopamine levels is by administering certain drugs. A notable/notorious example is methamphetamine, which elevates mood and ...


5

Short answer The physiological state of the postsynaptic cell ultimately determines the effect of an incoming action potential. Background An action potential occurring in a chemical synapse is neither inhibitory or excitatory. An action potential is a binary '1', an-all-or-nothing signal without any information, i.e., there is not a -1 or +1 action ...


5

Short answer Neural xenografts can survive and form functional connections in the host. Background Across-species (xenogeneic grafting) grafting of cerebral cortex from a fetal rat to an adult mouse brain and vice versa, have shown that immunocompetent hosts can reject a graft in less than 30 days. Rejection results in destruction of the graft tissue ...


3

I think before discussing "pain", we'd probably have to discuss whether plants actually can "feel". This is also down to how one wants to define this (hence "opinion based"), but I assume most people (?) would equal the lack of a brain/neurons with the lack of the capability to feel. And I presume so do you, as you show by using the tag "neuroscience". ...


3

Graded potentials are initiated by a stimulus that vary in magnitude depending on the strength of the stimulus. (The stronger the stimulus the more gated channels open causing larger depolarisation). Graded potentials occur in dendrites, cell bodies and sensory receptors. Graded potentials dissipate with distance from stimulus. On the other hand, action ...


2

Actually there is a way to determine the initial conditions for this problem. We assume that the gating variables $r$ and $s$ are at a steady state before the membrane potential jump from$u_0$ to $u'$. If we look at the first graph(the steady state relation versus membrane potential) we can see that at the membrane potential $u_0$ that $r(t=0)\approx 0$ ...


2

Since you didn't get the right answer to #6, let's review the basis for this model. The basis of the model is precisely the statement in #6: an individual channel has a defined conductance when it is conducting, and if all of them are conducting then the total conductance is the single-channel conductance times the number of channels (conductances in ...


2

Short answer Neuronal signals neither choose where to go, nor do they carry routing flags of some sort to guide them. Instead, neuronal signals are guided by the hard wiring of the nervous system. Background Neuronal signals (action potentials) basically follow a one-way path. When they encounter a cross roads, action potentials are simply propagated to all ...


2

Short answer Training increases white and gray matter densities in the brain. This may reflect increases in neuronal cell counts especially in the hippocampus. In the cortex, however, such observed changes are probably more reflective of other processes, such as synaptogenesis. Background Gray matter is generally viewed as being the neuronal cell bodies, ...


2

The definition of numbness has been answered by yourself, and I will focus on the second part of the question. In terms of the underlying physiological mechanism behind numbness I think it's good to narrow the question down and focus on local anesthetics, which numb a local area of the body for minor surgical procedures. Cocaine and related compounds have ...


2

Short answer A low dose of LSD has been shown to lead to larger, more regular webs. This obsessive perfection of the web comes with an increased effort and likely an increased required building time. Whether LSD-affected webs are more effective or not has not been assessed as far as I am aware. Personally I think that, if anything, larger webs are more ...


1

Short answer As far as I am aware, neurotoxic effects of chronic excitatory stimulation are not prevented by receptor trafficking. Background I think the question assumes that 1) neural damage related to continuous activation (excitotoxicity) is preventable by 2) the dynamic regulation of receptor numbers on the neuronal membrane. As far as I can see, ...


1

In principle, many neurotransmitter receptors work as ion channels and the actual mechanism of signalling involves allowing the influx/efflux of calcium, potassium, magnesium, etc. A good example of this is the acetylcholine receptor. Presumably, if the cell retained the same number of receptors even in the presence of abundant ligands, the cell would flood ...


1

An Initial clarification of what "loss of sensation" means: The history in the patient with “numbness” is extremely important. First of all, as with most neurologic complaints, you must determine what the patient means by “numbness.” Some patients are describing loss of sensitivity (anesthesia or hypesthesia) or distorted sensations (paresthesia), which ...


1

Short answer An action potential is a binary all-or-nothing event, while a graded potential is an analog signal. Background Action potentials, once initiated, are basically all-or-nothing events. Amplitudes may admittedly be variable, but basically it is the spike rate that is relevant to the neural code (Gerstner et al., 1997). In contrast, graded ...


1

Dendrites Means Trees in Greek; Are the input of the neuron; Receive information from other neurons or the external environment; Transfer information to the cell body and axons; Are numerous, relatively short, and branch extensively in a tree-like fashion May have numerous spines on them to provide a greater surface area for other neurons to synapse on; ...



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