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8

Short answer The exact mechanism behind tinnitus (ringing in the ear) is unknown. Background Of the two theories you pose here, to the best of my knowledge the second one is the most widely accepted. It is a generally accepted phenomenon that whenever neural systems are being deprived of input, they start seeking new input, or even generate it ...


7

Short answer Color vision is mediated by spike rate modulation (frequency modulation if you like), as well as ganglion-cell specific stimulation. Background Ganglion cells exist that transmit opponent colors. The color opponency model predicts that we cannot perceive a greenish-red or yellowish blue, which is quite right. We can, however, see ...


6

If firing rate is from 1 Hz to 200 Hz, 100 trillion to 20 quadrillion synaptic firings. Neuronal (say, measured from soma) firings will add up to 86 billion to 17.2 trillion action potentials per second. It important to remember, that synaptic firings "sum up" in soma or interfere between each other, so the are more of those. Read more: ...


4

Short answer(s) Someone with a damaged larynx may still speak with the use of a speech aid (electronic larynx). The ability to understand speech does not necessarily mean one can speak normally. There are neurological disorders where folks can understand speech, but have difficulty producing it. Background A full removal of the larynx (laryngectomy) ...


3

Short answer Slowly adapting mechanoreceptors in the skin mediate the perception of static pressure stimuli, while rapidly adapting skin receptors mediate swiftly changing (e.g., vibratory) stimuli. Background There are various skin receptors. Hairy skin, such as that encountered on the arm, contains at least four specialized mechanoreceptors, namely ...


3

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 ...


3

You can whisper without a larynx. "Patients who have undergone partial or full laryngectomy are typically unable to speak anything more than hoarse whispers, without the aid of prostheses or specialized speaking techniques." (source) So the remainder of the vocal tract is capable of enough modulation to present typical human speech in many languages. I ...


2

Nice question(s). I will go through them in sequence. Safe current limits. With regard to electrical stimuli it is current density that determines safety limits. Therefore, in medical devices, it is not a matter of what is a safe maximum current level, but what is the maximum safe current level given the surface of the electrode? And in terms of skin ...


2

Sleeping is a biological stage which we presume as a relaxation period but its really a highly functional stage for brain. Most of the memory related processing such as management of working memory and cognitive functions such as decision making, reasoning, and episodic memory are closely related with sleep. Dolphins never sleep in the sense that we do, ...


2

Speech is generated by generating a frequency spectrum with the vocal folds, and then filtering it with the upper vocal tract. Whistling is done by blowing air over shaped tongue and lips. So, give someone a laryngectomy. They still retain the upper vocal tract (and so can still whistle), but they cannot generate the source vibrations to speak. Do it as ...


2

At the molecular level this is called receptor desensitization. This is the reason why for example spices (like red hot chili paper) taste more pungent the first time you put them in your mouth and less and less subsequent times (in this case the receptor is called TRPV1). Mechanosensory perception is mediated, at least in part, by similar transient ...


2

I was doing some more research and stumbled upon this paper here by Dr. Izhikevich that describe neurons as a system that can exhibit resonance. The author built a model that he calls the resonate and fire, which is a linear piece-wise model of a neuron. The interesting thing, and why I bring it up, is it can respond to a "two inhibitory pulses, that if ...


1

Short answer Action potentials are always generated after a depolarization step. Background Action potentials are generated by prior depolarization of a neuron, typically by the action of an excitatory neurotransmitter. An action potential is per definition a sharp depolarization, followed by a somewhat slower re-polarization step. The most important step ...


1

I think my mistake was to believe that the electric field has to be somewhat perpendicular to the membrane, so that it can directly apply a voltage difference across the membrane, and that the resistance inside and outside the axon was the same, so that a tangential field was useless. In fact these are false : depolarization and action potential creation ...



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