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There is a very different mechanism for generation (and detection) of ultraviolet, visible and infrared light vs radio waves. For the first, it is possible to generate it using chemical reactions (that is, chemiluminescence, bioluminescence) with a typical energy of order of 2 eV (electronovolts). Also, it is easy to detect with similar means - coupling to ...


20

Short Answer Myelination acts as an electrical insulator and allows saltatory propagation. By reducing membrane capacitance and increasing membrane resistance, myelination increases the velocity of signal (i.e., Action Potential) propagation. If you want to see a really wonderfully simplified explanation, see this Quora post by Edward Claro Mader. Four ...


17

There are two factors that need to be taken into account here: 1. Myelination decreases membrance capacitance. The rate at which sodium influx through a node can depolarize the axon at the next node is related to both the current and capacitance across the membrane (in addition to a few other factors). So while adding a new node to the axon would indeed ...


13

Fast-Fourier Transform (FFT) transforms a signal from the time domain into the frequency domain. Basically, any time-dependent signal can be broken down in a collection of sinusoids. In this way, lengthy and noisy EEG recordings can be conveniently plotted in a frequency power-spectrum. By doing so, hidden features can become apparent. By adding all the ...


12

While Luke's answer is perfectly correct, the answer can be given in a more intuitive manner. First, the main point is that it is increased positive voltage (inside the axon) that opens the sodium ion channels to propagate the action potential. The question is: how fast can this voltage get to the sodium channels? In an unmyelinated axon, the movement of ...


10

Because the intermediate stages are not evolutionarily favoured. That's why. Sound and light perception are useful without any generative capability. An organism with a tiny amount of perception for either of these things has an advantage over those without; and an organism with a tiny amount more has an advantage over those with a tiny bit less. This ...


7

The carriers of the charge are ions and they get repelled from each other well enough. Other than their charge there is only the size in which they differ (for all practical purposes). This means, as long as we are talking about membrane potential, the actors are just a mix of 1+ ions which don't come near each other. When size matters, for example in an ion ...


7

Actually, it would be better to say that action potential does not travel but is regenerated anew in a sequence along the axon. I would like to elaborate how this happens and why this is the reason why the action potential stays constant: In rest state, there is an ion gradient across the membrane of each cell. This causes a small voltage between the ...


7

I don't have the math at hand for the actually energy efficiency, but let's just start from the storage capacity. Basically, an electric eel wouldn't make a very good battery. They could be a decent, albeit fairly inefficient capacitor, but they actually store little energy. Using data from Wikipedia on Electric Eels it works out to something less than 2 ...


6

The pacemaker potential is interesting (to a biologist) as it involves your typical Na/K channels, Ca channel, as well as a funny current (If) or alternatively called hyperpolarization-activated current. The funny current is a mixed sodium-potassium current that activates upon hyperpolarization at voltages in the diastolic range (normally from -60/-70 ...


6

I'll give it a layman's attempt in sort of an "ELI5" approach. I hope the analogy isn't too simplistic, and please don't take it too literally. How do plants use K+? Plants control K+ concentrations and do work within the plant by pumping K+ between different compartments. Because water tends to follow solute concentrations (osmosis), plants can do things ...


5

Actually, electromagnetic communication is used by certain fish, the mormyrids and the gymnotids. Pulse modulated in the former and amplitude modulated in the latter. However, the frequencies used are not much greater than 1Khz, which is not what we ordinarily consider to be in the radio frequency spectrum. There is, too, another biological species in ...


5

I don't want to comment about the nature of electric signals in neurons (as I know only little about physiology and neurophysiology). But here is a short answer that may already help you. Neuronal electric signals are called action potential. If you register the voltage at a given location on the axon of a neuron through time you will see something like ...


5

I was able to do some reading and research and I found some interesting information that was a). news to me. And b). the answer is yes... And no. A spasm can be the cause of a heart attack by causing the coronary artery to contract. When that artery contracts, it causes a dramatic decrease in blood flow to the heart. When the heart looses access to ...


5

Short answer The distinction between Gram positive (Gram+) and negative bacteria (Gram-) has absolutely nothing to do with membrane potentials; it is all about the Gram staining procedure. Background The Gram staining was named after the Danish bacteriologist Hans Christian Gram, who originally devised it in 1882 (Gram, 1884). Gram staining is a common ...


5

First bump is called P point, middle is QRS wave (as in Q-down, R-up, S-down), and last bump is T. Every feature is representation of electrical activity in certain region of heart. E.g. P bump is contraction of atrium. See more here. Bumps are P/QRS/T. The reason why you see so many different recordings is that it was taken with many-lead ECG. Heart has ...


5

Representative ion concentrations are shown in Fig. 1: The membrane is mainly permeable to K+. Because the Na+,K+-ATPase pumps K+ inside of the cell, it tends to diffuse outward again, thereby taking positive charge outside the cell and making it negative inside (extracellular space is pretty much devoid of charge due to its vastness). Because the membrane ...


5

Short answer Any electrophysiological recording of potentials, including the electrocardiogram (ECG or EKG), measures a potential difference. Hence, two or more electrodes are necessary. Background The ECG measures the rhythmic voltages changes generated by the heart muscle. Voltage is defined as a potential difference between two points. Therefore, a ...


5

The Na,K-ATPase restores negative membrane potentials. When a cell is hyperpolarized, leaky K+ channels take care of that. Leaky K+ channels are always open. Generally, K+ has the tendency to diffuse back out of the cell along its chemical gradient through leaky K+ channels, after been pumped in, making the cell's inside more negative. However, in the ...


5

One can imagine that each action potential causes a small amount of $\ce{Na+}$ goes inside the cell, and a small amount $\ce{K+}$ goes outside the cell, thus weakening the electrochemical gradient of both ions. If each action potential has (approximately) the same flux of $\ce{Na+}$ and $\ce{K+}$ then higher frequency of action potentials means more flux, ...


5

Photoreceptors themselves dont act as oscilators, a single receptor is either 'on' or 'off' - it does not respond differently to different wavelenghts. Humans have Trichromatic vision, which means that we have 3 different kinds of photo-receptors that respond differently to light of a given wavelength at a given intensity. By combining multiple signals from ...


5

No, the human body cannot utilize externally applied electricity. Applying electricity to the body will either have no effect, if the amount is small, or will disrupt normal functions of the body or cause injury if the amount is larger. An overview of the effects of electricity (for doctors) can be found in "Conduction of Electrical Current to and Through ...


5

Gamma band oscillations (GBO) (Wikipedia) (NCBI) are 30-90 Hz electrical waves generated by the brain and are thought to possibly be associated with cognition and consciousness (Panagiotaropoulos, 2012). Some evidence for this putative relationship can be seen with experiments such as pre-pulse inhibition (PPI), which can describe how our sensations are ...


5

Neural info is contained in spike trains, mainly in terms of spike frequency and related parameters. These spike trains in individual neurons can be measured by techniques like patch clamp and Ca2+ imaging. These techniques are all pretty sophisticated and computer assisted for sure. However, by recording of action potentials in e.g. the optic nerve, we ...


5

To the best of my knowledge, the potential difference across the hair cells in the inner ear (cochlea) (Fig. 1) is the highest in the (human) body. It is about 120 mV, mainly due to the exceptionally high positive potential of the scala media as provided by the stria vascularis, referred to as the endocochlear potential. This potential is mainly built up by ...


4

I just found a research about possibility of organism with loop DNA (Mostly bacteria) could use there DNA as antenna to transmit and receive radio wave around 1kHz http://www.wired.com/2011/04/bacterial-radio/ But as other said. Communication mostly evolve from sensory organ. So the radio wave has too much noise and could not give useful information about ...


4

Electroencephalography has a good time resolution (milliseconds) but poor spatial resolution (several centimers). The usual estimated figure is that at least 50000 neurons need to fire simultaneously so that the activity can picked up by EEG. The answer provided by @Jeremy Kemball is not very accurate. The reason why the spatial resolution of EEG is poor is ...


4

Essentially all animal cells maintain an ionic balance causing a resting potential of about -70 mV in order to maintain their internal environment including pH, ion concentrations, osmotic pressure and volume. (Lodish, Molecular Cell Biology) Neurons developed from existing types of cells and it's unlikely that the cost of maintaining resting potential in ...


4

Very nice question! I'll go through your three questions sequentially. Q1: Why does lower capacitance increase "the effectiveness of nearby nodes" or allow the depolarizing voltage to "travel not by ion diffusion, but as an electric field"? A: Capacitance basically results in sequestering of charge of opposite polarities along the cell membrane, which ...


4

Good question. Just to set some stuff straight: In contrast to a comment placed earlier, there is definitely a current flow between electrodes in neural tissue, as long as the impedance is not too high. The potential difference between the electrodes and impedance determines how much current flows, basically following Ohm's law: I = U/R. As to your ...


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