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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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Interesting question. I will dissect your question into its assumptions before giving my view on the overall question. 1) ..that nerves became larger.. : Why should there be a general tendency for nerves to increase in size during the course of evolution when there is no need to? 2) ...that nerves became more myelinated...: A general tendency towards ...


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First the boring (but most important part) looking at the study: It is important to critique the study design FIRST to see what kind of information we can actually obtain from this study. This is a meta-analysis of cross-sectional studies (meaning there is no record of change over time) that include a variety of age ranges of ADHD patients (some on ...


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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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It is part of the CNS and does not secrete hormones into the bloodstream. Instead, it delivers input to the pituitary gland, which is an endocrine organ and secretes hormones into the bloodstream. Please refer to http://en.m.wikipedia.org/wiki/Hypothalamus and specifically the section "Neural Connections". Otherwise, any basic neuroscience or endocrinology ...


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As far as I am aware, it is specifically the class of specific serotonin reuptake inhibitors (SSRIs) that have delayed action (say, 2 weeks). This is because they stimulate 5HT1A receptors in the dendritic region that changes the firing pattern of the serotonergic neuron into a more fluttering mode over time, so that it releases more serotonin (5HT) Lucas et ...


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What you are talking about called synaptic plasticity, and sure it is possible to weaken connection between neurons, that's why for instance you can forget things. In neuroscience, synaptic plasticity is the ability of synapses to strengthen or weaken over time, in response to increases or decreases in their activity.1 Plastic change also results ...


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The connection is one way, the input comes in the dendrites, while the output goes on the single axon in the neuron. Figure 1 - wikipedia - neuron The axon of the presynaptic neuron can connect e.g. to the dendrite of a postsynaptic neuron, and so they can form synapses in which they use neurotransmitters to transmit the signal. Figure 2 - synapse ...


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Single synapses can undergo long term potentiation (LTP) or long term depression (LTD). As a typical example you can look up the process in hippocampal neurons. Basically, NMDA receptors strengthen the synapse when multiple incoming axons potentiate each other's responses (synchronous input). In contrast, uncorrelated inputs weaken the synapse.


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Neural axonal connections are physiologically one-way, in that an action potential would never back propagate. Since the signal is physiologically initiated near the cell body (dendritic input region) the normal flow of information therefore is dendritic-to-axonal. However, when axons are electrically activated (through neural implants such as auditory or ...


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I totally agree with Rumtscho. Kandel's Principles of Neural Science is excellent. Eric Kandel is a Nobel Laureate and one of the gurus in the field. As to the biology of neurons I can refer you to: Part II: Cell and Molecular Biology of the Neuron, and Part III: Elementary interactions Between Neurons: Synaptic Transmission. These sections cover the ...


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They are two different mechanisms. Opium is arguably one of the oldest herbal medicines, being used as analgesic, sedative and antidiarrheal drug for thousands of years. These effects mirror the actions of the endogenous opioid system and are mediated by the principal μ-, κ- and δ-opioid receptors. In the gut, met-enkephalin, leu-enkephalin, β-endorphin ...


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I can highly recommend Kandell's "Principles of neural science". I have not had any biology courses since highschool, but I was able to understand it well. It is really a book meant to teach. The style is beginner friendly, and not tedious/boring at all. It is an expensive buy and a very long read (I think the paper version is close to 2000 pages), but ...


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CNS refers to the brain and spinal cord. Its a very general term. Hypothalamus is part of the CNS structure but its unique in a sense that it secretes many chemicals into the bloodstream like glands hence part of the endocrine system! so they are both correct!


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Withdrawal reflex You asked specifically about the withdrawal reflex and the receptors that trigger this. The initiation of the reflex arc is determined at the level of the nociceptors (pain-transducing receptors) in the epidermis. For the most part, these are part of “free” (not encapsulated) nerve endings of sensory fibers. These fibers course within ...


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Well, to answer your question, both your hypothesis are true, at least partially true. The brain has several known specialized connections called neural pathways that connect specific areas of the brain and are responsible for determined functions. For instance, when you move your leg, the stimulus starts at the motor cortex and travels through the ...


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No. For instance, Broca's area exists only in the frontal lobe of one hemisphere, usually the left. (it's responsible for speech, btw)


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Normally, after an excitatory neuron fires it becomes more resistant to firing for a period of time (refractory period). This is due to electrical changes within the excitatory neuron. After depolarazing and reaching an action potential(firing) the neuron enters the refractory period, in which its charge will go back to normal (resting potential).This ...


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neural connections can be weaken below their original connection strength. from neuroscience, new memories mean new neural connections, and the new neural connections require repeated activation. neurons that fire together, wire together, so it neurons or groups of neurons donot fire together often enough, new connections do not form. i am not sure the ...


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Asymmetry to essential to neuronal function, particularly in the peripheral nervous system. This is because the dendrites of a neuron receive synaptic potentials, which are graded and decay with distance. Dendrites are typically short such that a synaptic potential is still above threshold by the time it reaches the axon hillock (sometimes called trigger ...


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When you say multiple simultaneous action potentials I assume that the stimuli for all of them are temporally overlapping. In such case a neuron can integrate the different stimuli and launch an action potential. Of the multiple stimuli some can be excitatory while others can be inhibitory. The net response would be an integration of all the signals [ref]. ...


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Yes, but there is an upper bound to the maximum amount of energy per axon. There is no empirical evidence of this. Just research topics about which I am not happy because their approaches to prove the thing are not enough. There is no sufficient imaging technology there openly which could be used to do some of the research.


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As you say, a neuron can have thousands of inputs via its thousands of dendrites. Each of those dendrites can have a synaptic connection to the (axonic) output of a different neuron. So the neuron can take inputs from thousands of different neurons, not just from one other neuron. At the other end of the neuron, the output of the axon can form synaptic ...


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First of all, let me clear up a small confusion: a connective tissue is a histological term and isn't relevant to this question :) Check https://en.wikipedia.org/wiki/Connective_tissue on that That already suggests that the depiction you describe isn't accurate. I would hope that you have seen something like this, which shows a neuron's structure in a very ...


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Are neural connections one-way? Yes. Action potentials travel only from dendrites towards axon. typically shown in pictures as an electric pulse traveling along a long, thin connective tissue. What connective tissue? That thin "wire" which carries the action potential is a part of the neural cell body called axon. Depending on what the axon ...


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The sensory and motor pathways can indeed be considered separately both in concept and physically. Of course the nervous systems is a single network of neurons, but that doesn't stop it from having separate components. One can indeed often simplify neural pathways as "IN (sensory) ===> (black box with decision-making magic) ===> OUT (motor)" Reflexes ...


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Check out Van Der Pol (chaotic) oscillator. It can be used to model heart rhythms. If a stimulus is applied to the oscillator, it will return to the curved envelope discussed in the article. However, if "pushed just right", the oscillator's current state will be pushed towards the very center of the loop, and it will stop oscillating. This is the mechanism ...


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There is no such thing as voltage gated or ligand gated NEURONS. I believe what you are refering to are what is known as voltage gated and ligand gated ion CHANNELS. Each neuron has both types of channels in their cell membrane. Voltage gated ion channels open in response to voltage (i.e. when the cell gets depolarized) where as ligand gated channels open ...


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Neurons do not divide due to the reasons mentioned in Cornelius's answer. However, some new neurons can be generated in adults (Ref: Neuroscience, 2nd edition). Generation of new neurons in adults was first demonstrated in birds, where labeled DNA precursors could be found in differentiated neurons. Experiments in mammals and humans demonstrated later that ...


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Morphological point of view Neurons cannot divide because they lack centrioles. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell [1]. Functional point of view New cells in the nervous system wouldn't do any good. The whole nervous system is based on ...


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Speed of transmission is going to vary depending on the neuron fiber subtype. Specifically, the biggest gains will be seen with cross-sectional area (feel free to ask why on physics.stackexchange.com) and neurons with myelin sheathes (fat wrappings which affect saltatory conduction rates). You're specifically asking about Efferent neuron transmission ...


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I and II depend on the type of electrical signal applied to the axon. for III, most receptors can perceive other sense as well, so for example striking a vision receptor may produce the perception of light (even in complete darkness) - my guess is the you would feel pain, even if you could isolate the destructive signal away from nearby pain receptors. ...


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It is generally not a one-way process. The lag also depends on which frequencies you look at (the brain and limbs kind of speak using several channels at the same time). Near 10 Hz the lag is few dozen milliseconds. Look for articles about EMG and EEG (or MEG) coupling for more precise info. Use the paper ...


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The nerves for sensation do travel intimately close to motor nerves outsides the spinal cord. In these locations only disease processes can preferentially target a particular class of nerves. Diabetic neuropathy is a common condition causing this kind of peripheral nerve injury resulting in sensory loss. In the spinal cord, afferent (incoming) and efferent ...


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Even if it were possible to selectively destroy sensory (afferent) nerves alone, the individual would not be able to walk/move normally immediately afterwards, because there would be no environmental stimuli with which to orient one's actions. Two of the senses people often overlook are balance (or spatial orientation) and proprioception (where the body ...



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