Brain Definition and 34 Discussions

A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a vertebrate's body. In a human, the cerebral cortex contains approximately 14–16 billion neurons, and the estimated number of neurons in the cerebellum is 55–70 billion. Each neuron is connected by synapses to several thousand other neurons. These neurons typically communicate with one another by means of long fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
Physiologically, brains exert centralized control over a body's other organs. They act on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain.
The operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. Recent models in modern neuroscience treat the brain as a biological computer, very different in mechanism from an electronic computer, but similar in the sense that it acquires information from the surrounding world, stores it, and processes it in a variety of ways.
This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, that are covered in the human brain article.

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  1. Strato Incendus

    Modern Sci-Fi Books and Their Apparent Obsession with Brain Implants

    Semi-rant incoming: In both of the two science-fiction novels I’ve touched most recently (“Braking Day” by Adam Oyebanji and “The Forever Watch” by David Ramirez), all the characters having a bunch of implants was simply the default. Now I came across a story named K3+ (by Erasmo Acosta) that...
  2. Ygggdrasil

    COVID COVID and the brain

    Here's a nice news piece from Nature summarizing various studies to find the underlying causes behind the neurological symptoms associated with COVID-19. In particular, the article highlights studies suggesting that SARS-CoV-2 can infect astrocytes in the brain, that SARS-CoV-2 can affect blood...
  3. M

    Medical Memory: Do some people have more “space” or just better retrieval?

    I’ve read that the human brain capacity has 2.5 petabytes worth of memory storage. I have an excellent memory for details; even super obscure things that happened decades ago. I only have an average IQ but my recall is very good especially when my memory is jogged or if I had read something...
  4. entropy1

    B Will brain-computer interfaces reveal more about QM?

    Will brain-computer interfaces that are hooked up to quantum measurement devices reveal more about quantum mechanics?
  5. S

    I Do all mental states really exist in some universe in Many-Minds?

    According to the Many Minds interpretation of quantum mechanics (, the distinction between worlds in the Many Worlds interpretation should be made at the level of the mind of an individual observer. I have read that, in this case, each...
  6. O

    I Efficiency of computers vs. brains

    Hi, I’m an undergraduate student interested in cognitive processes. I’m about to ask a very interdisciplinary question, and so hopefully I can find a physicists that can take on the challenge. What is the fundamental reason behind why modern electronic computers (transistor computers) are...
  7. José Ricardo

    I as a whole and not only in itself

    Biologically speaking, why I'm not a cell in my brain, or just heart, I'm me as a whole. How lucky was I to be myself as a whole, not just another cell inside my body?
  8. Anne Ross

    A Quantum electrodynamics and the brain

    Susan Pocket claims that part of the electromagnetic field of the brain is consciousness and that conscious qualities such as a red car are spatially patterned electromagnetic fields. She also claims that the quantum spatial scale is irrelevant. Intuitively it seems to me Quantum electrodynamics...
  9. platosuniverse

    How does the brain recall memories?

    I'm working on a project and I've been doing research about memory recall and I haven't found a lot of info on it. I've found info on how memories are formed. A study talks about how memories form in different parts of the brain and play back like a streaming video...
  10. Cartographers of the Brain: Mapping the Connectome

    Cartographers of the Brain: Mapping the Connectome

    One of the most ambitious programs in all of neuroscience, the Human Connectome Project, has just yielded a “network map” that is shedding light on the intricate connectivity in the brain. Join leading neuroscientists and psychologists as they explore more on the project.
  11. D

    Can brainless animals learn?

    Hi everyone Are brainless animals such as jellyfish and starfish capable of learning (for example by classical conditioning)? I would have thought not, but apparently there are plants that are capable of learning...
  12. M

    Having more than one mother language

    Some people claim that they have two mother languages. This seems to me very strange. Is it reasonable or scientific to have more than one mother language? As far as I know, mother languages and foreign/learnt languages belong to different parts of brain. One of them was a immigrant family...
  13. F

    Examination project of EEG, Opinions and feedback

    Hello! I don't really know how High School ends in other countries but in Sweden it ends with an examination project depending on the programme you've selected. Anyhow we were free to choose one research topic that is related to mathematics, physics, biology and chemistry. I choose the brain...
  14. Auto-Didact

    A Algebraic topology applied to Neuroscience

    Eugene Wigner once famously talked about the "unreasonable effectiveness of mathematics" in describing the natural world. Today again we are seeing this in action in particular with regard to the description of the biological brain from the perspective of neuroscience. Researchers from the Blue...
  15. P

    Can I become a better player by watching others play?

    So I put this question in this category because i think it might be too much on the medical/neurological side than on the general discussion , if i did a mistake sorry The question can be made in another way: do i create links between my neurons in my brain that i can use as i watch pros while...
  16. C

    Consciousness recreation

    If I am my brain and my brain makes me consciouss, then if i die and supposedly someone will make the EXACT copy of me with my brain, then logically the copy should be ME and i should be consciouss again. What do you think?
  17. Steven Ellet

    Audio Brainwaves? The above link explains what brain waves are. There are also visual/auditory equivalent to brain waves (also known as brainwave entrainment), explained below. Is this real...
  18. infactuality

    Schools Need An Idea for a Brain Project....

    Forgive me if this is in the wrong category or if there are any issues, this is my first post. My problem is that I need an idea for a brain project, as you may have noticed from the title. The class is a gifted enrichment course which, this year, is focused primarily on the brain. The gist of...
  19. I

    Are neurons that have been used for years ever re-delegated?

    I'm not sure if this specific question has been already covered. If a person in his 60s who had been say, a painter all his life, decides to instead learn to play an instrument, what happens to the neural processes in his brain? Will the brain use brand-new neurons to create a brand new...
  20. I

    Question about the specific effects of SSRIs

    I know that SSRIs inhibit the reuptake of serotonin from synapses, and therefore cause the receptors on the postsynaptic neuron to be activated for a longer period of time. Does this have any effect on the signal sent? (for example, does it make it so the signal takes longer to process?, etc)
  21. NatanijelVasic

    Binaural Beats Mystery

    Hello everyone, I have been thinking about binaural beats, and after learning about the inner workings of the ear, there is something that I cannot explain. A binaural beat is the pulsating effect perceived by the brain when slightly offset frequencies are played in each ear. In my example...
  22. I

    Schemas and their location(s) in the brain?

    I am trying to wrap my head around the concept of schemas overall. I am sure my picture is far from clear, especially since the schema concept seems to have its own meaning from psychology and I've been sifting through different definitions. My current understanding is that certain neural...
  23. Priyadarshini

    How does synaptic pruning happen?

    Hi, I was wondering how synaptic pruning occurs? I understand the need for pruning, but how do connections in the brain just disappear? Are there molecules or enzymes that break neurone cells down, causing the loss of a connection, or is there some other mechanism? Thanks!
  24. Tareq Naushad

    Medical How does our brain create a summarized/average representation

    When I try to imagine face of some persons like relative,friend, celebrities etc. I can visualize them in my mind. I wonder how do brain decide what to show to me in my mind about that person? I might have seen the person at his/her various ages, various dresses, various places. While...
  25. I

    Are different emotions in different areas of limbic system?

    Does anyone know if there has been any data on whether different emotions fire in different areas of the limbic system. Basically, are there "angry" neurons, and "sad" neurons, or to be more direct, neurons that fire exclusively when one is angry, and different neurons that always fire for when...
  26. Lymsleia

    What's control automate system in our body?

    all of automate system in our body. digesting food, put oxygen on our blood and pull carbon dioxide out, immune system, wound healing...etc does our brain control all that even without our awareness? or those can still work even without brain order? if true... wow, our brain may inferior to...
  27. CMATT

    Which of the following is/are true regarding glucose transport

    Homework Statement Which of the following is/are true regarding glucose transport to the brain? There could be multiple answers. a) Glucose uptake by the nerve cells of the brain is dependent on insulin b) Greater concentrations of glucose in the blood should increase the rate at which glucose...
  28. CMATT

    Choose each of the following statements that would be true regarding the brain

    Homework Statement Choose each of the following statements that would be true regarding the brain or special senses. There could be multiple answers. a) Properly using the captive bolt should result in pupils that constrict in response to a bright light b) The part of the brain that releases...
  29. N

    B If you raise the electron to other higher shell states, can it affect light transmission?

    If you raise the electron to other higher shell states, can light transmission throug -h a SOLID BLACK opaque object. Modified the original question because it was unclear. I won't repeat the same question over, and over, but what I have said in previous questions may get repeated in the...
  30. I

    Different animal sensory, short and long term memories?

    Is there any research that was done on animal long and short term memories? And short of empirical analysis, if there is none, is there much we could conclude, based purely on what we know about their brains? For example, from knowing which brain parts deal with explicit and which with...
  31. Z

    IQ, brain power, and brain endurance

    I was thinking about drawbacks to high IQ, and I thought that maybe the increased glucose consumption from more difficult cognitive tasks could be one of those drawbacks. So a smarter brain could be in a way a "gas guzzler", which could leave you with decreased performance afterwards, which...
  32. 1

    Biophysics brain research

    I am applying to graduate programs and I'm interested in biophysics, but I want to study the brain. I have yet to find a university that has a biophysics research project that is studying the brain/nervous system. Any information on people doing biophysics research concerning the brain would...
  33. Diploria

    Origin/fitness effect of brain coral's grooves?

    Hello, Brain corals, like my avatar's Diploria, get their moniker for visually obvious reasons. I wonder whether there are informed hypotheses how come they look that way. The answer to such a question would probably be partly a morphology/pattern formation story, and partly an adaptive story...
  34. D

    Analyzing Emotion Rigorously

    So... this may not be the right forum... but I figured biology was pretty close. While we have built a very strong correlation between let's say dopamine and happiness (not sure if that's right), I was wondering if anyone knows of research that looks at correlations between matter and emotions...