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Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal, about 1905

Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. Nevertheless, it is currently an interdisciplinary science that involves other disciplines such as psychology, computer science, statistics, physics, philosophy, and medicine. As a result, the scope of neuroscience has broadened to include different approaches used to study the molecular, developmental, structural, functional, evolutionary, computational, and medical aspects of the nervous system. The techniques used by neuroscientists have also expanded enormously, from biophysical and molecular studies of individual nerve cells to imaging of perceptual and motor tasks in the brain. Recent theoretical advances in neuroscience have also been aided by the use of computational modeling of neural networks. The term neurobiology is usually used interchangeably with the term neuroscience, although the former refers specifically to the biology of the nervous system, whereas the latter refers to the entire science of the nervous system.

Given the ever-increasing number of neuroscientists that study the nervous system, several prominent neuroscience organizations have been formed to provide a forum to all neuroscientists and educators. For example, the International Brain Research Organization was founded in 1960,[1] the European Brain and Behaviour Society in 1968,[2] and the Society for Neuroscience in 1969.[3]

Contents

History

The study of the nervous system dates back to ancient Egypt. Evidence of trepanation, the surgical practice of either drilling or scraping a hole into the skull with the aim of curing headaches or mental disorders or relieving cranial pressure, being performed on patients dates back to Neolithic times and has been found in various cultures throughout the world. Manuscripts dating back to 1700BC[4] indicated that the Egyptians had some knowledge about symptoms of brain damage.

Early views on the function of the brain regarded it to be a "cranial stuffing" of sorts. In Egypt, from the late Middle Kingdom onwards, the brain was regularly removed in preparation for mummification. It was believed at the time that the heart was the seat of intelligence. According to Herodotus, during the first step of mummification: "The most perfect practice is to extract as much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with drugs".[citation needed]

The view that the heart was the source of consciousness was not challenged until the time of Hippocrates. He believed that the brain was not only involved with sensation, since most specialized organs (e.g., eyes, ears, tongue) are located in the head near the brain, but was also the seat of intelligence. Aristotle, however, believed that the heart was the center of intelligence and that the brain served to cool the blood. This view was generally accepted until the Roman physician Galen, a follower of Hippocrates and physician to Roman gladiators, observed that his patients lost their mental faculties when they had sustained damage to their brains.

In al-Andalus, Abulcasis, the father of modern surgery, developed material and technical designs which are still used in neurosurgery. Averroes suggested the existence of Parkinson's disease and attributed photoreceptor properties to the retina. Avenzoar described meningitis, intracranial thrombophlebitis, mediastinal tumours and made contributions to modern neuropharmacology. Maimonides wrote about neuropsychiatric disorders and described rabies and belladonna intoxication.[5] Elsewhere in medieval Europe, Vesalius (1514-1564) and René Descartes (1596-1650) also made several contributions to neuroscience.

Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s that used a silver chromate salt to reveal the intricate structures of single neurons. His technique was used by Santiago Ramón y Cajal and led to the formation of the neuron doctrine, the hypothesis that the functional unit of the brain is the neuron. Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in 1906 for their extensive observations, descriptions and categorizations of neurons throughout the brain. The hypotheses of the neuron doctrine were supported by experiments following Galvani's pioneering work in the electrical excitability of muscles and neurons. In the late 19th century, DuBois-Reymond, Müller, and von Helmholtz showed neurons were electrically excitable and that their activity predictably affected the electrical state of adjacent neurons.

In parallel with this research, work with brain-damaged patients by Paul Broca suggested that certain regions of the brain were responsible for certain functions. At the time Broca's findings were seen as a confirmation of Franz Joseph Gall's theory that language was localized and certain psychological functions were localized in the cerebral cortex.[6][7] The localization of function hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly deduced the organization of motor cortex by watching the progression of seizures through the body. Wernicke further developed the theory of the specialization of specific brain structures in language comprehension and production. Modern research still uses the Brodmann cytoarchitectonic (referring to study of cell structure) anatomical definitions from this era in continuing to show that distinct areas of the cortex are activated in the execution of specific tasks.[8]

Foundations of modern neuroscience

The scientific study of the nervous systems underwent a significant increase in the second half of the twentieth century, principally due to revolutions in molecular biology, electrophysiology, and computational neuroscience. It has become possible to understand, in much detail, the complex processes occurring within a single neuron. However, how networks of neurons produce intellectual behavior, cognition, emotion, and physiological responses is still poorly understood.

The task of neural science is to explain behavior in terms of the activities of the brain. How does the brain marshal its millions of individual nerve cells to produce behavior, and how are these cells influenced by the environment...? The last frontier of the biological sciences – their ultimate challenge – is to understand the biological basis of consciousness and the mental processes by which we perceive, act, learn, and remember. — Eric Kandel, Principles of Neural Science, fourth edition
Stained neuron

The nervous system is composed of a network of neurons and other supportive cells (such as glial cells). Neurons form functional circuits, each responsible for specific tasks to the behaviors at the organism level. Thus, neuroscience can be studied at many different levels, ranging from molecular level to cellular level to systems level to cognitive level.

At the molecular level, the basic questions addressed in molecular neuroscience include the mechanisms by which neurons express and respond to molecular signals and how axons form complex connectivity patterns. At this level, tools from molecular biology and genetics are used to understand how neurons develop and die, and how genetic changes affect biological functions. The morphology, molecular identity and physiological characteristics of neurons and how they relate to different types of behavior are also of considerable interest. (The ways in which neurons and their connections are modified by experience are addressed at the physiological and cognitive levels.)

At the cellular level, the fundamental questions addressed in cellular neuroscience are the mechanisms of how neurons process signals physiologically and electrochemically. They address how signals are processed by the dendrites, somas and axons, and how neurotransmitters and electrical signals are used to process signals in a neuron. Another major area of neuroscience is directed at investigations of the development of the nervous system. These questions of neural development include the patterning and regionalization of the nervous system, neural stem cells, differentiation of neurons and glia, neuronal migration, axonal and dendritic development, trophic interactions, and synapse formation.

At the systems level, the questions addressed in systems neuroscience include how the circuits are formed and used anatomically and physiologically to produce the physiological functions, such as reflexes, sensory integration, motor coordination, circadian rhythms, emotional responses, learning and memory. In other words, they address how these neural circuits function and the mechanisms through which behaviors are generated. For example, systems level analysis addresses questions concerning specific sensory and motor modalities: how does vision work? How do songbirds learn new songs and bats localize with ultrasound? How does the somatosensory system process tactile information? The related field of neuroethology, in particular, addresses the complex question of how neural substrates underlies specific animal behavior.

Para-sagittal MRI of the head in a patient with benign familial macrocephaly

At the cognitive level, cognitive neuroscience addresses the questions of how psychological/cognitive functions are produced by the neural circuitry. The emergence of powerful new measurement techniques such as neuroimaging (e. g., fMRI, PET, SPECT), electrophysiology and human genetic analysis combined with sophisticated experimental techniques from cognitive psychology allows neuroscientists and psychologists to address abstract questions such as how human cognition and emotion are mapped to specific neural circuitries.

Neuroscience is also allied with the social and behavioral sciences, and burgeoning interdisciplinary fields such as neuroeconomics, decision theory, social neuroscience are addressing complex questions on the interactions of the brain with its environment.

Neuroscience and medicine

Neurology, psychiatry, and neuropathology are medical specialties that specifically address the diseases of the nervous system. These terms also refer to clinical disciplines involving diagnosis and treatment of these diseases. Neurology deals with diseases of the central and peripheral nervous systems such as amyotrophic lateral sclerosis (ALS) and stroke, while psychiatry focuses on behavioural, cognitive, and emotional disorders. Neuropathology focuses upon the classification and underlying pathogenic mechanisms of central and peripheral nervous system and muscle diseases, with an emphasis on morphologic, microscopic and chemically observable alterations. The boundaries between these specialties have been blurring recently, and they are all influenced by basic research in neuroscience.

Integrative neuroscience makes connections across these specialized areas of focus.

Major branches

Current neuroscience education and research activities can be very roughly categorized into the following major branches, based on the subject and scale of the system in examination as well as distinct experimental or curricular approaches. Individual neuroscientists, however, often work on questions that span several distinct subfields.

Branch Major topics Experimental and theoretical methods
Molecular and Cellular neuroscience neurocytology, glia, protein trafficking, ion channel, synapse, action potential, neurotransmitters, neuroimmunology PCR, immunohistochemistry, patch clamp, voltage clamp, molecular cloning, gene knockout, biochemical assays, linkage analysis, fluorescent in situ hybridization, Southern blots, DNA microarray, green fluorescent protein, calcium imaging, two-photon microscopy, HPLC, microdialysis
Behavioral neuroscience behavioral genetics, biological psychology, circadian rhythms, neuroendocrinology, neuroethology, hypothalamic-pituitary-gonadal axis, hypothalamic-pituitary-adrenal axis, neurotransmitters, homeostasis, dimorphic sexual-behavior, motor control, sensory processing, photo reception, organizational/activational effects of hormones, drug/alcohol effects animal models (gene knockout), in situ hybridization, golgi stain, fMRI, immunohistochemistry, functional genomics, PET, pattern recognition, EEG, MEG
Systems neuroscience primary visual cortex, somatosensory system, perception, audition, sensory integration, population coding, Pain and nociception, spontaneous and evoked activity, color vision, olfaction, taste, motor system, spinal cord, sleep, homeostasis, arousal, attention single-unit recording, intrinsic signal imaging, microstimulation, voltage sensitive dyes, fMRI, patch clamp, genomics, training awake behaving animals, local field potential, ROC, cortical cooling, calcium imaging, two-photon microscopy
Developmental neuroscience cell proliferation, neurogenesis, axon guidance, dendrite development, neuronal migration, growth factors, neuromuscular junction, neurotrophins, apoptosis, synaptogenesis Xenopus oocyte, protein chemistry, genomics, Drosophila, Hox gene
Cognitive neuroscience attention, cognitive control, behavioral genetics, decision making, emotion, language, memory, motivation, motor learning, perception, sexual behavior, social neuroscience experimental designs from cognitive psychology, psychometrics, EEG, MEG, fMRI, PET, SPECT, single-unit recording, human genetics
Theoretical and computational neuroscience cable theory, Hodgkin–Huxley model, neural networks, Voltage-gated ion channels, Hebbian learning Markov chain Monte Carlo, simulated annealing, high performance computing, partial differential equations, self-organizing nets, pattern recognition, swarm intelligence
Diseases and aging: Neurology and Psychiatry dementia, Parkinson's disease, stroke, peripheral neuropathy, spinal cord injury, traumatic brain injury, autonomic nervous system, schizophrenia, psychosis, depression, bipolar disorder, anxiety, obsessive-compulsive disorder, eating disorders, addiction, memory loss, sleep disorders clinical trials, neuropharmacology, deep brain stimulation, neurosurgery
Neural engineering Neuroprosthetic, Brain-computer interface (BCI) Signal acquisition through EEG, ECoG, MEG, fMRI, Near infrared spectroscopy, EMG; signal processing through pattern recognition algorithms
Neurolinguistics language, Broca's area, language acquisition, speech perception, sentence processing theoretical models from psycholinguistics, cognitive science, and computer science;
experimental methods include EEG and ERP, MEG, fMRI, PET, transcranial magnetic stimulation, aphasiology, direct cortical stimulation
Neuroscience studies Neuroscience education: undergraduate models, best practices, interface of neuroscience with all liberal arts disciplines, neuroscience and society, philosophy of neuroscience, interdisciplinary research, neuroscience and popular culture, neuroscience and the media
Neuroimaging structural imaging, functional imaging Computed tomography, diffuse optical imaging, event-related optical signal, magnetic resonance imaging, functional magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography

Note: In 1990s, neuroscientist Jaak Panksepp coined the term "affective neuroscience"[9] to emphasize that emotion research should be a branch of neurosciences, distinguishable from the nearby fields like cognitive neuroscience or behavioral neuroscience. More recently, the social aspect of the emotional brain has been integrated in what is called "social-affective neuroscience" or simply social neuroscience.

There has also been some research published arguing that some aspects of fair play and the Golden Rule may be stated and rooted in terms of neuroscientific and neuroethical principles.[10]

Public education and outreach

In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of knowledge and awareness about the nervous system among the general public and government officials. Such promotion has been by individual neuroscientists to large organizations. For example, individual neuroscientists have promoted neuroscience education among young students by organizing the International Brain Bee (IBB), which is an academic competition for high school or secondary school students worldwide.[11] Large organizations such as the Society for Neuroscience in the United States have promoted neuroscience education by developing a primer called Brain Facts,[12] collaborating with members of public education to develop Neuroscience Core Concepts for K-12 teachers and students,[13] and cosponsoring a campaign called Brain Awareness Week with the Dana Foundation to increase public awareness about the progress and benefits of brain research.[14]

In addition to promoting public awareness, neuroscientists have also collaborated with other education experts to study and refine educational techniques to optimize learning among students.[15] Federal Agencies in the United States such as the National Institute of Health (NIH) and National Science Foundation (NSF) have also funded research that pertain to best practices in teaching and learning of neuroscience concepts.

Future directions

See also

References

  1. ^ "International Brain Research Organization (IBRO)". http://www.ibro.info/Pub/Pub_Front.asp. 
  2. ^ "ABOUT EBBS". http://www.ebbs-science.org/about_ebbs.htm. Retrieved 2009-05-03. 
  3. ^ "Society for Neuroscience: Presidents". http://www.sfn.org/index.cfm?pagename=presidents&section=about_SfN. 
  4. ^ http://www.ibro.info/Pub/Pub_Main_Display.asp?LC_Docs_ID=3199
  5. ^ Martin-Araguz, A.; Bustamante-Martinez, C.; Fernandez-Armayor, Ajo V.; Moreno-Martinez, J. M. (2002). "Neuroscience in al-Andalus and its influence on medieval scholastic medicine", Revista de neurología 34 (9), p. 877-892.
  6. ^ Greenblatt, SH., (1995) "Phrenology in the science and culture of the 19th century, " Neurosurgery 37 790-805.
  7. ^ Bear, M. F.; B. W. Connors, and M. A. Paradiso (2001). Neuroscience: Exploring the Brain. Baltimore: Lippincott. ISBN 0-7817-3944-6.
  8. ^ Principles of Neural Science, 4th ed. Eric R. Kandel, James H. Schwartz, Thomas M. Jessel, eds. McGraw-Hill:New York, NY. 2000.
  9. ^ Panksepp, J., 1990 - A role for “affective neuroscience” in understanding stress: The case of separation distress circuitry. In: Puglisi-Allegra, S. and Oliverio, A., Editors, 1990, Psychobiology of stress, Kluwer, Dordrecht, pp. 41–58.
  10. ^ Pfaff, Donald W., "The Neuroscience of Fair Play: Why We (Usually) Follow the Golden Rule", Dana Press, The Dana Foundation, New York, 2007. ISBN 9781932594270
  11. ^ "The International Brain Bee". http://www.internationalbrainbee.com/index.html. 
  12. ^ "Brain Facts". http://www.sfn.org/index.cfm?pagename=brainfacts. 
  13. ^ "Neuroscience Core Concepts". http://www.sfn.org/index.cfm?pagename=core_concepts. 
  14. ^ "Brain Awareness Week". http://www.dana.org/brainweek/. 
  15. ^ "Goswami U (2004) Neuroscience, education and special education. British Journal of Special Education 31: 175-183". http://www.neuroscience.me/wp-content/uploads/Neuroscience-and-education.pdf. 

Further reading

  • Squire, L. et al. (2003). Fundamental Neuroscience, 2nd edition. Academic Press; ISBN 0-12-660303-0
  • Byrne and Roberts (2004). From Molecules to Networks. Academic Press; ISBN 0-12-148660-5
  • Sanes, Reh, Harris (2005). Development of the Nervous System, 2nd edition. Academic Press; ISBN 0-12-618621-9
  • Siegel et al. (2005). Basic Neurochemistry, 7th edition. Academic Press; ISBN 0-12-088397-X
  • Rieke, F. et al. (1999). Spikes: Exploring the Neural Code. The MIT Press; Reprint edition ISBN 0-262-68108-0
  • section.47 Neuroscience 2nd ed. Dale Purves, George J. Augustine, David Fitzpatrick, Lawrence C. Katz, Anthony-Samuel LaMantia, James O. McNamara, S. Mark Williams. Published by Sinauer Associates, Inc., 2001.
  • section.18 Basic Neurochemistry: Molecular, Cellular, and Medical Aspects 6th ed. by George J. Siegel, Bernard W. Agranoff, R. Wayne Albers, Stephen K. Fisher, Michael D. Uhler, editors. Published by Lippincott, Williams & Wilkins, 1999.
  • Andreasen, Nancy C. (March 4 2004). Brave New Brain: Conquering Mental Illness in the Era of the Genome. Oxford University Press. ISBN 9780195145090. http://www.oup.com/uk/catalogue/?ci=9780195145090. 
  • Damasio, A. R. (1994). Descartes' Error: Emotion, Reason, and the Human Brain. New York, Avon Books. ISBN 0-399-13894-3 (Hardcover) ISBN 0-380-72647-5 (Paperback)
  • Gardner, H. (1976). The Shattered Mind: The Person After Brain Damage. New York, Vintage Books, 1976 ISBN 0-394-71946-8
  • Goldstein, K. (2000). The Organism. New York, Zone Books. ISBN 0-942299-96-5 (Hardcover) ISBN 0-942299-97-3 (Paperback)
  • Llinas R. (2001). I of the Vortex: From Neurons to Self MIT Press. ISBN 0-262-12233-2 (Hardcover) ISBN 0-262-62163-0 (Paperback)
  • Luria, A. R. (1997). The Man with a Shattered World: The History of a Brain Wound. Cambridge, Massachusetts, Harvard University Press. ISBN 0-224-00792-0 (Hardcover) ISBN 0-674-54625-3 (Paperback)
  • Luria, A. R. (1998). The Mind of a Mnemonist: A Little Book About A Vast Memory. New York, Basic Books, Inc. ISBN 0-674-57622-5
  • Medina, J. (2008). Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. Seattle, Pear Press. ISBN 0-979-777704 (Hardcover with DVD)
  • Pinker, S. (1999). How the Mind Works. W. W. Norton & Company. ISBN 0-393-31848-6
  • Pinker, S. (2002). The Blank Slate: The Modern Denial of Human Nature. Viking Adult. ISBN 0-670-03151-8
  • Robinson, D. L. (2009). Brain, Mind and Behaviour: A New Perspective on Human Nature (2nd ed.). Dundalk, Ireland: Pontoon Publications. ISBN 978-0-9561812-0-6. 
  • Ramachandran, V. S. (1998). Phantoms in the Brain. New York, New York Harper Collins. ISBN 0-688-15247-3 (Paperback)
  • Rose, S. (2006). 21st Century Brain: Explaining, Mending & Manipulating the Mind ISBN 0099429772 (Paperback)
  • Sacks, O. The Man Who Mistook His Wife for a Hat. Summit Books ISBN 0-671-55471-9 (Hardcover) ISBN 0-06-097079-0 (Paperback)
  • Sacks, O. (1990). Awakenings. New York, Vintage Books. (See also Oliver Sacks) ISBN 0-671-64834-9 (Hardcover) ISBN 0-06-097368-4 (Paperback)
  • Sternberg, E. (2007) Are You a Machine? The Brain, the Mind and What it Means to be Human. Amherst, NY: Prometheus Books.

External links

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Mind and Brain portal
File:Neuro Neuroscience portal
MRI of the head in a patient with benign familial macrocephaly.]]

Neurobiology is the study of cells of the nervous system and the organization of these cells into functional circuits that process information and mediate behavior.[1] It is a subdiscipline of both biology and neuroscience. Neurobiology differs from neuroscience, a much broader field that is concerned with any scientific study of the nervous system. Neurobiology should also not be confused with other subdisciplines of neuroscience such as computational neuroscience, cognitive neuroscience, behavioral neuroscience, biological psychiatry, neurology, and neuropsychology despite the overlap with these subdisciplines. Scientists that study neurobiology are called neurobiologists.

Contents

Neurons and glial cells

Main articles: neuron, glial cell

Neurons are cells that are specialized to receive, propagate, and transmit electrochemical impulses. In the human brain alone, there are over a hundred billion neurons. Neurons are diverse with respect to morphology and function. Thus, not all neurons correspond to the stereotypical motor neuron with dendrites and myelinated axons that conduct action potentials. Some neurons such as photoreceptors, for example, do not have myelinated axons that conduct action potentials. Other unipolar neurons found in invertebrates do not even have distinguishing processes such as dendrites. Moreover, the distinctions based on function between neurons and other cells such as cardiac and muscle cells are not helpful. Thus, the fundamental difference between a neuron and a nonneuronal cell is a matter of degree.

Another major class of cells found in the nervous system are glial cells. These cells are only recently beginning to receive attention from neurobiologists for being involved not just in nourishment and support of neurons, but also in modulating synapses. For example, Schwann cells, which are a type of glial cell found in the peripheral nervous system, modulate synaptic connections between presynaptic terminals of motor neuron endplates and muscle fibers at neuromuscular junctions.

Neuronal function

One prominent characteristic of many neurons is excitability. Neurons generate electrical impulses or changes in voltage of two types: graded potentials and action potentials. Graded potentials occur when the membrane potential depolarizes and hyperpolarizes in a graded fashion relative to the amount of stimulus that is applied to the neuron. An action potential on the other hand is an all-or-none electrical impulse. Despite being slower than graded potentials, action potentials have the advantage of traveling long distances in axons with little or no decrement. Much of the current knowledge of action potentials comes from squid axon experiments by Sir Alan Lloyd Hodgkin and Sir Andrew Huxley.

Action potential

The Hodgkin-Huxley Model of an action potential in the squid giant axon has been the basis for much of the current understanding of the ionic bases of action potentials. Briefly, the model states that the generation of an action potential is determined by two ions: Na+ and K+. An action potential can be divided into several sequential phases: threshold, rising phase, falling phase, undershoot phase, and recovery. Following several local graded depolarizations of the membrane potential, the threshold of excitation is reached, voltage-gated sodium channels are activated, which leads to an influx of Na+ ions. As Na+ ions enter the cell, the membrane potential is further depolarized, and more voltage-gated sodium channels are activated. Such a process is also known as a positive-feedback loop. As the rising phase reaches its peak, voltage-gated Na+ channels are inactivated whereas voltage-gated K+ channels are activated, resulting in a net outward movement of K+ ions, which repolarizes the membrane potential towards the resting membrane potential. Repolarization of the membrane potential continues, resulting in an undershoot phase or absolute refractory period. The undershoot phase occurs because unlike voltage-gated sodium channels, voltage-gated potassium channels inactivate much more slowly. Nevertheless, as more voltage-gated K+ channels become inactivated, the membrane potential recovers to its normal resting steady state.

Structure and formation of synapses

. These cells convert their electrical impulses into bursts of neurochemical relayers, called neurotransmitters, which travel across the synapses to receptors on the dendrites of adjacent cells, thereby triggering further electrical impulses to travel down the latter cells.]]

Neurons communicate with one another via synapses. Synapses are specialized junctions between two cells in close apposition to one another. In a synapse, the neuron that sends the signal is the presynaptic neuron and the target cell receives that signal is the postsynaptic neuron or cell. Synapses can be either electrical or chemical. Electrical synapses are characterized by the formation of gap junctions that allow ions and other organic compound to instantaneously pass from one cell to another.[2] Chemical synapses are characterized by the presynaptic release of neurotransmitters that diffuse across a synaptic cleft to bind with postsynaptic receptors. A neurotransmitter is a chemical messenger that is synthesized within neurons themselves and released by these same neurons to communicate with their postsynaptic target cells. A receptor is a transmembrane protein molecule that a neurotransmitter or drug binds. Chemical synapses are slower than electrical synapses.

Neurotransmitter transporters, receptors, and signaling mechanisms

After neurotransmitters are synthesized, they are packaged and stored in vesicles. These vesicles are pooled together in terminal boutons of the presynaptic neuron. When there is a change in voltage in the terminal bouton, voltage-gated calcium channels embedded in the membranes of these boutons become activated. These allow Ca2+ ions to diffuse through these channels and bind with synaptic vesicles within the terminal buttons. Once bounded with Ca2+, the vesicles dock and fuse with the presynaptic membrane, and release neurotransmitters into the synaptic cleft by a process known as exocytosis. The neurotransmitters then diffuse across the synaptic cleft and binds to postsynaptic receptors embedded on the postsynaptic membrane of another neuron. There are two families of receptors: ionotropic and metabotropic receptors. Ionotropic receptors are a combination of a receptor and an ion channel. When ionotropic receptors are activated, certain ion species such as Na+ to enter the postsynaptic neuron, which depolarizes the postsynaptic membrane. If more of the same type of postsynaptic receptors are activated, then more Na+ will enter the postsynaptic membrane and depolarize cell. Metabotropic receptors on the other hand activate second messenger cascade systems that result in the opening of ion channel located some place else on the same postsynaptic membrane. Although slower than ionotropic receptors that function as on-and-off switches, metabotropic receptors have the advantage of changing the cell's responsiveness to ions and other metabolites, examples being Gamma Amino-Butyric Acid (inhibitory transmitter), Glutamic Acid (excitatory transmitter), Dopamine, Norepinephrine, Epinephrine, Melanin, Serotonin, Melatonin, and Substance P.

Postsynaptic depolarizations can be either excitatory or inhibitory. Those that are excitatory are referred to as excitatory postsynaptic potential (EPSP). Alternatively, some postsynaptic receptors allow Cl- ions to enter the cell or K+ ions to leave the cell, which results in an inhibitory postsynaptic potential (IPSP). If the EPSP is dominant, the threshold of excitation in the postynaptic neuron may be reached, resulting in the generation and propagation of an action potential in the postynaptic neuron.

Synaptic plasticity

Synaptic plasticity is the process whereby strengths of synaptic connections are altered. For example, long-term changes in synaptic connection may result in more postsynaptic receptors being embedded in the postsynaptic membrane, resulting in the strengthening of the synapse. Synaptic plasticity is also found to be the neural mechanism that underlies learning and memory.

Sensory systems

FIG. 722– Scheme showing central connections of the optic nerves and optic tracts.]]

The auditory system is a sensory system for the sense of hearing. It consists of the outer ear, the middle ear, and the inner ear.

The olfactory system is the sensory system used for olfaction. The accessory olfactory system senses pheromones. The olfactory system is often spoken of along with the gustatory system as the chemosensory senses because both transduce chemical signals into perception. Linda B. Buck and Richard Axel won the 2004 Nobel Prize in Physiology or Medicine for their work on the olfactory system.

The visual system is the part of the nervous system which allows organisms to see. It interprets the information from visible light to build a representation of the world surrounding the body. The visual system has the complex task of (re)constructing a three dimensional world from a two dimensional projection of that world. Note that different species are able to see different parts of the light spectrum; for example, some can see into the ultraviolet, while others can see into the infrared.

Neural development

Neural development is the process whereby the nervous system grows and develops. In humans, aside from the primitive gut, the nervous system is the first organ system to develop and the last system to reach maturity. Development of the nervous system begins when the ectoderm thickens to form a neural plate. The neural plate in turns thickens to form the neural tube, which then twists, turns and kinks to form the three primary brain vesicles and five secondary brain vesicles. Within this neural tube totipotent cells migrate and differentiate into neurons and glial cells.

References

  1. Shepard, G. M. (1994). Neurobiology. 3rd Ed. Oxford University Press. ISBN 0-19-508843-3
  2. Martin, A. R., Wallace, B. G., Fuchs, P. A. & Nicholls, J. G. (2001). From Neuron to Brain: A Cellular and Molecular Approach to the Function of the Nervous System. 4th Ed. Sinauer Associates. ISBN 0-87893-439-1

External links


Wikibooks

Up to date as of January 23, 2010
(Redirected to Neuroscience/Cellular Neurobiology article)

From Wikibooks, the open-content textbooks collection

< Neuroscience

Cellular Neurobiology is the study of the brain from a cellular perspective. That is, a study of the properties of cells in the brain, and how cells interact and communicate. The interaction of these cells mediates identifiable functions of different systems in the brain, and the goal of the cellular perspective of neuroscience is to understand these interactions. Specific applications of cellular neuroscience include the mechanisms that produce the symptoms of neurodegenerative diseases such as Parkinson's or Alzheimer's.

Topics

  1. Cells of the Brain
  2. Neuronal Membrane
  3. Action Potentials
  4. Synapses
  5. Neurotransmitters
  6. Nervous System Structure
  7. Somatic Sensory System

Simple English

Neurobiology or Neuroscience is not a biological discipline exactly. It is more an interdisciplinary field. This means that neurobiology is focused on the study of the nervous system, but uses techniques of biochemistry, physiology, cell biology, anatomy, molecular biology and others. Neurobiology looks at the brain and the nerve cells that connect to form the brain. Scientists try to figure out how all of the different parts of the brain interact. They also try to observe how the nerves send messages to the brain, such as when a person feels pain. There are many things neurobiologists study:

-Why we feel pain. -Why we feel emotions and what parts of the brain cause these emotions. -Can new brain cells form? Up until ten years ago, many scientists believed that the human body could not grow new brain cells or nerve cells. Some scientists now believe our brain can grow new cells. This could be useful for someone that has had an accident or sickness and has lost brain cells.


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