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Encyclopedia > Reptilian brain
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Location of the amygdala in the human brain

Located in the brain's medial temporal lobe, the almond-shaped amygdala (in Latin, corpus amygdaloideum) is believed to play a key role in the emotions. It forms part of the limbic system. In humans and other animals, it is linked to both fear responses and pleasure. Conditions such as anxiety, autism, depression, narcolepsy, post-traumatic stress disorder, and phobias are suspected of being linked to abnormal functioning of the amygdala owing to damage, developmental problems, or neurotransmitter imbalance. In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... Latin - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... In psychology and common terminology, emotion is the language of a persons internal state of being, normally based in or tied to their internal (physical) and external (social) sensory feeling. ... The limbic system is a group of brain structures that are involved in various emotions such as aggression, fear, pleasure and also in the formation of memory. ... Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa ?Myxozoa Superphylum Deuterostomia    Chordata (vertebrates, etc. ... Fear is an unpleasant feeling of perceived risk or danger, real or not. ... This article is about an emotion. ... In psychiatry, autism (called autistic disorder in the DSM) is considered a neurodevelopmental disorder that causes marked problems with social relatedness, communication, interest, and behavior. ... In ordinary conversation, nearly any mood with some element of sadness may be called depressed. However, for depression to be termed clinical depression it must reach criteria which are generally accepted by clinicians; it is more than just a temporary state of sadness. ... Narcolepsy is a neurological condition characterized by severe fatigue, irresistible episodes of sleep and general sleep disorder. ... Posttraumatic stress disorder (PTSD), is a term for the psychological consequences of exposure to or confrontation with stressful experiences, which involve actual or threatened death, serious physical injury or a threat to physical integrity and which the person found highly traumatic. ... The term phobia, which comes from the Ancient Greek word for fear (φόβος, fobos), denotes a number of psychological and physiological conditions that can range from serious disabilities to common fears to minor quirks. ... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a presynaptic and a postsynaptic neuron. ...


The amygdala is actually several separately functioning nuclei that have been grouped together by their anatomical proximity. Key among these nuclei are the basolateral complex, the centromedial nucleus, and the cortical nucleus. The basolateral complex receives input from the sensory systems and is necessary for fear conditioning. The centromedial nucleus is the main output for the basolateral complex and is involved in emotional arousal. It sends outputs to the hypothalamus for activation of the sympathetic nervous system, the reticular nucleus for increased reflexes, the trigeminal nerve and facial nerve for facial expressions of fear, and the ventral tegmental area, locus ceruleus, and laterodorsal tegmental nucleus for activation of dopamine, norepinephrine and epinephrine. The cortical nucleus is involved in olfaction and pheremone processing. It receives input from the olfactory bulb and olfactory cortex. In neuroanatomy, a nucleus is a central nervous system structure that is composed mainly of gray matter, and which acts as a hub or transit point for electrical signals in a single neural subsystem. ... (See also sense) A sensory system is a part of the nervous system that consists of sensory receptors, neural pathways, and those parts of the brain responsible for processing the information. ... Fear conditioning is a form of learning in which fear is associated with a particular neutral context (e. ... In the anatomy of mammals, the hypothalamus is a region of the brain located below the thalamus, forming the major portion of the ventral region of the diencephalon and functioning to regulate certain metabolic processes and other autonomic activities. ... The sympathetic nervous system (SNS) is one half of the autonomic nervous system; the parasympathetic nervous system (PNS) is the other. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the ear) and other muscles in the floor of the mouth. ... The facial nerve is seventh of twelve paired cranial nerves. ... A facial expression results from one or more motions or positions of the muscles of the face. ... The ventral tegmentum or the ventral tegmental area (VTA) is part of the midbrain, lying close to the substantia nigra and the red nucleus. ... The Locus ceruleus, also spelled locus coeruleus, (Latin for the blue bit) is a nucleus in the brain stem apparently responsible for the physiological reactions involved in stress and panic. ... Dopamine is a neurotransmitter in the brain. ... Norepinephrine, known as noradrenaline outside the USA, is a catecholamine and a phenethylamine with chemical formula C8H11NO3. ... Epinephrine (INN) or adrenaline (BAN) is a hormone and a neurotransmitter. ... Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water). ... Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone is any chemical produced by a living organism that transmits a message to other members of the same species. ... The olfactory bulb (1) is relatively large in the rabbit brain The olfactory bulb is a part of the brain that is a distinct outgrowth from the forebrain of mammals. ...


Fear conditioning, which trains animals to associate fear with other (previously neutral) stimuli, alters the information stored in the amygdala, as shown by experiments from Joseph LeDoux's lab and others. In this regard the amygdala serves as a simple Pavlovian learning machine that associates aversive events with neutral events, helping animals react to their world. Ivan Pavlov Ivan Petrovich Pavlov (September 14, 1849 - February 27, 1936) was a Russian physiologist who first described the phenomenon now known as conditioning in experiments with dogs. ...


If the amygdala is injected with a drug that blocks protein synthesis shortly after fear conditioning, it does not acquire long-term memory of the fear.


In language learning, some hypothesize that second language learning for adults may not make ready use of the amygdala in procedural memory usage and so emotional links to words are slower to form. Procedural knowledge or know-how is the knowledge of how to perform some task. ...


References

  • Eric Kandel, James H. Schwartz, and Thomas M. Jessell. 2000. Principles of Neural Science: 4th ed. McGraw-Hill: New York.

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