Neuron

Items

2007-12-31T23:59:00.000-08:00

Topics
action potential / axon / dendrite / dendritic spines / excitatory / inhibitory / integration /
interneuron / metabotropic / neuron / synapse

networks

2007-11-21T15:13:00.000-08:00

Gray Matters
Adeistic
Eine Kleine Nattermusing
eMusings
eVolition
Galaria
Godborygmi
Godspell Follies
MetaThoughts
Mimble Wimble
Naturalism
Logodaedaly
palimpsest
Salient
Science of Evolution
Sechuam
Sintheist
Tabula Flexuosa
The Scarlet A
Weltschauung

Atheism and Science Links

2007-09-14T13:16:00.001-07:00

Gray Matters
Adeistic
Avidity
Eine Kleine Nattermusing
eMusings
eVolition
Galaria
Godspell Follies
MetaThoughts
Mimble Wimble
Naturalism
Neologisms
palimpsest
Sechuam
Sintheist
Tabula Flexuosa
Weltschauung

action potential

2006-12-30T23:28:00.000-08:00

axon

2006-12-30T23:07:00.000-08:00

3D model - axons :

dendrite

2006-12-27T23:26:00.000-08:00

dendritic spines

2006-12-27T23:25:00.000-08:00

excitatory

2006-12-26T23:07:00.000-08:00

integration

2006-12-22T23:17:00.002-08:00

inhibitory

2006-12-22T23:17:00.001-08:00

interneuron

2006-12-22T23:17:00.000-08:00

metabotropic

2006-12-18T23:26:00.000-08:00

neuron

2006-12-17T23:26:00.000-08:00

synapse

2006-12-12T23:07:00.000-08:00

image gjh.md

Synaptic vesicles (2) containing neurotransmitters are transported from the cell body (soma) of the pre-synaptic neuron along microtubules (3) within axons and dendrites (1). Synaptic vesicles containing neurotransmitter peptides (11) are stored in the terminal button (4).When an incoming action potential reaches the terminal button, neurotransmitter is released from those vesicles (6) adjacent to the pre-synaptic membrane (7) into the synaptic cleft (8).

The neurotransmitter molecules diffuse rapidly across this cleft and interact with the post-synaptic density (9), a modification of the post-synaptic membrane (10) of the post-synaptic neuron (13). The post-synaptic density is rich in CaMKII, calcium/calmodulin-dependent protein kinase II, a Ca2+/calmodulin-activated dodecameric enzyme, which has the property of self-phosphorylation.

Molecular structures of the commonest neurotransmitters: 5-HT, acetylcholine, dopamine, GABA, glycine, norepinephrine.

Roughly 10 small-molecule transmitters and over 50 recognized neuroactive peptides comprise the commonly recognized neurotransmitters. Fatty acids are candidates for the endogenous canabinoid. Among the small-molecule neurotransmitters are: acetylcholine, 5 amines, and 3 0r 4 amino acids. Serotonin, or 5-HT is a product of the amino acid tryptophan. Aspartate, glutamate, and GABA are also derived from amino acids (aspartic acid, glutamic acid). Glycine is the smallest amino acid. Dopamine is a catecholamine and is a precursor the biosynthetic pathway to the other catecholamine neurotransmitters epinephrine (adrenaline) and norepinephrine (noradrenaline). Dopamine is synthesized in the body (predominantly in nervous tissue and adrenal glands) by the decarboxylation of DOPA by the enzyme aromatic-L-amino-acid decarboxylase. Dopamine beta hydroxylase converts dopamine to norepinephrine, and phenylethanoamine N-methyl transferase converts norepinephrine to epinephrine.

The terminal button also contains mitochondria (12), and the cisterna (13). The cisterna is a part of the Golgi apparatus : through the process of pinocytosis, it receives portions of the presynaptic membrane, recycling them into synaptic vesicles.

Wnt proteins

2006-12-08T23:24:00.000-08:00

Wnt Signaling Controls The Fate Of Stem Cells In Adult Brains: "Wnt proteins form a family of highly conserved signaling molecules that play a crucial role in controlling cell expansion and lineage decisions in many types of stem cells."

Neurons Generated In The Adult Brain Learn To Respond To Novel Stimuli

2005-11-23T18:23:00.000-08:00

Neurons Generated In The Adult Brain Learn To Respond To Novel Stimuli: "New brain cells that develop in the olfactory system of adult mice appear to play a role in the brain different from that of older neurons. The new olfactory neurons are especially sensitive to novel stimuli, preferentially learning to respond to new odors. This level of flexibility suggests that such newly-generated neurons could be induced to adapt to and integrate into other regions of the brain, perhaps allowing them to replace neurons lost to injury or disease. The report from researchers at the Massachusetts General Hospital (MGH)-Harvard Medical School (HMS) Center for Nervous System Repair (CNSR) appears in the Nov. 16 Journal of Neuroscience."

RNA Splicing Occurs in Nerve-Cell Dendrites

2005-11-23T14:37:00.000-08:00

UPHS News: RNA Splicing Occurs in Nerve-Cell Dendrites: "Dendrites, which branch from the cell body of the neuron, play a key role in the communication between cells of the nervous system, allowing for many neurons to connect with each other to form a network. Dendrites detect the electrical and chemical signals transmitted to the neuron by the axons of other neurons. The synapse is the neuronal structure where this chemical connection is formed, and investigators surmise that the synapse is where learning and memory occur."

synapse formation

2005-11-18T15:46:00.000-08:00

Scientists Visualize Key Molecular Interactions That Activate The Immune Response To Foreign Proteins: "Using their system, the researchers now can dissect the requirements for synapse formation. Many different membrane proteins are likely to have unique roles in this process. In addition, the biophysical rules that guide each protein also can be uncovered. Therefore, this work has the potential to uncover new factors involved in T cell activation, possibly leading to novel drugs for treating autoimmune diseases, organ transplant rejection, AIDS or cancer. "

Neural Stem Cells and Glial Progenitor Cells

2005-11-13T14:50:00.000-08:00

MEDICAL BIOLOGY: NEURAL STEM CELLS AND THE ORIGIN OF GLIOMAS: "It is now known that there are both neural stem cells and glial progenitor cells in multiple regions of the adult brain. Neural stem cells, which are multipotent and self-renewing, have been isolated from the subventricular zone, the lining of the lateral ventricles, the dentate gyrus, within the hippocampus, and the subcortical white matter. The largest of these germinal regions in humans, the subventricular zone, contains a population of astrocytes that can function as neural stem cells. In other adult mammals, glial progenitor cells -- self-renewing precursors capable of producing astrocytes and oligodendrocytes -- have also been observed throughout the neuraxis, including the cortex, the corpus callosum, the periventricular white matter, the subventricular zone, and the dentate gyrus. These stem-cell and progenitor elements, in addition to differentiated adult glia, constitute a substrate for neoplastic transformation."

Hox Genes Code for Motor Neuron Wiring

2005-11-03T15:35:00.000-08:00

Hox Code for Motor Neuron Wiring: "Earlier work performed by Dasen and Jessell, in collaboration with Jeh-Ping Liu, who is now at the University of Virginia, established that certain Hox proteins control the differentiation of motor neurons into columns in the spinal cord. These columns, which are arrayed along the anterior-posterior length of the spinal cord, form in the initial phases of motor neuron organization. That organization determines whether motor neurons grow to the limbs or to other targets.

According to Jessell, members of the Hox gene family had been known to regulate aspects of brain development, but "few people had paid attention to the fact that these genes are also expressed in the spinal cord." Earlier work performed by Dasen and Jessell, in collaboration with Jeh-Ping Liu, who is now at the University of Virginia, established that certain Hox proteins control the differentiation of motor neurons into columns in the spinal cord. These columns, which are arrayed along the anterior-posterior length of the spinal cord, form in the initial phases of motor neuron organization. That organization determines whether motor neurons grow to the limbs or to other targets. "

5HT: DOPAMINE, LEARNING AND MOTIVATION

2005-09-29T09:27:00.000-07:00

Nature Reviews Neuroscience - Reviews: "The hypothesis that dopamine is important for reward has been proposed in a number of forms, each of which has been challenged. Normally, rewarding stimuli such as food, water, lateral hypothalamic brain stimulation and several drugs of abuse become ineffective as rewards in animals given performance-sparing doses of dopamine antagonists. Dopamine release in the nucleus accumbens has been linked to the efficacy of these unconditioned rewards, but dopamine release in a broader range of structures is implicated in the 'stamping-in' of memory that attaches motivational importance to otherwise neutral environmental stimuli.

Brain dopamine has been linked to both motor and motivational functions. Several motivational hypotheses have been challenged and found inadequate, but it remains clear that dopamine is vital for the 'stamping-in' of stimulus–reward and response–reward associations.
Stimulus–reward associations are, in turn, crucial for the subsequent motivation in a previous-reward situation. Response habits are triggered by environmental stimuli that have been previously associated with reward, and the initiation of such response habits is not dependent on immediate dopamine function. If repeated with dopamine function blocked, however, the old stimulus–reward associations are extinguished and response motivation progressively weakens.
While the motivational effectiveness of reward-associated stimuli does not require immediate dopamine function, phasic dopamine elevations can nonetheless amplify stimulus effectiveness. This amplification is thought to be a dopamine function in the nucleus accumbens.
The role of dopamine in the stamping-in of reward associations might be much less localized. Dopamine seems to have important roles in the consolidation of memory in various structures — structures that are linked to different kinds of learning or to the learning of different things.
A full appreciation of the role of dopamine in motivation must be on the basis of an understanding of not only the role of dopamine in immediate behavioural arousal, but also its role in the learning and memory of learned motivational stimuli."

Roy A. Wise
DOPAMINE, LEARNING AND MOTIVATION
Nature Reviews Neuroscience 5, 483-494 (2004); doi:10.1038/nrn1406