FACTOID # 21: 15% of Army recruits from South Dakota are Native American, which is roughly the same percentage for female Army recruits in the state.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Substantia nigra
Brain: Substantia nigra
Section through superior colliculus showing path of oculomotor nerve.
Coronal slices of human brain showing the basal ganglia, globus pallidus: external segment (GPe), subthalamic nucleus (STN), globus pallidus: internal segment (GPi), and substantia nigra (SN).
Gray's subject #188 802
NeuroNames hier-527
MeSH A08.186.211.132.659.687

The substantia nigra, (Latin for "black substance", Soemering) or locus niger is a heterogeneous portion of the midbrain, separating the pes (foot) from the tegmentum (covering), and a major element of the basal ganglia system. It consists of two strongly contrasted ensembles, the pars compacta and adjacent dopaminergic groups, and another ensemble made up of the pars reticulata and the pars lateralis. The last two, along with the pallidal nuclei, are elements of the core of the basal ganglia. Although intricate and interconnected, the two ensembles must imperatively be clearly distinguished. Image File history File links Cn3nucleus. ... The superior colliculus is part of the brain that sits below the thalamus and surrounds the pineal gland in the mesencephalon of vertebrate brains. ... The oculomotor nerve () is the third of twelve paired cranial nerves. ... Image File history File links Basal-ganglia-coronal-sections-large. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The globus pallidus (Latin for pale body) is a sub-cortical structure in the brain. ... Coronal slices of human brain showing the basal ganglia, globus pallidus: external segment (GPe), subthalamic nucleus (STN), globus pallidus: internal segment (GPi), and substantia nigra (SN). ... The globus pallidus (Latin for pale body) is a sub-cortical structure in the brain. ... NeuroNames is a system of nomenclature for the brain and related structures. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Latin is an ancient [[Indo-European languages|Indo-well as the Roman CEuropean language originally spoken in Latium, the region immediately surrounding Rome. ... In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...

Contents

Pars compacta and adjacent dopaminergic groups

Anatomy

The pars compacta contains neurons which, in humans, are coloured black by the pigment neuromelanin that increases with age. This pigmentation is visible as a distinctive black stripe in brain sections and is the origin of the name given to this area. The neurons have particularly long and thick dendrites (François et al.). The ventral dendrites, particularly, go down deeply in the pars reticulata. Other similar neurons are more sparsely distributed in the mesencephalon and constitute "groups" with no clear borders, although continuous to the pars compacta, in a prerubral position. These have been given in early works in rats with not much respect for the anatomical subdivions the name of "area A8" and "A10". The pars compacta itself ("A9"!) is usually subdivided into a ventral and a dorsal tier, the last being calbindin positive[1]. The ventral tier is considered as A9v. The dorsal tier A9d is linked to an ensemble comprising also A8 and A10[2], A8, A9d and A10 representing 28% of dopaminergic neurons. The long dendrites of compacta neurons receive striatal information. This cannot be the case for the more posterior groups that are located outside the striato-pallidonigral bundle territory. Neurons of the pars compacta receive inhibiting signals from the collateral axons from the neurons of the pars reticulata[3]. All these neurons send their axons along the nigrostriatal pathway to the striatum where they release the neurotransmitter dopamine. There is an organisation in which dopaminergic neurons of the fringes (the lowest) go to the sensorimotor striatum and the highest to the associative striatum. Dopaminergic axons also innervate of other elements of the basal ganglia system including the lateral and medial pallidum[4], substantia nigra pars reticulata, and the subthalamic nucleus[5]. Neurons (also called nerve cells) are the primary cells of the nervous system. ... For animal and plant pigments, see Pigment, biology. ... Melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ... The nigrostriatal pathway is a neural pathway which connects the substantia nigra with the striatum. ... Coronal slices of human brain showing the basal ganglia, globus pallidus: external segment (GPe), subthalamic nucleus (STN), globus pallidus: internal segment (GPi), and substantia nigra (SN). ... Chemical structure of D-Aspartic Acid, a common Amino Acid neurotransmitter. ... This article or section is in need of attention from an expert on the subject. ... Coronal slices of human brain showing the basal ganglia, globus pallidus: external segment (GPe), subthalamic nucleus (STN), globus pallidus: internal segment (GPi), and substantia nigra (SN). ...


Function

The function of the dopamine neurons in the substantia nigra pars compacta is complex. Contrary to what was thought initially it is not directly linked to movements. "Dopamine neurons are activated by novel, unexpected stimuli, by primary rewards in the absence of predictive stimuli and during learning"[6]. Dopamine neurons are thought to be involved in learning to predict which behaviours will lead to a reward (for example food or sex). In particular, it is suggested that dopamine neurons fire when a reward is greater than that previously expected; a key component of many reinforcement learning models. This signal can then be used to update the expected value of that action. Many drugs of abuse, such as cocaine, mimic this reward response—providing an explanation for their addictive nature. Look up Sex in Wiktionary, the free dictionary. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Addiction is a chronic disorder proposed to be precipitated by a combination of genetic, biological/pharmacological and social factors. ...


Pathology

Degeneration of pigmented neurons in this region is the principal pathology that underlies Parkinson's disease. In a few people the cause of Parkison's disease is genetic, but in most cases the reason for the death of these dopamine neurons is unknown. Parkinsonism can also be produced by viral infections such as encephalitis or a number of toxins, such as MPTP, an industrial toxin which can be mistakenly produced during synthesis of the meperidine analog MPPP). Many such toxins appear to work by producing reactive oxygen species. Binding to neuromelanin by means of charge transfer complexes may concentrate radical-generating toxins in the substantia nigra. Pathological changes to the dopaminergic neurons of the pars compacta are also thought to be involved in schizophrenia (see the dopamine hypothesis of schizophrenia) and psychomotor retardation sometimes seen in clinical depression. Pathology (from Greek pathos, feeling, pain, suffering; and logos, study of; see also -ology) is the study of the processes underlying disease and other forms of illness, harmful abnormality, or dysfunction. ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... Parkinsonism describes the common symptoms of Parkinsons disease - tremor, rigidity, akinesia or bradykinesia and postural instability. ... Encephalitis is an acute inflammation of the brain, commonly caused by a viral infection. ... MPTP (1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine) is a chemical that is related to the opioid analgesic drugs. ... Pethidine (INN) or meperidine (USAN) (also referred to as: isonipecaine; lidol; operidine; pethanol; piridosal; Algil®; Alodan®; Centralgin®; Demerol®; Dispadol®; Dolantin®; Dolestine®; Dolosal®; Dolsin®; Mefedina®) is a fast-acting opioid analgesic drug. ... MPPP (1-methyl 4-phenyl 4-propionoxypiperidine) is an opioid analgesic drug. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid. ... A charge transfer complex is defined over a pair of a molecular groups, where one is electron donating and the other is electron accepting, where there is a partial transfer of electronic charge from the acceptor to the donor in an excited molecular state(excited state). ... The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a theory that argues that the unusual behaviour and experiences associated with schizophrenia (sometimes extended to psychosis in general) can be fully or largely explained by changes in dopamine function in the brain. ... Clinical depression (also called severe depressive disorder, major depressive disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individuals social functioning and/or activities of daily living. ...


Pars reticulata and lateralis

Anatomy

Neurons in the pars reticulata and lateralis are much less densely packed than those in the compacta (they were sometimes named pars diffusa). They are smaller and thinner than the dopaminergic neurons and conversely identical and morphologically similar to the pallidal neurons (see primate basal ganglia). Their dendrites as well as the pallidal are preferentially perpendicular to the striatal afferents[7]. The massive striatal afferences corresponds to the medial end of the striato-pallidonigral bundle. Nigral neurons have the same peculiar synaptology with the striatal axonal endings. They make connections with the dopamine neurons of the pars compacta whose long dendrites plunge deeply in the pars reticulata.The neurons of the pars reticulata and lateralis produce the neurotransmitter gamma-aminobutyric acid (GABA). The neurons of the pars reticulata through the nigrothalamic bundle send axons to a particular part of the motor thalamus. The nigral territory corresponds to the nucleus ventralis anterior VA (different from the pallidal VO). VA is the origin of one output of the basal ganglia system. It sends axons to the frontal and oculomotor cortex. In addition the pars reticulata sends neurons to the pars parafascicularis of the central region of the thalamus and to the pedunculopontine complex). The particularity of the pars lateralis is to send its axons to the superior colliculus[8], which is a too minimized output of the basal ganglia system. The basal ganglia system is a major cerebral system that has only recently been recognized. ... Gamma-aminobutyric acid (usually abbreviated to GABA) is an inhibitory neurotransmitter found in the nervous systems of widely divergent species. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


Function

The neurons of the pars reticulata are fast-spiking pacemakers, generating action potentials in the absence of synaptic input[9]. In primates they discharge at a mean rate of 68Hz in contrast to dopaminergic neurons (below 8Hz)[10]. They receive abundant afferrences from the striatum (mainly from the associative striatum) with the same very peculiar synaptology as the pallidum. It receives axons from the subthalamic nucleus and a dopaminergic innervation from the dopaminergic ensemble. A. A schematic view of an idealized action potential illustrates its various phases as the action potential passes a point on a cell membrane. ...


The pars reticulata is one of the two primary output nuclei of the basal ganglia system to the motor thalamus (the other output is the internal segment of the globus pallidus).The nigral neurons have their own territory distinct from the cerebellar and the pallidal in the nucleus ventralis anterior VA. This sends axons to the frontal and oculomotor cortex. Hikosaka and Wurtz[11] devoted four papers to "the visual and oculomotor functions of the monkey substantia nigra pars reticulata". This is largely involved in orientation and the control of eye movements in stabilisation of gaze and in saccades. 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. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The globus pallidus (Latin for pale body) is a sub-cortical structure in the brain. ... The human eye. ...


Pathology

The function of the neurons of the pars reticulata is profoundly changed in parkinsonism and epilepsy. These changes are thought to be mostly secondary to pathology elsewhere in the brain, but may be crucial to understanding the generation of the symptoms of these disorders. Parkinsons disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferers motor skills and speech. ...


References

  1. ^ Francois, C.; Yelnik, J.; Tande, D.; Agid, Y. & Hirsch, E.C.. "Dopaminergic cell group A8 in the monkey: anatomical organization and projections to the striatum". Journal of Comparative Neurology 414 (3): 334–347. PMID 10516600.
  2. ^ Feigenbaum Langer, L.; Jimenez-Castellanos, J. & Graybiel, A.M. (1991). "The substantia nigra and its relations with the striatum in the monkey". Progress in Brain Research 87: 81–99. PMID 1678193.
  3. ^ Hajos, M. & Greenfield, S.A. (1994). "Synaptic connections between pars compacta and pars reticulata neurones: electrophysiological evidence for functional modules within the substantia nigra". Brain Research 660 (2): 216–224. PMID 7820690.
  4. ^ Lavoie, B., Smith, Y., Parent, A. (1989). "Dopaminergic innervation of the basal ganglia in the squirrel monkey as revealed by tyrosine hydroxylase immunohistochemistry" 289 (1): 36–52. PMID 2572613.
  5. ^ Cragg S.J.; Baufreton J.; Xue Y.; Bolam J.P.; & Bevan M.D. (2004). "Synaptic release of dopamine in the subthalamic nucleus". European Journal of Neuroscience 20 (7): 1788–1802. PMID 15380000.
  6. ^ Schultz, W. (1992). "Activity of dopamine neurons in the behaving primate". Seminar in Neuroscience 4: 129–138.
  7. ^ François, C.; Yelnik, J. & Percheron, G. (1987). "Golgi study of the primate substantia nigra. II. Spatial organization of dendritic arborizations in relation to the cytoarchitectonic boundaries and to the striatonigral bundle". Journal of Comparative Neurology 265 (4): 473–493. PMID 3123530.
  8. ^ François, C.; Percheron, G. & Yelnik, J. (1984). "Localization of nigrostriatal, nigrothalamic and nigrotectal neurons in ventricular coordinates in macaques". Neuroscience 13 (1): 61–76. PMID 6387531.
  9. ^ Atherton, J.F. & Bevan, M.D. (2005). "Ionic mechanisms underlying autonomous action potential generation in the somata and dendrites of GABAergic substantia nigra pars reticulata neurons in vitro". Journal of Neuroscience 25 (36): 8272–8281. PMID 16148235.
  10. ^ Schultz, W. (1986). "Activity of pars reticulata neurons of monkey substantia nigra in relation to motor, sensory and complex events". Journal of Neurophysiology 55 (4): 660–677. PMID 3701399.
  11. ^ Hikosaka, O. & Wurtz, R.H. (1983). "Visual and oculomotor functions of monkey substantia nigra pars reticulata. I to IV". Journal of Neurophysiology 49 (5): 1230–1301. PMID 6864248, PMID 6864249, PMID 6864250 & PMID 6306173.

See also

To meet Wikipedias quality standards, this article or section may require cleanup. ... Mostly enveloped by the cerebrum and cerebellum (blue), the visible part of brainstem is shown in black. ... The cerebral peduncle, by most classifications, is everything in the mesencephalon except the tectum. ... In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... Human brain image constructed from MRI data // Brain (neural tube) Brainstem (rhombencephalon),(mesencephalon) Rhombencephalon (hindbrain) Metencephalon pons fourth ventricle cerebellum cerebellar vermis cerebellar hemispheres anterior lobe posterior lobe flocculonodular lobe cerebellar nuclei fastigial nucleus globose nucleus emboliform nucleus dentate nucleus Myelencephalon medulla oblongata medullary pyramids Mesencephalon (midbrain) tectum inferior colliculi...

External links


BrainMaps is an NIH-funded interactive zoomable high-resolution digital brain atlas and virtual microscope that is based on more than 10 million megapixels (30 terabytes) of scanned images of serial sections of both primate and non-primate brains and that is integrated with a high-speed database for querying...

Mesencephalon (midbrain)

cerebral peduncle: midbrain tegmentum (periaqueductal gray, ventral tegmentum, nucleus raphe dorsalis), pretectum, substantia nigra, red nucleus, pedunculopontine nucleus, medial longitudinal fasciculus, medial lemniscus, rubrospinal tract, lateral lemniscus In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... The cerebral peduncle, by most classifications, is everything in the mesencephalon except the tectum. ... The midbrain tegmentum is part of the midbrain extending from the substantia nigra to the cerebral aqueduct. ... Periaqueductal Gray (PAG; also called the central gray) is the midbrain grey matter that is located around the cerebral aqueduct within the midbrain. ... Grays FIG. 712– Transverse section of mid-brain at level of superior colliculi. ... The nucleus raphe dorsalis consists of rostral and caudal subdivisions. ... Pretectum is a structure located in the forebrain. ... The red nucleus is a structure in the rostral midbrain involved in motor coordination. ... The pedunculopontine nucleus (PPN) is located in the brainstem, caudal to the substantia nigra and adjacent to the superior cerebellar peduncle. ... The medial longitudinal fasciculus (MLF) is a group of axons on each side of the brainstem, that carry information about the direction that the eyes should move. ... The medial lemniscus, also known as Reils band or Reils ribbon, is a pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus. ... The rubrospinal tract is part of the indirect extra-pyramidal tract and is responsible for large muscle movement such as the arms and the legs. ... The lateral lemniscus is a tract of axons in the brainstem that carries information about sound to the inferior colliculus of the midbrain. ...


tectum: corpora quadrigemina, inferior colliculi, superior colliculi The tectum is the dorsal part of the midbrain, derived in embryonic development from the alar plate of the neural tube. ... Corpora quadrigemina (Latin: four twins) is the collective name given to both pairs of the inferior and superior colliculi. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... The superior colliculus is part of the brain that sits below the thalamus and surrounds the pineal gland in the mesencephalon of vertebrate brains. ...


cerebral aqueduct: oculomotor nucleus, trochlear nucleus, Edinger-Westphal nucleus The mesencephalic duct, also known as the Aqueduct of Silvius or the cerebral aqueduct, contains cerebrospinal fluid (CSF), is within the mesencephalon (or midbrain) and connects the third ventricle in the thalamus (or diencephalon) to the fourth ventricle, which is between the pons and cerebellum. ... The fibers of the oculomotor nerve arise from a nucleus in the midbrain, which lies in the gray substance of the floor of the cerebral aqueduct and extends in front of the aqueduct for a short distance into the floor of the third ventricle. ... The nucleus of the trochlear nerve is located in the midbrain, at the level of the inferior colliculus. ... The Edinger-Westphal nucleus is the accessory parasympathetic nucleus of the oculomotor nerve, supplying the constricting muscles of the iris. ...


  Results from FactBites:
 
Title (5316 words)
We have studied the sensory and oculomotor properties of cells in the monkey substantia nigra pars reticulata by recording extracellular unitary spikes of these cells while the monkey was performing behavioral paradigms that allowed the presentation of visual and auditory stimuli and the initiation of saccadic eye movements under different behavioral conditions.
These substantia nigra cells respond to the appearance of a light spot that the monkey is going to fixate or to the disappearance of a light spot that it was fixating.
For each of the substantia nigra cells that showed visual- or occulomotor-related responses, we determined the center of the visual receptive or movement field of the cell and compared it with the field center of the superior colliculus cells found at the lowest threshold point.
Dopamine and substantia nigra (17143 words)
Parkinson's disease is a movement disorder characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta.
In the present study, we assessed the feasibility of grafting embryonic DA neurons into the substantia nigra (SN) of adult parkinsonian monkeys as an approach to restoration of the DA modulation of striatal-nigral afferents that is lost after degeneration of SN neurons.
Inflammation and neuronal degeneration of the substantia nigra (SN) occur in Parkinson's disease (PD).
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m