nuclei คือ: คุณกำลังดูกระทู้
The basal ganglia consists of a number of subcortical nuclei. The grouping of these nuclei is related to function rather than anatomy – its components are not part of a single anatomical unit, and are spread deep within the brain.
It is part of a basic feedback circuit, receiving information from several sources including the cerebral cortex. The basal ganglia feeds this information back to the cortex, via the thalamus. In doing so, it acts to modulate and refine cortical activity – such as that controlling descending motor pathways.
Although widely used, the term basal ganglia is a misnomer, as ganglia are collection of cell bodies outside of the central nervous system. Since a collection of subcortical cell bodies inside the nervous system are known as nuclei, the name basal nuclei is more accurate.
Nuclei of the Basal Ganglia
The anatomy of the basal ganglia is complex since it is spread throughout the forebrain.
Its components can be divided into input nuclei, output nuclei and intrinsic nuclei. Input nuclei receive information, which is then relayed to intrinsic nuclei for processing, and further passed to output nuclei:
Input Nuclei
Intrinsic Nuclei
Output Nuclei
- Caudate nucleus and putamen (neostriatum)
- External globus pallidus
- Subthalamic nucleus
- Pars compacta of the substantia nigra
- Internal globus pallidus
- Pars reticulata of the substantia nigra
In the telencephalon, the caudate nucleus (CN) and the putamen (Pu) are collectively called neostriatum, and their functions are closely related. The most rostral aspect of the neostriatum, where the caudate nucleus and the putamen join together, is termed nucleus accumbens (Acb), which is part of a functionally separate domain named ventral striatum.
The globus pallidus is divided in an external (GPe) and an internal (GPi) domains, which are functionally different
The subthalamic nucleus (StN) lies in the diencephalon. In the mesencephalon, the substantia nigra is divided into two parts; the pars compacta (SNc) and the pars reticularis (SNr).
Caudate Nucleus
The caudate nucleus forms the lateral wall of the lateral ventricle and follows the telencephalic expansion during development. It has a characteristic ventricular C-shape when fully developed.
It can be identified as the collection of gray matter on the wall of the lateral ventricles. During development, the caudate nucleus is separated from the putamen by descending white matter fibres, which at this level are known as internal capsule.
Fig 1 – Coronal section. Note the relationship of the caudate nucleus to the lateral wall of the lateral ventricle
Lentiform Nucleus (Globus Pallidus and Putamen)
The lentiform nucleus is comprised of globus pallidus and the putamen. Although anatomically related, they share no functional relationship. It can be identified as a collection of gray matter laying deep within the hemispheres.
The putamen forms the lateral aspect of the lentiform nucleus. On its concave inner surface lies the most exterior of the globus pallidus, the GPe, and the most internal structure is the GPi. The putamen is separated from the GPe by the lateral medullary lamina, and the medial medullary lamina separates the GPe from the GPi
Note that, laterally to the putamen, there is another collection of white matter fibres known as external capsule. A thin bundle of grey matter can be seen lateral to the external capsule: this is the claustrum, once thought to be part of the basal ganglia. More lateral to the claustrum is the extreme capsule, which are white matter tracts separating the claustrum from the neocortical insula.
Fig 2 – Components of the basal ganglia and its anatomical relations.
Substantia Nigra
The substantia nigra is conspicuous in gross specimens and can be seen in cuts through the midbrain, having a dark appearance due to the neuromelanin present in the cells of the SNc.
Subthalamic Nucleus
The subthalamic nucleus, as the name implies, lies inferior to the thalamus, and right above the substantia nigra.
Function
In simple terms, the basal ganglia provide a feedback mechanism to the cerebral cortex, modulating and refining cortical activation.
Its main function is related to motor refinement, acting as a tonically active break, preventing unwanted movements to start. Much of this involves reducing the excitatory input to the cerebral cortex. This prevents excessive and exaggerated movements.
The basal ganglia also plays an important role in modulating cognitive and emotional responses. The putamen receives almost exclusive inputs from motor and somatosensory cortices and projects back to motor areas, and is thus related to the motor loop. The caudate nucleus receives input from cortical association areas and projects to prefrontal areas. In contrast, the ventral striatum (including the Acb) receives limbic inputs and is thus related to emotions.
Vasculature
The arterial supply to the basal ganglia comes mainly from the middle cerebral artery, a continuation of the internal carotid artery.
The main artery is named lenticulostriate artery and, as the name implies, provides most of the circulation to the striatum and the lenticular nucleus.
There is also a small amount of supply from the anterior cerebral artery and the anterior choroidal artery, both of which are also branches of the internal carotid artery, supplying the more anterior aspect of the ganglia, (i.e. the head of the caudate nucleus and the nucleus accumbens). This particularly large artery is referred to as medial striate artery (of Heubner).
The substantia nigra and the subthalamic nucleus are more posterior and thus receive its vasculature from branches of the posterior cerebral and posterior communicating arteries.
The venous drainage is via striate branches of the internal cerebral vein, which drain into the great cerebral vein.
Fig 3 – Arterial supply to the components of the basal ganglia via the lenticulostriate arteries.
[Update] Nucleus คืออะไร แปลภาษา แปลว่า หมายถึง (พจนานุกรมอังกฤษ-ไทย LEXiTRON) | nuclei คือ – NATAVIGUIDES
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The World’s First MRI of a SINGLE Atom Is Here, and It Could Revolutionize Imaging
Magnetic resonance imaging is nothing new, but scientists were able to perform an MRI on a single atom. But how?
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Scientists recently captured the smallest MRI ever while scanning an individual atom. The technique successfully reached a breakthrough level of resolution in the world of microscopy, the detailed MRI can reveal single atoms as well as different types of atoms based on their magnetic interactions.
This breakthrough has potential applications in all kinds of fields, like quantum computing where it could be used to design atomicscale methods of storing info or when it comes to drug development, the ability to control individual atoms could potentially be used to study how proteins fold and then lead to the development of drugs for diseases like Alzheimers.
In a sense, the researchers combined a version of an MRI machine with a special instrument called a scanning tunneling microscope, which turned out to be a match made in microscopy heaven.
An MRI scanner creates an extremely strong magnetic field around whatever it’s trying to image, temporarily realigning the protons in your body with that magnetic field. Then the MRI machine pulses the sample (or patient) with a radiofrequency, which pulls the protons slightly out of alignment with the magnetic field. And after the brief radiofrequency pulse is over, the protons snap back into alignment with the field, and the energy that’s released as the protons move back into place with the magnetic field is what is detected and visualized by the machine.
And a scanning tunneling microscope is used for imaging really tiny surfaces, and it can pick up certain properties like size and molecular structure.
So, take the classic MRI, add a scanning tunneling microscope and you’ve got yourself the world’s smallest MRI machine.
Scientists used the magnetized microscope to scan a metal wafer of iron and titanium, and while a magnetic field was applied to the wafer, a radiofrequency pulse was activated and deactivated making the electrons emit energy that could be visualized.
So what does this kind of breakthrough really mean, how is it a step up from previous attempts to capture images of tiny things, and what does it look like? Find out more on this episode of Elements.
MRI Atoms Breakthrough Seeker Elements Science
Why Elon Musk Wants to Implant an Electrical Wire in Your Brain https://youtu.be/VIWaIJllptc
Read More:
Scientists perform world’s smallest MRI on single atoms
https://www.upi.com/Science_News/2019/07/01/ScientistsperformworldssmallestMRIonsingleatoms/5911562010117/
\”Scientists attached another spin cluster to the microscope’s tip and passed it over the atomic sample. Like magnets, the spins of the atoms and clusters attracted and repelled each other as the cluster passed from one side to the other. By imaging the magnetic interaction, scientists were able to create an MRI of the individual atoms.\”
Scientists Took an M.R.I. Scan of an Atom
https://www.nytimes.com/2019/07/01/science/microscopeatommagneticmri.html
\”The tip of a scanning tunneling microscope is just a few atoms wide. And it moves along the surface of a sample, it picks up details about the size and conformation of molecules.\”
Magnetic Resonance Imaging (MRI)
https://www.nibib.nih.gov/scienceeducation/sciencetopics/magneticresonanceimagingmri
\”MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field. \”
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การทำงานของ Wellmune ในผลิตภัณฑ์ Nutri-Pro
Nuclear Fusion | Fusion energy explained with Hydrogen atom example | Physics animation video
Nuclear Fusion | Fusion energy explained with Hydrogen atom example | Physics animation video
In this video we will understand how to or more nucleons merge or fuse together to create something more powerful and meaningful.
Let us first understand the meaning of the word NUCLEAR FUSION, Nuclear meaning the process which involves Nucleus and Fusion in English means two or more entities coming together or merging together to form one single entity.
So, nuclear fusion can be simply defined as the fusion or Combination of Nuclei. Scientifically, Nuclear Fusion can be defined as a nuclear reaction, in which lighter nuclei are combined together to form heavier product nuclei with the release of enormous amount of energy.
Lighter Nuclei such as Lithium and Helium when combined together form a Heavier Nucleus. The mass of heavier nucleus is less than the initial reacting nuclei. The word ‘heavier’ here is phrased in terms of energy released, which is usually enormous, rather than mass. Therefore the law of conservation of energy is satisfied.
Consider the example of two hydrogen nuclei combining to form a deuterium.
The chemical equation for this reaction is1 1H + 1 1H → 2 1H + 0 +1e + 00 v.
Here, one Hydrogen atom combines with another Hydrogen atom giving Deuterium, one Positron and one Neutrino. This Deuterium in turn combines with another Hydrogen nucleus to form a Helium isotope.
That is, 21H + 1 1H → 3 2He(Helium Isotope)
If two such Helium isotopes are fused together, formation of heavier helium takes place.
In other words, 3 2He + 3 2He → 4 2He + 21 1H
These 3steps of nuclear process, where four protons are fused together to form a heavier 4 2He nucleus and enormous amount of energy is a nuclear fusion reaction.
The chemical equation for this nuclear fusion is:
41 1H → 4 2He + 2 0+1e + 2 00v + Q which is the Energy emitted in the Fusion reaction.
(4 protons when fused together give rise to 2 heavier nucleus, 2 positrons, 2 neutrinos and enormous energy.)
But how is this enormous amount of energy being liberated from such a seemingly simple nuclear reaction. To understand this, let us first calculate the loss of mass in the process.
The starting mass is that of four protons, that is 4 X 1.0078 = 4.0312amu, but the final mass of Helium nucleus is 2me= 4.001506amu.
Therefore the loss of mass is 4.0312 4.001506 = 0.0297 amu.
This is equivalent to an energy given by Q = (0.0297amu) X 931,5 Mev/amu =27.67 Mev.
Wow……That is a significant energy release coming from the fusion of 4 protons.
However, in spite of such substantial amounts of energy being released in nuclear fusion reactions, there are no fulltime nuclear reactors built so far for fusion reaction as it is very hard to control such enormous energy released.
What is a Chromosome?
https://www.patreon.com/statedclearly Ever get confused about the difference between DNA, genes, and Chromosomes? If so, don’t worry. We straighten it all out here!
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chromosome gene biology
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ขอบคุณมากสำหรับการดูหัวข้อโพสต์ nuclei คือ