magnocellular nuclei

Examples of magnocellular nuclei in the following topics:

• Reticular Formation

  • The lateral reticular formation is close to the motor nuclei of the cranial nerves and mostly mediates their function.
  • The raphe nuclei is the place of synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation.
  • The nuclei can be differentiated by function, cell type, and projections of efferent or afferent nerves.
  • The magnocellular red nucleus is involved in motor coordination, and the parvocellular nucleus regulates exhalation.
  • Reticular formation nuclei that modulate activity of the cerebral cortex are part of the reticular activating system.

• Visual Processing

  • Some axons constitute the magnocellular (big cell) pathway, which carries information about form, movement, depth, and differences in brightness.
  • In the thalamus, the magnocellular and parvocellular distinctions remain intact; there are different layers of the thalamus dedicated to each.
  • One stream that projects to the parietal lobe, in the side of the brain, carries magnocellular ("where") information.
  • A second stream projects to the temporal lobe and carries both magnocellular ("where") and parvocellular ("what") information.

• Control of the Pituitary Gland by the Hypothalamus

  • Whilst the pituitary gland is known as the 'master' endocrine gland, both of the lobes are under the control of the hypothalamus; the anterior pituitary receives its signals from the parvocellular neurons and the posterior pituitary receives its signals from magnocellular neurons.

• Nuclear Fusion

  • In nuclear fusion two or more atomic nuclei collide at very high speed and join, forming a new nucleus.
  • The sun is a main-sequence star and therefore generates its energy through nuclear fusion of hydrogen nuclei into helium.
  • It takes considerable energy to force nuclei to fuse, even nuclei of the lightest element, hydrogen.
  • This is because all nuclei have a positive charge due to their protons, and since like charges repel, nuclei strongly resist being put close together.
  • The fusion of lighter nuclei, which creates a heavier nucleus and often a free neutron or proton, generally releases more energy than it takes to force the nuclei together.

• Nuclear Fusion

  • Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse," to form a single heavier nucleus.
  • The nuclear force is stronger than the Coulomb force for atomic nuclei smaller than iron, so building up these nuclei from lighter nuclei by fusion releases the extra energy from the net attraction of these particles.
  • For larger nuclei, no energy is released, since the nuclear force is short-range and cannot continue to act across an even larger atomic nuclei.
  • Therefore, energy is no longer released when such nuclei are made by fusion; instead, energy is absorbed.
  • Therefore, the main technical difficulty for fusion is getting the nuclei close enough to fuse.

• Spin-Spin Splitting

  • This is usually observed if the spin-coupled nuclei have very different chemical shifts (i.e.
  • Nuclei having the same chemical shift (called isochronous) do not exhibit spin-splitting.
  • The splitting pattern of a given nucleus (or set of equivalent nuclei) can be predicted by the n+1 rule, where n is the number of neighboring spin-coupled nuclei with the same (or very similar) Js.
  • Spin 1/2 nuclei include 1H, 13C, 19F & 31P.
  • The spin-coupling interactions described above may occur between similar or dissimilar nuclei.

• Binding Energy and Nuclear Forces

  • Nuclear force is the force that is responsible for binding of protons and neutrons into atomic nuclei.
  • The nuclear force is the force between two or more component parts of an atomic nuclei.
  • Nuclear force is responsible for the binding of protons and neutrons into atomic nuclei.
  • Conversely, energy is released when a nucleus is created from free nucleons or other nuclei—known as the nuclear binding energy.
  • The binding energy of nuclei is always a positive number, since all nuclei require net energy to separate into individual protons and neutrons.

• Pons

  • The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that regulate sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
  • The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent column, the cochlear and vestibular nuclei (which form the special somatic afferent fibers of the vestibulocochlear nerve), the spinal and principal trigeminal nerve nuclei (which form the general somatic afferent column of the trigeminal nerve), and the pontine nuclei, which is involved in motor activity.
  • Basal plate neuroblasts give rise to the abducens nucleus (forms the general somatic efferent fibers), the facial and motor trigeminal nuclei (form the special visceral efferent column), and the superior salivatory nucleus, which forms the general visceral efferent fibers of the facial nerve.
  • A number of cranial nerve nuclei are present in the pons:

• Nuclear Stability

  • To an extent, nuclei become more stable with increasing neutron number.
  • Higher magic numbers have been calculated but were later dismissed, as it was found they were based on a spherical model of nuclei that does not apply to higher nuclei counts.
  • The term "double magic" is used to describe nuclei in which the numbers of protons and neutrons are both magic numbers.
  • Identify the fundamental forces which lead to stability and/or instability of atomic nuclei

• The Born-Oppenheimer Approximation

  • For diatomic molecules there is still a rotational symmetry about the line connecting the two nuclei.
  • The key simplification is that the electrons whip around a lot faster than the nuclei, so one can approximate the situation by assuming that the electrons sit in a particular eigenstate of the potential with the two ions fixed.
  • By looking a moleculle in terms of the electrons and the nuclei separately, we can estimate the energies of the various transitions of the molecule.
  • The nuclei are separated by a distance of order $a$ as well and the typical energy change from moving nuclei over a distance $a$ is the electronic energy (equation above), so we can define a spring constant for the nuclei
  • yielding a vibrational energy corresponding to changes in the distance between the nuclei of