NERVOUS SYSTEM
L4
Lecturer Dr. Firdous M. Jaafar
Department of Anatomy/Histology
section
objectives
•
•
•
•
1- describe the structure of cerebrum.
2- describe the structure of cerebellum.
3- describe the structure of spinal cord.
4- identify the process of nerve regeneration, and
enumerate the stages of nerve regeneration.
• 5- outline some clinical correlates .
Brain
• І- Cerebrum:, it shows two different regions;
1- Grey matter: forms the cerebral cortex, consists of
six layers which are poorly defined.
. The most prominent neuron is the pyramidal cell.
2- White matter: The main component is the myelinated
nerve fibers , and oligodendrocytes. It has no neuronal cell
bodies.
Cerebrum
cerebellum
• ІІ- Cerebellum: like cerebrum, it consists of an external
grey matter, and an inner white matter; the medulla.
• 1- Grey matter: consists of three layers:
• a- Molecular layer.
• b- Purkinje cell layer.
• c- Granular layer.
• 2- White matter: consists of myelinated nerve fibers.
cerebellum
Spinal cord
• In cross section, two regions are recognized; an outer
white matter, and an inner grey matter, with a central
opening called central canal.
• 1- Grey matter: it has an H- shape, The arms of the H
represent the posterior horns, while the legs represent
the anterior horns.
• Central canal is lined by epindymal cells, which are low
columnar, ciliated cells.
• 2- White matter: consists mainly of myelinated neve
fibers.
Spinal cord
Large motor neurons
Regeneration of injured nerve
• . After an injury to a nerve, the cell body will show certain
changes known as chromaotolysis, which includes:
• 1- The nucleus become eccentric.
• 2- dissolution of Nissll bodies.
• 3- accumulation of nurofillaments.
• 4- swelling of the perikarion.
Regeneration of injured nerve
Clinical correlates
•
If the distance between proximal and distal parts of the injured
nerve is large or the limb is amputated, the newly grown nerve will
form a swelling known as neuroma, which may cause continuous
pain (phantom pain).
Neural plasticity:
• After an injury, a new synapses might be formed to replace the lost
ones, giving rise to a new communications with functional recovery.
This process is controlled by many factors, known as neurotrophins,
which are produced by neurons, glial cells, Schwan cells, and target
cells.
• Recent studies showed that neural stem cells in some regions of
mammals brain and spinal cord might regenerate neurons,
astrocytes, and oligodendrocytes, or even some cells that not
related to nevous tissue. Retinal stem cells could produce retinal
neural cells, photoreceptors, and neuroglial cells.
summery
• 1- brain consists of cerebrum and cerebellum.
• 2- both cerebrum and cerebellum are composed of an
outer grey matter, and an inner white matter.
• 3- pyramidal neuron is the charectaristic cell in cerebral
cortex.
• 4- cerebellar cortex is composed of three distinct layers.
• 5- spinal cord section is composed of an outer white
matter and an inner grey matter.
• 6- if a nerve is injured, only the processes could be
repaired, the neuron is irreversable.