Neuronas y neuroglias

Sistema Nervioso
Prof. Claudio Berríos Bravo

Figure 1.1 Estimates of the number of
genes

Neurons never function in isolation; they are organized into ensembles or
neural circuits that process specific kinds of information and provide the
foundation of sensation, perception and behavior.

Figure 1.8 Relative frequency of action potentials (indicated by individual vertical
lines) in different components of the myotatic reflex as the reflex pathway is
activated. Notice the modulatory effect of the interneuron.

Figure 1.9 Intracellularly recorded
responses underlying the myotatic
reflex.

Figure 1.14 Somatotopic
organization of sensory
information. (Top) The
locations
of primary and secondary
somatosensory cortical
areas on the lateral surface
of the
brain. (Bottom) Cortical
representation of different
regions of skin.

Sistema nervioso
Neuronas y neuroglias
Claudio Berríos Bravo
Diferencial Universidad de Playa Ancha03-05-2017

Neurons have different shapes:
Unipolar: Has only one process extending from the soma, branching into dendrites or axon
terminals (typical of invertebrate animals)
Bipolar: The neuron, it has one input process from dendrites and one output process to dendrites
(typical of sensory neurons: visual, auditory, olfactory)
Multipolar: One axon but many dendrites extending directly from the soma (used for motor and
sensory processing). This is the prototypical neuron
Pseudounipolar: Were originally bipolar, but the dendrites and axon extensions have fused (typical
of the dorsal root ganglia in the spinal cord)

Neuroglia cells of brain shown by Golgi’s method. A. Cell with
branched processes. B. Spider cell with unbranched
processes.

Bipolar nerve cell from the spinal ganglion of the pike. (After Kölliker.)

Motor nerve cell from ventral horn of medulla spinalis of rabbit. The
angular and spindle-shaped Nissl bodies are well shown. (After Nissl.)

Pyramidal cell
from the cerebral
cortex of a
mouse. (After
Ramón y Cajal.)

Cell of Purkinje
from the
cerebellum.
Golgi method.
(Cajal.) a. Axon.
b. Collateral. c
and d.
Dendrons.

Diagram of medullated nerve fibers
stained with osmic acid. X 425. (Schäfer.)
R. Nodes of Ranvier. a. Neurolemma. c.
Nucleus.

• Células Gliales
• Neuronas
Neuroblastos

Células Gliales
• Astrocitos
– Protoplasmáticos
– Fibrosos
• Oligodendrocitos
– Interfasciculares
– Satélites
• Células de la Microglia
• Células Ependimarias
– Tanicitos
• Células de Schwann

Astrocitos
• Astrocitos Fibrosos
– proyecciones largas y no ramificadas
– se relacionan con piamadre y vasos sanguíneos
– se encuentran separados de ella por lámina basal
– se consideran reguladores iónicos, glutamatérgicos y
gabaérgicos
– descargan glucosa a partir de glucógeno
– constituyen la Brain -Blood- Barrier (BBB)

B R A I N R E S E A R C H R E V I E W S 6 4 ( 2 0 1 0 ) 3 2 8 – 3 6 3

P. Ballabh et al. / Neurobiology of Disease 16 (2004) 1–13

Astrocitos
 Astrocitos protoplasmáticos
abundante citoplasma, nucleo grande y proyecciones
ramificadas cortas.
Posee pedículos o pies vasculares
asociados a piamadre constituyen membrana piaglial

Oligodendrocitos
• Localizadas en S. Gris y Blanca
• Abundante RER, mitocondrias y Golgi
• Oligodendrocitos Interfasciculares
– Mielina sobre axones en SNC
– Una célula puede envolver a varios axones
• Oligodendrocitos Satélites
– Desarrollar migraciones entre otras células del SNC.

Schwann cell
03-05-2017 Diferencial Universidad de Playa Ancha

Células de la Microglia
• Microglia are a type of glial cell that are the
resident macrophages of the brain and
spina cord, and thus act as the first and
main form of active immune defense in the
central nervous system (CNS). Se originan de
la médula ósea

Células Ependimarias
 Células cuboídeas que constituyen un epitelio simple (
Epéndimo)
 Revisten los ventrículos cerebrales y el conducto central
de la m. Espinal
 Abundantes mitocondrias y haces filamentosos
intermedios
 Modificaciones constituyen al Plexo Coroideo
 Tanicitos ( especialización ) extiende proyecciones hacia
el hipotálamo, en la vecindad vascular y de células
neurosecretoras

Células de Schwann
• Se localizan en SNP
• Envuelven axones
• Células aplanadas
• Presentan Lámina Basal
• Existe tejido conectivo cubriendo la vaina de
mielina y las células de Schwann circundantes

Astrocytes in culture
(immunofluorescence for glial fibrillary acidic protein)Diferencial Universidad de Playa Ancha03-05-2017

Oligodendrocyte in culture
(Immunofluorescence for galactocerebroside)Diferencial Universidad de Playa Ancha03-05-2017

Microglia
Microglia are immune cells for the brain. After injury, they
migrate to the site of injury to help clear away dead and dying
cells. They can also produce small molecules called cytokines
that trigger cells of the immune system to respond to the injury
site. This clean-up process is likely to play an important role in
recovery of function following a spinal injury.
Les microglies (en vert) issues de la
moelle osseuse attaquent les plaques
de protéines (en rouge) responsables
de la mort des neurones chez les
patients atteints d'Alzheimer. Cette
spectactulaire photo, prise par
l'équipe de Serge Rivest, illustre la
couverture du dernier numéro de
Neuron.

Structural. A commonly accepted function is to physically structure the brain.
Metabolic support. A second function is to provide neurons with nutrients such as glucose.
Blood-brain barrier. The astrocyte end-feet encircling endothelial cells form part of the blood-brain barrier.
Transmitter reuptake and release. Astrocytes express plasma membrane transporters such as glutamate transporters
for several neurotransmitters, including glutamate, ATP and GABA. More recently, astrocytes were shown to release
glutamate or ATP in a vesicular, Ca2+-dependent manner.
Regulation of ion concentration in the extracellular space. Astrocytes express potassium channels at a high density.
When neurons are active, they release potassium, increasing its extracellular concentration. Because astrocytes are
so permeable to potassium, they rapidly clear its excess accumulation in the extracellular space. If this function is
interfered with, the extracellular concentration of potassium will rise, leading to neuronal depolarization by the
Goldman equation. Abnormal accumulation of extracellular potassium is well known to result in epileptic neuronal
activity.
Modulation of synaptic transmission. In the supraoptic nucleus of the hypothalamus, rapid changes in astrocyte
morphology have been shown to affect heterosynaptic transmission between neurons (Piet et al., Proc Natl Acad Sci
U S A. 2004 Feb 17;101(7):2151-5).
Vasomodulation. Astrocytes may serve as intermediaries in neuronal regulation of blood flow (Parri and Crunelli, Nat
Neurosci. 2003 Jan;6(1):5-6).
Astrocito

Journal of Neuroimmunology 171 (2006) 72 – 85

Journal of Neuroimmunology 171 (2006) 72 – 85
Proposed mechanism of
stress-induced microglia
proliferation.
Following exposure to
restraint stress, there is an
elevation in circulating
glucocorticoids. As
glucocorticoids enter the
CNS, they bind to
glucocorticoid receptors on
multiple cell types.

Célula de Schwann

Signaling at cerebellar parallel fiber synapses. Glutamate released by parallel
fibers activates both AMPA-type and metabotropic receptors. The latter produces
IP3 and DAG within the Purkinje cell. The IP3 causes Ca2+ to be released from
the endoplasmic reticulum, while DAG activates protein kinase C. These signals
together change the properties of AMPA receptors to produce LTD.

Regulation of tyrosine hydroxylase by protein phosphorylation. This enzyme governs the synthesis of the
catecholamine neurotransmitters and is stimulated by a number of intracellular signals. In the example
shown here, neuronal electrical activity (1) causes influx of Ca2+ (2). The resultant rise in intracellular
Ca2+ concentration (3) activates protein kinases (4), which phosphorylates tyrosine hydroxylase (5) to
stimulate catecholamine synthesis (6). This, in turn, increases release of catecholamines (7) and enhances
the postsynaptic response produced by the synapse (8).

Generalidades de SinapsisDiferencial Universidad de Playa Ancha03-05-2017

Sinapsis colinérgicaDiferencial Universidad de Playa Ancha03-05-2017

Sinapsis serotoninérgicaDiferencial Universidad de Playa Ancha03-05-2017

Sinapsis GABAérgicaDiferencial Universidad de Playa Ancha03-05-2017

Sinapsis glutamatérgicaDiferencial Universidad de Playa Ancha03-05-2017

A typical neuron of a vertebrate. The arrows indicate the direction in which
signals are conveyed. The neuron shown is from the retina of a monkey. The
longest and largest neurons in a human extend for about 1 million mm and have
an axon diameter of 15 mm. (Drawing of neuron from B.B. Boycott, in Essays on
the Nervous System [R. Bellairs and E.G. Gray, eds.]. Oxford, UK: Clarendon
Press, 1974.)

The three phases of neural development.

Migration of immature neurons

Signaling by neurotransmitter release at a synapse The arrival of a nerve impulse
at the terminus of the neuron signals the fusion of synaptic vesicles with the plasma
membrane, resulting in the release of neurotransmitter from the presynaptic cell into
the synaptic cleft. The neurotransmitter binds to receptors and opens ligand-gated
ion channels in the target cell plasma membrane.

Modes of cell-cell signaling

Acetylcholine 2D Structure

Neuronas y neuroglias

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