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SINAPSIS
¿Qué libera la vesícula sináptica?
¿Cómo recibe al mensajero la neurona postsináptica?
Dos clasesdereceptores para los NT
A. Receptores inotrópicos. Receptores que unen el NT y ellos mismos son
un canal iónico.
B. Receptores metabotrópicos. Receptores que unen el NT y através de
ProteinasG (proteinas que unen GTP) regulan actividad de canales ionicos
Receptores inotrópicos. Receptor nicotínico de ACh
-Son diferentes de los canales voltaje-dependientesdel Na y del K:
canal grande que permite el paso de ambos Na y Ka favor de
gradiente.
• Neurotransmision mediada
por segundos mensajerosDiseño:
• ligando-receptor –transductor
(proteinaG) -efector primario
(adenilciclasa) mensajero
secundario (AMPc) -efector
secundario- proteinkisanarespuesta celular
• Efectode lafosforilaciónde
proteinas
• A. Proteinkinasa fosforila las
proteinas de un canal de Kapertura canal –paso de K –
propagación del potencial
sináptico
(respuestaenminutos)
• B. Proteinkinasa fosforila
proteinas de transcripcion
(reguladoras) regulación de
expresión genica (reprimiendo
y/o expresando genes).
Respuesta tardía y sostenida
en el tiempo.
Neurotransmisores:
Receptores:
derivados de aminoácidos y
neuropéptidos.
Neurotransmisión y neuromodulación
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1. Sinápsisquímica implica:
a.síntesis del neurotransmisor;
b.liberacióndelneurotransmisor;
c.interacción NT-receptor;
d.remoción del NT.
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2.Conceptode NT:
Sustancia liberada en la sinapsis por una neurona y que afecta a otra célula
de una manera especifica. Principio de Dale-Ecclesactualizado:una
neurona hace uso de la misma combinaciónde mensajeros quimicos
entodas sus terminaciones sinapticas.
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El sistema nervioso utiliza dos clases de mensajeros químicos:
a. moléculas pequeñas
b. neuropéptidos.
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Schematic representation of the life cycle of a classical neurotransmitter. After
accumulation of a precursor amino acid into the neuron (1), the amino acid precursor is
metabolized sequentially (2) to yield the mature transmitter. The transmitter is then
accumulated into vesicles by the vesicular transporter (3), where it is poised for release
and protected from degradation. Once released, the transmitter can interact with
postsynaptic receptors (4) orautoreceptors(5) that regulate transmitter release, synthesis,
or firing rate. Transmitter actions are terminated by means of a high-affinity membrane
transporter (6) that is usually associated with the neuron that released the transmitter.
Alternatively,tranmitteractions may be terminated by diffusion from the active sites (7) or
accumulation into glia through a membrane transporter (8). When the transmitter is taken
up by the neuron, it is subject to metabolic inactivation (9).
Sinapsis Noradrenergica
Sinapsis noradrenergica
Characteristics of a norepinephrine
(NE)-containing catecholamineneuron.
Tyrosine (Tyr) is accumulated by the
neuron and is then metabolized
sequentially by tyrosine hydroxylase
(TH) and L-aromatic aminoacid
decarboxylase (L-AADC) to dopamine
(DA). The DA is then taken up through
the vesicular monoamine transporter
into vesicles. In DA neurons, this is the
final step. However, in this NEcontaining cell, DA is metabolized to NE
by dopamine-b-hydroxylase (DBH),
which is found in the vesicle. Once NE
is released, it can interact with
postsynaptic noradrenergic receptors
or presynaptic noradrenergic
autoreceptors. The accumulation of NE
by the high-affinity membrane NE
transporter (NET) terminates the actions
of NE. Once taken back up by the
neuron, NE can be metabolized to
inactive compounds (DHPG) by
degradative enzymes such as
monoamineoxidase (MAO) or taken
back up by the vesicle.
Sinapsis Seroninergica
Sinapsis serotoninergica
Aminas derivada de triptofamo
(indolaminas-Serotonina(SER),
melatonina-Serotonina
triptófano+triptofano hidroxilasa-->
5-Hidroxi triptofano***5-Hidroxi
triptofano decarboxilasa--> 5-HT
(SER) Serotonergic neuron.
Tryptophan(Trp) in the neuron is
metabolized sequentially
bytryptophan hydroxylase
(TrypOHase) and L-AADC to yield
serotonin (5-HT). 5-HT is
accumulated by the vesicular
monoamine transporter. When
released, 5-HT can interact with
both postsynaptic receptors
andpresynaptic autoreceptors. 5HT is taken up by the high-affinity
5-HT transporter (SERT), and
once inside the neuron it can be
reaccumulated by vesicular
transporter or inactivated
metabolica
Acetilocolina
Production of
acetylcholine
Breakdown of
acetylcholine
(choline acetyltransferase)
(acetylcholinesterase)
Sinapsis colinergica
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Acetylcholine (ACh) synthesis,
release, and termination of action
are shown. Acholinetransporter
accumulatescholine. The
enzymecholine
acetyltransferase(ChAT)
acetylates thecholineusing acetylCoA(Ac-CoA) to form the
transmitterACh, which is
accumulated into vesicles by the
vesicular transporter. The
releasedAChmay interact with
postsynapticmuscarinicor
nicotiniccholinergicreceptors or
can be taken up into the neuron
by acholinetransporter.
Acetylcholine can be degraded
after release by the enzyme
acetylcholine esterase (AChE).
Sinapsis Gabaérgica
Alpha-Ketoglutarate
GABA-oxoglutarate
transaminase (GABA-T)
Glutamate
Glutamic acid decarboxylase
(GAD)
GABA
F I N