SINAPSIS

¿Qué libera la vesícula sináptica? ¿Cómo recibe al mensajero la neurona postsináptica?

Dos clasesdereceptores para los NT A. Receptores inotrópicos 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 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 mensajeros-Diseño: ligando-receptor –transductor (proteinaG) -efector primario (adenilciclasa) mensajero secundario (AMPc) -efector secundario- proteinkisana-respuesta celular

Efectode lafosforilaciónde proteinas A. Proteinkinasa fosforila las proteinas de un canal de K-apertura 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: derivados de aminoácidos y neuropéptidos Neurotransmisores: derivados de aminoácidos y neuropéptidos. Receptores: Neurotransmisión y neuromodulación 1. Sinápsisquímica implica: a.síntesis del neurotransmisor; b.liberacióndelneurotransmisor; c.interacción NT-receptor; d.remoción del NT. 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. El sistema nervioso utiliza dos clases de mensajeros químicos: a. moléculas pequeñas b. neuropéptidos.

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 NE-containing 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. 5-HT 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 (choline acetyltransferase) Breakdown of acetylcholine (acetylcholinesterase)

Sinapsis colinergica Acetylcholine (ACh) synthesis, release, and termination of action are shown. Acholinetransporter accumulatescholine. The enzymecholine acetyltransferase(ChAT) acetylates thecholineusing acetyl-CoA(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

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