Propagacao do PA
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Transcript of Propagacao do PA
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Propagação do sinal nervoso e Circuito
NeuralFelipe Beijamini – UNIOESTE - 2016
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• Propagação do potencial de ação• Diâmetro do axônio• Mielinização
• Sinapses• Elétricas• Químicas
• Circuito neural simples
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Propagação do PA.• Em uma célula imaginária:
A despolarização
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Direção da propagação
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A distância e a mudança no potencial de membrana:
Dist
ânci
a
Mud
ança
no
pote
ncia
l de
mem
bran
a
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Para pensar: Por que Unidirecional?
Por que?Por que?Por que?Por que?Por que?Por que?
E para que?
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Peças do quebra-cabeças• Zona de gatilho (disparo);
• O que há de tão especial nela?
• Período refratário;
• Relação entre distância vs propagação.
Agora é com vocês.
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Velocidade de condução do Potencial de ação
Shinkansen anabolizado!
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Um pouco de histologia do SN
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Coadjuvante? Nem tanto: A glia
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A bainha de mielina e os nodos de Ranvier
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Dois fatores importantes na velocidade de condução do PA:• Diâmetro do axônio• Menor diâmetro menor velocidade• Maior diâmetro maior velocidade
• Resistência da membrana do axônio ao vazamento de íons.• Menor resistência menor velocidade• Maior resistência maior velocidade.
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Para pensar: o que acontece em patologias que destroem a bainha de mielina?
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Intensidade do sinal:
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Sinapses:• Químicas
• Elétricas
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Elétricas
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Químicas:• Terminal axônico da
célula pré-sináptica
• Membrana da célula pós-sináptica;
• Fenda sináptica
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Como funciona?
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Inibitórias ou Excitatórias!• Dependendo do neurotransmissor!• Quem são os neurotransmissores? Quantos
tipos/classes? (Vamos deixar um pouco para a Fisiologia).
• Dependendo do receptor!
• Inibitórias Hiperpolarização
• Excitatórias Despolarização
Nosso interesse!
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Para pensar: uma vez na fenda, à fenda
pertencerá?O que acontece com o neurotransmissor
liberado na fenda sináptica?
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Circuitos neurais
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Cadeia neural
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Convergência e divergência
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Mapa mental:• Da gametogênese à implantação do blastocisto!