Name: sympathetic stress response and body changes
Uploaded: 2019-03-11T09:21:26.000Z
Duration: 1 min 25 s
Channel: JoVE

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From Molecules to Organisms: Structures and Processes

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The Sympathetic Nervous System

O sistema nervoso simpático prepara o corpo para agir durante tempos de ameaça, estresse, ou excitação, incluindo a ativação da resposta de lutar ou fugir. É uma das principais divisões do sistema nervoso autónomo que controla funções involuntárias regulando a atividade do músculo liso em órgãos viscerais, do músculo cardíaco no coração, e de certas glândulas, como as glândulas sudoríparas. Quando o sistema nervoso simpático é ativado, neurônios pré-ganglionares na região torácica e na medula espinhal lombar enviam sinais ao sistema nervoso periférico.Alguns enviam os seus sinais a uma cadeia de gânglios, aglomerados de corpos celulares neuronais que descem do lado da coluna vertebral. A partir daqui, neurônios pós-ganglionares transmitem o sinal para os tecidos-alvo, causando respostas, tais como aumento da frequência cardíaca e constrição dos vasos sanguíneos, trazendo mais sangue para os músculos. Outros neurônios pré-ganglionares enviam sinais para neurônios pós-ganglionares em gânglios perto dos seus órgãos-alvo, onde eles têm efeitos, como inibir a digestão no estômago e a excreção da bexiga, processos que são de baixa prioridade em tempos de estresse.Um terceiro grupo de neurônios pré-ganglionares viaja diretamente para a glândula adrenal, onde estimulam a produção de hormônios, como a epinefrina, que medeiam a resposta a o estresse em todo o corpo.

McEwen, Bruce S. e John H. Morrison. "Cérebro sob estresse: vulnerabilidade e plasticidade do córtex pré-frontal ao longo da vida." Neurônio 79, nº 1 (10 de julho de 2013): 16–29. [<a href="https://doi.org/10.1016/j.neuron.2013.06.028" target="__blank">Fonte</a>]

o sistema nervoso simpático

<h4>Visão Geral</h4>
 
 O sistema nervoso simpático—uma das duas principais divisões do sistema nervoso autónomo—é ativado em alturas de stress. Ele prepara o corpo para enfrentar os desafios de uma circunstância exigente, ao mesmo tempo em que inibe funções corporais essenciais—como a digestão—que são uma prioridade menor no momento.
 
 <h4>O Sistema de “Lutar ou Fugir”</h4>
 
 Como estudante, já pode ter tido a experiência de entrar na aula e encontrar um exame surpresa do qual não estava à espera. No momento em que se apercebe, pode sentir o intestino apertar, a boca secar, e o coração começa a acelerar de repente. Estes são sinais do sistema simpático a preparar-se para reagir. Embora possa não estar em perigo imediato, o sistema evoluiu para facilitar a reação imediata ao stress ou ameaças: o sangue é direcionado para longe do sistema digestivo e da pele para aumentar o fornecimento de energia aos músculos. Além disso, a frequência cardíaca e o fluxo sanguíneo aumentam, e as pupilas dilatam para maximizar a percepção visual. Ao mesmo tempo, a glândula suprarrenal liberta epinefrina no sistema circulatório. O corpo está pronto para agir, quer isso signifique fugir rapidamente do perigo ou lutar contra qualquer ameaça que possa estar à mão.
 
 <h4>Controlo do Sistema Simpático</h4>
 
 O sistema nervoso simpático pode ser ativado por várias partes do cérebro, com o hipotálamo a desempenhar um papel particularmente importante. Instruções simpáticas do sistema nervoso central são enviadas de neurónios pré-ganglionares nas partes torácicas e lombares da medula espinhal para o sistema nervoso periférico—onde têm os seus efeitos finais—através de três vias principais.
 
 A primeira via envolve neurónios pré-ganglionares que se ligam a uma cadeia próxima de gânglios—aglomerados de corpos celulares neuronais—que corre ao longo de cada lado da coluna vertebral, muitas vezes chamada de cadeia simpática. Aqui, o sinal ativa neurónios pós-ganglionares que viajam até órgãos ou glândulas alvo para regular a sua função. Os seus efeitos incluem a dilatação das pupilas—permitindo que mais luz entre nos olhos; relaxamento das vias aéreas—trazendo mais oxigénio, e constrição dos vasos sanguíneos e aumento da frequência cardíaca—levando mais sangue para os músculos.
 
 Na segunda via, neurónios pré-ganglionares enviam sinais para gânglios mais distantes da medula espinhal, perto dos órgãos alvo. Aqui, eles ativam neurónios pós-ganglionares que controlam a atividade de órgãos como estômago, pâncreas, fígado, intestinos, bexiga e genitais. Os efeitos desta via incluem inibição da digestão e urinação, e estimulação de orgasmos.
 
 Na terceira via, um pequeno grupo de neurónios pré-ganglionares viaja da medula espinhal diretamente para a glândula suprarrenal, onde estimula a secreção das hormonas epinefrina e norepinefrina para a corrente sanguínea—ajudando a mediar a resposta ao stress em todo o corpo.
 
 <h4>Stress Crónico</h4>
 
 O sistema nervoso simpático evoluiu para permitir que os animais respondessem melhor a ameaças imediatas, como o encontro repentino com um predador ou rival. Embora os humanos tenham deixado a maioria desses medos primitivos para trás, o sistema simpático do corpo ainda pode responder a situações stressantes da mesma maneira que ao encontrar um gato feroz da savana. Isso inclui a libertação das hormonas epinefrina—também chamada de adrenalina—e cortisol.
 
 Em condições normais, o sistema é brevemente ativado, e essas hormonas não estão presentes no sistema circulatório por muito tempo. No entanto, fatores de stress modernos na nossa vida diária podem ativar demasiado esse sistema e expôr o corpo por períodos mais longos, o que pode ter efeitos debilitantes. Estes podem incluir ansiedade, depressão, doenças cardíacas, ganho de peso e distúrbios do sono. As exigências da vida universitária podem ser desafiantes, por isso é fundamental se fazer uma gestão saudável do stress. Algumas estratégias para gerir o stress incluem uma alimentação saudável, dormir adequadamente, manter relações sociais e procurar aconselhamento profissional quando necessário.

O Sistema Nervoso Simpático

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O sistema nervoso simpático - uma das duas principais divisões do sistema nervoso autônomo - é ativado em momentos de estresse. Ela...

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sympathetic stress response and body changes

The sympathetic nervous system helps the body respond to stress and danger. It is one of the two main divisions of the autonomic nervous system. When it turns on, it prepares the body for action and puts lower-priority functions, such as digestion, on hold.

This response is often called the fight-or-flight system. A surprise exam can trigger it, and students may notice a tight stomach, a dry mouth, and a fast heartbeat. In a real threat, the system shifts blood away from the digestive system and skin and sends more energy to muscles. It also raises heart rate and blood flow, and it dilates the pupils to improve vision. At the same time, the adrenal gland releases epinephrine into the blood. The body is then ready to flee or fight.

The sympathetic nervous system is controlled by parts of the brain, especially the hypothalamus. Its signals start in preganglionic neurons in the thoracic and lumbar spinal cord and then travel through the peripheral nervous system. These signals follow three main pathways to reach organs and glands.

In the first pathway, preganglionic neurons connect to a nearby chain of ganglia, which are clusters of nerve cell bodies along each side of the spinal column. This chain is often called the sympathetic chain. The signal then activates postganglionic neurons, which act on target organs and glands. Their effects include pupil dilation, airway relaxation for more oxygen, and blood vessel constriction with a faster heart rate to move more blood to muscles.

In the second pathway, preganglionic neurons send signals to ganglia that are farther from the spinal cord and closer to the target organs. These postganglionic neurons control organs such as the stomach, pancreas, liver, intestines, bladder, and genitals. Their effects include slowing digestion and urination, and they can also stimulate orgasms.

In the third pathway, a small group of preganglionic neurons goes directly from the spinal cord to the adrenal gland. This triggers the release of epinephrine and norepinephrine into the bloodstream. These hormones help spread the stress response through the body.

The sympathetic nervous system evolved to help animals handle immediate threats, such as a predator or rival. Humans still use the same response during stressful events, and it can involve epinephrine, also called adrenaline, and cortisol. Under normal conditions, this reaction is brief. But modern stress can keep the system active for too long, which may lead to anxiety, depression, heart disease, weight gain, and sleep disorders. Healthy stress management can include good food, enough sleep, social support, and professional counseling when needed.

Sympathetic Stress Response and Body Changes

sympathetic-stress-response-and-body-changes

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The nervous system is a network of specialized cells that keeps the body working and helps it respond to the world around it. It controls essential functions such as heart rate and breathing. It also supports movement that helps an organism escape danger. In vertebrates, the nervous system has two major parts: the central nervous system, or CNS, and the peripheral nervous system, or PNS. The CNS includes the brain, spinal cord, and retina, which is the sensory tissue of the visual system. The...

the parasympathetic nervous system

Rest and Digest: Parasympathetic Control

The parasympathetic nervous system helps the body stay calm and return to a rested state. It is one of the two major divisions of the autonomic nervous system, which controls many unconscious functions such as heart rate and digestion. Its neurons are found in the brain and the peripheral nervous system, and they send axons to muscles, organs, and glands. This system is often called the “rest and digest” system because it supports body processes that restore homeostasis. It is most active...

the sympathetic nervous system

The sympathetic nervous system helps the body respond to stress and danger. It is one of the two main divisions of the autonomic nervous system. When it turns on, it prepares the body for action and puts lower-priority functions, such as digestion, on hold. This response is often called the fight-or-flight system. A surprise exam can trigger it, and students may notice a tight stomach, a dry mouth, and a fast heartbeat. In a real threat, the system shifts blood away from the digestive system...

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Long-term depression, or LTD, is a form of synaptic plasticity that weakens chemical synapses over time. It acts between presynaptic and postsynaptic neurons. LTD works in opposition to long-term potentiation, or LTP, which strengthens synapses. Together, LTD and LTP are two of the main mechanisms behind learning and memory. LTD helps the brain avoid staying locked in a fully strengthened state. If synapses were always maximally strengthened, the brain would become less efficient and it would...

the synapse

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Neurons communicate through synapses, the points where two neurons meet to pass on signals. At a synapse, the sending neuron is the presynaptic cell, and the receiving neuron is the postsynaptic cell. Most neurons can serve in both roles because they send and receive information. Electrical synapses move signals directly between cells. The presynaptic and postsynaptic cells are linked by gap junctions, which are proteins that physically connect them. This type of synapse can pass electrical...

key terms and concepts

Explore how the sympathetic nervous system triggers fight-or-flight body changes, from pupil dilation and faster heart rate to adrenal hormone release and stress control.

Sympathetic Stress Response and Body Changes | JoVE K12

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A coleção JoVE Core dá vida à biologia através de mais de 300 vídeos de animação concisos e fáceis de entender que explicam conceitos-chave de biologia, além de mais de 150 vídeos de Cientistas em ação que mostram experimentos reais em pesquisa realizados nos laboratórios atualmente.

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

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Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

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Sympathetic Stress Response and Body Changes

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