Mary's nervous system played a crucial role in her reactions during this scenario. When someone suddenly grabs her arm, her body perceives this unexpected stimulus as a potential threat. This activates her sympathetic nervous system, which is part of the autonomic nervous system responsible for the "fight or flight" response.
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Startle Response: Upon feeling the grab, Mary’s sensory receptors send signals to her brain. The amygdala, which processes emotions such as fear, triggers an immediate response, causing her muscles to tense up. This is an involuntary reaction, as it occurs automatically without conscious thought to prepare her for a reaction, whether to escape or confront the threat.
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Cognitive Processing: Once the initial startle has passed, Mary quickly identifies her friend Denise as the source of the grab. This involves higher cognitive functions, primarily in the cerebral cortex, which helps her assess the situation and make sense of what just happened.
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Emotional Response: Upon realizing it’s Denise, Mary’s nervous response shifts from fear to relief. This emotional shift involves the release of neurotransmitters like dopamine, which can enhance feelings of happiness and comfort.
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Voluntary Action: Mary then leaps up and hugs Denise, an action that is voluntary. This behavior involves conscious control from the motor cortex of the brain, as she decides to express her joy and relief through this physical gesture.
In summary, Mary's initial reaction of muscle tension and startle response was reflexive and involuntary, governed by her autonomic nervous system, while her later action of jumping up and hugging Denise was a voluntary choice facilitated by her conscious thought processes.