6C · Sensing, perceiving, and responding

Responding to the world

PsychBio

How we feel (emotion — its components, the competing theories, the brain regions) and how we handle threat (stress — appraisal, the stress response, and coping).

Depth
Full detail
Filters

Emotion

PsychBio high-yield

Emotion has three components — physiological (arousal), behavioral (expression), and cognitive (subjective experience) — and four theories disagree about their order.

There are universal, cross-cultural basic emotions (happiness, sadness, fear, anger, surprise, disgust). The limbic system drives emotion: the amygdala (fear, threat detection), the hypothalamus (autonomic arousal), and the prefrontal cortex (regulation, interpretation). The four theories:

TheorySequenceOne-line
James-Langestimulus → physiological arousal → emotionyou feel afraid because you tremble
Cannon-Bardstimulus → arousal and emotion simultaneouslytrembling and fear happen at once, independently
Schachter-Singer (two-factor)stimulus → arousal → cognitive label → emotionarousal + your interpretation of it = the emotion
Lazarus (appraisal)stimulus → cognitive appraisal → arousal + emotionthe emotion depends first on how you appraise the situation

How AAMC tests it

A scenario specifies what comes first (the racing heart, or the interpretation) and asks which theory fits. Schachter-Singer is signaled by misattributing arousal (the "shaky bridge" study); Lazarus by appraisal preceding everything.

Stress

PsychBio med-yield

Stress begins with appraisal, runs through a three-stage physiological response (the general adaptation syndrome), and is managed by problem- or emotion-focused coping.

Primary appraisal evaluates whether a stimulus is a threat; secondary appraisal evaluates your ability to cope. Stressors include cataclysmic events, daily hassles, and life changes; distress (negative) vs. eustress (positive). Selye's general adaptation syndrome (GAS) has three stages: alarm (fight-or-flight, sympathetic activation, cortisol release), resistance (sustained coping), and exhaustion (resources depleted, illness risk rises). Chronic stress harms immune function and health. Coping: problem-focused (act on the stressor) vs. emotion-focused (manage the feelings); social support buffers stress, and tend-and-befriend (protecting others and seeking support) is an alternative to fight-or-flight.

Don't confuse

Primary vs. secondary appraisal (is it a threat? vs. can I handle it?) — and note GAS's alarm/resistance/exhaustion order.

The HPA axis drives the hormonal stress response: hypothalamus (CRH) → pituitary (ACTH) → adrenal gland (cortisol), with cortisol feeding back to shut the loop down.
Diagram of the HPA (hypothalamic-pituitary-adrenal) axis: the hypothalamus releases CRH, stimulating the pituitary to release ACTH, which stimulates the adrenal gland to release cortisol, with a negative-feedback loop from cortisol back to the hypothalamus and pituitary.

The HPA axis drives the hormonal stress response: hypothalamus (CRH) → pituitary (ACTH) → adrenal gland (cortisol), with cortisol feeding back to shut the loop down.

Worked question

While hiking, a woman's heart suddenly pounds. Noticing both her racing heart and the bear on the trail ahead, she concludes she is terrified. Which theory of emotion best fits this sequence?

Spotted an error? Email hello@alex.study.

© 2026 alex.study, a product of MCAT Tools LLC. MCAT is a registered trademark of the Association of American Medical Colleges (AAMC), which is not affiliated with us.

V 8dd4692