Cardiovascular Surge: Heart rate and blood pressure increase to pump oxygenated blood and glucose to the skeletal muscles more efficiently.
Respiratory Expansion: Bronchial passages in the lungs dilate (widen) to increase oxygen intake, supporting the high metabolic demands of physical action.
Resource Redirection: Blood flow is diverted away from 'non-essential' systems, such as the digestive and reproductive systems, toward the brain and muscles.
Visual Acuity: Pupils dilate to allow more light into the eyes, improving peripheral vision and the ability to detect movement in the environment.
| Feature | Sympathetic Nervous System (SNS) | Parasympathetic Nervous System (PNS) |
|---|---|---|
| Nickname | Fight or Flight | Rest and Digest |
| Primary Goal | Energy mobilization and survival | Energy conservation and recovery |
| Heart Rate | Increases significantly | Decreases to resting levels |
| Digestion | Inhibited (slows down) | Stimulated (increases) |
| Pupils | Dilated (widened) | Constricted (narrowed) |
Terminology Precision: Always distinguish between the adrenal cortex (long-term stress/cortisol) and the adrenal medulla (acute stress/adrenaline). In the context of fight or flight, the medulla is the primary actor.
Mechanism Mapping: When asked to describe the response, follow the sequence: Stimulus → Amygdala → Hypothalamus → SNS → Adrenal Medulla → Adrenaline → Physiological Effect.
Functional Justification: Don't just list effects; explain why they happen. For example, 'Pupils dilate to increase light intake and improve visual awareness.'
Recovery Phase: Remember to mention the role of the Parasympathetic Nervous System in returning the body to homeostasis after the threat is gone.
The 'Only Physical' Myth: Students often assume this only happens in life-or-death situations. In reality, the body cannot distinguish between a physical predator and a psychological stressor like a difficult exam.
Digestion Confusion: A common error is thinking digestion increases to provide energy. In fact, digestion is an energy-intensive process that is inhibited so that energy can be used by the muscles instead.
Instant Recovery: Recovery is not instantaneous. Adrenaline remains in the bloodstream for a period after the threat is gone, which is why people often feel 'shaky' or hyper-alert even after the danger has passed.
