Scientific Stress Glossary: Key Concepts & Definitions
A referenced educational index of the hormones, neural pathways and biomarkers involved in stress.
The Scientific Glossary is an evidence-based medical and physiological reference. Here you will find clear, jargon-free explanations of how hormones, neural pathways, and physiological feedback loops interact during acute demands and chronic pressure - along with direct links to comprehensive deep-dive guides and interactive calming tools.
Hormones & Endocrinology
Cortisol
The primary glucocorticoid hormone produced by the adrenal cortex via the HPA axis. Regulates glucose metabolism, immune activity, and energy mobilization.
Read Full Guide on Cortisol →Adrenaline (Epinephrine)
Fast-acting hormone released by the adrenal medulla that triggers rapid heart rate acceleration, pupil dilation, and bronchodilation in acute fight-or-flight states.
Explore in Stress Biology →HPA Axis
Hypothalamic-Pituitary-Adrenal axis: the complex neuroendocrine feedback loop coordinating long-term physiological adaptation to prolonged demands.
Read HPA Axis & Cortisol →Autonomic Nervous System & Neural Circuits
Vagus Nerve
The principal nerve of the parasympathetic nervous system. Acts as a physiological brake to decelerate heart rate, modulate inflammation, and calm the brainstem.
Read Vagus Nerve Guide →Sympathetic Nervous System
The "fight-or-flight" division responsible for accelerating cardiovascular output, suppressing non-essential digestion, and priming muscles for rapid physical exertion.
See Body Effects →Parasympathetic Nervous System
The "rest-and-digest" branch that conserves energy, promotes cellular repair, slows heartbeat, and facilitates emotional downshifting through vagal pathways.
Learn Calming Practices →Biomarkers & Physiological Metrics
Heart Rate Variability (HRV)
The variation in time intervals between consecutive heartbeats. Higher HRV reflects greater autonomic flexibility, vagal tone, and stress resilience.
Read HRV Deep Dive →Allostatic Load
The cumulative physiological wear-and-tear that accumulates across cardiovascular, metabolic, and immune systems under unrelenting, chronic stress.
Read Allostatic Load Guide →Cardiac Coherence
A state of cardiovascular resonance where HRV synchronizes harmonically with rhythmic 0.1 Hz breathing (6 breaths per minute).
Launch Coherence Timer →Stress Classifications & Models
Acute vs. Chronic Stress
Understanding the critical boundary between adaptive, short-term survival mobilization (acute) and maladaptive, systemic exhaustion (chronic).
See Comparison Table →Eustress
Beneficial, motivating stress that feels manageable, sharpens cognitive focus, and enhances performance without chronic cellular strain.
Read Causes & Triggers →Sensory Grounding
Cognitive-sensory protocols (like 5-4-3-2-1) that engage visual, tactile, and auditory processing to disrupt acute panic and racing thoughts.
Open Grounding Tool →Put Science into Practice: Interactive Tools
Box Breathing (4-4-4-4)
Stimulate vagal afferents and restore immediate cognitive focus with square breathing.
Start Box Breathing →
Cardiac Coherence Timer
Boost HRV and autonomic balance with our free 5-minute visual timer.
Launch 5-Min Timer →
4-7-8 Relaxing Breath
Extended exhalations designed to engage the parasympathetic brake before sleep.
Start 4-7-8 Session →
5-4-3-2-1 Sensory Grounding
Interrupt acute panic attacks and depersonalization with step-by-step sensory prompts.
Open Grounding Tool →Frequently Asked Questions
What is the Teachers Know Scientific Glossary?
The Teachers Know Scientific Glossary is an educational reference providing peer-reviewed, clear explanations of key physiological, neurobiological, and endocrinological terms related to stress and autonomic recovery.
Who writes and reviews the glossary definitions?
Definitions are written by our multidisciplinary educational team and rigorously cross-referenced against primary medical literature (PubMed, WHO, NIH, and major neuroscience journals).
How can understanding biological terms help manage stress?
Understanding the biological mechanisms of the autonomic nervous system, cortisol rhythms, and vagal tone demystifies stress responses, helping you choose evidence-grounded breathing and lifestyle interventions.
Is this glossary a substitute for medical diagnosis?
No. The glossary is an educational resource and is not intended to diagnose, treat, or replace professional medical advice.
Scientific Sources & References
- Endocrine Reviews - The Hypothalamic-Pituitary-Adrenal Axis and Neuroendocrine Regulation (Chrousos et al., PMID: 15734912). pubmed.ncbi.nlm.nih.gov
- Annals of the New York Academy of Sciences - Protective and Damaging Effects of Stress Mediators: Allostasis and Allostatic Load (McEwen BS, PMID: 9701826). pubmed.ncbi.nlm.nih.gov
- Frontiers in Neuroscience - The Vagus Nerve in the Neuroimmune Axis and Autonomic Regulation (Tracey KJ, PMID: 19543458). pubmed.ncbi.nlm.nih.gov