Everyday definitions for the gut, sleep, stress, movement, nutrition, hormones, and recovery.
Understand the networks connecting organs, signals, and behavior.
The bidirectional communication network linking the central nervous system (brain and spinal cord) with the enteric nervous system of the gut. Signals travel via the vagus nerve, hormones, immune molecules, and microbial metabolites.
A mesh-like network of roughly 500 million neurons embedded in the walls of the gastrointestinal tract. It can operate independently of the brain and is often called the "second brain."
The longest cranial nerve in the body, running from the brainstem to the abdomen. It serves as the primary communication cable between the gut and the brain. Roughly 80% of its fibres carry information upward — from gut to brain.
The collective genetic material of all microorganisms — bacteria, fungi, viruses, and archaea — living in a particular environment. In common usage, "gut microbiome" refers to the community of microbes and their genomes residing in the intestinal tract.
The actual community of microorganisms (the living organisms themselves, not their genes) inhabiting a specific environment such as the gut. The gut microbiota comprises roughly 38 trillion microbial cells.
A signaling molecule with distinct roles in the brain and body. Most total-body serotonin is produced by intestinal enterochromaffin cells and acts peripherally; it does not cross the blood–brain barrier.
A neurotransmitter involved in movement, motivation, learning, and reward. Microbes can interact with dopamine-related compounds in experimental settings, but gut production does not directly set brain dopamine levels.
The primary inhibitory neurotransmitter in the central nervous system. Some microbes can produce GABA in laboratory or gut contexts, but this does not establish an anxiety treatment effect in people.
A hormone involved in normal stress, metabolic, immune, and circadian physiology. Persistent changes are associated with several health factors, but symptoms alone cannot establish an abnormal level or gut effect.
A broad research term for a microbial community pattern associated with disease or altered function. There is no single universal composition that defines dysbiosis or independently diagnoses a condition.
Increased intestinal permeability is a measurable change in gut-barrier function seen in some diseases and research settings. “Leaky gut” is an informal term, not a standalone diagnosis, and does not mean undigested food routinely enters the bloodstream.
Live microorganisms that, when consumed in adequate amounts, confer a health benefit on the host. Common probiotic strains include Lactobacillus and Bifidobacterium species.
Non-digestible dietary fibres and compounds that selectively stimulate the growth and activity of beneficial gut bacteria. Common prebiotics include inulin, fructooligosaccharides (FOS), and resistant starch.
Metabolites produced when gut microbes ferment certain carbohydrates. Acetate, propionate, and butyrate participate in intestinal and metabolic physiology; brain-related effects remain under study.
A short-chain fatty acid produced by microbial fermentation of certain carbohydrates. It is an important energy source for colon cells; proposed neurological effects remain under investigation.
The brain’s ability to change its connections and activity in response to learning, experience, injury, and other influences. Possible relationships with gut-derived signals remain under study.
A neuroendocrine system involving the hypothalamus, pituitary gland, and adrenal glands. Microbiome features have been associated with HPA-axis activity, while human causal mechanisms remain under study.
The roughly 24-hour timing system involved in sleep–wake cycles and many physiological processes. Microbial patterns can vary across the day, with clinical implications still under study.
A protein involved in neuron survival, growth, and plasticity. Exercise is associated with BDNF changes; direct claims that a specific diet or microbiome reliably increases it are not established for individuals.
A biological response involving immune signaling. Inflammatory markers and microbiome features are associated with some mental-health and neurological outcomes, but this does not establish a gut cause for an individual condition.
A broad description of sleep duration, timing, regularity, quality, and the absence of untreated sleep disorders. Individual needs and clinical concerns vary.
The processes through which the body adapts after physical or mental demands. Sleep, nutrition, workload, health status, and time all contribute.
Exercise in which muscles work against external resistance. Established guidance generally recommends muscle-strengthening activity for major muscle groups on two or more days per week for adults, adjusted for ability and health status.
An educational whole-person lens that considers how health behaviors and body systems interact. It is not a medical specialty, diagnosis, or substitute for clinical care.
Throughout the app, you'll see scientific terms highlighted with a dotted underline. Click on any highlighted term to instantly see its definition in a popup. Definitions remain educational and explain where scientific language does—and does not—support personal interpretation.