Overview
This lecture explores interoception—the sense of self that arises from detecting internal bodily states—and explains how brain-body communication shapes health, mood, and performance. Actionable strategies to enhance interoceptive awareness and support gut and nervous system function are included.
Interoception: The Sense of Self
- Interoception is the ability to sense internal bodily states like heartbeat, breathing, and digestion.
- Communication between brain and organs is bidirectional and crucial for physical and mental health.
- Two key signals are detected: mechanical (e.g., organ stretch, heart rate) and chemical (e.g., acidity, nutrient levels).
Brain-Body Communication: The Vagus Nerve
- The vagus nerve, the 10th cranial nerve, connects the brainstem to organs, regulating functions like breathing, digestion, and immune response.
- It transmits both sensory (from organs to brain) and motor (from brain to organs) information.
- Most organs relay their status to the brain; the brain itself lacks pain and touch receptors.
Breathing, Heart Rate, and Alertness
- Inhaling deeply or vigorously increases heart rate; exhaling slowly decreases it.
- Emphasizing long exhales (e.g., double inhale, slow exhale 'physiological sigh') calms and lowers heart rate.
- Repeated deep inhales with short exhales increase alertness and adrenaline.
Gut-Brain Axis and Nutrition
- Gut fullness is detected by stretch receptors, influencing hunger or satiety signals to the brain.
- GLP1R neurons sense both stretch and nutrients (fat, protein, sugar) in the gut, driving eating behavior regardless of taste.
- Foods rich in omega-3s or amino acids can reduce sugar cravings.
Gut Chemistry, Microbiome, and Inflammation
- The gut’s acidity/alkalinity (pH) determines which microbiota thrive, impacting inflammation levels and overall health.
- Regular consumption of fermented foods supports gut microbiome, reduces inflammation, and benefits brain and immune function.
Sensing Danger: Nausea and Fever
- Specialized brainstem neurons (area postrema) trigger vomiting when blood chemistry signals toxicity.
- Ginger (1-3g) and cannabis can reduce nausea by acting on these brainstem circuits.
- Fever arises when brain sensors detect toxins, prompting body temperature increase to fight pathogens; safe cooling targets are palms, soles, and face.
Interoception, Emotions, and Social Connection
- The vagus nerve aggregates internal signals (gut, heart, breathing) to shape emotional states.
- Stress can disrupt vagus communication, impairing gut-brain signals and digestion.
- Facial expressions and even physiological states may synchronize between closely connected individuals.
- Focusing on perceiving your own heartbeat enhances interoceptive awareness and mind-body connection.
Key Terms & Definitions
- Interoception — sensing the internal state of the body (heartbeat, gut, breath).
- Vagus Nerve — major nerve linking brain and organs, enabling brain-body communication.
- GLP1R Neurons — gut neurons detecting stretch and nutrients, influencing hunger.
- Microbiome — community of microorganisms in the gut affecting health.
- Area Postrema — brainstem region that senses toxins and can trigger vomiting.
- OVLT (Organum Vasculosum of the Lateral Terminalis) — brain structure detecting blood chemistry, involved in fever.
Action Items / Next Steps
- Practice sensing your heartbeat for 1–2 minutes daily to improve interoceptive awareness.
- Incorporate fermented foods into your daily diet to support gut and brain health.
- Use slow, extended exhales (physiological sighs) for stress reduction and alertness control.