9.2 Cardiovascular, Endocrine, and Digestive Systems

Three systems, one competency, zero medical license

Yoga Alliance's RYS 200 physiology list groups cardiovascular/circulatory, endocrine, and digestive systems as they relate to yoga practice. School tests want a teacher who can sketch each system, connect it to common class shapes, and stop before diagnosis. This independent OpenExamPrep section covers that cluster. It does not replace a clinician, a registered dietitian, or the inversion-asana chapter that already covers cervical load and pose regressions.

SOP Principle 2 lets you teach yoga. SOP Principle 4 lets you share physiology with sources cited. SOP Principle 5 forbids services you are not licensed to provide. An RYT 200 credential is not a license to practice medicine, nutrition, or endocrinology.

Cardiovascular and circulatory basics for teachers

The heart is a muscular pump. Arteries generally carry blood away from the heart; veins generally return it; capillaries are the exchange beds. Blood pressure is the force of blood on vessel walls. Heart rate is beats per minute. You may observe that a Sun Salutation sequence often leaves people warmer and puffing; you may not take a diagnostic blood-pressure reading and then 'prescribe' a pose to replace their medication.

Gravity is the yoga-specific circulatory talking point. In standing, more hydrostatic pressure sits in the legs and feet. In a full inversion (hips and feet above the heart and head, as in many versions of Sirsasana or Sarvangasana), the hydrostatic story toward the head and eyes changes. That is a teaching flag, not a treatment claim. Chapter 5 already maps pose alternatives such as Viparita Karani (Legs-Up-the-Wall) and Downward-Facing Dog as a milder invert. This section answers the physiology why you listen when a student mentions pressure in the head or eyes.

Common marketing myths to refuse on a written test:

• Inversions do not 'rest the heart' as a cardiology procedure.
• You cannot promise that a pose 'increases blood flow to the brain' as a medical benefit. Blood-flow regulation is complex; teachers do not run that experiment on a stranger.
• Legs-up-the-wall is often better teaching than a full invert for mixed-level classes. That is pedagogy and load management, not a claim that the pose treats venous disease.

If dizziness, chest pain, sudden severe headache, or neurological symptoms appear, you are in first-aid and emergency-services territory, not asana coaching. Stop the pose, follow studio emergency policy, and do not improvise a diagnosis.

Endocrine stress chemistry at 200-hour level

The endocrine system uses hormones in blood as slower, longer-range messengers than nerves. For RYS 200, the pathway you must be able to name is the hypothalamic–pituitary–adrenal (HPA) axis and cortisol.

Trace it in one direction:

1. The hypothalamus in the brain can release corticotropin-releasing hormone (CRH) when the organism reads a stressor.
2. The anterior pituitary can respond with adrenocorticotropic hormone (ACTH).
3. The adrenal cortex can then secrete cortisol, a glucocorticoid that helps mobilize energy (raising available glucose) and participates in many other body-wide effects.

The adrenal medulla, sitting next to that cortex, is the sympathetic-adjacent burst pathway: epinephrine (adrenaline) for rapid mobilization. Students mix cortisol and adrenaline into one 'stress hormone.' On a school quiz, keep them in the right building: cortex/HPA for cortisol; medulla/sympathetic for epinephrine.

Cortisol is not a villain in a cape. An acute rise can be adaptive (you need fuel to move). Problems associated with chronic HPA drive belong to medicine and public health, not to a 200-hour script that says 'this class will cut your cortisol 23 percent.' Yoga research on cortisol is mixed, population-specific, and not a license to advertise hormone therapy.

Classroom application: vigorous standing work can match a student who wants heat. A restorative close, longer exhale, and fewer sudden commands are a reasonable way to reduce stimuli. You still do not claim you completed an endocrine treatment. If a student describes fainting, unexplained weight change, or steroid-medication questions, refer to their licensed clinician.

Digestive system: general teaching points, hard limits

The digestive system is the tube from mouth to anus plus accessory organs (liver, gallbladder, pancreas). Motility and secretions are heavily autonomic. Parasympathetic tone is the 'rest and digest' nickname you already met. Eating a large meal and then taking a jumping vinyasa is often uncomfortable because the gut and the skeletal muscles are competing for blood and attention. That is a comfort and pacing point, not a diagnosis.

Twists (for example Ardha Matsyendrasana) and forward folds (for example Paschimottanasana) are classically described in yoga rooms as 'good for digestion.' At 200-hour level, keep the claim modest and mechanical:

• A twist changes pressure in the abdomen. Some students report gas movement or a sense of 'wringing.' That is anecdotal classroom language, not proof you massaged the liver into detoxification.
• A forward fold can compress the abdomen and is often sequenced toward the quiet end of class. Some students find that soothing. Others with reflux, hernia history, or pregnancy need less compression — and you take their word plus school policy, not a GI workup you are not qualified to run.
• After a heavy meal, skip deep abdominal compression as a courtesy.

Myths to fail on purpose:

• Twists do not 'wring toxins out of the liver and kidneys' like a sponge. The liver and kidneys are not laundry. Detoxification is a physiologic job those organs already do; you do not squeeze them clean with a seated twist.
• You do not 'reset the microbiome' with a lunchtime vinyasa.
• You do not diagnose irritable bowel syndrome (IBS), inflammatory bowel disease, celiac disease, or food intolerance from a student's symptom list in the lobby.

Scope of Practice limits (memorize these for ethics crossover questions):

• Do not diagnose IBS or any other digestive disease.
• Do not prescribe diets, supplements, juice fasts, or 'yoga diets' as medical nutrition therapy unless you are separately and currently credentialed to do that work, and even then you do not use RYT letters to advertise the other license.
• Do not tell a student to stop a gastroenterologist's plan.
• Do offer optional shapes, props (bolster to reduce fold depth), and the sentence: 'I can share general yoga practices; I cannot treat your gut. A licensed clinician is the right person for diagnosis and diet.'
• Do keep a referral list if your studio policy allows: physicians, mental-health professionals, and other local resources. SOP Principle 5 names referral as an option; it does not name you as the specialist.

A written-test scenario

A student says, 'I have IBS. Put me in twists and tell me what to eat this week. Also I have high blood pressure — inversions will fix that, right?'

A passing answer has three parts. One: you do not confirm or reject the IBS label, and you do not write a meal plan. Two: you may offer a mild twist or skip it, with the student in charge of sensation, and you refuse the detox story. Three: you treat unmanaged blood pressure as an inversion flag, offer a non-inverted rest shape, and you do not claim inversions treat hypertension. That answer shows physiology literacy and SOP. The trainee who 'fixes' both conditions with poses fails the competency even if their Sanskrit is perfect.

Assessment traps

• Medical claims for inversions (treat glaucoma, stroke, hypertension).
• Hormone percentages and 'adrenal reset' protocols.
• Diet prescription and IBS diagnosis.
• Liver-wringing detox myths.
• Using RYT 200 to imply a medical, nutrition, or mental-health license.

Stay a yoga teacher. Name the systems. Offer adaptations. Refer out.