Human Anatomy and Physiology Relevant to Yoga Practice
What is examined
Basic anatomy and physiology applied to yoga: bones, joints, muscles, respiration, circulation, nervous and endocrine control, and the physiological effects of practice. Questions ask you to predict what a posture or breath does.
Key structures
- Skeletal: 206 bones; vertebral column 7 cervical, 12 thoracic, 5 lumbar, sacrum, coccyx. The thoracic curve and rib cage affect breathing.
- Muscular: diaphragm (primary inspiratory muscle), intercostals, rectus abdominis, transversus abdominis, erector spinae, psoas, hamstrings, iliopsoas.
- Respiratory: tidal volume ~500 mL; vital capacity ~4.8 L; residual volume ~1.2 L. Diaphragmatic contraction creates negative intrathoracic pressure and draws air in.
- Cardiovascular: heart rate, stroke volume, cardiac output; baroreceptors and vagal tone.
- Nervous: CNS and PNS; autonomic sympathetic (fight/flight) and parasympathetic (rest/digest); vagus nerve (cranial X) slows heart rate.
- Endocrine: cortisol from adrenal cortex; adrenaline from medulla; insulin from pancreas.
Yoga effects
Slow breathing at about 6 breaths/min increases vagal tone and baroreflex sensitivity, reduces sympathetic arousal and lowers cortisol. Forward bends tend to calm; backbends can be stimulating. Inversions alter venous return and baroreceptor input.
Worked example
Question: during ujjāyī with a 1:2 inhale-to-exhale ratio, what happens? Reasoning: a longer exhale increases parasympathetic outflow via the vagus, reduces heart rate, and improves HRV. It does not increase oxygen saturation directly.
Traps
Equating prāṇa with oxygen; confusing residual volume with vital capacity; saying the sympathetic nervous system lowers heart rate; attributing all benefits to one posture.