The Axial Skeleton: the Spine

1. The Axial Skeleton: the Spine

2. The human skeleton consists of 206 bones. Many of which move or hinge at joints. In conjunction with over 600 muscles these bones enable the human body to achieve a variety of movements. • The functions of the skeletal system include: - • To provide a lever system against which muscles can pull. • To provide a large surface area for the attachment of muscles. • To protect delicate organs such as the brain. • To give shape to the body. • To give support to the body. • To manufacture red blood cells and to store fat calcium and phosphate.

3. The bones of the body are grouped into two major divisions. • The axial skeleton consists of the bones, which lie around the longitudinal axis of the body. These include the SKULL, VERTEBRAL COLUMN, STERNUM & RIBS. • The appendicular skeleton consists of the bones of the LIMBS, PECTORAL (shoulder) GIRDLE, & PELVIC (hips) GIRDLE.

4. Bone is considered a connective tissue. Its internal structure somewhat resembles that of coral in that it is not solid, but filled with holes. Nonetheless, it provides sufficient structure to keep us upright and stable.

6. Joints are where two or more bones articulate (move). • Joints are classified according to how much movement they allow. 1. Fibrous – these are fixed or immovable joints such as the cranium, sacrum and the coccyx. 2. Cartilaginous – these are slightly movable joints such as the vertebrae. 3.Synovial – these are freely movable joints such as the shoulder and hip.

7. All synovial joints have the following in common:

8. In asana the synovial joints are the most important to understand. There are 6 types of synovial joint. 1.Ball & socket – hip and shoulder. 2. Hinge – knee, elbow and ankle. 3. Pivot – radio-ulna, atlas/axis. 4. Saddle – thumb. 5. Condyloid – wrist. 6. Gliding – between vertebrae in spine.

9. Atlas/axis: a pivot joint In this joint the atlas and axis bones articulate to allow rotation as in shaking or nodding your head.

10. The rest of the spine is comprised of gliding joints and has five areas with reciprocating curves in order to bear weight, provide support and create stability for the body.

12. Spinal vertebrae are specialized according to location and function.

13. Cervical Vertebrae Sacrum and coccyx

14. Each vertebra, except for those at the sacrum, is separated from the one above and below by discs, which are comprised of a gelatinous substance that helps the vertebrae glide smoothly as they move to create axial range of motion.

15. ***A healthy spine moves in 6 directions: forward and backward, side to side and twisting side to side. The anatomical name for these movements are Flexion----- forward bending; angle between front of trunk and legs is decreased Extension--- back bending; angle between front of body and trunk is increased Lateral flexion---side bending; angle between side of trunk and legs is diminished Rotation--twisting; vertebrae spin around invisible line down center of spine

16. The spine is the support for the nervous system, and because the spinal cord runs through the vertebral bodies and the nerve fibers for our internal organs as well as for our muscles and connective tissue diverge from the spinal column, yoga’s primary activity can be seen as keeping the spine supple and free of compromise. Disc injury and deterioration is one of the primary causes of both pinched nerves and back pain. Maintaining space between the vertebrae and discs assists in optimum functioning of both the spine and nervous system. .

19. Discs and vertebrae are held together by ligaments.

20. LIGAMENTS (from manual): 1. most ligaments are not designed to stretch 2. if overstretched will return to normal length if chronically overstretched, will become flaccid, creating instability in the joint if stretched beyond 6% of normal, will tear give joints their stability

21. Yoga Principles for the Skeletal System 1. warm joints before stretching and/or strengthening 2. balance opposing muscle groups in terms of strength flexibility 3. maintain relaxed attitude to avoid releasing cortisol stress hormones 4. be fully conscious of points of contact between parts of skeletal system and floor, other body parts and in space 5. draw bones into joint capsules when practicing 6. use muscles to create space in the joints

22. The nervous system is divided into the central nervous system (CNS) = brain and spinal cord and the peripheral nervous system (PNS) = what is outside brain and spinal cord.

23. The peripheral nervous system further divides into • 2 branches: • the somatic nervous system (SNS), which coordinates bodily movements and receives external stimuli and is largely under volition • the autonomic nervous system (ANS), which is largely NOT under conscious control. This is further divided into the Sympathetic Nervous System, the Parasympathetic Nervous System and the Enteric Nervous System

24. The Sympathetic Nervous System • responds to impending danger • is responsible for the increase of one's heartbeat, • blood pressure and adrenaline in the system, • creates "fight or flight" responses, • slows down the digestive system • so that more blood is available to carry • oxygen to the vital organs such • as brain, heart and muscles.

25. The enteric nervous system manages every aspect of digestion, from the esophagus to the stomach, small intestine and colon. It has been described as a “second brain” because it can operate autonomously. It normally communicates with the central nervous system through the vagus nerve, a part of the parasympathetic system and via the prevertebral ganglia of the sympathetic nervous system. But, studies have shown that if the vagus nerve is severed, the enteric nervous system continues to function.

26. The parasympathetic nervous system is operative when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and genitourinary systems (rest and digest)

28. We begin our yoga classes by asking students to focus on their breathing so that we can stimulate the parasympathetic nervous system. Through activation of this nervous system, we encourage a non-competitive form of physical conditioning that heightens awareness, releases tension and constriction in the tissues, and creates inner peace. We create an environment in which our students can “rest and digest” their sensations, their thoughts, their emotions and the events in their lives.

29. Sthira sukham asanamThe posture is firm and soft.Patanjali’s Yoga Sutras 2. 46orAsana must have the dual qualities of alertnessand relaxation.Desikachar, The Heart of Yoga, p. 181

30. Yoga and the Spine: Leslie Kaminoff Important Points The 4 reciprocating spinal curves set humans apart from other primates (17). Human beings have the smallest base of support, t the highest center of gravity, the heaviest brain, and they are the least mechanically stable of all creatures. The spine exhibits extraordinary balance between firmness/rigidity and softness/plasticity. His discussion of intrinsic equilibrium is essentially based on the mechanics of force and tension.

31. Intrinsic equilibrium: the axial skeleton will right and support itself when all mechanical forces are removed from it. These forces amount to muscular tension in our efforts to resist gravity. Removal of this tension releases stored energy in the body. Yoga removes this tension and thus releases energy. As we move about in the gravitational field, we apply tension and contraction to the spine by the application of muscular effort. The spine is wonderfully able to neutralize these forces by virtue of its construction.

32. The reciprocating curves dissipate load (force/weight) and the discs absorb compression. The discs, being filled with fluid, are soft and mobile. The vertebral bodies are firm/structure. The front of the spinal column is designed to support the body’s weight, while the back of the column, comprised of arches, distribute the forces into the ligaments/connective tissues (20). The discs, when healthy, are self-correcting. In twisting and weight bearing, some of the liquid from the discs leak into the porous bone tissue. When the compressive forces are withdrawn, moisture returns. *11. Flexion, extension and lateral flexion produce asymmetrical forces/movement on the nucleus of the discs.

33. Each time the front part of the spine is compressed, a corrective tension occurs in the ligaments at the back of the spine and vice versa(23). The primary curves are kyphotic: thoracic and sacral. A way to identify these are to note which curves touch the floor in sivasana. 14. The secondary curves are lordotic: cervical and lumbar. *15. Spinal flexion is defined as an increase in primary curves and spinal flexion and extension in cat-cow replicate the shape change of breathing(25). Lordosis/lordotic. . .curved into the front of the body. Kyphosis/kyphotic. . .curved away from thefront of the body.

34. NOTE: Kaminoff’s definition of spinal movement differs radically from the traditional definition. Flexion and extension defined as relationships among primary and secondary curves. Forward and back bending defined as movements of body in space. AND, he recommends a recuction of the thoracic curve as a safe extension instead of the usual backbend.

35. In reference to lateral flexion and twisting, Kaminoff’s recommendation is to look closely at the spine to see what’s happening. We can lengthen the sides of the body w/ lateral flexion and we can twist from the hips and shoulders instead of from the spine. Demo Axial extension is an additional spinal movement, which results in taking all curves out of the spine.

36. Back Muscles Erector Spinae