Yoga postures provide many benefits on physical, psychological and spiritual levels. We direction, insight and inspiration during asana practice when reminded of the benefits of individual postures. The benefits of a given posture are often myriad, able to be viewed from infinite angles. Here the benefits of the postures are approached through the dominant chakra center affected, and this is related in terms of its relationship with the associated endocrine gland.
Chakras are astral centers in the form of a lotus that store pranic energy. As nerve plexus centers are composed of interconnecting spinal nerves, the chakras are located at the convergence of the nadis, the pranic currents.
The endocrine glands secrete hormones that enter the blood or lymph systems to regulate activity in other parts of the body. The emotions and the glands of the endocrine system affect one another. (For example adrenaline from the adrenal medulla fine tunes the senses, while an over-stimulation causes edginess and eventual exhaustion.) Yoga therapy uses asana to restore endocrine function to a balanced state.
The pituitary glands secrete eight important hormones. As such they are associated with the Sahasrara chakra, the thousand-petal lotus chakra, and the gateway to spiritual understanding. The sahasrara is located at the top of the head and relates to thought, understanding and spiritual connection. Imbalances in the sahasrara manifest as neurological disorders, depression, apathy, alienation, confusion or being overly intellectual. The pituitary structure lies in a small bony cavity at the base of the brain. The structure is actually composed of two separate units that serve as distinct glands. First, the anterior pituitary gland secretes six hormones: 1. Growth hormone, 2. Thyroid stimulating hormone, 3. Adrenocorticotropic hormone, 4. Prolactin, 5. Follicle-stimulating hormone, and 6. Leutinizing hormone.
Growth hormone functions throughout the body's life. During the growing phase, it promotes development and enlargement of all body tissues. After adolescence, growth hormone increases the rate of protein synthesis in all body cells, decreases the rate of carbohydrate utilization, and increases the mobilization of fats and the utilization of fats for energy.
The anterior pituitary gland completely controls the thyroid through thyroid stimulating hormone. Without this hormone the thyroid, associated with the visshudha chakra, becomes so incapacitated that it secretes almost no hormone.
In a similar manner, the anterior pituitary gland controls the function of the adrenal glands, located on the kidneys and associated with the muladhara chakra. The anterior pituitary gland secretes adrenocorticotrophic hormone to control the secretion of adrenocortical hormones associated with the manipura chakra.
Prolactin is secreted during pregnancy and throughout lactation. On giving birth the prolactin level returns to the non-pregnant level. While a mother nurses her baby, the prolactin level rises to a series of peaks. At the onset of nursing, the level reaches ten times that amount to stimulate milk production for the next feeding. If prolactin is not secreted due to hypothalamic or pituitary malfunction, the ability to produce milk is lost in a few days.
The anterior pituitary gland also produces two gonadotrophic hormones, with roles in ovarian and testicular function, associated with the svadhisthana chakra. In the female, once follicle-stimulating hormone (FSH) is secreted upon puberty the ovarian follicles mature and release ova. FSH along with luteinizing hormone causes the ovaries to release estrogen. It is the interplay between the levels of these three hormones and progestin with their built-in feedback mechanisms that regulate the reproductive cycle in the female.
In the male, FSH promotes sperm development and luteinizing hormone stimulates the testes to secrete testosterone.
The second section of the gland, is called the posterior pituitary gland. This structure only stores--rather than secretes-- the hormones antidiuretic hormone and oxytocin, which are secreted by the hypothalamus. Antidiuretic hormone allows the kidneys to recoup water that would otherwise be lost in the urine. Oxytocin stimulates muscle contraction in the uterus and the breasts for giving birth and lactating.
Descending the sushumna nadi, the next chakra is the ajna, located at the forehead or "third eye." This center of mental activity controls perception and intuition. As such, an imbalance in this chakra alters mental perception, evidenced by headaches, nightmares, or hallucinations. The ajna is associated with the pineal gland, whose function is not fully understood scientifically. It is believed, however, believed to have widespread influences. The secretion of one of its hormones, melatonin, is based on the number of hours of darkness. Light striking the eyes inhibits melatonin production. This control mechanism is used in seasonally breeding species to initiate the mating season. In humans, melatonin may have a role in initiating puberty. The pineal gland may initiate responses such as temperature regulation
and immune response according to time of year. This theory would support the use of postures emphasizing ajna such as spinal twist and yoga mudra with forehead on the floor as a treatment for seasonal affective disorder.
The visshudha chakra is located in the throat and is intimately associated with the thyroid gland. It deals with speaking and communication and is associated with the throat, arms, mouth, ears, hands and skin (imagine the additive communication from those parts!) Imbalances manifest as thyroid disorder, sore throat, neck ache, poor communication and holding back truth.
The thyroid gland is shaped like a bow tie and is located on the trachea beneath the larynx. Hormones of the thyroid gland increase metabolic rate and are essential to normal growth and nerve development. Thyroid hormone increases the body's overall metabolic rate and has a heat-producing effect. It also increases the effects of epinephrine and norepinephrine (see muladhara chakra, below) and increases the rate and force of heart contraction. Finally, thyroid hormone affects growth, development and regulation of the central nervous system, by regulating the secretion of growth hormone and promoting its effects.
Asanas that balance the visshudha chakra include bridge, wheel, inclined plane and half shoulder stand.
The heart center is the base of love. Poses emphasizing the heart center and its associated chakra, the anahata, include fish, camel and wheel. Imbalances manifest as asthma, heart problems, resentment and bitterness. With the anahatha is associated the thymus gland. The thymus gland helps form specific types of immune cells and helps control the entire immune process. Thymus secretion decreases after about thirty to forty years of age, and a link has been suggested between this decrease and increased susceptibility to viral infections and cancer as one ages.
Located at the solar plexus, the manipura chakra represents power, control and ego. Endocrine glands associated with it are the adrenal and pancreas. Blockages in the manipura chakra manifest as ulcers, diabetes, hypoglycemia, timidity, domination and digestive problems.
The pancreas has specialized cells that differ from the majority of its cells, which secrete digestive juices that are delivered through ducts to the digestive tract. These groups of specialized cells are called islets of Langerhans and the hormones they secrete are carried in the blood vessels. The two hormones produced, insulin and glucagon, are the primary regulators of fuel metabolism. Insulin is secreted upon an increase in blood glucose levels. It lowers blood glucose levels and promotes the storage of fats. Glucagon mainly serves to the opposite effect, increasing blood sugar levels and promoting the breakdown of fats.
Also associated with the manipura chakra are the hormones secreted by the adrenal cortex. The adrenal glands, located on the kidneys, actually comprise two distinct structures, one surrounding the other. The adrenal cortex is the outer layer and secretes several steroid hormones. They fall into several categories affecting carbohydrate, fat, and protein metabolism; regulating kidney secretion of sodium and potassium and androgen sex hormones.
Asanas that pertain to the manipura chakra include the navasana, shalabhasana, and dhanurasana.
Located in the lower abdomen and meaning "sweetness," the svadhisthana chakra is associated with the ovaries in the female and testes in the male. It regulates the sexuality, emotions, desire and passion. In a balanced state it produces fluidity, pleasure and relaxation; imbalances manifest as isolation, emotional instability and bladder problems.
The male sex hormone is testosterone and is responsible for the development of the male physical characteristics. It also has roles in the generation of sperm and promotes male hair growth patterns; it causes the pitch of the voice to deepen, and the body to become larger and more muscular.
The two ovarian hormones are estrogen and progesterone. They are responsible for the female sexual characteristics and the female monthly fertility cycle. Estrogen causes the main physical differences distinguishing the female from the male by causing the proliferation of cells in the corresponding regions of the body. In contrast, progesterone promotes fertility by causing the lining of the uterus to thicken; and it causes the breasts to enlarge and to be able to secrete milk. It also inhibits uterine contractions from expelling the new life.
The conditions associated with the svadhisthana chakra are kept in balance with the practice of bidalasana, bhujangasana, navasana, and ekapada rajakapotasana.
At the base of the spine is the muladhara chakra, the root, dealing with survival, security and safety. The endocrine function associated here is the secretion of the adrenal medulla, the center of the adrenal glands. Balance of this chakra is manifest as stability, grounding, prosperity and right livelihood.
The secretory cells adrenal medulla are modified sympathetic nerve cells whose secretions, epinephrine and norepinephrine, reach cells with no direct sympathetic nerve contact. These hormones support "fight or flight" response by causing an increase in metabolic rate, blood pressure and glucose levels, and enhanced mental activity.
Balance of the muladhara chakra is maintained with the standing asanas, bhekasana, paschimottanasana and janu shirshasana.
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