The Endocrine System is considered the “second great control system” of the body and interacts closely with the nervous system to produce and regulate hormones. Endocrine glands secrete hormones into the blood stream while exocrine glands have ducts and secrete non hormonal substances such as tears or oil or sweat. Hormones are chemicals responsible for regulating the metabolic functions of cells in the body and drain into the bloodstream and the lymphatic system. There are 9 glands (or organs) which produce hormones and these glands comprise the endocrine system and the study of these hormones and glands are called endocrinology.
The endocrine glands are located in the trunk and head, and run along the midline of the body. They include the hypothalamus, pineal, pituitary, thyroid, parathyroid, thalamus, adrenals, pancreas, and/or ovaries and testis. The hypothalamus is considered a neuroendocrine organ because the gland interacts the nervous system with the endocrine system.
Most of the hormones in the body are made up of amino acids except those from the adrenal and sex glands which are steroid hormones. Steroid hormones are made from cholesterol and have an easier time getting in and stimulating the desired target cells – the amino acid based hormones which use ATP (energy molecule) to move inside the target cell membrane. Hormones can survive in the blood from a fraction of a minute up to 30 minutes and the steroid hormones last longer in the blood stream and the make take days before their effects are seen.
The hormonal system attempts to keep the body in homeostasis but the nervous system can override the normal hormonal functions and turn off, or on, hormonal activity. A typical example is that blood sugar rises when the hypothalamus and sympathetic nervous system is under severe stress, to provide the body for more activity potential if required.
The Hypothalamus – the master gland which secretes hormones into the pituitary. It is located just above the pituitary and sphenoid bone (in the upper palate).
The Pineal Gland – Is tiny and resides posterior to the hypothalamus and secretes melatonin.
The Pituitary- the size of a pea and connected by a thin stalk to the hypothalamus. It has two lobes – the anterior one is glandular, derived from oral mucosa, and the posterior one is made of nerve fibers derived from the brain. The adenohypophyseal (anterior) lobe is responsible for making 6 hormones including growth hormone, thyroid stimulating hormone, adrenocorticotropic, hormone and gonadotropins and mainly are responsible for regulating the secretion of other endocrine glands. The posterior lobe hormones are released as needed from the nervous system and include oxytocin and antidiuretic hormone.
The Thyroid Gland- secretes two hormones, thyroxine and triiodothyronine which are responsible for munitioning the bodies metabolism. An under active or overactive thyroid causes major metabolic disturbances.
The Parathyroid Glands- are typically 4 tiny glands and reside in the posterior thyroid. The parathyroid hormone is responsible for regulating the calcium in the blood.
The Thymus Gland- is deep in the sternum and is most active in childhood and young adulthood. It produces thymosins which assists with a healthy immune response and creating mature T cells out of bone marrow.
The Adrenal Glands- are located on top of the kidneys and are comprised of an innner and outer portion. The outer adrenal cortex covers the gland and makes the corticosteroids which help the body deal with stress. Cortisol is the hormone most released with stress and is responsible for affecting metabolism to handle stress. The inner adrenal medulla is made from nervous system tissue and responsible for producing epinephrine (also called adrenaline) initiates the fight/flight response and norepinephrine constricts blood vessels in increases blood pressure.
The Pancreas- Is flat and located behind the stomach. It produces insulin and glucagon which regulate blood sugar. Glucagon releases glucose into boodstream. Insulin lowers blood sugar levels.
The Gonads- Ovaries and Testes produce male and female steroid sex hormones. The ovaries produce estrogen and progesterone and the testes produce testosterone.
Chronic Conditions that Affect this System:
HIgh Blood Pressure
Diabetes (Type 1 and 2)
Chronic Fatigue Syndrome
Excessive carbohydrate intake
Lack of exercise
Marie, Elaine (2004) – Human Anatomy & Physiology, Pearsons Education, San Francisco, Ca.
Siegfried, Donna Rae (2002) – Anatomy & Physiology for Dummies, Wiley Publishing, NY, NY.
Coulter, H. David (2001) – Anatomy of Hatha Yoga, Body and Breath, Honesdale, PA.
Le Page, Joseph (2006) – Professional Yoga Therapist Manual, Chapter 5: Systems of the Body.
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