Endocrine System

• a network of glands throughout the body that manufacture and secrete hormones The endocrine system and the nervous system work together in order to regulate the physiological processes in the human body. uses blood vessels to deliver hormones to their target sites in the body
• A network of glands makes up the endocrine system which includes the pituitary gland, adrenal glands and the reproductive organs (testes, ovaries). All of these glands secrete different hormones which regulate the activity of organs and tissues in the body. Hormones are chemical messengers that regulate the activity of cells in the body. They are secreted directly into the bloodstream, where they travel to their “target cells
• Hormones usually affect only a limited number of cells, known as target cells. Target cells respond to a particular hormone because they have receptors for that hormone. Cells that do not have a receptor cannot be influenced directly by that hormone. When enough receptor sites are stimulated by hormones, this results in physiological reaction in the target cell. Timing and the correct levels of hormone released are critical for normal functioning. Too much or too little release at the wrong time = dysfunction or abnormalities.
• hypothalamus receives info from many sources about the functions of the body. As a consequence it controls the release of hormones from the pituitary gland. The ‘master gland’ of the body is the pituitary because many of the hormones released by the pituitary gland control the secretions of other endocrine glands. These hormones either directly cause changes in physiological processes in the body or stimulate other glands to produce other hormones.
• pituitary gland - the anterior (front) pituitary and the posterior (back) pituitary. E.g. the anterior pituitary releases ACTH as a response to stress. ACTH stimulates the adrenal glands to produce cortisol. anterior pituitary also produces two hormones important in the control of reproductive functioning and sexual characteristics: In females these hormones stimulate the ovaries to produce oestrogen and progesterone and in males they stimulate the testes to produce testosterone and sperm. The posterior pituitary releases oxytocin which stimulates bonding between mother and infant.
• The outer part of the adrenal glands is the adrenal cortex which releases hormones necessary for life. The inner part is the adrenal medulla which releases hormones that are not necessary for life.
• The adrenal cortex produces cortisol - supports bodily functions - cardiovascular and anti-inflammatory functions. Cortisol production also increases in response to stress. If the cortisol level - high, = poor immune function and an inability to deal with stress.
• The adrenal medulla releases adrenaline and noradrenaline which are hormones that prepare the body for fight or flight eg by increasing heart rate & blood flow to the muscles. The adrenal medulla releases adrenaline and noradrenaline, hormones that prepare the body for fight or flight e.g. by increasing heart rate & blood flow to the muscles.