Chapter 21 Human Endocrine System
Endocrine System Consist of endocrine glands that secrete hormones which regulate a wide range of activities in humans Hormones- are secreted by glands and diffuse directly into the bloodstream
(1) Hypothalamus Small region of the brain It controls the release of hormones by the pituitary gland Considered to be a major link between the nervous system and the endocrine system
(1) Hypothalamus
(2) Pituitary Gland Located at the base of the brain Called the master gland because it controls the activities of other glands Secretes three major hormones: GH, TSH, and FSH
(2) Pituitary Gland
Growth Hormone (GH) This hormone controls the growth of the body by stimulating the elongation of bones
Growth Hormone (GH) Gigantism: Oversecretion of HGH.
Growth Hormone (GH)
Growth Hormone (GH) Gigantism and dwarfism. Dwarfism: an undersecretion of HGH.
Growth Hormone (GH) Gigantism and dwarfism. Dwarfism: an undersecretion of HGH. Tattoo from fantasy island.
Thyroid Stimulating Hormone (TSH) Stimulates the thyroid gland to produce its hormone thyroxin
Follicle Stimulating Hormone (FSH) Stimulates the activities of the ovaries and testes
(3) Thyroid Gland Located in the neck below the larynx and in front of the trachea This gland secretes thyroxin which contains iodine
(3) Thyroid Gland Located in the neck below the larynx and in front of the trachea This gland secretes thyroxin which contains iodine
Thyroxin Regulates the rate of metabolism in the body and is essential for normal physical and mental development Secretion of thyroxin is regulated by TSH, which is secreted by the pituitary gland Lack of iodine in the diet will lead to lack of thyroxin secretion. This produces enlargement of the thyroid gland and is called Goiter Goiter- is the result of iron deficiency in the diet
(4) Parathyroid Gland Are tiny oval glands embedded in the walls of the thyroid gland Secretes parathormone Parathormone controls calcium metabolism Calcium is necessary for proper growth of teeth and bones, blood clotting, and nerve function
(4) Parathyroid Gland Are tiny oval glands embedded in the walls of the thyroid gland Secretes parathormone Parathormone controls calcium metabolism Calcium is necessary for proper growth of teeth and bones, blood clotting, and nerve function
(5) Adrenal Gland Located on the top of each kidney Each gland consists of two layers: Adrenal cortex Adrenal medulla
(5) Adrenal Gland
Adrenal Cortex Secrete steroid hormones that: a) regulate water balance and blood pressure by controlling the reabsorption of sodium salt into the blood from the kidneys b) stimulate the conversion of fat and protein into glucose
Adrenal Medulla Secretes adrenalin Adrenalin increases the blood sugar level and accelerates the heart and breathing rate
(6) Pancreas Both an exocrine gland and an endocrine gland The exocrine portion secretes digestive juices into the small intestine The endocrine portion consists of small clusters or islands of hormone-secreting cells called the Islets of Langerhans The Islet of Langerhans secrete insulin and glucagon
Pancreas
The Islets of Langerhans secrete insulin and glucagon
(6) Gonads Sex organs 1. Males- testes that secrete testosterone which influences the development of the male secondary sex characteristics 2. Females- ovaries that secrete estrogen which influences the development of secondary sex characteristics
Insulin Facilitates the entrance of glucose into the cells Insulin lowers blood sugar levels by promoting the movement of sugar out of the blood and into the liver where it is stored as glycogen
Glucagon Stimulates the release of sugar from the liver and into the blood Therefore: insulin lowers sugar level in blood glucagon raises sugar level in blood
Diabetes When the Islets of Langerhans fail to produce enough insulin As a result, glucose that enters the cell decreases, and glucose levels in the blood increases
Negative Feedback Is a type of self-regulation associated with endocrine regulation Functions like a thermostat. Only activated when there is a need. Shuts off once that need has been met.
Negative Feedback It operates on the principle that the level of one hormone in the blood stimulates or inhibits the production of another hormone Ex: TSH regulates the secretion of thyroxin by the thyroid gland
Normal Thyroid Thyroid with Goiter