1. D.5: HORMONES & METABOLISM

2. Endocrine glands Endocrine glands secrete hormones directly into the blood stream. Hormones travel to target cells, examples of hormones include: Steroids, proteins, glycoproteins, polypeptides, amines. An example of an endocrine gland is the thyroid.

3. Iodine deficiency Thyroid hormones include two derivatives of tyrosine, triiodothyronine (3 iodine atoms) and tetraiodothyronine (4 iodine atoms). Therefore the thyroid requires iodine to function properly. Consequences of deficiency Goiter (swelling of the neck) as a result of the thyroid being continually stimulated by the hypothalamus & anterior pituitary gland. During pregnancy, iodine deficiency can affect fetal nervous development  mental retardation in children. There is currently a global effort to reduce iodine deficiency.

4. Steroid hormones These hormones bind to receptor proteins in the cytoplasm of the target cell to form receptor- hormone complex. Peptide & lipid hormones differ in their solubility. This means they behave differently, but they both bind to receptors. http://highered.mheducation.com/sites/00725074 70/student_view0/chapter18/animation__mechani sm_of_steroid_hormone_action__quiz_1_.html Estrogen is an example of a steroid hormone.

5. Calciferol Another steroid hormone, crosses the intestinal cell membrane and binds to a receptor within the nucleus of the cell. The receptor-hormone complex effects the expression of the calcium transport protein, calbindin in the small intestines. Calcium is then able to be absorbed in the intestine.

6. Mechanisms of peptide hormones Peptide hormones bind to receptors in the plasma membrane of the target cells. Protein hormones are typically hydrophilic so they cannot pass through the membrane directly. Therefor they must bind to receptors and pass through the membrane using a series of reactions caused by secondary messengers. Secondary messengers are small, water soluble molecules that quickly spread through the cytoplasm. Calcium ions & cAMP (cyclic AMP) are the most common messengers. Example of use: Epinephrine mediates fight/flight. Supply of blood glucose is essential in this instance. When epinephrine reaches the liver, it binds to a receptor called G-protein couple receptor. This activates the G-protein which uses GTP as an energy source to activate the enzyme adenylyl cyclase. The converts ATP to cAMP. The cAMP activates the protein kinase enzymes which activate the processes of glycogen breakdown and inhibit glycogen synthesis http://highered.mheducation.com/sites/0072943696/student_view0/chapter10/animation__second_ messenger__camp.html

7. Pituitary hormones Hormones secreted from the pituitary gland control growth, developmental changes, reproduction and homeostasis. Anterior pituitary Synthesis & secretion of FSH, LH (as well as other hormones responsible for growth, homeostasis & reproduction) Posterior pituitary Oxytocin and ADH (these hormones are not produced here)

8. Hypothalamus Controls hormone secretion by the anterior and posterior lobes of the pituitary gland. The hypothalamus is the region of the brain linking the nervous system to the endocrine system, using the pituitary gland. The hypothalamus releases secreting factors which stimulate the pituitary to release hormones. The hypothalamus is linked to multiple receptors to detect changes in the body to regulate negative feedback.

9. Milk secretion Controlled by oxytocin and prolactin. Prolactin: hormone. Produced by the anterior pituitary, stimulates growth of mammary glands and the production of milk. During pregnancy estrogen stimulates production of prolactin but also inhibits the production of milk. Oxytocin: hormone. Stimulates the contraction of cells surrounding the milk storing structures, causing milk to be released. Oxytocin is produced in the hypothalamus and stored in the posterior pituitary gland.

10. Growth hormones & athletes Growth hormone also produced in the anterior pituitary gland. Liver cells are the target. The hormone binds to receptors and causes the release of an insulin-like growth factor. Growth factor circulates in the blood, stimulates bone, cartilage growth and a gain in muscle mass. For this reason it has been used as a performance enhancing drug.