Hormones and functions

• Hormones are chemical messengers produced by specific cells or organs, which travel through the blood to target tissues where they bind to receptors on cell surfaces or inside cells.
• Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands (including the adrenal medulla), pancreas, ovaries/testes, pineal body, thymus, hypothalamus, and placenta.
• The endocrine system is responsible for regulating various bodily processes such as growth, metabolism, reproduction, sexual development, water balance, and response to stress.
• GOAT FLAP stands for, Growth hormone, Oxytocin, Anti-diuretic hormone, thyroid stimulating hormone, follicle stimulating hormone, luteinising hormone, adrenocorticotropic hormone, and prolactin
• Anti-diuretic hormone increases water retention/reabsorption in the nephron (kidneys)
• Growth hormone regulates body growth such as bone growth and muscle mass. Is an anterior pituitary gland hormone
• Oxytocin stimulates contractions in child birth and contractions of the lobules in the breast for lactation
• Thyroid stimulating hormone (TSH) stimulates the thyroid gland to secret thyroxine (which controls basal metabolic rate)
• Follicle stimulating hormone stimulates sperm production/maturation in males and egg maturation
• Luteinising Hormone (LH) triggers ovulation in women by acting on ovaries to stimulate oestrogen production and testes to stimulate testosterone production/release in men
• Adrenocorticotropic Hormone (ACTH) stimulates adrenal glands to produce hormones - especially cortisol. Is an anterior pituitary gland hormone
• Prolactin promotes lactation in mothers
• Melatonin is involved in sleep-wake cycles
• The endocrine system function/physiology: Cellular communication throughout the body and assists the autonomic nervous system in maintaining homeostasis by coordinating and regulating the activity of cells.
• The endocrine system consists of a group of glands that control the organs by sending chemical messages (e.g. hormones) in the blood. There are 2 types: Exocrine and Endocrine
• Exocrine – secrete their contents through tiny tubes or ducts onto an interior or exterior body surface.

    Eg. Sweat & lacrimal (tear)
• Endocrine(ductless) glands secrete hormones directly into the blood stream, which then delivers them to their specific target cells or tissues.
• Organs that are purely endocrine organs are the Pituitary gland, Pineal gland, Thyroid gland, Parathyroid glands and Adrenal glands: Cortex and Medulla
• Endocrine cells in other organs are the Pancreas, Thymus, Gonads (Ovaries and Testes) and Hypothalamus
• The Hypothalamus is located in the brain and secretes hormones that regulate the pituitary gland
• The Pituitary Gland is located in the brain and has 2 lobes - anterior & posterior. It secretes hormones that control the function of the other glands in the endocrine system.
• The Thyroid Gland is located in the neck and produces thyroxine which increases cellular metabolism.
• Parathyroid Glands are four small glands on the back of the thyroid gland that produce parathyroid hormone (PTH) which controls calcium metabolism.
• Adrenal Glands have two parts and are found on top of the kidneys; cortex and medulla. The adrenal cortex produces steroid hormones such as aldosterone, glucocorticoids and sex hormones. The adrenal medulla produces catecholamine hormones such as epinephrine and norepinephrine.
• The Pancreas has both exocrine and endocrine glands and releases pancreatic juices into the duodenum (exocrine). The Pancreas also releases insulin (lowers blood sugar) and glucagon (increases blood sugar) into bloodstream (endocrine).
• The Thymus is located just above the heart and produces a group of hormones called thymosins. It is involved in the maturation white blood cells.
• The gonads are Ovaries in women, Testes in men. Ovaries produce oestrogen (secondary sexual characteristics) and progesterone (maintains endometrium) Testes produce testosterone.
• The Pineal Gland is located in the brain and produces melatonin which regulates the day/night response.
• Hormones are chemical messenger molecules secreted by endocrine glands transported by the blood.
• Hormones can affect a particular group of cells (target cells) or particular organs (target organs).
• Hormones are only able to influence cells that have the specific hormone receptors. Hormones will continue to bind until saturation occurs.   
• Hormones alter cellular activity by: Changing the permeability of the cell membrane or Changing the rate of chemical reactions which occur in the cell.
• Hormones also alter the type, activities or quantities of proteins produced. Hormones may: Activate certain genes (Nucleus) (enzyme/protein), Change shape/structure of enzyme, Change rate of transcription/translation of proteins (change rate of production)
• Hormones that activate enzymes cause enzyme amplification.
• There are three types of hormones: proteins, steroids or amines.
• Steroid hormones – enter through plasma membrane into cytoplasm and bind to receptor molecules. The activated receptor complex passes into the nucleus and directly acts on genes.  This stimulates or inhibits particular protein synthesis.
• Steroid hormones are fat soluble hormones. Eg. Hormones secreted by gonads and adrenal cortex (oestrogen, progesterone, testosterone, aldosterone and cortisol)
• Protein-based / amine hormones – activate specific receptors on the plasma membrane, cannot pass through plasma membranes. Secondary messenger diffuses into cell and triggers physiological changes. Protein and amine hormones are water soluble
• Protein/amine hormones inhibit or stimulate particular enzymes. Eg. Hormones secreted by the adrenal medulla, pituitary and pancreas (insulin, growth hormone, adrenaline and oxytocin).
• Hormones made by the anterior pituitary gland include: Adrenocorticotropic hormone, Growth Hormone, Luteinising Hormone, Follicle Stimulating Hormone, Prolactin, and Thyroid Stimulating Hormone