Lecture 17 – June 30, 2011The endocrine system and the nervous system are sister systems because the endocrine system is controlling hormones and in a way some hormones are neurotransmitters (as used in the nervous system). If it is released in a synaptic space, it will be a neurotransmitter. If it is produced in, for example, the medulla of the adrenal gland, it is acting as a hormone.Hormones are substances released from a cell that will enter a nearby capillary bed and will be carried in the blood to various places in the body. Examples of hormones include estrogen, testosterone, epinephrine, thyroxin, oxytoxin, progesterone, LH (lutenizing hormone), FSH (follicle stimulating hormone), ADH (anti dieuretic hormone), dopamine, glucagon, insulin, parathormone, and thyrocalcitonin.Nervous System vs. Endocrine SystemThe main difference between these two systems is that the nervous system causes something to happen quickly and end quickly. The endocrine system might start slowly and have a longer range for it to be effective, and then die out.Endocrine vs. ExocrineThe most effective way to separate exocrine glands is holocrine (whole cell is product), apocrine, and merocrine. Exocrine glands have ducts which carry substances to the outside world while endocrine glands are groups of cells that make something to be transported primarily by blood, usually a hormone.Local vs. TraditionalLocal hormones are putting things outside of themselves and are not picked up by capillaries, such as:Histamines – causes, for example in your nose, if you are allergic to something it sets up a response in your nose only and is local because it doesn’t leave.Prostaglandins – reside in smooth muscle cells in uterus – crampsNitric oxide – not a protein – produced and acts like a hormone.Traditional hormones are made by something and picked up by capillaries. The capillaries, in glandular tissue, have bigger holes than other capillaries are fenestrated (have bigger holes). They are then carried throughout the body via blood. Some are just proteins (insulin) and some are derived by steroids and other things.Hydrophobic vs. HydrophilicHydrophobic means that the substance is not soluble in water. Steroidal-based hormones, such as testosterone, are hydrophobic. This makes a difference on how they are carried throughout their body.Hydrophilic means that the substance is soluble in water. Insulin is hydrophilic.Hydrophilic will usually be unbound and hydrophobic will usually be bound, but there are exceptions – such as thyroxin (thyroxin hormone) and is not a steroid but comes from an amino acid, tyrosine, and does not like water and is fat soluble.Bound vs. UnboundIf you have a cell that just made insulin, the insulin will enter the capillary and is water-soluble. It can go right on into the plasma of the blood and can just float along with the flow. It has no need to be carried, it is said to be unbound. Unbound are much more vulnerable because they are just swimming along and their half-life is shorter.However, if the product of the cell is steroidal-based (such as testosterone, estrogen, progesterone, cortisol, aldosterone, etc.), when it gets into the capillary it is not soluble and must be assisted and is picked up by a protein, usually it is albumin, which is a solute in blood that keeps your blood pressure and volume stable and comes from the liver (primary secretory gland of body). If a person’s liver is badly diseased cannot make albumin anymore and has fluid in their joints because they don’t have the albumin to hold the water in the blood. Another job is to pick up cholesterols and steroidal-based hormones and carry them. Otherwise, they’ll be carried by something and are said to be bound. If it is bound, it is more secure and not as vulnerable. Its half-life is greater.Osmotic pressure: If you have blood in your blood vessels and it gets to a capillary, which is thin, what will keep the water of your blood in that capillary? What keeps the water in there is albumin.Cyclic AMP vs. Gene ActivatingThere are two ways in which hormones can be found working.cAMP – sometimes called the second messenger system; hormones that work like cAMP are those that are water soluble. Water-soluble hormones use cAMP, even though some use a variation of cAMP.Gene activating – hormones that work like gene activation are those that are not water-soluble and are sometimes steroidal such as estrogen, progesterone, testosterone, cortisol, aldosterone, and thyroxin (thyroid hormone), however thyroxin is not steroid based.The standard glucose level is 90 mg / 100 ml. The sensor, if it rises, is the beta cells which says to release insulin (first messenger), in the islets of Langerhans in the pancreas. The first messenger goes into the blood is water-soluble and is unbound and looks for a target cell (such as this fat cell in the hip). The first messenger will have to find a receptor on the target cell. Here, it will join its receptor.This piece of cell membrane is depicted in the target cell near it. The molecule of insulin will be attracted to a peripheral protein receptor. It makes the protein, which on the inside has attached to it an inactive GTP (guanine triphosphate) and is an intraperipheral protein and the union of insulin with this allows it to become activated (G protein). The activated molecule then turns on the enzyme adenylcyclase.Insulin (first messenger) cannot go into the cell because it is water soluble, which means it is not soluble in fat. However, cAMP (second messenger) knows that the insulin is trying to tell the cell to take in a glucose molecule so it can either burn it up for energy or store it away as fat or glycogen.Near the membrane of the cell, there are whirls of ATP made in the mitochondrion with six seconds available. That ATP is sitting there waiting to be used. In the presence of the turned on adenylcyclase and will take two phosphates from ATP and make sure they’re chopped off and turns it into cAMP, which is called your second messenger.cAMP runs all around your cell and living in your cell are various kinds of protein kinases, which are enzymes that are responsible for setting up a cascade effect of chemical reactions in the cell if they are turned on – and they’re only turned on if the other steps occur. Protein kinases allow for opening and closing and also to make the product or turn off/on an enzyme. Once cAMP has done its job, we must shut it down by