Hormones are chemical messengers. They are secreted into the blood by endocrine organs. They are carried around the body in the blood system to “target organs” which are controlled by specific hormones. Insulin is produced by the islets of Langerhans (small groups of cells in the pancreas); these islets (little islands) are endocrine organs. Insulin has an effect on the liver: it makes the liver convert glucose into glycogen. The liver stores glycogen. The effect of insulin is to reduce the amount of glucose in the blood. See my page on Insulin and Blood Sugar. We call the liver a “target organ” because insulin is aimed at it rather like aiming an arrow at a target. The arrow strikes the target. Insulin strikes the liver. Insulin also has an effect on all the other tissues of the body: insulin is necessary for tissue respiration because it is involved in the very first step in the breakdown of glucose. Diabetics cannot respire glucose without an injection of insulin. If they do not get their injection they are likely to use fat as a source of energy and this causes problems.
Adrenalin is another hormone. In this case the endocrine gland is the adrenal gland. Adrenal means attached to the kidney. The first part of the word “ad” literally means “onto”. The second part of the word “renal” means belonging to the “kidney”. Adrenalin produces all sorts of responses. The overall effect is sometimes called the “fight or flight” reaction. Adrenalin prepares your body for the extra effort required if you need to defend yourself or run away from a predator. So you can predict what will happen if you are frightened. Adrenalin will make your heart beat faster. It will make you breathe more deeply. It will bring you out into a cold sweat. It will give you goose pimples (your skin will look like a dead goose which has had all of its feathers pulled out): you could call this chicken pimples but it would not sound so good. Adrenalin may even make you vomit or wet yourself! All of this helps you to survive a dangerous situation.
You should try to compare the effects of nerves and hormones. Both are used to control your body. Nerves produce very rapid responses which may only last a few seconds. Each nerve affects on part of your body. On the other hand, hormones can affect lots of parts of the body at the same time and their effects last much longer; this may be hours, days or even years.It takes a little longer for hormones to produce an effect, but the effect lasts longer. You should know something about the interesting hormones; these are the ones which have effects lasting a long time. Oestrogen, Progesterone, Prolactin, Oxytocin, Testosterone, Follicle Stimulating Hormone (FSH), Leutenising Hormone (LH) and Interstitial Cell Stimulating Hormone (ICSH) are all great fun. These are the ones which control the more interesting//fun parts of our bodies. You will learn about them when you study the Human Reproductive System!!!!!
Thyroxin is another interesting hormone. This one controls how fast your body works. So it is there all day and night every day of your life unless you run out of Iodine. Iodine is a mineral salt which must be present in small quantities in your diet. If you have no Iodine, you will not be able to make thyroxin. You will suffer from a disease called goitre or Derbyshire neck. It has probably got other names which I have not heard. So if anyone can tell me what it is called in French, German , Arabic, Russian or any other language I would be interested (and will add the name to this page). Imagine that the tiny thyroid gland in your neck swells up to the size of a football: as well as being extremely uncomfortable, everyone should know what is wrong with you.
This is only the first draft: there is a lot more fun to be had from this topic and I hope to update it over the summer holidays. Perhaps some detail of the hormones involved in controlling sexual cycles etc..