Everything is made of parts or building blocks. The parts of human beings are as follows:
Organs (skin, liver, heart, ovaries, testes)
Bones
Muscles
Blood
Nerve
Body parts are made of cells—skin cells, blood cells, fat cells. Each cell has a membrane which is like the skin. This membrane or wall can be crossed by some things but it prevents other things from getting into the cell. Each cell has three functions: (1) to keep itself alive; (2) to reproduce itself and (3) to do some job to keep the body working (make skin cells, digest food, mature an egg).
In each cell there is a nucleus, which is like the brain of the cell and keeps it functioning. Inside the nucleus of each cell is the computer program or the recipe to follow for each of these functions. The recipes are called the genetic material. It is made up of chromosomes which carry genes. Every cell carries every gene needed for that person’s body to live and function. There are two kinds of recipes in the nucleus: DNA which reproduces itself and RNA which directs the cell to make something or do something that is that cell’s job. All cells are made of different kinds of molecules and compounds of molecules. Molecules can be fats (lipids), amino acids, carbohydrates (sugars), or nucleic acids.
When amino acids join together, they make proteins, compound molecules. Molecules, like water, are built of elements like hydrogen, oxygen and nitrogen. Water is made of two hydrogen and one oxygen (written as HO). Elements are made of protons, neutrons, and electrons. Things stick together or push each other away because protons and electrons act like magnets. When they pull each other together, they fit snugly like pop-beads.
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In this lesson, we’re going to talk about how compound molecules make organs work. Particularly, we’re going to talk about compounds called hormones. Hormones are responsible for the growth and development of human beings. They are messengers which are made in one part of the body, in glands (pituitary, gonads, adrenal), but not needed or useful there.
Hormones travel through the bloodstream and cause things to happen elsewhere. There are many different kinds of hormones which control and regulate many different activities of the body. Each hormone has its own unique shape. We will focus here on the hormones which affect the growth, development and functioning of the sexual organs. They are GNRH, FSH, LH, EST. Prog., Testosterone.
The glands which are involved in human sexual development are the hypothalamus, the pituitary and the gonads (the sexual organs/glands: testicles in men and ovaries in women).
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Let’s think about this as a rail system. The blood is the train. Veins and arteries are the
tracks
.
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All the glands are factories which make packages of hormones and load them on the train. Glands (like the pituitary) make hormones only in response to orders they receive and read from the hypothalamus. The hypothalamus is the headquarters or central command office for the whole railroad system. It works like a computer, reading messages and keeping track of the amounts of all the different hormone packages everywhere in the system. The hypothalamus changes its orders to the glands based on that information, keeping all the hormones in balance. (This is called homeostasis). Orders come from the hypothalamus in the form of a hormone.
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The messenger hormones get unloaded from the train at the stations (organs). Organs only accept packages which are meant for them. They identify them by their shape which fits exactly into a window (receptor) in the wall of that station (like a pop-bead). Each hormone and each receptor have exactly matching shapes and magnetic pull.
In response to the message, the organ does its job. Part of its job is to act like a gland and make other hormones which are loaded back onto the train and end up causing still other organs to do something and signaling the hypothalamus that they are doing what they’ve been told. When there is enough of this hormone in the blood (on the train, the hypothalamus (with its computer) reads that message. In answer, it changes its instructions to the pituitary. That makes the pituitary change what it is making and therefore the message which the organs receive.