Homeostasis+and+Chemical+Aspects

= __Content Summary:__ =

**//Unit Overview://**
Physiology is the study of normal biological funtion in the body. It describes how body systems and cells work together in order to maintain homeostasis - a fundamental part of life. There are also many basic chemical aspects (protons, neutrons, electrons, and different types of bonds) that are very important in physiology. Because of the chemical properties of cells, proteins and DNA/RNA can be made and carbohydrates, lipids, etc. can be broken down for energy.

//1. __Homeostasis__//
Homeostasis is the state of dynamic constancy of conditions within the body. This doesn't necessarily mean that conditions are always the same, but that they are constantly within a normal range. If these conditions fall below or exceed the normal limits, the cells of the body can't function properly which leads to sickness and/or death. Homeostasis within body cells can be measured by the vital signs that health professionals take. Vital signs are clues as to which parts of homeostasis are being disrupted.

Homeostasis is maintained through either positive or negative feedback loops which are implimented by either hormones (hormonal) or nerves (neural). **Positive feedback** is less commonly seen in the body than negative feedback and is when a change in a condition leads to a response which amplifies that change. For example, when an infant suckles on his/her mother's breast, it stimulates the hypothalamus to produce oxytocin which is then released by the pituitary gland and leads to more milk let down in the mammary glands (shown below). This leads to an endless supply of milk for the infant as long as the mother chooses to breast feed.

**Negative feedback** is the most common type of feedback loop in the body and is when a change in a condition leads to a response that counteracts that change. An example of a neural negative feedback loop is when an individual rises from the laying position and the blood pressure drops. This drop in blood pressure causes the heart rate to increase, and - in turn - raises the blood pressure. An example of a hormonal negative feedback loop is when carbohydrates (sorce of sugar in the diet) are ingested which increases blood glucose and stimulates the islet cells of the pancrease to secrete insulin. Insulin allows glucose to enter the cells which causes blood glucose to decrease (or vise versa) as shown in the figure below.

The maitanence of homeostasis within the body is the main purpose of the physiological processes that take place in the body. It's the most important thing for the body to do = maintain ballance.



//2. __Chemistry:__//
 Chemistry is a major factor in physiology and how the body maintains homeostasis. The smallest unit of life is the **atom** which contains protons and neutrons in its nucleus, with electrons orbitting around the atom. **Protons** are positively charged particles, **neutrons** have no charge and are said to be 'neutral', and **electrons** are negitively charged. The **atomic number** of an atom is the number of protons inside the nucleus (carbon=6 protons=atomic # of 6). The **atomic mass**, though, is the average total number of protons and neutrons in atoms of an element. This takes into account that the number of neutrons may differ between atoms of the same element (**isotopes**). C12 and C14 , for example, are the same element, but C14 has two additional neutrons in comparison with C12.

Atoms can combine to make up molecules by forming bonds between the individual atoms. **Covalent bonds** are formed when two or more atoms share pairs of valence electrons (electrons in the outer orbital). //Nonpolar// covalent bonds are when these electrons are shared equally (H 2 ), but //polar// covalent bonds are when the electrons are shared unequally which causes regions of slight charges on the molecule (H 2 O).

**Ionic bonds** are formed when one or more valence electrons are completely transferred from one atom to another (NaCl). These bonds can form cations (positively charged ions) or anions (negatively charged ions) which are attracted to each other because 'opposites attract'. **Hydrogen bonds** are the weakest type of bond that forms in the human body, but are deffinitely not any less important for chemical functions. Hydrogen bonds are formed when a slightly positively charged end of one polar molecule is attracted to the slightly negatively charged end of another polar molecule. There is a weak electrostatic attraction between the molecules that participate in hydrogen bonds. It is because of this type of bond that water bugs can run on water, trees can get water into the highest leaves, and proteins can retain they're shape. All chemical bonds are extremely important in how the body functions, and without one, the body would not remain in homeostasis and would, thus, become diseased and possibly die.

//__3. Organic Molecules:__//
<span style="font-family: Georgia,serif; font-size: 110%;"> Organic molecules are molecules that contain carbon. There are four main organic molecules in the human body (carbohydrates, lipids, proteins, and nucleic acids). **Carbohydrates** are molecules made up of carbon, hydrogen, and oxygen that are either used as quick energy or stored as glycogen. Carbohydrates are also a structural component in the body and are antigens that help determine the specific type of cells, blood type, etc. Glucose, sucrose, and galactose are __//monosaccharides//__ (simple sugars of only one sugar molecule). Sucrose, maltose, and lactose are __//disaccharides//__ (two monosaccharides linked together), and glycogen is a __//polysaccharide//__ (many monosaccharides linked together).

<span style="font-family: Georgia,serif; font-size: 110%;">In the figure below, glucose and fructose are being combined to form sucrose through a process called //dehydration//**.** This reaction is one in which a H+ ion and a OH- ion are taken from the glucose and fructose molecules to make room for the two molecules to combine together. Water (H20) will be a byproduct of this type of reaction. <span style="font-family: Georgia,serif; font-size: 110%;">**Lipids** are classified as either triglycerides, phospholipids, or steroids, but every lipid has a nonpolar part to its molecule. Lipids provide energy to the body, provide insulation, cushion joints, make the skin water-proof, and protect the body. The first type of lipids is the __//triglycerides//__ - fats, oils, and waxes composed of a glycerol molecule and three fatty acids. These are primarily found in foods that are ingested into the body. They come in the form of saturated or unsaturated fatty acids. //Saturated fatty// acids are the 'bad' triglycerides that affect the liver, increase cholesterol, and lead to atherosclerosis (plaque buildup in the arteries). //Unsaturated fatty acids// are the better fats because they are more fluid than saturated fatty acids because they contain one or more double bonds (versus only single bonds which cause the fat to be very thick). Another type of lipids is the __//phospholipids//__ which are really important in the composition of cell membranes. They are made up of a phosphate group, a glycerol molecule, two fatty acids, and the rest of the molecule. They have a polar (water soluble) head and a nonpolar (fat soluble) tail. When these phospholipids line up together, they make a semipermeable cell membrane (discussed in "Cells to Systems") which is very important in homeostasis. The last type of lipids is the __//steroids//__ which are composed of four interlocking carbon rings and a functional group. Cholesterol is a very important steroid that helps regulate the cell membrane fluidity and is a precursor for corticosteroids and the sex steroids. <span style="font-family: Georgia,serif; font-size: 110%;">Another type of organic molecule, **protein**, is made up of an amino group, a carboxyl group, and a functional group which - when combined - make up an individual **amino acid**. Proteins provide support and elasticity in the body, function as antibiotics and clotting factors, and also assist in chemical reactions as enzymes and cell transport as receptor cells. There are four levels of structure that a protein may have (see figure below). The first level is the call the __//primary structure//__ and is a chain of many amino acids. In the __//secondary structure//__, hydrogen bonds form between amino acids and causes regular patterns of folding (either a helix or beta sheet formation. When the proteins begin folding in irregular patterns and form their shape, they have a __//tertiary structure//__. Finally, the __//quarternary structure//__ is when multiple amino acid chains (proteins) bond together. <span style="font-family: Georgia,serif; font-size: 110%;">The final major organic molecule that is found in the body is **nucleic acids**. Nucleic acids are made of **nucleotides** which are composed of a pentose sugar, a phosphate group, and a nitrogenous base (adenine, thymine/uracil, cytosine, or guanine). DNA (pictured below) and RNA are both nucleic acids with only a few differences. The major differences are that DNA is found in the nucleus of cells, while RNA is not, the thymine base in DNA is changed to uracil in RNA, and RNA is only single-stranded while DNA is a double helix. Nucleic acids make up chromosomes and are the 'recipe' for making you. It is very important to have a basic understanding of the four main organic molecules before continuing to study physiology since they are so abundantly used in the body. = __Application:__ = = = <span style="font-family: Georgia,serif;">Homeostasis is the body's most important function as a system, and there are many ways to apply this aspect to the nursing field. Homeostasis can be measured by taking a patient's vital signs or by assessing lab values. **Vital signs** are a measurement of the body's overall condition and include: temperature, pulse, respirations, (usually) blood pressure and (sometimes) oxygen saturation levels. For an adult, the normal temperature is 98.6 F, the normal pulse is 60-100 beats/min, the normal respiration rate is 12-20 breaths/min, the normal blood pressure is 100-120/60-90 mmHg, and the normal oxygen saturation in the blood is above 90%.

<span style="font-family: Georgia,serif;">Using these normal ranges, it is possible to analyze vital signs and get a general idea of what might be occuring in the patient's body. For example, if the temperature is elevated, it may indicate an infection. If the pulse or blood pressure is elevated, it may indicate a problem of the circulatory system (arteries, veins, heart, etc.). And if the respiration rate is elevated or the oxygen saturation is decreased, it may indicate a breathing or perfusion problem. These are only some examples, though, because abnormal findings may indicate many different things.

<span style="font-family: Georgia,serif;">There are also laboratory tests that can be done on a blood or urine sample, that may indicate different bodily ailments. These tests - just like vital signs - have normal ranges, and if the results exceed or fall below the normal levels, there is indication of a specific type of problem within the body. When the body does not maintain homeostasis, there are always problems. The cells can't function properly any more and the level of health of the individual decreases dramatically. = __Essential Questions:__ =

===**//1. <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">Describe feedback and how insulin is controlled by a negative feedback inhibition. Why is it essential that insulin and other molecules be regulated?//**===

<span style="font-family: Georgia,serif;">Feedback is when the output from a regulatory mechanism is put back into a feedback loop as the input part of that system. Insulin is controlled by a hormonal negative feedback loop. This means that when the blood glucose levels increases, insulin will be produced in order to decrease the blood glucose levels and bring them back to normal. When carbohydrates are digested, glucose enters the blood stream and acts as a stimulus. The islet cells of the pancreas sense this increase and secrete insulin. Insulin then allows the glucose to leave the blood and enter the cells and thereby decreases the blood glucose levels.

<span style="font-family: Georgia,serif;">It is essential for insulin and other molecules to be regulated because if they weren't, the cells of the body would not function correctly and illness or disease would result. For instance, if the body is not capable of secreting insulin - or secreting enough insulin - diabetes results. If this happens, the individual is at a high risk for hyperglycemia (high blood glucose levels) which can result in coma and death if not treated. Regulation of molecules in the body is of extreme importance.

===//**2. Create a chart that reviews the four major organic molecules that make up the human body and that interact in the intricate molecule interactions. Include type of organic molecule, role(s) of molecule in body, monomers, and specific examples of molecules.**//===

//**3. What are enzymes? What role do they play in human physiology?**//
<span style="font-family: Georgia,serif;">Enzymes are specialized proteins that speed up (catalyze) specific reactions the take place in the body. Enzymes catalyze these chemical reactions by binding the reactants together and lowering the activation energy - energy needed to begin a certain chemical reaction. Without enzymes, our body would take a really long time to metabolize carbohydrates, or carry out other reactions in the body. Enzymes are very important in human physiology.