E.+CELL+PHYSIOLOGY

= Cell Physiology =



http://en.wikibooks.org/wiki/File:Animal_cell_structure_en.svg __ESSENTIAL QUESTIONS __ Cells are considered the basic structure and function of the human body. What is meant by that statement? Cells are the basic building blocks of all life. Every living organism is made up of cells or groups of cells called organs. Cells are what we actually see when we look at an individual and cells are what makes up our organs, blood, bones, nerves, etc., without the cells that make us, we would not function or even exist.

Compare and contrast passive and active transport. characteristics and examples of each type of transport cells use to maintain homeostasis. Transport is the essential way cells maintain homeostasis. Transport is the net movement of molecules and ions across a semipermeable membrane of a cell. Two important forms of transport cells are passive transport and active transport.  In passive transport ions and molecules move from a high concentration to a low concentration, requiring no metabolic energy. Some examples of passive transport are simple diffusion, osmosis and facilitated diffusion. Simple diffusion refers to small molecules and ions that are non-polar and can easily pass through the plasma membrane, to equal out the concentration differences. Osmosis is simply the diffusion of water through the cell membrane from an area of high to an area of low concentration. Facilitated diffusion requires a carrier protein to allow it to enter or exit the cell membrane to equalize the concentration gradients, an example of this would be in the picture below.  In active transport the molecules move against the concentration gradient going from lower concentration to an area of higher concentration. Active transport and Secondary Active Transport require the use of metabolic energy (ATP), and carrier proteins to enter the cells plasma membrane. An example of active transport is the Ca2+ pump, proton (H+) pump, and Sodium-Potassium Pump. These pumps use ATP energy which is hydrolyzed into ADP and P when the ion/molecule (calcium, sodium, potassium, etc.) binds to the carrier protein site (the pump), phosphorylation of ATP into ADP and P causes a reaction and the pump opens up and allows the ion/molecule to travel into the cell or out of the cell. Secondary Active Transport occurs the same way as Active Transport except when one molecule/ion enters or leaves a cell, another ion/molecule sneaks it way through the open door (pump) and enters or leaves the cell, this is also known as antiport. Another example would be if a ion/molecule hitches a ride and moves in the same direction as the ion/molecule when the pump's door open, this is known as symport. In the picture below is an example of facilitated diffusion (form of passive transport), notice how it uses carrier proteins to allow Ca+2 to enter the plasma membrane. It is passive transport because it does not utilize ATP for energy and its net movement is from a higher to a lower concentration gradient. 

http://people.eku.edu/ritchisong/RITCHISO/301notes1.htm

Why do cells need to bring molecules and and out of the cell membrane? Cells need to bring molecules in and out of the cell in order to make actions occur. It is vital that cells are able to bring molecules/ions into and out of the cell in order to maintain homeostasis in our body. For example, active transport by the Ca2+ pump removes calcium from the cells in striated muscle, when this pump opens, due to the concentration difference between the intracellular and extracellular fluids, calcium rushes into the cell. The increase in calcium in the cell is a signal to the cell for muscle contraction; when the muscle is relaxed, the calcium will again be pumped out of the cell by the Ca2+ pump. This is just one of many examples, all actions take place in the cell, whether it be by means of direct access to the nucleus for transcription by hydrophilic molecules or the use of a carrier proteins and secondary messengers by hydrophobic and larger molecules.

How do cells communicate? Cells communicate by using chemicals. There are four kinds of cell signaling,they are gap junctions, paracrine signaling, synaptic signaling and endocrine signaling. Gap junction is when molecules and ions travel through the cytoplasm of cells that are adjoined. This is rare. Paracrine signaling is when cells inside an organ secrete regulatory molecules that then diffuse through the extracellular matrix to nearby target cells. Synaptic signaling is when chemical neurotransmitters are released by axon ending. Endocrine signaling is when regulatory hormones are released into the bloodstream to reach their target cells. media type="youtube" key="U6uHotlXvPo?fs=1" height="330" width="543"

Fun website I found about cells: Inside a Cell



__Content Summary __

Cell physiology. This chapter is about the function of a cell, functions of each of the organelles in a cell and also goes into great detail on how a protein is formed and how each organelle assists in the formation of the protein. This chapter also emphasizes the production of RNA in the nucleus and goes into detail on the four types of RNA: pre-mRNA, mRNA, rRNA, and tRNA and how they help form new proteins for the body's use. This unit also explains how cells replicate themselves, how cells communicate with one another, how cell allows different proteins and enzymes to enter, the different solutions in the body that cause the cells to alter from their isotonic state.

__**Tonicity:**__ Tonicity is a word used to describe the effect of a solution on the osmotic movement of water. Osmosis is the net diffusion of water across the cell membrane. There are 3 main types used in a hospital setting : 1.) **Isotonic**: solutions such as 0.9% NS, 5% Dextrose in water, 5% Dextrose in 0.225% saline, and Ringer's Lactate are considered isotonic solutions because they have the same tonicity as blood plasma. Cells in an isotonic solution do not shrink nor swell in size, because they have the same osmotic pressure (H20/solutes) on both sides of the cell. Times you would use an isotonic solution may be in trauma situation, blood transfusions (hung with the unit of blood), hyperkalemia, and hyponatremia. 2.) **Hypertonic**: solutions such as 10% Dextrose in water, 5% Dextrose in 0.45% saline, 5% Dextrose in 0.9% saline, and 5% Dextrose in Ringer's Lactate. Cells in a hypertonic solutions will shrink, because their is more fluid being taken out of them in order to maintain the same osmotic pressure, hence, more fluid is being put into the extracelluar compartment. Times you would use a hypertonic solution would be in cases of cerebral edema, dehydration from severe diarrhea or vomiting, and some the early treatment of burns. 3.) **Hypotonic**: a hypotonic solution is 0.45% saline. Cells in a hypotonic solution will expand or become "fat" because their is more fluid being taken in to the cells and more fluid leaving the extracellular compartment. Times you would use a hypotonic solution would be to supply normal daily salt and water requirements to the patient intravenously.



__**The 8 stages of mitosis:**__ Interphase is the stage (3 stages) in which the cell is not dividing and is carrying out its designated duties. **1.) G1** (G= Gap) stage is the cells "resting" stage, where they perform their functions as needed; if cell is going to divide (replicate itself), the cell will replicate its centrioles. **2.) S** (synthesis) stage is where the DNA is going to replicate itself. **3.) G2** stage is where the chromatin is going to condense and finish its final growth and activity, it is in this stage that the DNA has doubled. Mitosis (5 stages) is the stage where active cell division will occur. **4.) Prophase**: Chromosomes consist of two chromatids joined by a centromere, spindle fibers are produced and extend from each centerosome, the centrioles separate and move to opposite sides of the cell, the nucleolus (center of nucleus) is no longer seen, and the outer membrane of the nucleus starts to disappear. **5.) Metaphase:** The chromosomes line up single filed at the equator of the cell, the spindle fibers from each centriole on opposite sides of the cell are attached to the centromeres of the chromosomes, and the nuclear membrane has completely disappeared. **6.) Anaphase:** Centromeres split a part and the spindle fibers shorten, causing the two chromatids in each chromosome to be pulled towards opposite sides of the cell.
 * 7.) Telophase:** The chromosomes become longer, thinner, and less distinct in appearance, new nuclear membranes form around soon to be two genetically identical cells, and the nucelolus re-appears in both of the soon to be two cells. **8.) Cytokinesis**. Cytokinesis is a term used to describe the division of the cytoplasm between the two soon to be cells, once the division of cytoplasm is complete, you are left with two genetically identical cells.



http://www.accessexcellence.org/RC/VL/GG/mitosis.php


 * __Types of RNA:__** There are four types of RNA produced within the nucleus by transcription; pre-mRNA, mRNA, tRNA, and rRNA. __**pre-mRNA**__ is the precursor for mRNA and is found in the nucleus. It consists of all the DNA genes, including non-coding DNA genes that are called introns. The coding regions which are bodies use and are active in the formation of new proteins are called exons. __**mRNA**__ is called messenger RNA. When the specific coding region of the DNA (exons) is identified and ready to be spliced from the mRNA, it is done so by a macromolecule called a snRNP. Once the splicing is complete, you are left with a functional mRNA that will leave the nucleus of the cell and enter the cytoplasm, where it will attach to a ribosome. __**rRNA**__ is known as ribosomal rRNA and it is made in the nuclolus of the nucleus in the cell and along with proteins, forms part of the ribosomes. Ribosomes which all contain rRNA, help in the genetic translation of the mRNA for protein synthesis. **__tRNA__** is It is responsible for the decoding of mRNA. tRNA is in the cytoplasm of the cell and is shaped in an upside down L; it contains an anticodon which will pair up to only one specific codon of mRNA. By this form of DNA translation and transcription the genetic material is able to be maintained accurately and our bodies are able to maintain homeostasis and provide our bodies with what it needs. Below is a picture of a tRNA, notice of the top is the amino acid accepting end and the bottom is the anticodon end which will bond to a specific codon on mRNA.

http://people.eku.edu/ritchisong/RITCHISO/301notes1.htm

Application:

As a nurse it is very important to know and understand the different types of fluids and chemicals that we put into our patients body. For example, the doctor normally writes the order for the type of intravenous fluid and the rate at which it is to be dispensed. If we have a patient who has had severe head trauma and is bleeding in his brain (cerebral hemorrhaging) causing an increase of pressure, the last thing we would want to give is a hypotonic solution which would only make the internal pressure in the brain greater. You would more than likely be given an order for a hypertonic solution to be give intravenously, if not it is your duty as a nurse to question the doctor's order and be that patient's advocate. Knowledge as a nurse on why the doctor is doing a certain treatment is very important because we as nurses spend more time with the patient and their loved ones than the doctor; being able to answer certain questions (some questions the doctor must answer due to liability) about the treatment, gives the family and patient a sense of safety in that the nurse knows what she is doing.

A nursing application of cell physiology would be how gas is exchanged by diffusion in the lungs. Gas exchange occurs between cells and their extracellular environment in the lungs. Oxygen diffuses from air to the blood because the O2 concentration of air is higher in the lungs than in the blood. O2 therefor travels down it's concentration gradient. Diffusion of O2 from air to blood happens very rapidly because of the large surface area within the lungs. I use this type of application at the nursing home that I work at. We have several residents that are on continuous O2. Sometimes, the residents are not so compliant and I will find one without their O2 cannula on. I will check their O2 level and of course find it low. The other morning, I had a resident down to 80%. Once I put the nasal cannula back in place, within just a few minutes, their oxygen level increased to 87%, then to 95% which made me feel much better! I also find that when their O2 levels are low there is an increased of confusion that goes along with it. Now, when it is reported to me that a resident is acting funny, the first thing I ask is if they had their oxygen on!!!!

In my line of work as a nurse I will be administering phenobarbital to residents so therefore i am going to have to understand that when this drug is taken over a long period of time then the patient can build a tolerance to this drug and dosage will have to be increased as time goes on and this results in growth of the agranular ER which in turn when this drug is discontinued an increase in the enzymes will occur, which react in steroid hormone production and inactivation.

Sources: Fox, Stuart Ira. (2009). //Human Physiology//. New York, NY: McGraw-Hill.  Comerford, Karen and Donofrio, Jo. (2006). //Pathophysiology Made Incredibly Easy//. New York, NY:Lippincott Williams & Wilkins. <span style="font-family: 'Times New Roman','serif';"> Genetic Science Learning Center (2010, February 11) Inside a Cell. //Learn.Genetics//. Retrieved February 11, 2010, from [] <span style="font-family: 'Times New Roman','serif';">Dewitt, Susan C. (2009). Fundamental Concepts and Skills for Nursing. 3rd Edition

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