Department of Physiology & Neurobiology

Unlike the abdominal viscera, the thoracic viscera are separated into two cavities by an area called the mediastinum. What is the clinical importance of this compartmental arrangement? The clinical importance of this compartmental arrangement is that the mediastinum region contains a lot of major and essential parts of the human body. The mediastinum contains the pericardial cavity, thymus, trachea, esophagus, and major blood vessels. The fact that it’s placed in a sort of central space of the upper body provides these major parts with a protective barrier of tissues and serous membranes. Even though the mediastinum itself doesn’t have a serous membrane most of the thoracic cavity does. Also this region encloses the heart by two layers of pericardium; serous membrane. The mediastinum creates a barrier in between the two compartments which enclose the lungs. This is clinically beneficial to the human body because if one lung gets injured, diseased, or infected, the other one may remain functional due to the protective barrier of the mediastinum (McKinley). The process of hemostasis is associated with positive feedback. Describe the specific events that confirm this statement.Homeostasis is the state of equilibrium, or constant internal environment, in the body (McKinley).

The specific event that confirms that positive feedback is in-fact associated with homeostasis is how positive feedback brings the body back to homeostasis after an injury. Due to injury, homeostasis of the body is thrown off and positive feedback leads to speeding up of blood clotting where the injury occurred. The process consists of platelet plug formation, coagulation, vascular spasm, and arterial dilation. Out of this process the step that shows the most positive feedback is the platelet plug formation. In this step in damaged tissue, platelets aggregate to form a plug that seals off the broken blood vessel in undamaged tissue, platelets are prevented from sticking together by nitric oxide and prostacyclin. As platelets stick together, they swell and release ADP, serotonin, and thromboxane A2 which cause more platelets to aggregate and release their chemicals. This one step shows a positive feedback cycle (oakparkusd.org).

How do the following systems serve to maintain homeostatic regulation of body fluid volume? (a) Urinary (b) digestive (c) integumentary (d) cardiovascular. Be sure to include the interaction of ECF and ICF. By filtering the blood and other extracellular fluids the urinary system maintains homeostatic regulation of body fluid volume .The kidneys play a large role within filtering about 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine, composed of wastes and extra fluid (personal knowledge) Within the digestive tract the food is broken down to nutrient molecules small enough to be absorbed by the villi of the small intestine. Digestive enzymes are produced by the digestive tract and by the pancreas (personal knowledge). In addition the liver produces bile, an emulsifier that plays a role in the digestion of fats. Bile, which is stored in the gallbladder, enters the small intestine along with the pancreatic enzymes. Following the absorption of nutrients, blood passes from the region of the small intestine to the liver by way of the hepatic portal vein. The liver, which monitors the blood, is a very important organ of homeostasis. The liver breaks down toxic substances like alcohol and other drugs, and it produces urea, the end product of nitrogenous metabolism.

The liver produces the plasma proteins and stores glucose as glycogen after eating. In between eating it releases glucose, thereby keeping the blood glucose concentration constant. The liver destroys old blood cells and breaks down hemoglobin…hemoglobin breakdown products are excreted in bile (McGraw-Hill College Division). In this system the extracellular and intracellular fluid concentrations are controlled by osmosis. If the fluid inside the cell is concentrated water will flow into the cell, if the opposite occurs water will flow out of the cell. Perspiration is the main way the integumentary system goes through homeostasis. Perspiration is sweat that mostly consists of water and inorganic salts. The movement of liquid thru perspiration also controls the body temperature. People sweat when they are hot while doing physical activities in order to cool down the body. Dehydration is known by signals sent through the concentrations of sodium in the extracellular and intracellular fluids. The cardiovascular system is responsible for transporting blood carrying oxygen through the body. Homeostasis is especially important in this system because the blood cells maintain the human body functioning.

The water and intracellular fluids are constantly performing osmosis as the cells travel through the body. An important buffer system in the human body involves carbon dioxide (CO2) and bicarbonate ion (HCO-) in the reversible reaction CO2 + H2O  H2CO3  H+ + HCO3-. If a person becomes excited and exhales large amounts of CO2, how will the pH of the person’s body be affected? The rate of cellular respiration (and hence oxygen consumption and carbon dioxide production) varies with level of activity. Vigorous exercise can increase by 20-25 times the demand of the tissues for oxygen. Getting excited has that similar effect and also increase the tissues desire for oxygen. This is met by increasing the rate and depth of breathing. It is a rising concentration of carbon dioxide not a declining concentration of oxygen that plays the major role in regulating the ventilation of the lungs. Certain cells in the medulla oblongata are very sensitive to a drop in pH. As the CO2 content of the blood rises above normal levels, the pH drops and the medulla oblongata responds by increasing the number and rate of nerve impulses that control the action of the intercostal muscles and diaphragm. This produces an increase in the rate of lung ventilation, which quickly brings the CO2 concentration of the alveolar air, and then of the blood, back to normal levels (www.scribd.com)

How does excessive boiling or heating of proteins (e.g.; fever) affect the ability of the protein molecule to perform its normal biological functions? Be specific and provide physiological examples. Increasing the temperature increases the energy of the bonds and atoms in the protein, to the point at which there is enough energy to overcome the force of the intermolecular reactions, resulting in them breaking. Excess boiling or heating of proteins causes great changes within the molecular bonds. The proteins tend to fold up and denature an enzyme so that it is no longer functional. Each protein part consists of a specific shape that allows it to perform a specific task or action. After boiling a protein in can no longer due the function it was originally meant to do. Also increasing the temperature increases the energy of the bonds and atoms in the protein, to the point at which there is enough energy to overcome the force of the intermolecular reactions, resulting in them breaking. An example of denatured proteins because of boiling would be a raw egg being fried or boiled. In a reaction pathway that consists of four steps, how would decreasing the amount of enzyme that catalyzes the second step affect the amount of product produced at the end of the pathway? Provide two physiological examples.

By decreasing the amount of enzyme that catalyzes the second step the product produced would be greatly decreased and the whole process would be slowed down. The two examples of this occurrence would be glycolysis and the amino acid synthesis pathway. In both of these occurrences if less of the main enzyme was to be used, both of the processes would be so to speak crippled and their products wouldn’t be the same. So in glycolysis the production of energy would be slowed down an incredible amount. In the amino acid synthesis pathway the production of arginine would be slowed down and less arginine would be produced. All cells are enclosed by a cell membrane that is necessary for cellular homeostasis. What specific benefits would cellular organelles have if enclosed by a cell membrane similar to the plasma membrane? Identify all of the membrane-bound organelles in animal cells and their associated specific functions. Organelles that are enclosed by a membrane are regulating homeostasis and controlling specific functions of maintaining the body. In a eukaryotic cell there are six main membranes bound organelles that are important. The Endoplasmic Reticulum(ER) is responsible of the synthesis of proteins and membrane molecules.

The rough ER synthesizes proteins for secretion, new proteins for the plasma membrane, and lysosomal enzymes it also transports and stores molecules. The smooth ER is responsible for synthesizing lipids, metabolizing carbohydrates, and detoxifying drugs & alcohol. Ribosomes attached to the rough ER help with the production of proteins. Lysosomes digest materials or microbes ingested by the cell they also remove old/damaged organelles. Lysosomes also have an interesting ability to self-destruct (autolyze). The mitochondria which produce the ATP needed to run almost every function of the body on a molecular level (personal knowledge). The Golgi apparatus is the UPS of a cell that modifies, packages, and sorts newly synthesized proteins for secretion, inclusion in new plasma membrane or lysosomal enzyme synthesis. Another important organelle is a peroxisome which converts hydrogen peroxide formed during metabolism to water. The peroxisomes contain oxidase enzymes, which detoxify alcohol, hydrogen peroxide, and other harmful chemicals. Without a cell membrane the balance of chemicals in the cytoplasm would be disturbed and the cell could no longer function (McKinley).

A patient recovering from surgery was mistakenly given an IV transfusion of five percent (5%) salt solution instead of a 0.9 percent physiological saline solution. The patient immediately went into shock and soon after died. What are the specific manifestations of shock? What caused the patient to go into shock? The specific manifestations of shock consist of a life-threatening condition that occurs when the body is not getting enough blood flow. Due to the amount of salt that was injected into the blood stream the blood cells have completely dehydrated. Due to osmosis and diffusion the water that was within the cells has now diffused out of the cells since the blood stream was filled with a 5% salt solution. The 5% NaCl solution in place of the 0.9% NaCl solution causes vascular fluid buildup which includes fluid drawn from the tissues into the bloodstream, and this could lead to heart failure from a fluid overload. Another issue due to such a high concentration of salt is lack of blood flow meaning that the cells and organs do not get enough oxygen and nutrients to function properly. Multiple organs can suffer damage as a result (Jones/Rivers). Based on the varied cell population in connective tissue proper, describe the specific immune response expected at the site of injury or damaged tissues.

The body’s response to any type of injury or infection is inflammation. Inflammation is a protective response involving host cells, blood vessels, and proteins and other mediators that is intended to eliminate the initial cause of cell injury, as well as the necrotic cells and tissues resulting from the original insult, and to initiate the process of repair. Inflammation accomplishes its protective mission by first diluting, destroying, or otherwise neutralizing harmful agents. It then sets into motion the events that eventually heal and repair the sites of injury. When a microbe enters a tissue or the tissue is injured, the presence of the infection or damage is sensed by resident cells, mainly macrophages, but also dendritic cells, mast cells, and other cell types. These cells secrete molecules (cytokines and other mediators) that induce and regulate the subsequent inflammatory response. Inflammatory mediators are also produced from plasma proteins that react with the microbes or to injured tissues. Some of these mediators promote the efflux of plasma and the recruitment of circulating leukocytes to the site where the offending agent is located.

The recruited leukocytes are activated and they try to remove the offending agent by phagocytosis. An unfortunate side effect of the activation of leukocytes may be damage to normal host tissues (Kumar). (a) How does exposure to optimum amounts of UVA and UVB sunlight radiation promote proper bone maintenance and growth in children? (b) The general adult public associates excess sunlight exposure (a “tan”) with good health. Explain in detail why this thought process is deadly wrong! For proper functioning, a healthy human body uses around 3,000-5,000 IU of vitamin D per day. It is the UVB rays that stimulate the body to produce vitamin D. When exposed to direct sunlight, the body will produce vitamin D at a rate up to 1,000 IUs per minute. The body won’t make too much vitamin D from sunlight exposure because the body has a built-in mechanism to halt vitamin D production once it has enough. While getting sunburn from too much sunlight is possible, the human body can’t develop vitamin D toxicity. Vitamin D has enormous health-promoting benefits and effects.

It plays a huge role in calcium metabolism, which is vital for the normal functioning of the nervous system, as well as for bone growth and maintenance of bone density. Vitamin D also plays a major role in immunity, cell proliferation, insulin secretion, and blood pressure. All cells in the body have vitamin D receptors, meaning that every cell and tissue in the body needs vitamin D for its optimal functioning and well-being. Vitamin D prevents osteoporosis, depression, and even effects diabetes and obesity (thrivechiropracticstudio.com). The main risk factor which damages skin and can lead to a melanoma is damage from the sun. It is the ultraviolet (UV) radiation in the sunshine and in sunbeds which does the damage. About 6 in 10 cases of melanoma are thought to be caused by UV damage. UV light damages the DNA (genetic material) in your skin cells which can then lead to skin cancers developing. People most at risk to UV skin damage are people with fair skin – in particular, those with skin which always burns and never tans, red or blond hair, green or blue eyes. Melanoma is uncommon in dark-skinned people, as they have more protective melatonin in their skin (Dr. Tim Kenny).

Work Cited

“Human Anatomy” 3rd edition by Michael McKinley & Valerie Dean O’Loughlin Copyright 2012, Published by The McGraw-Hill Companies, Inc. “Skin Cancer – Melanoma” by Dr Tim Kenny
http://www.patient.co.uk/health/skin-cancer-melanoma
“Vitamin D & Sunlight”
http://thrivechiropracticstudio.com/2013/07/
“Respiratory System”

“Hemostasis”
http://www.oakparkusd.org/cms/lib5/CA01000794/Centricity/Domain/307/Hemostasis.pdfJones AE, Kline JA. Shock. In: Marx JA, ,Hockberger RS, Walls RM, et al, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, Pa: Mosby Elsevier; 2013:chap 6. “Robbins Basic Pathology”9th edition, by Vinay Kumar, Abul K. Abbas, and Jon C. Aster https://www.inkling.com/store/book/robbins-basic-pathology-kumar-abbas-aster-9th/?chapterId=4eca681364e34e9c9de63067aca4f513 Rivers EP. Approach to the patient in shock. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 106. “Body Systems and Homeostasis” by McGraw-Hill College Division http://www.mhhe.com/biosci/genbio/maderbiology/supp/homeo.html