Understanding Skeletal Muscle Contraction Physiology Essay

Understanding Skeletal Muscle Contraction Physiology Essay Introduction Muscle contractions are a result of the buildup of tension within the muscle, and for muscles to contract, they must have a continuous supply of energy in the form of a molecule called adenosine triphosphate or ATP (Silverthorn, D.U., 2010). Through muscle contractions, we are able to run, walk, lift, push, sit, and even chew our food (Stabler, et.al, 2009). In addition to an energy requirement, skeletal muscles must be stimulated to contract (Stabler, et.al, 2009). Skeletal muscles are stimulated from an action potential that originates from within motor neurons (Stabler, et.al, 2009). Motor neurons are those that send electrical signals to skeletal muscle cells (Stabler, et.al, 2009). An action potential is the electrical signal that occurs when positively charged ions flood into the motor neuron as a result of a chemical, electrical, or other type of stimulus (Stabler, et.al, 2009). This signal, an area of intracellular positivity, self propagates down the length of the neuron tow ards the muscle cell (Silverthorn, D.U., 2010). Once this signal reaches the muscle cell, it is converted into a muscle contraction through a process called excitation-contraction coupling (Stabler, et.al, 2009). The interior of muscle cells also becomes very positive resulting in a muscle contraction. Muscle contractions have 3 different phases which include the latent period, contraction phase, and the relaxation phase (Silverthorn, D.U., 2010). The latent period occurs between the start of an action potential and the beginning of a muscle contraction (Stabler, et.al, 2009). This is the phase that will be studied later. The contraction period begins at the end of the latent period and ends when muscle tension ends (Stabler, et.al, 2009). The relaxation period occurs begins at the end of the contraction period until the muscle becomes free of tension (Stabler, et.al, 2009). To initiate a muscle contraction, the stimulus must reach its threshold. This is the minimal stimulus required to generate the action potential within a muscle cell causing the internal cellular environment to become positive (Stabler, et.al, 2009). In addition, the change in stimulus intensity can play a role in how strongly the muscle generates force when it contracts which is referred to as the active force (Stabler, et.al, 2009). As a stimulus is repeatedly applied to a muscle, fatigue will eventually occur. Fatigue can refer to a deficit in muscle functioning or a gradual decline in the force sustained by a muscle (Enoka and Duchateau, 2008). Other research has shown that fatigue could be the result of metabolic changes that occur within the contractile mechanisms within the muscle fibers such as changes in ion concentrations (Allen and Westerbland, 2001). If the latent period length is dependent upon the strength of the stimulus, increasing the electrical stimulus intensity should also increase the latent period, and since a threshold stimulus needs to be reached for a contraction to occur, then there will be a minimal amount of electrical stimulation required to generate a muscle contraction. In addition, if the active force strength is dependent upon the strength of the stimulus intensity, an increase in stimulus intensity should increase the active force. If muscle fatigue is occurring due to repeated stimuli over a period of time, then applying a stimulus at a constant rate should result in a decrease of sustainable force within the muscle. These experiments will be carried out using an electrical stimulus by passing a known amount of voltage through an isolated skeletal muscle attached to a metal holder that will transmit the data to a recorder and an oscilloscope screen for analyses (Stabler, et.al, 2009) Materials and Methods In order to understand muscle contraction physiology, I evaluated 4 different experiments. The first 3 experiments were designed to use a single stimulus to evaluate the latent period of a muscle contraction, to evaluate the threshold stimulus of a muscle contraction, and to evaluate the effects of increased stimulus intensity on a muscle contraction. The fourth experiment was designed to demonstrate the effects of muscle fatigue. The following materials were used for these experiments: an isolated skeletal muscle (75mm in length), a metal holder to measure force generated by the skeletal muscle, an oscilloscope, an electrical stimulator (single and multiple stimulus), and a data collection box. The first experiment was designed to determine the latent period of a muscle contraction. First, the muscle was attached to the metal holder. The electrode from the electrical stimulator was rested on the surface of the muscle. The electrical stimulator was set to 6.0 volts. A muscle contract ion was induced by applying a single electrical stimulus using the electrical stimulator. The data generated a tracing on the oscilloscope screen which was used to determine the latent period by selecting the point where the flat line began to rise. The data were recorded using the data collection box. I repeated this experiment using the following voltages: 1.0 volts, 3.0 volts, and 10.0 volts. These voltages were used to see if changes occurred within the latent periods. For the second experiment, the data generated was used to determine the threshold voltage. The threshold voltage occurred when the active force measured in grams was greater than 0. The equipment setup was the same as the last experiment, and the electrical stimulator was set to 0.0 volts. At 0.0 volts, the muscle was stimulated and the results observed and recorded using the oscilloscope and data recorder respectively. This experiment was repeated multiple times by increasing the voltage by 0.1 volts until the mi nimal threshold voltage was determined. For the third experiment, the effects on muscle contractions due to an increase in the electrical stimulus intensity were explored. Again the same equipment setup was used. The initial voltage was set to 0.5 volts followed by stimulation of the skeletal muscle. The data were observed and then recorded. This experiment was repeated multiple times by increasing each subsequent voltage by 0.5 volts. This continued until the data showed there was no change in the increase in active force. For the final experiment, fatigue was induced in the skeletal muscle. The equipment setup for this experiment was similar to the first three experiments. However, a different electrical stimulator was used which incorporated a multiple stimulus option as well as a single stimulus option. The multiple stimulus option added the ability to start and stop the stimulus activity. This experiment was designed so that several stimuli per second were being applied to the skeletal muscle if so desired. The electrical stimulator voltage was set to 7.0 volts, and the number of stimuli per second was set to 100. The muscle was then stimulated for approximately 400 seconds by selecting the multiple stimulus option, and the graphical data were recorded from the oscilloscope. Results For experiment one, the latent period was recorded in milliseconds and was compared to its corresponding stimulus voltage. The time measurement (latent period) reflected the start of the flat line until it began to rise. Below is a summary of the recorded data. Latent Period Determination Stimulus Voltage (V) Latent Period (msec) 1 3.89 3 2.78 10 2.22 For experiment two, the threshold stimulus determination data was collected by measuring the electrical stimulus voltage and its corresponding active force generated. Once the active force became greater than 0, the experiment was stopped. Below is a table with the collected data. Threshold Determination Stimulus Voltage (V) Active Force Generated (gms) 0 0 0.1 0 0.2 0 0.3 0 0.4 0 0.5 0 0.6 0 0.7 0 0.8 0.02 For experiment three, the data were collected in order to determine the effects of increased stimulus voltage on muscle contractions. The data reflected 0.5 volt interval increases in the electrical stimulus until 10 volts were reached. Below is the summary of the data. Muscle Contractions Increased Stimulus Effects Muscle Contractions Increased Stimulus Effects Stimulus Voltage (V) Active Force Generated (gms) Stimulus Voltage (V) Active Force Generated (gms) 0.5 0 5.5 1.59 1 0.15 6 1.65 1.5 0.43 6.5 1.7 2 0.66 7 1.74 2.5 0.87 7.5 1.78 3 1.04 8 1.81 3.5 1.19 8.5 1.82 4 1.32 9 1.82 4.5 1.42 9.5 1.82 5 1.51 10 1.82 For experiment four, data was graphed in order to demonstrate the effects of fatigue. The rate of the multiple stimulus was 100 stimuli/second at a constant setting of 7.0 volts. The data were recorded over a 400 second interval. Below is a graphical representation of the collected data. Muscle Fatigue Effects of Prolonged Stimuli Over Time (Stabler, et.al, 2009) C:Sheas StuffHuman PhysiologyFatigue.jpg Citations Allen, D.G. and H. Westerbland. (2001). Topical Review: Role of phosphate and calcium stores in muscle fatigue. Journal of Physiology 536.3: 657-665. Enoka, R. and J. Duchateau. (2008). Muscle Fatigue: what, why and how it influences muscle function. Journal of Physiology 586.1: 11-23. Silverthorne, D.U. 2010. Human Physiology: An Integrated Approach. 5th Edition. Pearson Benjamin Cummings, pp. 408-422. Stabler, T., Smith, L., Peterson, G., and Lokuta, G. 2009. PhysioEx 8.0 for Human Physiology à ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬ Laboratory Simulations in Physiology. pp. 17-22.

Infectious Disease :: science

Infectious Disease What is the stake of the American People and the Government by International Agencies to control Infectious Disease in Developing Countries? More people are at risk of infectious diseases than at any other time on history. Infectious diseases are worldwide problem requiring worldwide attention. Infectious diseases can weaken the strength of a nation's resources. In developing nations this poses even a greater threat. Diseases are threatening the economic stability of many developing nations. 50,000 people die everyday from infectious disease. Rift Valley Fever infects both livestock and humans. Rift Valley Fever is most commonly found in regions of eastern and southern Africa. It also exists in Madagascar and sub-Saharan Africa. The Bunyaviridae family includes the Rift Valley Fever disease. It is primarily spread from infected mosquitoes, who then infect animals. Generally they infect domestic animals, such as buffalo, cattle, sheep, camels and goats. Once the livestock are infected, other mosquitoes can spread the disease. It is also possible that the infection can be spread from other biting insects. The Rift Valley Fever outberak of 1997-1998 in eastern Africa killed both humans and livestock. It economically hurt trase in animals and the dairy indusrty.. the economy was crushed by trade imbargoes. Humans can get Rift Valley Fever in numerous ways. Humans can be infected from the mosquitoes or the bodily fluids of the infected animal. Contact such as slaughtering the infected animal can occur also. Symptoms include, an infuenza like illness, fever, liver abnormalities, muscle and back pain and vomitting. In the early stages of Rift Valley Fever, these symptoms are some times mistaken for meningitis. This fever may also perceive itself to be haemorrhagic fever. Fatalities occur mostly in patients who have developed haemorrhagic fever. In diagnosing Rift Valley Fever, tests have demostrated the presence of antibodies to the disease. Studies in animals have given antiviral drugs for the use of humans. Herdsman and animal workers in areas where Rift Valley Fever is present are at a greater risk of being infected. The risk of transmission can be reduced by, wearing gloves, insect repellent, the use of protective clothes, and avoiding outdoor activity during peak biting times. Surveillance is important to form effective measures for reducing the number of infections. Cholera is a diarrheal illness that is spread by contaminated water and food. It is caused by an infection of the intestine, and in many cases it can be very severe.

Buisness Environment

The business environment of candy wrapping is lively and quite encouraging for start-ups to commence and operate business. There are always emerging candy companies with new flavors and tastes covering the entire age market of children, youth, men and women and even elderly. Specially lolly pops, lozenges, eclairs, are all time favorites for all group of ages and wrappers are everywhere. Especially after the launch of Internet technology, candy-wrapping business has emerged as a specialized business with profit making margins.In fact stay at mom candy wrapping business have been inviting individuals to take up candy wrapping business. Candy wrapping is an excellent ebusiness which can be in small volumes as well in large volumes whereas the demand for candy wrapping can never be halted. Candies are 24Ãâ€"7 business which are available at every occasion beginning from birthdays to wedding celebrations. The strengths that are required in candy wrapping business is to possess skills of designing software of graphics to extend colorful view on candy wrappers.Lot of creativity and imaginary work that must work in designing of wrappers which will prove beneficiary for business. There are no particular weaknesses in the business of candy wrapping without the concern of entrepreneur such as poor customer relation management, untimely deliveries, poor quality paper, spoilt / broken candies, poor packing are some of the keen areas where business will be lost. Website is no guarantee proof that business will be developed at a fast pace whereas it must be advertised through proper channels.A wide variety of opportunities are available in candy wrapping business. The business includes multinationals such as nestle, Cadbury Schweppes, and service oriented organizations viz. , wedding planners, birthday parties, florists, toy stores, infant and children shops, can be undertaken. Equipment that is required for designing candy wrappers is, a computer, ebusiness kit, software f or designing wrappers, color printer and paper. It is also a fact competitors can never be taken a back as loss except to the fact that the quality of paper must be excellent with attractive designs.Timely delivery of goods must be undertaken with utmost care and neatly packed to gain brand image of ebusiness. There are many successful companies which are involved in candy wrapping business. (1) candywrapper lady (2) custom candy wrappers (3) CJ’s Candy Wrap-ups (4) Party411. com (5) chocolatecovers. com. Although there is a stiff competition in the market, each company is specialized with a particular design which is the quality work according to the requirement and liking of a client.Each company is specialized in a particular software and design and focuses only those areas of clients. This also extends lot of benefits for companies and clients who are offered with variety, wide choice and with quality work. Conclusion For every ebusiness owner, a complete and thorough kno wledge of candy wrapping, internet research to build client base, market analysis and finance control is required while the basic skill of top quality designs must be focused.There can also be another alternative to work for a candy wrapping company before starting an own business, in order to gain sufficient knowledge, experience and guidance to avoid a novice experiments in ebusiness. References Start your own business get the bizymoms candy wrapper career kit Accessed 20 June 2007 http://www. bizymoms. com/cart/careers/candywrap_kit. html The candy wrapping business Accessed 20 June 2007 http://www. talewins. com/homepreneurs/candywrapping. htm

The Benefits of a Standing Desk and Risks of Sitting

Standing desks offer many benefits for your health and ergonomics. Break free from the chains of sitting at a desk and stand up for yourself and your health. Health Benefits of a Standing Desk The first major benefit of using a standing desk is avoiding all of the negatives that make sitting at a desk bad for you! Sitting for long periods of time causes metabolic issues–you dont produce chemicals necessary for processing sugars and fats, and your circulation suffers. Your skeleton and muscles form a reactive frame for your body which wants to move and respond to outside forces. Additionally, your muscles need to regularly flex to support healthy functions and chemical production. Standing allows your body to adjust and move easily, flexing your muscles continuously. It also keeps your blood circulating well. Movement regulates your blood sugar and keeps your blood pressure lower. And this lets you live longer! Risks of Sitting Sitting increases your chances of developing diabetes, cardiovascular disease, and blood clots or thrombosis. Studies have shown some dramatic effects of sitting for long periods of time. Those who sit a lot are 54 percent more likely to have a heart attack. Men who sit more than six hours a day have a 20 percent higher mortality rate; women have a 40 percent higher mortality rate. If you sit for more than 23 hours a week, you are 64 percent more likely to die from heart disease. In addition, studies have also shown that regular exercise does not counteract the effects of prolonged sitting. The only way to reduce or eliminate the negative impact of prolonged sitting is to not do it. Working at a standing desk will accomplish that for most people. Another benefit of a standing desk is that you burn more calories throughout the day. That will help with weight loss or maintain a healthy weight. Standing while working will burn one-third more calories than sitting will, which could account for an additional 500 calories burned in a day. Standing Can Reduce Pain There is anecdotal and scientific evidence to show that standing while working will alleviate back pain and other repetitive stress injuries. The problem usually comes from not using your back enough. When you sit, you dont hold your upper body with your muscles; rather, you let the chair hold you. This leads significant compression within the chest and abdominal cavities, slouching of the shoulders and rolling of the spine. These are classic causes of repetitive stress injuries and back pain. Working at a standing desk will keep your core and back muscles engaged throughout the day and improve your posture. Mental Benefits of Standing Another benefit of a standing desk is an increase in your focus, alertness, and activity level. When standing, it is easier to release restless energy. Combine that with the good circulation, stable blood sugar, and an active metabolism, and it is easier to focus on the task at hand. Standing while working will burn one-third more calories. Many authors and statesmen throughout the centuries who swear by working at a standing desk have claimed that it helps get the creative juices flowing. It also fights fatigue and improves lethargy. While this may sound like a contradiction, it is not. Standing while working helps fight off the naturally occurring slumps and bouts of fatigue that often happen mid-morning or early afternoon. Those are often related to metabolic drops after meals are processed by the body. Keeping your blood sugar level helps avoid those. Staying active and releasing restless energy also promotes a satisfying tiredness when it is time to sleep. Your mind isnt racing and your body is ready to rest.