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Muscle Fatigue
Muscle Fatigue
The purpose of the muscle function lab is to become familiar with basic properties of the skeletal muscle: such as types of contractions and muscle twitch. The main method behind this lab is to dissect a gastrocnemius muscle of a frog and stimulate it. Various results will show a threshold stimulus and a maximal stimulus. Contraction length, summation, tetanus, and muscle fatigue are also shown in this specific lab. Also, through this electrical stimulation we can visually see the relationship between length and tension with the presence of an isotonic and isometric contraction. Chemically, calcium ions have an effect on muscle contraction. A prolonged stimulation of the muscle, causing muscle fatigue, as we learned also affects muscle contraction. In this experiment we used a physiologic stimulator. This device delivers something like an electric shock directly to the frog’s gastrocnemius muscle. A force transducer was used to convert mechanical movements produced into a form of electrical signals. In this particular experiment we used a string to help measure the force of the muscle contraction, and with the help of the force transducer we were able to see this movement in electrical signals. The MacLab/4 is computer hardware that we used to help display the data in which we encountered. And lastly we used a Macintosh Computer to read and analyze the data that was found with the help of the MacLab/4 program.
The second part of this experiment was a direct stimulation of the human forearm muscle and induction of finger movements. Once again, this involved stimulation of the muscle with a direct electrical current. We placed the electrical stimulator on the flexor digitorum sperficialis muscle of the forearm. When we did this experiment we found the minimal electrical stimulus required to achieve a movement and contraction of the FDS. During this experiment there was a time from when the electrical charge starts to move through the sarcolemma to the time when the muscle contraction begins. The brief period of time we learned is called the latent period. We also found that there is a greater latent period in the human than the frog. In this experiment we used a stimulator, which is the same device as earlier stated. The McADDAM is part of the computer, which moves the signals from the Physiogrip trigger to electronic signal. With these electronic signals, the computer is able to recognize what is happening with the muscle movement. The Physiogrip Transducer is shaped like a pistol trigger and the twitching finger will be placed on and the transducer will help display the mechanical force to an electrical signal for the Macintosh computer to read. Therefore, in both labs we were able to determine an intensity-tension relationship, length-tension relationship, and frequency-tension relationship.
This lab was an excellent source to learn about how the muscular system functions and helps us understand how some muscular disorders come into play in our lives.
For the physiology mid term paper, we are focussing on the muscle function lab. In this lab, we became familiar with skeletal muscle, by isolating a frog’s gastrocnemius muscle. As a class, we learned about the use of direct electrical stimulation of muscle, the relationship between intensity-tension, muscle-length, and frequency-tension, stimulus, and muscle fatigue.
When an area of the body is stimulated, the message is sent to the brain by an electrical signal. This happens due to the nervous system. It is made up of nerves, “which connect the central nervous system with the periphery” (Germann 782), and neurons, which are cells of the nervous system. These cells have many parts, which aid in the transmission of messages throughout the body. The soma (cell body) is where the nucleus is found. The dendrites branch out from the soma, and form synapses with other neurons. This is important because this is how other neurons receive messages. The axon of the neuron sends the information down the whole cell. It is mylenated to speed up the process. This is why it does not take a very long time to feel a pain sensation, or to move a muscle. Between the mylinated portions of the axon are nodes of Ranvier. These areas of the cell are the places that the neurons are able to become excited, and make an action potential. This simply means that sodium ions flow into the cell, depolarizing it, so that signals in the form of neurotransmitters can be sent. An action potential only occurs in excitable cells, and follows the all-or none rule. This simply means that an action potential will occur only if the neuron is stimulated to the threshold or above. If the stimulation does not reach the threshold, there will be no action potential, and no message sent. A graded potential differs from this because it does not follow the all-or-none rule. Graded potentials are smaller then action potentials and result from the opening or closing of an ion channel. A single graded potential will not elicit a response or action potential (Germann 186). When they overlap, however, they can add together. This can happen in two ways. In temporal summation, “stimuli are applied in such rapid succession that the graded potential from one stimulus does not dissipate before the next graded potential occurs” (Germann 186). Spatial summation is closely related to temporal summation, except is occurs in when different synapses are stimulated simultaneously.
Ion channels are places on the neuron where sodium (NA+) flows in to the cell, or potassium (K+) flows out. These channels open when they see a change of voltage along the neuron. As this happens the Na+ channels on the muscle open so the acytlecholine can bind to its receptors. When the distribution of these ions change, the cell either becomes depolarized or hyperpolarized. When a neuron has been depolarized and begins to be repolarized, it enters an absolute refractory period, in which any stimulus will not elicit a response. This is because the neuron has reached its maximum threshold. After repolarization, there is a chance that the action potential may be excited again. This happens during the relative refractory period. In this period, an extremely large stimulus may elicit a response.
The body has many different types of neurotransmitters that have an array of functions. Some are excitatory, and others are inhibitory. As stated before, when a neuron becomes excited, Na+ flows into the cell, depolarizing it. Inhibitory neurotransmitters have the opposite effect, and inhibit neuron activity. They are released when the neurons are hyperpolarized, and an influx of K+ flows out of the cell (Kapit, 87). In the nerve lab, the neurotransmitters that were being tested were acetylcholine and norepinephrine. Acetylcholine can be found at the neuromuscular junction. It is involved with the contraction and twitch of muscles. When added to the muscle, it should increase the contraction. Norepinephrine can be found in the nerve, and when added to the nerve it should also increase muscle contraction. When acetylcholine is released, it binds to the acetylocholine receptors on the post-synaptic neuron. This is how the neurotransmitters are sent from the brain to the muscle. As acetylcholine enters the synaptic gap, acetylcholineserase breaks it down into acetate and choline, in order for it to be able to bind to its receptors. This is important because without all of these chemicals muscles would not be able to contract.
As the frequency was increased, the muscle went through summation. The twitches added together until they reached their maximum, and tetanus was achieved. This is because the calcium ions did not have time to go back into the Sarcoplasmic Reticulum and restart the entire process. The sarcomeres are the smallest unit of muscle cell that are separated by elastic fibers called z-lines. We can find within each sarcomere two typed of myofilaments. These myofilaments are positioned along the sarcomere’s length. Thick myofilaments are made up of myosin, and thin myofilaments are made up of actin molecules. A sliding movement of the thin filaments with the thick filaments causes contraction. This results in the shortening of the sarcomere.
This act of the muscle tissue being stimulated directly with electric shocks will then send a release of calcium ions and activate the muscle’s contraction. A twitch of the muscle shows a single muscle fiber or a whole muscle fiber activated.
The skeletal muscle is a fixed muscle attached to bones and skin and it is responsible for all voluntary and involuntary movements. The skeletal muscles are controlled by the somatic nervous system (Vander, 288). The gastrocnemius is a whole skeletal muscle, comprised of many single muscle fibers. “The gastrocnemius muscle is one of the frog’s extensor muscles and it aids the frog in its jumping movement” (Meisami, 100). It is possible to do the same experiment on a single muscle fiber, as well as the whole muscle fiber.
In the experiment we dissected the gastrocnemius muscle, attached it to the force transducer, and studied the effects of the intensity-tension relationship first. While doing this part of the experiment, we had to conclude what was going to happen to the tension amplitude when we raised the voltage. In the next part of the experiment, we tested the relationship between length and tension. While doing this part of the experiment we studied the effects of what would happen to the tension when the length of the muscle was increased. The last relationship we tested in this lab was the relationship between frequency and tension. In this part of the experiment, we determined what would happen to the muscle tension when the frequency of stimulation was increased. One is able to learn by looking at the graph on page 115, in the Laboratory Manuel, that muscle tension gradually increases with increasing frequency of stimulation. The highest frequency that we were supposed to test our gastrocnemius muscle at is 16 Hz. Therefore, we can conclude that at 16Hz the state of muscle contraction is called tetanus, meaning the contraction becomes continuous (Meisami, 114). The last thing that we tested in this experiment was muscle fatigue. “When a skeletal muscle is repeatedly stimulated, the tension developed by the fiber decreases even though stimulation continues” (Vander, 309). This stimulation in a muscle can resolve in muscle fatigue. We tested muscle fatigue by increasing the frequency of stimulation until tetanus started to occur. After tetanus was occurring in the muscle for a short time, the muscle tension decreased. This decline in muscle tension brought about muscle fatigue.
The general objectives of the muscle function lab are “to familiarize you with some of the basic functional properties of the skeletal muscle. By use of a frog’s gastrocnemius muscle, calf muscle, you will learn the properties of muscle including muscle twitch and maximal contraction, the isometric and isotonic types of contraction and the relationship between length and tension. Summation of muscle twitches, occurrence of muscle tetanus and muscle fatigue and the effects of calcium ions on muscle contraction will also be studied” (Meisami 116). Furthermore, there are a few specific objectives listed in the lab manual or found below. These include understanding procedures for dissection and isolation of the frog and its muscle, understanding the use of direct electrical stimulation, understanding the concepts of isometric and isotonic forms of muscle contraction, study the different relationships, and study muscle fatigue after prolonged stimulation (116).
The Muscle Function Lab involves the usage of three different pieces of scientific equipment. These three scientific pieces include the physiologic stimulator, force transducer, and MacLab/4-Chart. The physiologic stimulator works to provide electric stimuli at various strengths that are measured in voltage, durations that are measured in milliseconds, and frequencies that are measured in hertz. The force transducer works to convert the movements into electrical readings. The string that is attached by the experimenter to the frog’s gastrocnemius aids this. Finally the MacLab/4-Chart takes the electrical readings and forms them on a chart onto paper. In the first part of the lab dealing with the intensity-tension relationship, the voltage delivered to the frog’s gastrocnemius muscle is changed to a higher voltage to help determine threshold intensity and maximal intensity.
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Chapter Eight Social and Political Philosophy
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Chapter Eight: Social and Political Philosophy
Chapter eight of the book, “Philosophy: A Text with Reading” by Manuel Velasquez discusses social and political philosophy. The chapter opens by trying to elaborate on the relationship between an individual and society as well as the problems to do with justice. The subject of social and political philosophy tends to analyze the substantial role of a government towards its citizen, what it should do for the underprivileged, how an individual relates to the society as well as discussing on the issue of justice, for example, the justification of state authority. All these issues center on social and political philosophy. Social philosophy is defined as a philosophical study of problems that are affecting the society and the application of moral values for countering those issues, for instance, human rights and freedom.
On the other hand, political philosophy is a branch of social philosophy, and it discusses the role of the government or state in society. The government or state is the supreme authority, and hence it has the power to define the interests of the public and impose its rule on the public. By doing this, it tends to answer the question of justification of the state and its authorities. For example, the state implements this through the income tax method. That is, it sets its primacies by defining the programs that it feels are according to the public interest and afterward, it implements those programs by taxing the citizens. For example, the American government taxes its citizens according to their incomes.
Moreover, the issue of justification of the state and its authorities are well analyzed through the contract theory which is based on the philosophies of John Locke and Thomas Hobbes. John Rawls rejuvenated the theory during the twentieth century. Rawls contends that social contract is a fictional means for establishing what a fair society is and what the government in this society looks like. However, this theory has faced some criticism for example by communitarians who claim that the theory disregards the social l beings of individuals. Also, the feminists argue that the theory undertakes a nonconsensual division whereby women tend to be downgraded to the contentious issues in the society like in economics as well as politics where men dominate.
The issue of justice in society is also well discussed in this chapter. According to Velasquez, justice comprises retributive justice and distributive justice. Retributive justice analyzes how impartial punishments exist while distributive justice examines how the impartial society distributes benefits and burdens to society. Due to the different views of philosophers concerning the issue of justice, it exists in many forms, for example, justice as social utility, justice as strict equality and justice as moderate egalitarianism among other significant types. Plato and Aristotle link justice with merit. Their sentiments are according to the conventional Greek view of Justice. The egalitarians on their side claims for strict equality or evenhandedness of political rights as well as in economic opportunities. Their claim tends to be supported by society liberals; for example, Rawls who contends that justice entails financial support for the deprived. There are other liberals like Robert Nozick who also argues that individuals’ free choices need to be respected in all dimensions, particularly in economic matters.
The chapter closes with discussing the limits of the state towards the society. Although the section has different authors with diverse views concerning the issue of justice, it is evident that they all agree that it is the responsibility of the state to promote justice. For example, Aquinas maintains there is a great need for the laws of the state to be consistent with natural law. Moreover, these laws need to be compatible with the right to freedom. The right of freedom is entailed in the Bill of Rights, and it protects the citizens against interference by the state. In this chapter, the subject of human rights is also well analyzed by classifying it into positive and negative rights. This is according to how different individuals regard and view the issue of human rights. Even though every individual approves that it is necessary for changing the state laws when they seem to be conflicting with human rights, there are others who argue that there is a need for the state to enforce only the individual’s negative rights. On the other hand, others maintain that the government must obey and afford individuals positive rights.
The last end of the chapter is about the morality of war. Under the morality of war, political realism, pacifism as well as just war theory are discussed by the author. According to Velasquez, political realism maintains that morality is not effective to war while pacifism arguers on the immorality of war to the society at large. There is also the description of just war theory which discusses on the evil nature of war. For the just war to be justified, it has to achieve the following conditions according to this theory: it has to be I regard to the legitimate authority, it should have the right intention, it is real, and it has a just cause and finally if it is the last and only option. Moreover, just war tends to condemn some evil vices in society like terrorism.
Chapter 15 Single-serve coffee makers are an example of continuous innovation
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Chapter 15
Single-serve coffee makers are an example of continuous innovation. Coffee lovers around the world have switched from drip coffee makers to the newer and more innovative sing serve ones. This change is classified as continuous because consumers have switched from one type of coffee maker to another, which they view to be more superior. There has been no significant change in customer habits, because they still continue to drink coffee, only using a better machine. Companies have taken advantage of the growing competition in the market for coffee machines that are the most efficient for consumers. Consumers prefer the single-serve machines because they are much faster, and they can have their coffee in a few seconds after the press of a button. Companies making such machines have experienced significant growth over the past few years compared to drip machines. Nespresso and Keurig are the most prominent players in the coffee maker market, and they are reaping big from their innovations. Nestle is a leading producer of coffee across the world, and producing efficient coffee makers is a practical step for the company. Continuous innovation involves marginal changes (Björk et al. 387), and this is how these companies have continuously grown their market margins by building upon the habits of their consumers.
The innovation has been well received in the market, facing little resistance. The main reason why continuous innovation faces little resistance is that it does not alter customer habits significantly. Single-serve coffee makers have simply built upon the existing popularity of coffee consumption and made the experience of brewing coffee faster and more efficient. Customers find these machines to be different from existing drip machines, and this is a point of attraction (Ries 26). The new single-serve coffee machines are more expensive than the drip ones, but customers are willing to pay more for the convenience that the new machines bring. Companies are building towards more sophisticated espresso machines, which is another example of continuous innovation.
Works Cited
Björk, Jennie, Paolo Boccardelli, and Mats Magnusson. “Ideation capabilities for continuous innovation.” Creativity and innovation management 19.4 (2010): 385-396.
Ries, Eric. The lean startup: How today’s entrepreneurs use continuous innovation to create radically successful businesses. Currency, 2011.