Superior Flexor Muscle Cells :: Biology Essays Research Papers

Effects of Extracellular Potassium Concentration on Membrane Potentials in Crayfish Superior Flexor Muscle Cells Intracellular measurement of membrane potentials in cells of the crayfish superficial flexor muscle can reveal the effects of varying the extracellular concentrations of potassium ion on the resting potential. Our results suggest that at high extracellular potassium concentrations, the resting potential resembles that of the potassium’s equilibrium potential, and at low potassium concentrations, resting potential is less related to potassium equilibrium potential. We suggest that the equilibrium potential of other ions, especially sodium, contribute more heavily to the resting potential when extracellular potassium concentration is low, which accounts for the resting potential having a less negative voltage than the potassium equilibrium potential. The determination of resting potential by the equilibrium potentials of numerous ions reduces the effect that concentration changes in any single ion will have on the resting potential, lending stability to neural cell function even during changing environmental conditions. We tested the effect of extracellular potassium concentration on membrane potentials in the crayfish superficial flexor muscle cells. We compared five different extracellular concentrations of K+ and measured resting potentials by recording extracellularly and intracellulary, using an electrode that was inserted into the muscle via a micropipette. Our results confirm the relationship between voltage across the membrane and equilibrium potentials of the most prevalent ions that is stated by the Goldman Equation. Micropipettes were constructed from capillary tubes with tip diameter of a fraction of a micron. A micropipette and holder were filled with 3M KCl; use of this saturated solution ensured that intracellular K+ did not diffuse from the cell up the pipette. The top of the holder, which connected to the Neuroprobe amplifier circuitry, contained an Ag/AgCl electrode to prevent the hydrolysis of water, which would have created bubbles of hydrogen gas that would interfere with current conduction. The crayfish superficial muscle was exposed by making a U-shaped cut in the dorsal carapace and removing the dorsal muscles, leaving only the ventral carapace, its attached muscles, and possibly the nerve cord. This region was then placed in a small plasticene dish covered with one of five crayfish Ringers’ solutions. Normal (1x) crayfish Ringer’s solution contained [K+] = 5.4 mM and was used as a control; the four experimental solutions contained [K+] of .54 (.1x), 16.2 (3x), 54 (10x), and 162 (30x) mM respectively. Despite the non-uniformity of total osmolarity, the proportion of K+ to Cl-, the other important diffusible ion, remained constant, satisfying the Donnan Equilibrium.

Nature and Function of Literary Criticism Essay

The word criticism is derived from the Greek word meaning † judgment†. Hence, criticism was known to be the exercise of judgment on works of literature, or it can be said that criticism is the play of mind to observe the merits and defects on the work of literature. A critic , therefore, is a person who expresses judgment on works of literature or poetry or the art of an artist or a painter. The critic is also defined as a person who is possessed of the knowledge necessary to enable him to pronounce right judgments upon the merits or worth of such works as come within its province. However, the question that is always asked, does the critic has the right to judge or not ? Indeed, no one has the right to judge the people because of two reasons. Firstly, to judge the people is something subjective ; in other words, when a critic evaluate a literary work he is judge based on or influenced by his personal feelings, tastes, or opinions. Second, when a critic judge and evaluate a literary work , he eliminates the reader’s mind and deactivate his faculty of thinking and analysis. It’s known that the target group of the critics is the public reader, so what do they want from the reader and what is the ultimate objective of criticism?. Actually, the modern understanding of criticism is regarded as having two different functions which helps to achieve the main purposes of criticism. The Modern Understanding of Criticism Criticism is the process of analysis and description and interpretation of literary works for the purpose of increasing understanding and raising appreciation.   This means that the critic should penetrate to the heart of the literary work to analyze and formulate its meaning , to disengage and describe its qualities of power and beauty , and to elucidate by direct examination the artistic and moral principles which, whether the writer himself was conscious of them or not , have actually guided and controlled his labors, and then to pronounce a right evaluation of a literary work. It’s worth to realize that criticism does not depend on a critic’s views or his opinions , but it depends on scientific basis which is † Critical  Theories†. As a result, criticisms are completely different depending on the theory that the critic uses. Thus, the objective of literary criticism is to determine the artistic values, poetic beauty, or the features being regarded as inadequate existing in the works of literature in order to 1-Helping the reader to gain a better understanding of nature and value of literature, and a better appreciation of the pleasure proper to literature, then to form an evaluation of his own. 2- Helping the writer to improve his skills and facilitate to achieve the merits while allowing him to overcome the flaws if any. At this stage, it would be appropriate to say that criticism is not just † fault- finding† , but helping the writer or poets or artists in achieving the excellence in their works and leading the reader to a better understanding and appreciation. At this point , the saying of T.S Eilot is worth mentioning, † The end of criticism is the elucidation of works of art and to correction of taste†.

Physics Mechanical And Chemical Interactions - 1432 Words

From analyzing the students’ choices of models of friction and lubrication, two overarching themes emerged regarding mechanical and chemical interactions. We see in table III that about 81% of the students interviewed used mechanical interactions to explain friction and when asked to explain microscopic friction the majority referred to their â€Å"interlocking-intertwining† or â€Å"rubbing-hitting† models. Most agreed friction is the force required to move atoms over bumps and valleys because of intertwining and interlocking of the atoms or friction is the force caused by the rubbing and sliding of an atom past another. Also when the students with the interlocking model were question about the outcome if the surface was to become automatically smooth they all agreed friction would persist because â€Å"there is still some contour in the them (atoms).† Likewise when asked to explain why oil reduces friction, the majority said the â€Å"oil molecules roll † like a â€Å"ball bearings rolling on a surface†. The theme that the thematic analysis revealed about the chemical interactions was that around 27% of the students think that microscopic friction is the force needed to break the bonds required to break bonds between the atoms of the surfaces that are touching. 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