This investigation sought to determine the effect of changes in extracellular potassium concentration [K+] on resting membrane potential in the muscle cells of the adult crayfish Orconectes rusticus. Due to the knowledge of the highly negative equilibrium potential of K+, which, in normal, biological conditions, causes the ion to be transported toward more negative regions, it was hypothesized that as the extracellular [K+] increased, [K+] inside the cell would also increase. This would cause intracellular charge to reach a larger, positive value, and the resting voltage across the membrane would become more positive as well; however, differential membrane permeability to various ions accounted for in the Goldman-Hodgkin-Katz equation would …show more content…
In solutions of 5.4, 10, 20, 40, and 80mM [K+] solutions, membrane voltage followed the hypothesized trend, but the membrane voltage actually became more negative in the 100mM [K+] solution, likely due to factors such as small sample size, differential membrane permeability, a changing [Na+], and sample deterioration. Furthermore, the differential response of different muscle groups was analyzed and found to have no significant effect on membrane potential. Introduction: The resting membrane potential of a cell in part dictates its response to an action potential (Sidorov, et al. 2003). In particular, the K+ ion gradient has been shown to play a role in setting this resting membrane potential and impacting cell excitability; therefore, this investigation aimed to determine how changes in extracellular [K+] would affect resting membrane potential in the muscle cells of adult crayfish Orconectes rusticus (Lin, 2012). Hodgkin and Huxley showed in 1952 that the K+ current responds to changes in membrane voltage, and this experiment would explore how changes in [K+] would change membrane
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
This is an experimental lab that tested if drinking water passes the United States maximum phosphate standard. The results of this lab can help the American who drink the water know if there are too much phosphate in the water. Each group made a Potassium phosphate dilution from a stock solution. The concentration of the solution that needed to made affected the amount of Potassium phosphate that was diluted. To create a calibration curve, each group used the different concentrated Potassium phosphate solutions in their test. The lab utilized a spectrophotometer to figure out the absorbance of the five different Potassium phosphate solution and the absorbance of an unknown concentration solution. The absorbance of the unknown solution was used
There are a series of nodes along the axon where there is a high concentration of sodium (Na+) and K+ channels. There is a high concentration of Na+ outside the cell and a high concentration of K+ inside the cell. As the nodes sen...
To gain a better understanding of compound action potentials (CAPs), we observed extracellular recordings from an isolated sciatic nerve of the leopard frog, Rana pipiens. We analyzed properties of CAPs in regards to membrane potential threshold, temporal summation, refractory period, and conduction velocity through various experiments. First we applied increasing stimulus voltage to determine the threshold and maximal CAP amplitude. Our threshold was recorded at 70 mV, which was observed by the first recordable CAP elicited. In order to determine what stimulus would cause all individual neurons to be fired, we continued to increase the voltage by 10 mV until there was no
ii. An action potential is caused by the stimulus received by the dendrites of nerve cells. This stimulus causes the sodium channels to open. Opening of these channels causes the interior potential to go from -70 mV up to -55 mV. This allows for the cell to reach its action potential. When this potential is reached voltage gated sodium channels open and drive the potential inside the cell membrane to increase to around 30 mV. This is called depolarization. This action potential is conducted along the length of the fiber and causes the next adjacent space to open voltage-gated sodium ion channels to open. Once depolarized the sodium channels close and the potassium channels open, which allow for the membrane to repolarize to around -90 MV in a process called hyperpolarization. Hyperpolarization prevents the neuron from receiving another stimulus. After hyperpolarization the membrane goes back to its resting potential of -70 mV.
resting membrane voltage than perhaps other ions -> Ek for other ions using Nernst at values
The experiment is aimed at giving a better understatement of osmosis process and the different conditions in which osmosis occurs.
Through the experimentation of reactions between iron (III) nitrate and potassium thiocyanate, as well as cobalt (II) chloride hexahydrate in water, equilibrium systems disturbed by stress (changing the amount of reagents and temperature) will shift in order to minimize the stress. Therefore, if the concentration of reactant increases, the rate of the forward reaction will increase and equilibrium will reestablish when the concentration of products increase (vice versa). This can be observed through color changes of the solutions.
To improve this experiment, a better control for the experimental treatments needs to be established. Instead of comparing the experimental treatment against cold saline, a baseline period needs to be taken prior to the application of any experimental conditions. In addition, each experimental treatment should be conducted on a different frog of the same mass and health or at the very least on the same frog after ample recovery time has been given and the heart beat has stabilized instead of consecutive experimental treatments. Also, the temperature of the treatments and dosages of each neurotransmitters need to be standardized to prevent any discrepancies or
Action potential is another method of transmission of chemical information from one neuron to another. It takes place in an area of plasma membrane in which high concentration of voltage-gated 〖Na〗^+ and K^+channels. The only ions involved in action potential are 〖Na〗^+ and K^+. As chemical reach a certain level, the neuron will eject the extra concentration into the adjacent neuron. One of the keen differences between graded and action potential is that the presence of refractory period does not make summation possible because of its “all or none” nature.
The current efficiency is an important parameter that determines the optimum range of applicability of electrodialysis. It is a measure of how effective ions are transported across the ion exchange membranes for a given applied current. It is calculated using the following equation [20, 21]:
Activity 3: Investigating Osmosis and Diffusion Through Nonliving Membranes. In this activity, through the use of dialysis sacs and varying concentrations of solutions, the movement of water and solutes will be observed through a semipermeable membrane. The gradients at which the solutes NaCl and glucose diffuse is unproportional to any other molecule, therefore they will proceed down their own gradients. However, the same is not true for water, whose concentration gradient is affected by solute ...
The second part of this lab was a computer simulation program to illustrate a frog’s electrocardiogram using various drugs in an isolated setting. The computer program entitled “Effects of Drugs on the Frog Heart” allowed experimental conditions to be set for specific drugs. The different drugs used were calcium, digitalis, pilocarpine, atropine, potassium, epinephrine, caffeine, and nicotine. Each of these drugs caused a different electrocardiogram and beats per minute reading. The calcium-magnesium ration affects “the permeability of the cell membrane”(Fox). When calcium is placed directly on the heart it results in three physiological functions. The force of the heart increases while the cardiac rate decreases. It also causes the appearance of “ectopic pacemakers in the ventricles, producing abnormal rhythms” (Fox). Digitalis’ affect on the heart is very similar to that of calcium. It inhibits the sodium-potassium pump activated by ATP that promotes the uptake of extracellular calcium by the heart. This in return strengthens myocardial contraction (Springhouse). Pilocarpine on the other hand
...regions of the fish, there are electroreceivers that detect distortions in the electric field (1993). The arrangements of the electrocytes are important because it allows the gymnotid to detect what’s ahead and then use its tail to produce a charge. If electroreceivers were in the tail region, the mammal would detect electric signals a lot slower. In ion-poor waters, like freshwater, allows the gymnotid to generate electric signals because little current is needed to sustain a detectable voltage (Stoddard, 2009).
The overall purpose of the experiments in this lab was to introduce the function and structure of the plasma membrane, describe the workings of diffusion and osmosis, and to demonstrate how different factors such as particle size, temperature, and space of diffusion area affect the rate of diffusion. With the results from the experiments, it can be concluded that all of the factors listed do affect diffusion, and there may be many more than are unaccounted for.