Physioex 9.0 Exercise 3

c. If the frequency of action potentials in this presynaptic cell (#10a) increases, what happens to the number of action potentials in the postsynaptic cell?

Action potentials can occur more frequently as long there is a continued source of stimulation, as long as the relative refractory period has been reached, which in experiment 2 the refractory period was complete.

13. Understand the transportation of potassium and sodium across plasma membranes. (p. 10 bottom right, p. 20 bottom right, p. 21 diagram)

3. What would happen to the amount of H+ secreted into the renal tubule if the activity of the Na+ /K+

Resting potentials require ions as they play a vital role in the process. In the surface membrane of a cell there are protein carriers. These actively pump Na+ ions out of the cytoplasm to the outside of the cell. At the

Because fEPSP increased in all four of the groups of brain slices, this indicates that LTP can be induced over a range of burst frequencies. Grover et al. (2009) found that LTP occurred with burst frequencies ranging from 0.05 to 10 Hz. However, unlike Grover et al. (2009) who found that stimulation in the delta range induced the most prominent LTP, this experiment did not find this same effect. However, in the two groups of brains slices kept at a temperature of 25°C it appears as though a burst

The difference between diffusion and facilitated diffusion is that facilitated diffusion transport through unique protein channels whilst normal diffusion does not.

There are several other electrolytes that are affected by DKA. One electrolyte that is most affected by DKA is potassium. Potassium levels are usually high due to acidosis. Acidosis causes the potassium to shift from the cells into the extracellular fluids (Giddens, 2013). Acidosis causes hydrogen ions to diffuse from the blood into the interstitial fluid because there is an excess of hydrogen ions in the blood. When they diffuse they push the potassium ions out of the cell (Van Meter, 2013).

As a result, the K+/Na+ ATPase pump actively transports potassium into the cell and sodium out of the cell in order to maintain the membrane potential of the cell. This process requires energy because the pump goes against the concentration gradient of the ions. As a result, the potassium concentration is higher inside of the cell than outside and the sodium concentration is higher outside of the cell than inside. This causes a large net diffusion of potassium out of cell and only a small net diffusion of sodium into the cell in order to establish equilibrium potential (Sherwood et al. 2013). More potassium diffuses via the membrane than sodium because the membrane is 25X more permeable to potassium than to sodium (Purves et al. 2001). The resting membrane potential value for a typical cell is -70 millivolts, which is closer to the equilibrium potential of potassium due to its high

The second, or immediately dim, phase of the experiment showed a decrease in vision with an average of 8/16 responses correct. The rod’s delayed response to send an action potential could explain this phenomenon; the eyes underwent a sharp change in illumination and the rods were adapting/converting the remaining light into an action potential as the participants matched the lines on the paper. Therefore, the rods didn’t have enough time to send an action potential before the participants recorded their results. In the third phase, the rods had enough time to adapt to the dim lighting and send an action potential; rhodopsin may have also helped perceive whatever light was left in the room. This resulted in increased recognition, with an average of 13/16 correct responses. The final phase had similar results to the second condition; the rods began adjusting to the twenty seconds of light, but then had to quickly readjust after diming the room again. Therefore, like the second phase, participants’ may have experienced a delayed action potential and their averaged responses greatly decreased to

The Cl- ions will move more easily from the outside into the cell through the permeable membrane, assuming it is the dominant ion in the cell and the concentration of Cl- is greater externally than internally. Since the equilibrium potential of Cl- is not equal to the membrane potential, Cl- will be able to pull the membrane potential towards its equilibrium potential (-70 mV to approximately -81mV) until the current equilibrates close to -81 mV. Chances are there are more ions involved that also go in and out of the membrane which is why the membrane potential will be close to the equilibrium potential and not equal to it.

There are many different types of transport within a cell that can end up being very complex. On the outside of the cell is the plasma membrane that protects it from the outside environment. The plasma membrane is very picky about what it allows through it. It wants to let in oxygen and nutrients, but keep out harmful bacteria. It also wants to keep in the proteins and nutrients that are already in the membrane. Because of this property, the plasma membrane is called a selectively permeable membrane and it has two basic transport processes. In passive transport processes it is the concentration differences that drives the movement. The two passive transports are diffusion and filtration. In active transport processes the cell provides energy in the form of Adenosine Triphosphate (ATP) to power the process. The two active transport processes are primary which is driven directly by ATP or secondary which is driven indirectly by ATP (Marieb P61). For the most part, molecules will diffuse passively through the plasma membrane if they are small enough, but they must be aided by a concentration gradient. A concentration gradient is when there is a difference in concentration of a substance from one area to another (Amerman P75). This property of the plasma membrane is critical to the cell. Without this property the cell would not be able to exchange the oxygen and nutrients it needs to with the extracellular fluid (the fluid located in the spaces between the cells). The

The inhibition of calcium influx via the L-type calcium channels may be mediated by direct inactivation by the G-protein[6] and/or through induced hyperpolarization by activation of ATP-sensitive K+ channel[6]. Activation of the G-proteins results to activation of ATP-sensitive K+ channels. The active transport of K+ ion intracellularly results to hyperpolarization of the membrane. The hyperpolarization inactivates the voltage-sensitive L-type Ca2+ channels which only opens during membrane depolarization[8,6].

It is activated tasks in real-time periodic (release) regularly fixed rates (periods). The majority of sensory processing is cyclical in nature. For example, the radar that tracks flights produce data at a constant rate [4, 1.7, and 3]. Is activated aperiodic tasks in real-time is a regular at some unknown rate and perhaps indefinitely. . The bounded rate is characterized by a minimum inter-arrival period; that is, a minimum interval of time between two successive activations. The time constraint is usually a deadline [4, 1, 7, and 3].