Physio Ex 9.0 Exercsie 3

2. Novocain blocks action potential production at the site of injection. How do you think Novocain works on the axon membrane, and how does it block the sensation of pain?

The voltage gated potassium-complex are made of single ion pore with subunits. Located in the postsynaptic fold. The voltage gated potassium complex has a significant amount of roles such

1. Exceeding the threshold depolarization at the trigger zone DECREASES the likelihood of generation of action potential.

This experiment seeks to analyze how the resting membrane potential of Orconectes rusticus muscle cells changes in response to increasing [K+]o solution concentrations. By recording the intracellular voltage of the DEM, DEL1, and DEL2 crayfish muscle cells at six concentrations of [K+]o solution, we determined whether the observed resting membrane potentials (Vrest) were significantly different from the predicted Nernst equilibrium potential values. We hypothesized that the Vrest of the crayfish muscles at each concentration would not significantly differ from the Nernst potential, which solely considers the permeability of potassium ions to the cell membrane. However, our findings suggested differently, and results indicated that the Nernst equation did not accurately predict the obtained values of the resting membrane potential. The differences in muscle cell Vrest reveal instead that the membrane is differentially permeable to other ions.

In this experiment we will be dealing with two chemicals that intend to inhibit a nerve impulse.

To inhibit a neuron, the action potential is taken away from the threshold. This is also known as hyperpolarization. The neuron is less likely to react to stimulus and depolarize (Marieb and Hoehn 414). 5.

2.2). These axonal regions contain high densities of voltage gated sodium (Na+) channels, while potassium channels are restricted in the juxtaparanodal region (Kaplan et al., 1997; Peles and Salzer, 2000; Rasband and Shrager, 2000; Kaplan et al., 2001). The isolation properties and the segmental formation of myelin, leading to the clustering of the ion channels, enable the saltatory conduction of electrical nerve pulses. Pulses are jumping from node to node, instead of progressing slowly along the whole axonal surface as along unmyelinated axons (Huxley and Stampfli, 1949). As a result the conduction velocity along myelinated axons is 10 to 100-fold faster as compared to unmyelinated ones (Waxman, 1980), while the energy consumption is reduced (Waxman, 1977; Hartline and Colman,

Brain is the most complex organ in the human body. Brain and spinal cord made up part of the nervous system called central nervous system (CNS). The cerebral cortex which is the largest part of human brain has more than 100 billion of neurones, and each connected by synapses that communicate to other neurons (Pelvig DP, et al., 2008). There are several types of ion channels present along the neurons, one of these is potassium channels. Potassium channels are the integral membrane proteins that span through phospholipids bilayer of cell surface membrane which rapidly conduct potassium ions down their electrochemical gradient (Mark S.P. Sansom, et al., 2002). There are many forms of potassium channels with different functional properties. Therefore, how the tremendous diversity of potassium channels contribute well to the biological process in brain? It is vital for us to understand the important of potassium channel diversity and know benefits for the existence of the potassium channels diversity in the brain?

Lidocaine blocks the voltage-gated Na+ channels between R1 and R2, which blocks the propagation of the action potential from R1 to R2. The effect of lidocaine differs

The measurement of resistance in the Muller cell with the endfoot still intact was much lower than when the resistance in the cell after the endfoot had been removed. Additionally, when researchers cut a part of the cell above the endfoot, leaving the endfoot untouched, the cell resistance did increase slightly, but not by very much. These observations helped to prove that the endfoot, not other parts of the cell, contributes to most of the cell’s resistance, and therefore conductance. When measuring impedance in the cell, the endfoot impedance increased when penetrated, while other parts of the cell showed no real changes. When KCl solution was added into the cell and the amount of potassium ion efflux was recorded along the cell, it was found that about the same amount of potassium efflux occurred all along the cell membrane, with the endfoot having a much greater efflux of potassium ions than anywhere else on the Muller cell. All in all, it was determined that the Muller endfoot is not only where the highest conductance and lowest membrane resistance in the cell is locate, but also where the most potassium channels are located. Therefore, the endfoot greatly controls how much potassium ion movement. This goes for Muller

Hence, this would allow for an influx of sodium into the cell down its electrochemical gradient. It would also allow for the flow of potassium outward, as it has a 140mM concentration inside the cell and wants to shift down its concentration gradient to 5.4mM. Therefore, this great driving force for the influx of sodium and efflux of potassium helps to explain the findings at this point. As Table 1 shows, the findings within this figure are statistically supported. The fact that there is not significant difference between the findings of this experiment and the calculated Nernst at the 10, 20 and 40mM of potassium is an indicator that sodium is the largest determinant of the resting membrane potential. However, some findings defy the expectations, as the last two concentrations elicit a resting membrane potential significantly more negative than expected. This can be explained by the fact that at this point, each muscle at their respective muscle groups has been protruded many

The process of firing an action potential happens in many steps and there are key players to the process. On the cell membrane of the axon of a pre-synaptic neuron, specifically in the Nodes of Ranvier, there are non-gated ion channels, voltage-gated ion channels, and ion pumps. All of these are special proteins that are specific to ions and carry out specific functions. At resting membrane potential, when an action potential is not being fired and the cell is at rest, there is Na2+ (sodium ion) in high concentration outside the cell and K+ (potassium ion) in high concentration inside the cell. Both are separated by a phospholipid bilayer that makes up the cell membrane and the cell is slightly more negative inside the cell than outside the cell. At this time, sodium and potassium ions are free to move

Anesthetics inhibits nerve conduction by blocking sodium channels (prevent increase of membrane permeability to sodium ions) so the raising phase of action potential is inhibited, hence no action potential is generated and no nerve impulses are conducted to the central nervous system. Nerve cells are selectively permeable to ions. During rest, potassium channels are open in nerve cells and sodium channels are closed. If a nerve cell is excited, the membrane opens due to its permeability to sodium ions. A positive charge is gained, and the propagated action potential is passed along. The opening of more potassium leak channels means that more potassium ions will flow out of the cell, consequently resulting in the hyperpolarization of the cell.

Serum potassium is regulated by the sodium potassium pumps of mitochondria within the intercellular fluid of our cells. Cells travel along in the extracellular fluid which contains sodium and water. Osmolality between intracellular fluid of the cell and extracellular fluid is dependent upon the shift of water and chemicals in and out of the cell membrane. The distribution of potassium between the intercellular and extracellular fluids can fluctuate and is influenced by several factors. These factors either facilitate or hinder the shift of potassium into and out of the cells. Maintaining the proper distribution of potassium across the cell membrane is critical for normal cell function.

Whenever the balance is altered, the process of transmitting electrical signals, which is called action potential initiates by carrying information across a neuron’s axon; which is called resting membrane potential. This process occurs as uneven ions distribution flow across cell membrane, creating electrical potential. As a result, the duration of active potential can be as fast as 1 ms. Similarly, the average resting membrane is between -40 mV and -80 mV. Since the membrane from inside is more negatively charged than the outside, it reflected on the negative average voltage readings of the resting membrane.