Cellular and Molecular Neuroscience

Question: Discuss about the Cellular and Molecular Neuroscience. Answer: Introduction The fact sheet is about the role of action potential and its use in the field of physiology. The fact sheet gives insight into the process of action potential and its function in cell to cell communication. The characteristics related to its function well-defines its importance in contraction of muscle cells and movement. The fact sheet also gives detail on the recovery period after an action potential and the consequences of manipulation in action potential. Action potential is a an event occurring in the membrane of the nerve cell or muscle cell which leads to the reversal of electric polarization of the membrane of the nerve cell. In the neuron, an action potential travels down the axon to change the polarity across the membrane. It results in the opening of the Na+ and K + gated ion channel. This gate closes once the threshold potential is reached. The initiation of the action potential is associated with depolarization (due to the transport of Na+ ions into the axon). Repolarization occurs when the K+ channel opens and moves out of the axon. Due to the change in polarity, the impulse travels down from the axon to other neurons (1). The main function of action potential is to engage in cell to cell communication by means of transmission of signals from axon to axon terminals and then into other neurons. It is also involved in activating intracellular processes in muscle cells. For example, action potential leads to contraction of muscle cells. During the action potential, positively charged ions move inside the neural membrane and the negatively charged ions moves out. The increase in the positive charge results in the generation of electric impulse, which passes down the nerve. In the muscle cells, it helps to produce the necessary contraction required for movement (2). As reflected from the explanation of the function role of action potential, potassium and sodium ion channel are mainly involved during this process. Both the channel plays role in all the stages of action potential such as the depolarization, repolarization and the refractory stage (3). The detail regarding the process in each stage and the involvement of both the channels is explained below. During the action potential, neourotransmitters or sensory receptors stimulate the cell in the membrane. As the sodium on diffuse into this part of the cell, the membrane slowly shift towards negative polarization stage. Finally, the potential reaches a threshold potential resulting in the opening of the calcium ions. This is followed by depolarization so that the impulse moves and takes place in other parts of the membrane. Characteristics related to its function The main characteristics of action potential are related to the depolarization of the cell due to transmit signals. Its function also reflect communication characteristics as generation of electric impulse during action potential act as a form of communication between the sensory receptors, muscles, brain and spinal cord. There is no strong or weak signal in action potential. It reaches either threshold value or the resting potential (4). There are three stages of action potential. They are: Depolarization stage- First the neuron is in resting potential due to high concentration of positive ions outside the cell and negative ions inside the cell. Depolarization occurs when positive sodium ions rushes inside the cell and reverses the polarity of the membrane. Repolarization stage- Once the electric gradient has reached the threshold value, the Na+ and K+ gate opens and positive charged potassium ions comes out from the neuron. In this way, the negative membrane potential is restored. Refractory phase- This occurs during the action potential when the sodium gate can open only when the membrane is repolarized to its resting potential. Hence, another action potential cannot occur in this stage (5). Recover after an action potential The period after the action potential has taken place in a neuron is called the refractory period in which another action potential cannot take place. Refractory period can be called a recovery time in which similar action cannot be repeated by cell. It is also defined as the time required for a second stimulus to occur once an excitable membrane returns to its resting stage. In this period, the potassium channel opens again and the sodium channel closes (6). Hence, the neuron returns back to its resting potential. After this recovery, another action potential is possible in the cell. The action potential is often manipulated to obtain a predetermined motor action from specific muscle. In some case the extra-cellular concentration of sodium and potassium ion is manipulated due to get a desired result. Manipulation is also done for cardiac potential to stimulate cardiac Calcium channel to open early. This results in increased contraction force. The advancement in molecular technology also lead to cloning of genes for different channels. By this experimental manipulation of the channels, genes were expressed. Researchers could easily identify the specific function properties of different parts of the channel such as the voltage sensitivity and kinetics of cellular interaction (7). Reference Sherwood L. Human physiology: from cells to systems. Cengage learning; 2015. Levitan IB, Kaczmarek LK. The neuron: cell and molecular biology. Oxford University Press, USA; 2015. Wolff M, Schnbel-Ehehalt R, Mhling J, Weigand MA, Olschewski A. 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