Dr Gawad Physiology Course Online Exam - Excitable - Lecture 1 (Introduction, Resting Membrane Potential)

Isopotential refers to having the same potential. In this context, it means that all points or regions being referred to have the same electrical potential. This means that there is no difference in the electrical potential between these points or regions, indicating a state of equilibrium or balance in terms of electrical charge.

The correct answer is K (potassium). Potassium ions play a crucial role in establishing the negative resting membrane potential (RMP) in cells. Inside the cell, there is a higher concentration of potassium ions compared to the outside. This concentration gradient creates an electrochemical potential difference, leading to the negative RMP. The movement of potassium ions through specific channels helps maintain this negative charge, which is essential for various cellular processes, including nerve conduction and muscle contraction.

The main cause of RMP, or resting membrane potential, is the unequal distribution of ions. This refers to the difference in concentration and distribution of ions, such as sodium (Na+), potassium (K+), and chloride (Cl-), inside and outside the cell. This unequal distribution creates an electrical charge across the cell membrane, resulting in a potential difference. This potential difference is essential for various cellular processes and the transmission of nerve impulses.

The resting membrane potential (RMP) is due to a combination of factors. Passive movements of ions along the membrane contribute to the establishment of the RMP. The selective permeability of the membrane allows certain ions to pass through more easily than others, further influencing the RMP. Active transport of sodium (Na) and potassium (K) ions across the membrane also plays a role in establishing and maintaining the RMP. Additionally, the impermeability of the membrane to proteins contributes to the RMP. Therefore, all of these factors together contribute to the resting membrane potential.

The given statement suggests that all the statements mentioned are true. According to the active (Na-K) pump, there is a transmembrane protein with a large number of binding sites on its interior aspect. The inner ATPase activity is responsible for producing a conformational change, which leads to the pumping of 2 K+ ions inside. The ions migrate uphill against both the concentration and electrical gradient. The binding of (Na-K) to their respective binding sites activates the inner ATPase. Therefore, all the statements mentioned in the question are true.

The correct answer suggests that the transportation of K during RMP is limited by the positivity of the outer membrane. This implies that the movement of K ions is influenced by the positive charge on the outer membrane, which acts as a barrier or restriction for the transport process. This limitation could potentially affect the overall speed or efficiency of K transportation during RMP.

The correct answer is "membrane impermeability to protein". The resting membrane potential (RMP) is the electrical potential difference across the cell membrane when the cell is at rest. It is mainly maintained by the movement of ions across the membrane. In this case, the impermeability of the membrane to protein means that proteins cannot freely move across the membrane, which can disrupt the balance of ions and result in a negative RMP. The other options, K outflux and Na inflow, can contribute to changes in the RMP but are not the main cause of a negative RMP.