tailieunhanh - Applied Surgical Physiology Vivas - part 2

Xác định thâm hụt cơ sở. Thâm hụt cơ sở là lượng axit hoặc kiềm cần thiết để khôi phục lại 1 lít máu đến một độ pH bình thường tại một pCO2 là 5,3 kPa và ở 37 C. Đây là một chỉ số của các thành phần trao đổi chất để một rối loạn acid-base. Phạm vi bình thường là 2-2 mmol / l. | APPLIED SURGICAL PHYSIOLOGY VIVAS 8. Define the base deficit. The base deficit is the amount of acid or alkali required to restore 11 of blood to a normal pH at a pCO2 of kPa and at 37OC. It is an indicator of the metabolic component to an acid-base disturbance. The normal range is 2 to 2mmol l. A ACID-BASE 7 APPLIED SURGICAL PHYSIOLOGY VIVAS A ACTION POTENTIALS 1. What is meant by the equilibrium potential for an ion The equilibrium potential of an ion is the potential difference at which that ion ceases to flow down its electrochemical gradient across the cell membrane. It is calculated by the Nernst equation. ACTION POTENTIALS 2. What is meant by the resting membrane potential for a cell This is the potential difference across the cell membrane. This occurs due to the ionic fluxes of Na K and Cl across the membrane the sizes of which are determined by their electrochemical gradients. It is calculated by the Goldman equation which takes into account the contribution of the equilibrium potentials of each species of ion that crosses the membrane. 3. What is the typical value of the resting membrane potential for a neurone A typical value is 70 mV. The value is negative because the interior of the cell is negatively charged with respect to the exterior. 4. What is the importance of the Na K pump for the equilibrium potential This pump which is ATPase-driven transports 3 Na out of the cell for 2 K pumped in. It helps to maintain the internal and external ionic environment that progressively alters as ions naturally flow down their electrochemical gradients. In doing so it maintains and sustains the potential difference across the cell Resting membrane potential . 8 APPLIED SURGICAL PHYSIOLOGY VIVAS 5. What is an action potential Draw and label the axes of a typical action potential for a neurone. This is defined as the rapid change in the membrane potential depolarisation that occurs following stimulation of an excitable cell. It is followed by a rapid return to