NURS 5315 Advanced Patho Exam 1 Questions & Answers

Steps of the Action Potential - ANSWERSDepolarization Repolarization Hyperpolarization Depolarization - ANSWERSmovement of the intracellular charge towards zero (more positive charge) Voltage gated Na channels open and allow Na to enter the cell -> voltage inside the cell moves towards zero Repolarization - ANSWERSOnce the intracellular charge reaches zero, the negative polarity of the inside of the cell is restored back to its baseline of -70 to -85 mV -Na channels close, K channels open Hyperpolarization - ANSWERSwhen the cell's resting membrane potential is greater than -85mV. Is less excitable, because there is a greater distance between the resting membrane potential and the threshold potential. In order for the action potential to be sucessful - ANSWERSt has to depolarize by 15-20 mV (threshold potential) to reach -55 to -65 mV. An alteration in action potential may result from - ANSWERSneurologic diseases, muscle disease or electrolyte imbalances. What is the main protein responsible for maintaining the correct balance of extracellular Na and intracellular K, which is needed for cellular excitation and membrane conductivity. - ANSWERSNa+-K+ ATPase Resting membrane potential - ANSWERSwhen the cell is in a nonexcited state and is at -70 to -85 mV. Refractory Period - ANSWERSis a period of time during most of the action potential which the cell membrane resists stimulation and it cannot depolarize Absolute refractory period - ANSWERSoccurs when the membrane will not respond to ANY stimulus no matter how strong. Relative Refractory Period - ANSWERSoccurs when the membrane is repolarizing and will only respond to a very strong stimulus. Hyperpolarized - ANSWERSwhen the cell's resting membrane potential is greater than -85mV. Is less excitable, because there is a greater distance between the resting membrane potential and the threshold potential. Hypopolarized - ANSWERSwhen the cell's resting membrane potential is closer to zero, for instance it is -65mV. Is more excitable because the resting membrane potential is closer to the threshold potential, there is less distance between them. Action potential altered by hypokalemia - ANSWERS(serum outside of cell is low) -Hyperpolarized (cell becomes more negative, ex: -100) -Affects the resting membrane potential of cells -The cell is less likely to depolarize and transmit impulses Can cause a decrease in neuromuscular excitability and leads to weakness, smooth muscle atony, paresthesias, and cardiac dysrhythmias Action potential altered by hyperkalemia - ANSWERSHypopolarized -Also has an effect on the resting membrane potential -If the ECF potassium increases without any change in the ICF potassium levels, the resting membrane potential of the cell becomes more positive. -The cells are more excitable and conduct impulses more easily and more quickly because the resting membrane potential is closer to the threshold potential. Therefore, the person will have peak T waves on EKG. -As potassium rises, the resting membrane potential will continue to become more positive and it will eventually become equal to the threshold potential. As this happens the EKG will show a widening QRS complex. If the resting membrane potential equals the threshold potential, an action potential will not be generated and cardiac standstill will occur. Paralysis and paresthesias may also occur. Action potential altered by hypocalcemia - ANSWERS-Causes an increase in the cell permeability to Na causing a progressive depolarization -Causes the RMP and the TP to be closer to one another & making it easier to initiate an action potential - the cells are more excitable. -Results in tetany, hyperreflexia, circumoral paresthesias, seizures, dysrhythmias Action potential altered by hypercalcemia - ANSWERS-Causes a decrease in cell permeability to Na -Causes the RMP and the TP to increase in distance - the cells are less excitable and requires more of a stimulus to initiate an action potential. -Leads to weakness, hyporeflexia, fatigue, lethargy, confusion, encephalopathy, a shortened QT segment and depressed widened T waves on EKG. Atrophy - ANSWERSdecrease or shrinkage in the size of the cell -Imbalance between protein synthesis and degradation, , reduction of the intracellular contents, also includes a self-eating process called autophagy. -Example: aging brain cells, malnutrition, uterus decreasing in size after childbirth Hypertrophy - ANSWERSincrease in the size of cells, which ultimately increases the size of the organ -Etiology: triggers include repetitive stretching, chronic pressure, volume overload -Pathophysiology: hormonal stimulation or increased functional demand, which increases the cellular protein in the plasma membrane, endoplasmic reticulum, myofilaments, and mitochondria Hyperplasia - ANSWERS-increase in number of cells, not the size of the cell, which results from an increased rate of cell division, it can only happen in cells that are capable of mitosis * -Etiology: results from the production of growth factors which stimulate cells to produce new cellular contents and divide Dysplasia - ANSWERS-abnormal changes in the size, shape, and organization of mature cells due to persistent, severe cell injury or irritation -Disordered cell growth and is mainly found in epithelial tissue of the uterine cervix, the endometrium, GI and respiratory tract mucosa, -Ex: pap smears often show dysplastic cells of the cervix, uterine cells Referred to as atypical hyperplasia - ANSWERSdysplasia - abnormal changes in size, shape, and organization of mature cells due to persistent, severe cell injury or irritation Metaplasia - ANSWERS-reversible change in which one adult cell is replaced by another adult cell -Etiology: found in tissue damage, repair, and regeneration -Results from the exposure of the cells to chronic stressors, injury, or irritation. If the influences that cause the cellular changes remain present, they can induce a malignant change in the cells -Ex: most common is the change from columnar cells to squamous cells - this occurs in chronic smokers or gastroesophageal reflux (GERD) Physiologic Example of Hyperplasia - ANSWERS-Occurs when there is an increase in tissue mass after damage or partial resection, allowing the organ to regenerate Ex - removal of part of the liver and the cells regenerating, uterine and mammary gland enlargement occur during pregnancy to meet the demands of the increased work load, callus on foot Ex: (Hormonal) Breast and uterine enlargement during pregnancy. Pathological Example of Hyperplasia - ANSWERS-Is an abnormal proliferation of normal cells usually caused by increased hormonal stimulation Ex - endometrial hyperplasia (imbalnce in estrogen & progesterone with increase in estrogen - risk for cancer), Benign prostatic hyperplasia (BPH), thyroid enlargement - thyroid goiters Pathological Example of Hypertrophy - ANSWERSleft ventricular hypertrophy cardiomegaly Physiological Example of Hypertrophy - ANSWERSSkeletal muscle, when a kidney is removed and the other kidney steps in to function as both and increases in size Physiological Example of Atrophy - ANSWERSShrinking of the thymus gland during childhood, uterus decreasing in size after childbirth Disuse - skeletal muscle atrophy that occurs from a person being immobilized or bed ridden for a period of time (arm in a cast, Pathological Example of Atrophy - ANSWERSDecrease in workload, pressure, use, blood supply, nutrition, hormonal stimulation, or nervous stimulation Cellular Injury - ANSWERS-Occurs when the cell is no longer able to maintain homeostasis with the result being disease. May or may not be reversible. This is dependent on the type of cell, level of differentiation, ability to adapt and the type, severity and duration of the injury. Causes of cellular injury - ANSWERShypoxia, free radicals, chemicals, radiation, direct mechanical trauma, genetics, nutrition, infections, immunologic reactions and inflammation. Mechanisms of Cellular Injury - ANSWERS-ATP Depletion -Oxygen and Oxygen derived free radicals -Intracellular Calcium and loss of calcium steady state Cellular Injury (partially ischemia) triggers an increase in - ANSWERSIintracellular calcium -The more damage which is done, the higher the calcium concentration becomes. The elevated calcium level causes damage to the cell membrane. It also causes damage to the intracellular contents by activating enzymes which cause the damage directly. ATP Depletion - ANSWERSresults from the loss of mitochondrial production of ATP. This contributes to cellular swelling, decreased protein synthesis, and impairs cellular membrane transport systems. All of these changes impair cellular membrane integrity. Oxygen and Oxygen derived free radicals - ANSWERSdecrease oxygen delivery to cells results in the production of activated oxygen species (free radicals, H2O2, NO) which destroy the cell membranes and structures. Most common cause of cellular injury - ANSWERSHypoxic Injury Clinical Manifestations of Hypoxic Injury - ANSWERSReduced ischemia, loss of hemoglobin, diseases, etc. Heart attack, etc