Hepatic encephalopathy is caused by an increase of –
Correct Answer: Ammonia
Description: Ans. is 'c' i.e., Ammonia* Hepatic encephalopathy is characterized by altered level of consciousness, caused by liver disorder.* Liver disorder is characterized by elevation of ammonia. As liver is considered with detoxification of ammonia to form urea, in liver failure ammonia level is elevated.* Hepatic encephalopathy basically presents with manifestations of CNS depression* Pathogenesis:# Ammonia crosses Blood Brain Barrier and is taken up astrocytes. Astrocytes contribute to 30% of cells in the Central Nervous System. Within astrocytes, as pKa of ammonia is very high, it sequestrates hydrogen ions to form ammonium ions. Ammonium ions are positively charged. Additionally, ammonia reacts with glutamate to form glutamine. Glutamine is also positively charged. Both ammonium ions and glutamine, being positively charged, they attract water (Ammonium and glutamine are osmotically active). This causes astrocytes swelling. Neuronal swelling in respiratory centre causes hyperventilation and the person presents with repiratory alkalosis.# As glutamate levels are low, the neuronal activity is reduced. This explains depression, coma and EEG abnormalities (characteristic slowing of waves with high amplitude)* Hence, all features of hepatic encephalopathy are explained by hyperammonemia.
Category:
Biochemistry
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