Regulation of Blood Glucose

 REGULATION OF BLOOD GLUCOSE

Adequate concentrations of glucose in the blood are necessary for brain cells as they cannot metabolize substances other than glucose and ketone bodies as energy sources nor can they store or synthesize glucose. After a meal, any released glucose is absorbed by the gastrointestinal tract enters the bloodstream and is delivered to the peripheral tissues where it may be metabolized to allow ATP production. Surplus glucose is converted to glycogen and stored in the liver and skeletal muscles or converted to triacylglycerols and stored in adipose tissue. During fasting, the liver produces glucose by glycogenolysis or gluconeogenesis and this is used to maintain blood glucose concentration (Figure 7.22).




The concentration of glucose in plasma is regulated by the hormones insulin and glucagon. Insulin is synthesized as preproinsulin in the β cells of the islets of Langerhans in the pancreas but during its secretion is enzymatically converted to active insulin (Figures 7.3 (B) and 7.23). Insulin has a number of functions. It inhibits glycogenolysis, gluconeogenesis, lipolysis, ketogenesis



and proteolysis and stimulates glucose uptake by muscle and adipose tissues, glycolysis, glycogenesis, protein synthesis and uptake of K+ and Pi. Glucagon is released by the α cells of the pancreas. Its effects are antagonistic to those of insulin. An increase in blood glucose stimulates the pancreas to produce insulin which, in turn, promotes the uptake and utilization of glucose by cells lowering its concentration. A reduction in blood glucose stimulates release of glucagon that promotes glycogenolysis in the liver thereby increasing blood glucose levels (Figure 7.24). Disorders of insulin release or activity can cause an increase in blood glucose, hyperglycemia, or its reduction, hypoglycemia.

Comments

Post a Comment

Popular posts from this blog

Preventing Infectious Diseases

Image
  PREVENTING INFECTIOUS DISEASES Infections are the commonest cause of human morbidity and mortality. In developing countries at the beginning of the last century diseases, such as TB, pneumonia and bacterial infections secondary to influenza, were major causes of death. However, in the developed world their impact has been lessened by public health measures such as improved housing, better sanitation and advanced social and economic conditions. Unfortunately, in developing countries infectious diseases, such as malaria, TB, respiratory and GIT infections, are still major causes of death, particularly in children. The prevention of infectious disease is achieved by the use of vaccines . Vaccination works by stimulating the immune system to produce antibodies against the pathogenic organism by introducing bacteria or viruses that have been rendered ‘harmless’ in some way. The simplest, though not necessarily the most effective, method of preparing vaccines is by killing whole microo...
Read more

Hypoglycemia - Regulation of Blood Glucose

Image
  HYPOGLYCEMIA Hypoglycemia is defined as a blood glucose concentration less than 2.2 mmol dm –3  in a random specimen collected into a tube containing an inhibitor of glycolysis. Hypoglycemia occurs because of an imbalance between glucose intake, endogenous glucose production and glucose  utilization.   Its clinical features are mainly due to abnormal function of the CNS (neuroglycopenia) and can be acute or chronic. Acute features include tiredness, confusion, hunger, dizziness, blurred vision, convulsions, coma, anxiety, profuse sweating and tachycardia. The typical signs and symptoms are more likely to occur if blood glucose falls rapidly: in children and young adults the symptoms often present when the glucose concentration is less than 2.2 whereas neonates develop symptoms only when it is less than 1.5 mmol dm –3 . Acute hypoglycemia is usually associated with diabetics who have taken too much insulin. Its chronic features include personality changes, memory lo...
Read more

Gastrointestinal Tract and its Accessory Organs

Image
  THE GASTROINTESTINAL TRACT AND ITS ACCESSORY ORGANS The GIT may be described as a tubular system with distinctive regions that begin with the mouth leading to the pharynx, esophagus, stomach, the small and large intestines and terminating at the anus ( Figure 11.1  ( A )). It is associated with several accessory digestive organs, such as the pancreas, liver and gall bladder ( Figure 11.1  ( B )). The walls of the GIT have a fairly common substructure ( Figure 11.2  ( A ) and ( B )) and its interior is called the lumen. The GIT and accessory organs are bound to each other and to the inner wall of the abdomen by the  peritoneum . This is a strong, colorless membrane with a smooth surface that consists of two parts; the parietal peritoneum, which lines the abdominal cavity, and the visceral peritoneum that covers most of the organs in the abdomen ( Figure 11.3 ). The thin space between the two parts, called the peritoneal cavity, is filled with serous fluid. In m...
Read more