Skip to main content

Insulin - action on peripheral cells

Insulin binds to receptor on target sites. These sites have an intrinsic tyrosine kinase activity that lead to receptor autophosphorylation and recruitment of intracellular signalling molecules. The latter result in widespread metabolic and mitogenic effects of insulin as shown in the diagram above.

Another effect is the activation of phosphatidylinositol 3 kinase that fastens the translocation of GLUT-4 containing vesicles to the cell surface. This is important to allow uptake of glucose by skeletal and fat cells.
When insulin action ceases, the transporter-containing patches of membrane are endocytosed and the vesicles are ready for the next exposure to insulin.

On the other hand, in the liver, this is not the mechanism of glucose uptake. Instead, it induces glucokinase, and this increases the phosphorylation of glucose, so that the intracellular free glucose concentration stays low, facilitating the entry of glucose into the cell by diffusion.

Insulin-sensitive tissues like muscles also contain a population of GLUT 4 vesicles that move into the cell membrane in response to exercise, a process that occurs independent of the action of insulin. This is why exercise lowers blood sugar.


Popular posts from this blog

Hypokalemia - Potassium replacement calculation

 DEFINITION  Hypokalemia is defined as a serum potassium level of less than 3.5 mmol/L. Normal level= 3.5-5.5 mmol/L. It is encountered in >20% of patients. Patients are usually asymptomatic but severe arrhythmias and rhabdomyolysis can occur. Non-specific complaints include easy fatiguability and skeletal muscle weakness. The preferred method of replacement is via the oral route but at times this is not possible. The article below will give you an idea about how to calculate the amount of KCl to be given I.V. 1) Potassium deficit in mmol is calculated as given below: K deficit  (mmol) = (K normal lower limit  - K measured ) x kg body weight x 0.4 2) Daily potassium requirement is around 1 mmol/Kg body weight. 3) 13.4 mmol of potassium found in 1 g KCl . ( molecular weight KCl = 39.1 + 35.5 = 74.6) Suppose we get an asymptomatic patient of  70 Kg with a serum potassium level of 3.0 mmol/L and he is on nil by mouth but having an adequate diuresis, w

The plantar reflex - Babinski's sign

The plantar response is an important test to identify an upper motor neuron lesion.  PROCEDURE  To elicit it, the muscles of the lower limbs must be relaxed. The outer edge of the sole of the foot is stimulated by firmly scratching a blunt object like a key or a stick along it from the heel towards the little toe. This is what  Joseph Babinski did in the year 1896. He described the 'great toe sign' that year and then in 1903 the 'toe abduction or fan sign'. Nowadays, a final medial movement across the sole of the metatarsus is also done. i.e. we start at the heel to the little toe and finally arcing to the big toe. The final arcing movement is absent in the original Babinski plantar response test. Babinski sign refers to a combination of 'the great toe sign' and the 'fan sign'.  SIGNIFICANCE  The normal response is plantar flexion of the toes (down going) and they are drawn together. More precisely, there is flexion of the big toe and addu

Differences between hyperemia and congestion

Hyperemia and congestion both indicate a local increased volume of blood in a particular tissue. Hyperemia is an active process that result from augmented blood flow due to arteriolar dilation (e.g. at sites of inflammation or in skeletal muscle during exercise). The affected tissue is redder than normal because of engorgement with oxygenated blood. Congestion, on the other hand, is a passive process resulting from impaired venous return out of a tissue. It may occur due to systemic causes like cardiac failure or a local cause like isolated venous obstruction. The tissue is cyanosed because the worsening congestion leads to accumulation of deoxygenated hemoglobin in the affected tissues. 

Apgar scoring - table, mnemonic

 INTRODUCTION  The  Apgar score  was devised in 1952 by Dr Virginia Apgar (anesthesiologist) as a simple and repeatable method to quickly and summarily assess the health of newborn children immediately after birth.  This helps to identify those requiring resuscitation and can also be used to predict survival in the neonatal period.   MNEMONIC  A mnemonic for learning purposes includes: A - Appearance (skin colour) P - Pulse (heart rate) G - Grimace (reflex irritability) A - Activity (muscle tone) R - Respiration  Another mnemonic is also useful:  How -   Heart rate Ready - Respiration Is -        Irritability This -    Tone Child -   Colour Apgar scoring is divided into 1 and 5-min scores.  1-MIN SCORE    Sixty seconds after complete birth, the five parameters specified in the table above must be evaluated and scored. A total score of 10 indicates that the baby is in the best possible condition. A score between 0-3 me

Chickenpox - dew on rose petal appearance

Definition: Chickenpox is a benign viral disease of childhood, characterized by an exanthematous vesicular rash. It is an extremely common and contagious condition. It is caused by the varicella-zoster virus which is a herpes virus and contains a double stranded DNA in its center. Epidemiology: Age group affected- 5 to 9 years. The infection can be there at other ages too but it is less frequent. It is highly contagious and it affects all races and both sexes equally. The attack rate is around 90% among seronegative persons. Pathogenesis: Incubation period- 10 to 21 days but is usually 14 to 17 days. Patients are infectious around 48 hours from onset of vesicular rash, during the period of vesicular formation (around 4-5 days) and until all vesicles are crusted. Transmission occurs by respiratory route. The virus is believed to be localized in the nasopharynx, in the reticulo-endothelial system. It then enters the blood. This stage of viremia is characterized by diffused ski