The document summarizes key details about glucagon and its role in regulating blood sugar levels. It notes that glucagon is secreted by alpha cells in the pancreas' islets of Langerhans and has the opposite effect of insulin by increasing blood glucose levels. Glucagon stimulates glycogenolysis and gluconeogenesis in the liver to release more glucose into the bloodstream. It also decreases glucose uptake in muscles and adipose tissues while inhibiting glycogen synthesis and insulin secretion.

1. The endocrine part is
composed of the islets of
Langerhans
• pancreas has 1-2 millions of
these islet,
• what is about 1-2% of the
volume of the gland
• In the middle of each islets
it has a small capillary, into
which its cells secrete their
hormones.

2. A cells of the pancreas and glucagon

3. • A cells account for about 25% of the cells in the islets of
Langerhans.
• Glucagon
• effects opposite to insulin effects
• is the increase of glucose concentration in
circulation
• half-life of glucagon is 6 minutes

4. Preproglucagon -> proglucagon -> glucagon

5. glucagon effects
• activation of glycogenolysis
• increased gluconeogenesis in liver
• what increases the glucose release
into the blood

6. glucagon
• Decreases
• the glucose uptake in muscles and
adipose tissues
• Inhibits
• glycogen synthesis
• insulin secretion
• The result is an increased glucose level
for brain cells

7. Regulation of glucagon
• Glycaemia
• Most effective factor
• BS decreases -> Glucagon increases

8. Glucagon secretion
• Is stimulated by
• cortisol
• the physical activity
• increased levels of glycogenic amino
acids
• alanine, arginine, cysteine
• Stimulates
• glucose formation from glycogenic
amino acids

9. Glucagon secretion
• Is inhibited by
• fatty acids,
• insulin,
• Somatostatin
• stimulation of 𝛼-adrenergic receptors.