Endocrine Pancreas Flashcards
What are the Islets of Langerhans innervated by?
Sympathetic (splanchnic nerve)
Parasympathetic (vagus nerve)
What do sympathetic fiber’s of the islets of Langerhans cause?
Beta adrenergic activation increases glucagon secretion
What do parasympathetic fiber’s of the islets of Langerhans cause?
Stimulate insulin and glucagon secretion
cephalic phase of insulin secretion
What direction is blood flow in islet vasculature and what does this allow?
From core to mantle
Beta cells get first pass on circulating glucose levels - modulate downstream endocrine cells
What do factors influence insulin secretion?
GIT hormones
Elevated blood glucose concentration
How do beta cells sense glucose?
Glucose enter cell quite freely via GLUT2 - ATP formed from glycolysis - ATP inhibits K+ channel - membrane depolarised which opens V-gated Ca2+ channels - calcium enters cell - insulin released
What are insulin’s target organs?
Liver
Skeletal muscle
Adipose tissue
What two organs is the entry of glucose into cells insulin dependent?
Muscle and adipocytes
What does insulin promote?
Energy utilization and storage
What is the main insulin responsive glucose transporter in skeletal muscle?
GLUT4
What is GLUT4?
Isoform regulated by insulin
High capacity and insulin dependent transporter of glucose
What is the precursor for glucagon?
Proglucagon - made in alpha cells
What is glucagon secretion’s major stimulus?
Drop in blood glucose levels
What is glucagon’s main target?
Liver
What does glucagon increase?
Gluconeogenesis
Glycogenolysis
Ketogenesis
Hepatic protein breakdown
