The Pancreas and Release of Insulin Flashcards
What are beta cells?
Cells found in the islets of Langerhans that secrete the hormone insulin
What is glucagon?
A hormone that causes an increase in blood glucose concentration
What is insulin?
The hormone, released from the pancreas, that causes blood glucose levels to go down.
Where is the pancreas situated in the body?
Just below the stomach
What are the two main secretions of the pancreas?
Pancreatic juices containing enzymes which are secreted into the small intestine.
Hormones which are secreted from the islets of Langerhans into the blood.
How do exocrine glands secrete substances?
Into a duct.
What is the exocrine function of the pancreas?
The synthesis and release of digestive enzymes.
Describe the placements of the exocrine cells.
The exocrine cells are in small groups surrounding each tiny tubules. Each group of cells is call acinus (plural acini)
How are the acini grouped?
They are grouped together into small lobules separated by connective tissue.
Where do the cells of the acini secrete the enzymes they synthesise?
Into the tubule at the centre of the group.
What do the tubules of the acini join up to form?
Intralobular ducts that eventually combine to form the pancreatic duct.
What does the pancreatic duct do?
Carries the fluid containing the enzymes into the first part of the small intestine (duodenum)
What enzymes does the fluid in the pancreatic duct contain?
Pancreatic amylase
Trypsinogen
Lipase
What does pancreatic amylase do?
It is a carbohydrase that converts amylose to maltose.
What is Trypsinogen?
It is an inactive protease which will be converted to the active form trypsin when it enters the duodenum.
What does lipase do?
Digests lipid molecules.
Why is hydrogen carbonate found in the pancreatic fluid?
It helps to neutralise the contents of the digestive system that have just left the acidic environment of the stomach.
What do alpha cells secrete?
Glucagon.
What do the islets of Langerhans contain?
Alpha and beta cells.
What does insulin do?
It brings about affects that lower the blood glucose concentration.
What channels do the beta cells contain and why?
They contain both calcium and potassium ion channels The channels are used to control the potential difference across the membrane of the beta cells.
At rest what is the potential difference of a beta cell membrane?
-70mV
Why are potassium ion channels closed when blood glucose levels increase?
When glucose levels increase glucose molecules enter the beta cells which cause the immediate production of ATP through a metabolic process. The ATP then causes the potassium ion channels to close.
Which enzyme converts glucose into an immediate supply of ATP?
Glucokinase.
What occurs as a result of the potassium ion channels closing?
The potassium can no longer diffuse out and this alters the potential difference across the cell membrane - it becomes less negative inside.
What happens as a result in the change of the potential difference?
It causes the calcium ion channels to open and calcium ions enter the cell.
What happens as a result of calcium ions entering the cell?
They cause the secretion of insulin by making the vesicles containing insulin to move to the cell surface membrane and fuse with it, releasing insulin by exocytosis.
