The Pancreas and Release of Insulin

Question 1

What are beta cells?

Answer 1

Cells found in the islets of Langerhans that secrete the hormone insulin

Question 2

What is glucagon?

Answer 2

A hormone that causes an increase in blood glucose concentration

Question 3

What is insulin?

Answer 3

The hormone, released from the pancreas, that causes blood glucose levels to go down.

Question 4

Where is the pancreas situated in the body?

Answer 4

Just below the stomach

Question 5

What are the two main secretions of the pancreas?

Answer 5

Pancreatic juices containing enzymes which are secreted into the small intestine.
Hormones which are secreted from the islets of Langerhans into the blood.

Question 6

How do exocrine glands secrete substances?

Answer 6

Into a duct.

Question 7

What is the exocrine function of the pancreas?

Answer 7

The synthesis and release of digestive enzymes.

Question 8

Describe the placements of the exocrine cells.

Answer 8

The exocrine cells are in small groups surrounding each tiny tubules. Each group of cells is call acinus (plural acini)

Question 9

How are the acini grouped?

Answer 9

They are grouped together into small lobules separated by connective tissue.

Question 10

Where do the cells of the acini secrete the enzymes they synthesise?

Answer 10

Into the tubule at the centre of the group.

Question 11

What do the tubules of the acini join up to form?

Answer 11

Intralobular ducts that eventually combine to form the pancreatic duct.

Question 12

What does the pancreatic duct do?

Answer 12

Carries the fluid containing the enzymes into the first part of the small intestine (duodenum)

Question 13

What enzymes does the fluid in the pancreatic duct contain?

Answer 13

Pancreatic amylase
Trypsinogen
Lipase

Question 14

What does pancreatic amylase do?

Answer 14

It is a carbohydrase that converts amylose to maltose.

Question 15

What is Trypsinogen?

Answer 15

It is an inactive protease which will be converted to the active form trypsin when it enters the duodenum.

Question 16

What does lipase do?

Answer 16

Digests lipid molecules.

Question 17

Why is hydrogen carbonate found in the pancreatic fluid?

Answer 17

It helps to neutralise the contents of the digestive system that have just left the acidic environment of the stomach.

Question 18

What do alpha cells secrete?

Answer 18

Glucagon.

Question 19

What do the islets of Langerhans contain?

Answer 19

Alpha and beta cells.

Question 20

What does insulin do?

Answer 20

It brings about affects that lower the blood glucose concentration.

Question 21

What channels do the beta cells contain and why?

Answer 21

They contain both calcium and potassium ion channels The channels are used to control the potential difference across the membrane of the beta cells.

Question 22

At rest what is the potential difference of a beta cell membrane?

Answer 22

-70mV

Question 23

Why are potassium ion channels closed when blood glucose levels increase?

Answer 23

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.

Question 24

Which enzyme converts glucose into an immediate supply of ATP?

Answer 24

Glucokinase.

Question 25

What occurs as a result of the potassium ion channels closing?

Answer 25

The potassium can no longer diffuse out and this alters the potential difference across the cell membrane - it becomes less negative inside.

Question 26

What happens as a result in the change of the potential difference?

Answer 26

It causes the calcium ion channels to open and calcium ions enter the cell.

Question 27

What happens as a result of calcium ions entering the cell?

Answer 27

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.