The pancreas functions as an exocrine gland because pancreatic acini produce digestive enzymes and an alkaline fluid called pancreatic juice, and secrete them via ducts into the duodenum to aid in digestion.

1. An increase in the blood glucose concentration causes glucose to enter β cells via a transporter protein
2. Glucose is metabolised in mitochondria, producing ATP
3. ATP binds to ATP-sensitive potassium ion (K⁺) channels in the cell-surface membrane, triggering them to close
4. The cell-surface membrane depolarises as K⁺ cannot enter the cell
5. Depolarisation causes voltage-gated calcium ion (Ca²⁺) channels to open
6. Ca²⁺ enters the cell, triggering secretory vesicles to release insulin via exocytosis

Adrenaline also increases blood glucose concentration when it is too low by:

1. Activating enzymes in liver cells that break down glycogen to glucose (glycogenolysis)

Adrenaline can also activate enzymes in muscle cells that break down glycogen to glucose.

Glucagon increases blood glucose concentration when it is too low by:

1. Activating enzymes in liver cells that break down glycogen to glucose (glycogenolysis)
2. Activating enzymes in liver cells that promote gluconeogenesis
3. Inhibiting the secretion of insulin from β cells via negative feedback

Insulin lowers blood glucose concentration when it is too high by:

1. Increasing the rate of glucose absorption into cells, especially muscle cells
2. Increasing the rate of respiration
3. Promoting glycogenesis
4. Activating enzymes that convert glucose to glycogen and fat
5. Decreasing gluconeogenesis
6. Inhibiting the secretion of glucagon from α cells via negative feedback

The liver carries out the following to increase or decrease blood glucose concentration:

1. Glycogenesis - the conversion of glucose into glycogen when blood glucose concentration is high
2. Glycogenolysis - the breakdown of glycogen to glucose when blood glucose concentration is low
3. Gluconeogenesis - the production of glucose from sources other than carbohydrates like fats and amino acids

1. Glucose is needed for respiration
2. If blood glucose is too low or high it can cause osmotic problems in cells and even cell death

1. α cells in the islets of Langerhans - produce glucagon
2. β cells in the islets of Langerhans - produce insulin