• The pancreas is an organ found in the abdomen of mammals
• It functions as both an?endocrine gland?and an?exocrine gland
  • Endocrine glands secrete hormones?directly?into the blood, whereas exocrine glands secrete substance?via a duct
  • The?exocrine?function of the pancreas is to?produce digestive enzymes?to be delivered to the small intestine
  • The?endocrine?function of the pancreas is to?produce the hormones glucagon and insulin
• Within the pancreas, these two functions are performed by?different tissues
  • Most of the cells of the pancreas secrete digestive enzymes, but throughout the organ, there are small sections of cells known as the?islets of Langerhans?that produce hormones
  • The islets of Langerhans contain?two?cell types:?alpha cells?(α cells), which secrete?glucagon, and?beta cells?(β cells), which secrete?insulin

The location and structure of the pancreas

The control of blood glucose by glucagon and insulin

• If the concentration of glucose in the blood?decreases?below a certain level, cells may not have enough glucose for?respiration?and so may not be able to function normally
• If the concentration of glucose in the blood?increases?above a certain level, this can also?disrupt the normal function of cells, potentially causing major problems
• The control of blood glucose concentration is a key part of?homeostasis
• Blood glucose concentration is controlled by?glucagon?and?insulin:
  • Glucagon?is synthesised and secreted by?α cells?when?blood glucose falls?and?stimulates liver and muscle cells to?convert stored glycogen?into?glucose?to be released into the blood,?increasing blood glucose concentration
  • Insulin?is?synthesised and secreted by?β cells?when?blood glucose rises?and stimulates liver and muscle cells to?convert excess glucose into glycogen?to be stored,?decreasing blood glucose concentration

Control of blood glucose levels

• There are over 3 million people suffering from diabetes in the UK
• Diabetes is a condition in which the homeostatic control of blood glucose has failed or deteriorated
• In individuals with diabetes their?insulin function is disrupted?which allows the?glucose concentration in the blood to rise
• An elevated blood glucose level can lead to noticeable symptoms, some of which are harmful, e.g.
  • The kidneys are unable to filter out this excess glucose in the blood and so it is often present in the?urine
  • The increased glucose concentration also causes the kidneys to produce large quantities of urine, making the individual feel thirsty due to?dehydration
  • Continuously elevated blood glucose levels can also damage tissues, in particular their proteins
• There are two different types of diabetes:?type I?and?type II

Type I diabetes

• Type 1 diabetes?is a condition in which the pancreas fails to produce sufficient insulin to control blood glucose levels
• It normally begins in childhood due to an?autoimmune response?whereby the body’s immune system?attacks the β cells?of the islets of Langerhans in the pancreas
  • The β cells?produce?and??release?insulin
• Insulin causes the cells to take up glucose from the blood for?respiration?and for storage as?glycogen; without insulin the glucose remains in the blood, resulting in an individual feeling?fatigued
• If the blood glucose concentration reaches a dangerously high level after a meal then?organ damage?can occur
• Type 1 diabetes is normally treated with regular blood tests to check glucose levels,?insulin injections?and a diabetes appropriate?diet
  • Health authorities encourage type I diabetics to eat a similar diet to the general public. They suggest five portions of fruit and veg a day, minimally processed food and consuming more polysaccharides than monosaccharides or disaccharides
• The insulin used by diabetics can be?fast-acting?or?slow-acting; each allowing for a different level of control

Type II diabetes

• Type II diabetes is more common than type I
• It usually develops in those?aged 40 and over,?however more and more young people are developing the condition
• In type II diabetes the pancreas still produces insulin but the receptors have reduced in number or no longer respond to it
• The lack of response to insulin means there is a?reduced glucose uptake?by the cells, which leads to a?high blood glucose concentration
  • This can cause the?β cells?to produce more and more insulin in the attempt to lower blood glucose levels
  • Eventually the β cells can no longer produce enough insulin and blood sugar becomes uncontrollable
• For type II diabetes treatment involves a?sugar and fat controlled diet?and an?exercise regime
  • Any food that is rapidly digested into sugar will cause a sudden, dangerous spike in blood sugar
• Obesity?is a major risk factor for type II diabetes

Type I Diabetes and Type II Diabetes Table

• Thyroxin?is a?hormone?that is released from the?thyroid gland,?located in the neck
• Thyroxin's main role is to?regulate?the?basal metabolic rate?(BMR); this is the speed at which?metabolic reactions?occur?in the body when it is at rest
  • Thyroxin therefore?targets almost all cells in the body,?as all cells metabolise
  • However, the most metabolically active cells, such as those of the?liver,?muscle?and?brain, are most affected
• Thyroxin plays a role in regulating body temperature
  • If the body becomes?cooler, this triggers?increased thyroxin secretion?by the thyroid gland
  • The increase in thyroxin?increases the metabolic rate, which??increases the generation of body heat
  • This causes?body temperature?to?rise
• Thyroxin?deficiency,?caused by a condition known as?hypothyroidism,?has the following effects on the body:
  • Lack of energy
  • Low mood
  • Forgetfulness
  • Weight gain
    • Less glucose and fat is broken down by cellular respiration to release energy
  • Constantly feeling cold
    • Less heat is generated by respiration
  • Constipation
    • Muscular contractions in the gut wall slow down due to reduced energy from respiration
  • Impaired brain development in children