Physiology
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Endocrine
Which of the following pancreatic hormones regulates appetite and satiety:
Answer:
Ghrelin is a hormone that is produced and released mainly by the stomach with small amounts also released by the small intestine, pancreas and brain. Ghrelin has numerous functions. It is termed the ‘hunger hormone’ because it stimulates appetite, increases food intake and promotes fat storage. It circulates in the bloodstream and acts at the hypothalamus, an area of the brain crucial in the control of appetite. Ghrelin has also been shown to act on regions of the brain involved in reward processing such as the amygdala. Ghrelin also stimulates the release of growth hormone from the pituitary gland, which, unlike ghrelin itself, breaks down fat tissue and causes the build-up of muscle. Ghrelin also has protective effects on the cardiovascular system and plays a role in the control of insulin release. Levels of ghrelin in the blood rise just before eating and when fasting, with the timing of these rises being affected by our normal meal routine. Hence, ghrelin is thought to play a role in mealtime ‘hunger pangs’ and the need to begin meals. Levels of ghrelin increase when fasting (in line with increased hunger) and are lower in individuals with a higher body weight compared with lean individuals, which suggests ghrelin could be involved in the long-term regulation of body weight. Eating reduces concentrations of ghrelin. Different nutrients slow down ghrelin release to varying degrees; carbohydrates and proteins restrict the production and release of ghrelin to a greater extent than fats. Somatostatin also restricts ghrelin release, as well as many other hormones released from the digestive tract.Endocrine Pancreas
Physiology / Endocrine / Pancreatic Function
Last Updated: 7th December 2023
The endocrine pancreas refers to those cells within the pancreas that synthesise and secrete hormones.
The endocrine portion of the pancreas takes the form of many small clusters of cells called islets of Langerhans or, more simply, pancreatic islets. Humans have roughly one million islets.
Pancreatic islets house five main cell types, each of which produces a different endocrine product:
- Alpha cells producing glucagon
- Beta cells producing insulin (most abundant cells)
- Delta cells producing somatostatin
- Epsilon cells producing ghrelin
- PP cells (gamma cells or F cells) producing pancreatic polypeptide
Islets are richly vascularised, allowing their secreted hormones ready access to the circulation. Although islets comprise only 1-2% of the mass of the pancreas, they receive about 10 to 15% of the pancreatic blood flow. Additionally, they are innervated by parasympathetic and sympathetic neurons, and nervous signals clearly modulate secretion of insulin and glucagon.
Overview of pancreas localisation and anatomy. (Image adapted and modified from an OpenStax College resource, available from https://www.researchgate.net/figure/Overview-of-pancreas-localization-and-anatomy-The-pancreas-is-composed-of-an-endoand_fig3_328475917)
Ghrelin
Ghrelin is a hormone that is produced and released mainly by the stomach with small amounts also released by the small intestine, pancreas and brain. Ghrelin has numerous functions. It is termed the ‘hunger hormone’ because it stimulates appetite, increases food intake and promotes fat storage. It circulates in the bloodstream and acts at the hypothalamus, an area of the brain crucial in the control of appetite. Ghrelin has also been shown to act on regions of the brain involved in reward processing such as the amygdala. Ghrelin also stimulates the release of growth hormone from the pituitary gland, which, unlike ghrelin itself, breaks down fat tissue and causes the build-up of muscle. Ghrelin also has protective effects on the cardiovascular system and plays a role in the control of insulin release.
Levels of ghrelin in the blood rise just before eating and when fasting, with the timing of these rises being affected by our normal meal routine. Hence, ghrelin is thought to play a role in mealtime ‘hunger pangs’ and the need to begin meals. Levels of ghrelin increase when fasting (in line with increased hunger) and are lower in individuals with a higher body weight compared with lean individuals, which suggests ghrelin could be involved in the long-term regulation of body weight. Eating reduces concentrations of ghrelin. Different nutrients slow down ghrelin release to varying degrees; carbohydrates and proteins restrict the production and release of ghrelin to a greater extent than fats. Somatostatin also restricts ghrelin release, as well as many other hormones released from the digestive tract.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
