The Endocrine Pancreas Flashcards
What two centres of the brain govern food intake?
Feeding centre and satiety centre (both in the hypothalamus)
What two theories govern food intake?
- Glucostatic theory
2. Lipostatic theory
What does glucostatic theory state?
Food intake is determined by blood glucose concentrations - as [BG] increases the drive to eat decreases
What does the lipophilic theory state?
Food intake is determined by fat stores - as fat stores increase, the drive to eat decreases
What peptide hormone plays a role in depressing feeding activity?
Leptin
How can obesity arise from the threories of food intake?
Disruption of the pathways
What three categories of energy output are there?
- Cellular work
- Mechanical work
- Heat loss
What is the only type of energy output we can regulate?
Mechanical
What is the definition of metabolism?
Integration of all biochemical reactions in the body
What three elements comprise metabolism?
- Extracting energy from nutrients in food
- Storing that energy
- Utilising that energy for work
What two metabolic pathways are there?
Anabolic and catabolic
What phase of metabolism do we enter after eating?
Absorptive phase - anabolic
What phase of metabolism do we enter between meals and overnight?
Post-absorptive phase (fasting) - catabolic
What is an obligatory glucose user? Give an example?
An organ that can only utilise glucose as a respiratory substrate
State the normal range of blood glucose
4.2-6.3mM/L (80-120mg/L)
What do alpha cells secrete in the pancreas?
Glucagon (peptide hormone)
What is the primary action of glucagon?
Raise blood glucose by stimulating the liver to undergo glycogenolysis
What is the half life of glucagon?
5-10 mins
What hormone is secreted by the beta cells?
Insulin
What is the primary action of insulin?
To decrease blood glucose
What hormone do delta cells secrete?
Somatostatin
What hormone do F cells secrete?
Pancreatic polypeptide (functionally irrelevant)
Outline the sequence of events that insulin instigates to decreased blood glucose
- Actives tyrosine kinase receptors
- Stimulates mobilisation of specific GLUT-4 receptors which reside in the cytoplasm of unstimulated muscle and adipose cells
What are the additional secondary effects of insulin?
- Glycogen synthesis
- Increase uptake of amino acids
- Inhibits proteolysis
- Increases TAG synthesis
- Inhibits gluconeogenesis
- Permissive effect on growth hormone
What tissues are insulin sensitive?
Muscle and fat
Other tissues use other glucose transporters to uptake glucose; give a few examples
GLUT-1 - brain, kidneys and RBCs
GLUT-2 - Pancreas and liver
GLUT-3 - similar to GLUT-1
List stimuli that increase insulin release
- Increase in [BG]
- Increase [Amino acid]plamsa
- Glucagon
- Other (incretin) hormones increasing GI motility/secretion
- Vagal nerve activity
List stimuli that inhibit glucose release
- Low [BG]
- Somatostatin
- Sympathetic alpha2 effects
- Stress e.g. hypoxia
What receptors does glucagon work on?
GPCR linked to adenyl cyclase which activate cAMP to phosphorylate liver enzymes
What stimuli cause secretion of glucagon?
- Low [BJG]
- High [AAs]
- Sympathetic innervation
- Cortisol
- Stress e.g. exercise and infection
What inhibits the release of glucagon?
- Glucose
- FFAs and ketones
- Insulin
- Somatostatin
What is the main action of somatostatin?
Inhibits activity in the GI tract
How can synthetic somatostatin be used clinically?
In the treatment of life-threatening diarrhoea associated with pancreatic tumours
