3.2 Endocrine Pancreas and Blood Glucose Control Flashcards
What comes from alpha cells of pancreas?
Glucagon
When is glucagon secreted?
In response to low glucose and elevated amino acids
What does glucagon activate?
Glycogenolysis (glycogen in liver broken down) and gluconeogenesis (endogenous glucose production in fasting state)
Lipolysis in adipocytes
When is somatostatin released?
elevated glucose (anti-insulin)
What is the structure of insulin and what is released with it?
alpha and beta chain joint by 2 disulphide bonds - C peptide is released with it in a 1:1 ratio
Where do you find GLUT 1,2,3,4
1: all cells
2: especially liver and pancreatic beta cells (bidirectional)
3: high affinity in neurons and placenta
4: adipose tissue and muscle
Describe the process of insulin secretion in pancreatic beta cells
- glucose uptake
- glucose metabolism
- increase ATP/ADP ratio
- closure of ATP sensitive K+ channel
- depolarisation of plasma membrane
- opening of voltage dependent Ca++ channels
- influx oc Ca
- Ca induced insulin vesicle exocytosis
what leads to the action of insulin?
phosphorylation of the beta subunits of the receptor
What increases glucose medicated insulin secretion?
FFAs, AAs
Glucagon like peptide 1
glucose dependant insulinotropic polypeptide
Parasympathetic nervous system
What inhibits glucose mediated insulin secretion?
Sympathetic NS, adrenaline and somatostatin
how does insulin promote glucose uptake into cells
induces translocation of GLUT4 to the plasma membrane in insulin sensitive tissues
What are the glucose metabolism actions of insulin?
Stimulates glucose transport (skeletal muscle, heart, adipose tissue)
Suppresses endogenous glucose production in the liver
What are the protein metabolism actions of insulin?
sitmulates amino acid transport
promotes protein synthesis
Inhibits protein degredation
Opposes cortisol
What are the lipid metabolism actions of insulin?
Suppresses lipolysis in adipose tissue
promotes hepatic VLDL triglyceride secretion
Activates lipoprotein lipase allowing fat uptake into peripheral tissues
What does insulin stimulate?
Glucose uptake and glycolysis in muscle and liver
Glycogen synthesis in muscle
Lipogenesis in liver
Protein synthesis in muscle
What does insulin inhibit?
Gluconeogenesis in liver Glycogen breakdown in liver Lipolysis in adipose tissue Fatty acid oxidation in muscle Protein degradation in muscle
Why is there 2 phases of insulin secretion?
The first phase is due to the prepackaged insulin present in the beta cells, the second phase occurs as there is preformed AND newly synthesised insulin available
What are the symptoms of hypoglycaemia
BSL <3.5
Activation of sympathetic NS: sweating, palpitations, anxiety
Brain dysfunction: parasthesia, confusion, seizures, coma
What are the acute responses to hyperglycaemia
Glycosuris: polyuria, thirst, dehydration
Blurred vision
Impaired immune function: candidiasis, bacterial infection
What are the chronic responses to hyperglycaemia?
End organ damage: microvasculature (eyes, kidneys, nerves), macrovasculature (IHD, PVD, CVD), glycation of proteins (glycated Hb)
