Section 9 part 2 Flashcards
Major factors controlling the release of insulin from β-cells
Major factors controlling insulin secretion
Major factors controlling the release of glucagon from α-cells
What is the longest nerve in our body?
Vagus aka cranial X nerve
Is vagus a motor or a sensory neuron?
Acts as a sensory neuron and as a motor neuron (providing and receiving signals from peripheral organs)
What are the functions of vagus nerve?
v Acts as a sensory neuron and as a motor neuron (providing and receiving signals from peripheral organs)
v Main neuronal coordinator of appetite control, digestion and metabolism
v Release of acetylcholine (cholinergic) in the pancreas stimulates insulin release
Mechanism of insulin release from β-cells
- Uptake of glucose by the type 2 facilitative glucose transporter (Glut 2)
- Aerobic glycolysis and increase of the ATP/ADP ratio.
- Inhibition of ATP-sensitive K+ channels → reduction of K+ efflux → membrane depolarization
- Opening of voltage gated Ca2+ channels (VDCC)
- Increased intracellular Ca2+ triggers exocytosis of insulin containing granules
- Opening of Ca2+ activated potassium channels (K-Ca), leading to the repolarization of the membrane (resetting)
- Metabolic coupling factors generated during glucose metabolism facilitate exocytosis and/or proinsulin synthesis (amplification pathway). Examples are plasma FFA (stimulates exocytosis via G-protein receptor) and intracellularly formed succinate.
- Glucagon-like peptide 1 (GLP-1 from intestine) or related peptides bind to GLP-1 receptors and trigger cAMP production. It potentiates the amplification pathway, ion channels and exocytosis
Regulation of blood glucose post-meal and in fastign state
meal-> increased blood glucose
- this blood glucose is made available for muscle and energy storage as glycogen or TGs
- TGs are made from glucose by the liver-> conversion into glycogen and TGs
- Glucose is also taken up by the adipose tissue and is converted into TGs for energy storage
- glucose is also used by other cells as nerves and RBC
In fasted state
- no glucose
- protien degradation-> AA-> taken by the liver-> gluconeogenesis-> glucose
- Within the liver glycogen is degraded and glucose is released into the circulation
- adipose tissue releases fatty acids through hydrolysis of TGs
- These FA are used by other tissues or are taken up by the liver-> converted into ketone bodies
- ketone bodies are now available as energy
what is the serum glucose level in the fasting state?
3-5 mM
What is the serum, BG in post-prandial state? When does glycosuria start?
Rise to 7 mM after meal (glycosuria if exceeding 10 mM)
What are the anabolic effect of insulin
synthesis of protein, lipid and glycogen and inhibition of their degradation (usage of glucose)
What are the key targets of insulin?
liver, muscle, adipose tissue
Insulin promotes cell __
Insulin promotes cell growth
Glucagon increases many __ processes particularly in the __ (production of __)
Glucagon increases many catabolic processes particularly in the liver (production of glucose)
Which hormone production is stimulated by Neural anticipatory stimulation?
glucagon (subsequently suppressed by insulin)
GLUT functions and locations according to their types?
Glucagon signalling
Glucagon signals via a GPCR-> PKA or IP3-Ca pathway through adenylyl cyclase or phospholipase C receptively
PKA pathway leads to phosphorylase activation (involved in cleavage of glucose subunits its from glycogen storage; phosphorylase increases glycogenolysis-> increase glucose levels
These pathways also reduce glycolysis and glycogenesis
Glucagon stimulates gluconeogenesis from non-CHO sources especially viia AA metabolism
all this increases glucose available in the liver
Endocrine functions of insulin
Endocrine functions of glucagon & GLPs
on islet cells, liver, stomach, intestine, brain
How does Obesity predispose Type II diabetes
Gastrointestinal Hormones: site of production and effect
Types and action of gastrointestinal hormones
