Flashcards in Endocrine Pancreas Deck (45)
The endocrine cells of the pancreas secrete 3 separate hormones
Beta cells secrete ____
Alpha cells secrete ____
Delta cells secrete ______
Insulin (and C peptide)
The beta, alpha, and delta cells of the pancreas are organized into clusters called ____
Islets (of langerhans)
Which cells of the pancreas are neuronal in appearance and send dendrite like processes to beta cells?
Most ____ cells of the pancreas are centrally located, while most _____ are peripherally located
How do individual islets in the endocrine pancreas communicate with each other?
Via gap junctions - rapid cell-cell communication
Describe blood supply to the endocrine pancreas - which cells receive blood first?
Venous blood first flows to center for insulin; venous blood from beta cells carries insulin to alpha and delta cells
[flows through periphery, insulin rich blood inhibits glucagon release from alpha cells]
What is the major stimulating factor for insulin secretion?
Insulin is a _____ hormone made up of 2 chains linked by _____ bridges
_______ = signal peptide with A and B chains with connecting C peptide - NO disulfide bonds
[preproinsulin —> proinsulin —> Insulin + C peptide]
______= no signal peptide because C peptide still attached to insulin; packaged into secretory granules, proteases can cleave it
Once synthesized, insulin and cleaved C peptide are packaged together in ______
What compound can be used as a marker of endogenous insulin secretion?
Steps for insulin release:
1. Glucose enters cell via ______
2. Glucose is phosphorylated by a ________
3. G6P is oxidized, promoting ___ generation
4. ATP closes the inward rectifying ____ channel
5. Plasma membrane is depolarized
6. Activation of voltage gated ___ channels leading to its entry into the cell
7. Mobilization of insulin is initiated
Rises in ATP have what effect on K channels in beta cells?
Rises in ATP close the K channels
The sulfonurea receptor associated with ATP-dependent K channels increase insulin secretion. what effect does this have on membrane depolarization?
Causes membrane depolarization to occur more easily d/t increased Ca entry - so this can be targeted and used for tx of T2DM
C peptide secretion is used as a tool to measure function of beta cells and endogenous insulin secretion. C peptide is typically secreted in the ____
Describe the biphasic release of insulin and how this is affected in diabetics
When plasma glucose increases:
Phase 1 = initial spike in insulin secretion
Phase 2 = gradual sustained rise in insulin secretion
In diabetes — phase 1 is the first phase lost
Besides blood glucose levels, what are some other modulators of insulin secretion?
Once insulin binds its receptor, it ________ itself and other proteins. The entire complex is internalized by target cell, leading to anabolic growth effects and metabolic effects, eventually leading to activation of ______ and ______ which have a negative feedback effect on the receptor itself
Autophosphorylates; mTORC1; SREBP1c
Glucose uptake occurs through _______, once vescicles containing this transporter to the membrane
Activation of _______ results in GLUT4 transloaction to the plasma membrane INDEPENDENT of insulin
[active in times of low energy]
Actions of insulin on skeletal muscle
Increased glucose uptake via GLUT4
Increased glycogen synthesis via activity of hexokinase and glycogen synthase
Increased glycolysis and CHO oxidation via activity of hexokinase, PFK, PDH
Increased protein synthesis
Decreased protein breakdown
Action of insulin on liver
Promotes glycogen synthesis via glucokinase and glycogen synthase
Increases glycolysis and CHO oxidation via glucokinase, PFK, PK
increases hexose monophosphate shunt (protein anabolism)
Increases pyruvate oxidation
Increases lipid sotrage and decreases lipid oxidation
Increases protein synthesis and decreases protein breakdown
Insulin actions on adipose tissue
Increased glucose uptake via GLUT4
Promotes uptake of fatty acids
What effect does insulin have on K+ uptake into cells?
Increases K uptake into cells (thus decreasing blood levels of K)
Which of the following increases insulin secretion?
Type 1 diabetes is often d/t autoimmune destruction of ___ cells, leading to inadequate insulin secretion
Results in increased BG, fatty acids, _______, amino acids
Decreased utilization of ketoacids results in ______
DKA (diabetic ketoacidosis)
What effect does T1DM have on blood potassium levels?
Increases shift of K+ out of cells —> hyperkalemia
[intracellular concentration of K is low, lack of insulin effect on Na/K ATPase, total K levels usually low d/t polyuria and dehydration]
What effect does T1DM have on diuresis?
Causes osmotic diuresis and glucosuria
[also polydipsia d/t increased polyuria]