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Flashcards in Endocrine Pancreas Deck (45)
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1

The endocrine cells of the pancreas secrete 3 separate hormones

Beta cells secrete ____

Alpha cells secrete ____

Delta cells secrete ______

Insulin (and C peptide)

Glucagon

Somatostatin

2

The beta, alpha, and delta cells of the pancreas are organized into clusters called ____

Islets (of langerhans)

3

Which cells of the pancreas are neuronal in appearance and send dendrite like processes to beta cells?

Delta cells

4

Most ____ cells of the pancreas are centrally located, while most _____ are peripherally located

Beta; alpha

5

How do individual islets in the endocrine pancreas communicate with each other?

Via gap junctions - rapid cell-cell communication

6

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]

7

What is the major stimulating factor for insulin secretion?

Glucose

8

Insulin is a _____ hormone made up of 2 chains linked by _____ bridges

Peptide; disulfide

9

_______ = signal peptide with A and B chains with connecting C peptide - NO disulfide bonds

Preproinsulin



[preproinsulin —> proinsulin —> Insulin + C peptide]

10

______= no signal peptide because C peptide still attached to insulin; packaged into secretory granules, proteases can cleave it

Proinsulin

11

Once synthesized, insulin and cleaved C peptide are packaged together in ______

Secretory vesicles

12

What compound can be used as a marker of endogenous insulin secretion?

C peptide

13

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

GLUT2
Glucokinase
ATP
K
Ca

14

Rises in ATP have what effect on K channels in beta cells?

Rises in ATP close the K channels

15

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

16

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 ____

Urine

17

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

18

Besides blood glucose levels, what are some other modulators of insulin secretion?

Activating:
GI peptides
Glucagon
ACh

Inhibitory:
Somatostatin

19

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

20

Glucose uptake occurs through _______, once vescicles containing this transporter to the membrane

GLUT4

21

Activation of _______ results in GLUT4 transloaction to the plasma membrane INDEPENDENT of insulin

AMP-kinase

[active in times of low energy]

22

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

23

Action of insulin on liver

Promotes glycogen synthesis via glucokinase and glycogen synthase

Increases glycolysis and CHO oxidation via glucokinase, PFK, PK

Decreases gluconeogenesis

increases hexose monophosphate shunt (protein anabolism)

Increases pyruvate oxidation

Increases lipid sotrage and decreases lipid oxidation

Increases protein synthesis and decreases protein breakdown

24

Insulin actions on adipose tissue

Increased glucose uptake via GLUT4

Increased glycolysis

Decreased lipolysis

Promotes uptake of fatty acids

25

What effect does insulin have on K+ uptake into cells?

Increases K uptake into cells (thus decreasing blood levels of K)

26

Which of the following increases insulin secretion?

A. Fasting
B. Somatostatin
C. Cortisol
D. Exercise
E. Diazoxide

C. Cortisol

27

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 ______

Beta

Ketoacids

DKA (diabetic ketoacidosis)

28

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]

29

What effect does T1DM have on diuresis?

Causes osmotic diuresis and glucosuria



[also polydipsia d/t increased polyuria]

30

Which type makes up 95% of DM cases?

T2DM