Midterm 3 - Lecture 18

Question 1

What are the pancreatic hormones?

Answer 1

Insulin and glucagon
- synthesized from region known as the islets of Langerhans
- B-cell = insulin
- A-cell = glucagon

Question 2

Molecular characteristics of insulin

Answer 2

51 aa protein hormone

Question 3

What is insulin secreted by?

Answer 3

beta cells in pancreatic islets

Question 4

What is the most important hormone in the regulation of glucose metabolism?

Answer 4

Insulin
- increases upon feeding and decreases in postabsorptive state
- insulin increases anabolic processes; CHO, protein and fat deposition

Question 5

What is insulin induced by?

Answer 5

gastric inhibitory peptide (GIP) before blood glucose levels rise

Question 6

What is the half-life of insulin in plasma?

Answer 6

5-8 minutes

Question 7

What are 4 ways that insulin counteracts high blood glucose?

Answer 7

1. increase glucose uptake by cells
2. stimulate synthesis of glycogen/inhibit degradation
3. increase consumption for ATP
   - inhibit gluconeogenesis

Question 8

Insulin increases glucose uptake in cells, increases glycogen synthesis, and decreases gluconeogenesis, what effect does this have on plasma concentration?

Answer 8

• decreases plasma concentration of glucose
• increases cell stores of glycogen

Question 9

Insulin increases triglyceride synthesis and decreases lipolysis, what effect does this have on plasma concentration?

Answer 9

• decreases plasma concentration of FFA
• increases cell stores of triglycerides

Question 10

Insulin increases aa uptake in many cell types and increases protein synthesis, what effect does this have on plasma concentration?

Answer 10

decreases plasma concentration of AA

Question 11

How is insulin linked to a decrease in plasma concentration of glucose and an increase of cell stores of glycogen?

Answer 11

• increase glucose uptake in many cell types
• increases glycogen synthesis
• decreases gluconeogenesis

Question 12

How is insulin linked to a decrease in plasma concentration of FFA and an increase in cell stores of triglycerides?

Answer 12

• increases triglyceride synthesis
• decreases lipolysis

Question 13

How is insulin linked to a decrease in plasma concentration of AA?

Answer 13

• increases aa uptake in many cell types
• increases protein synthesis

Question 14

What is glucagon secrete by?

Answer 14

• alpha cells in the pancreas

Question 15

What hormone is secreted in response to low blood glucose? What effects does it have?

Answer 15

Glucagon
- stimulates glycogenolysis in the liver
- stimulates gluconeogenesis in the liver
- stimulates lipolysis in adipose through activation of hormone sensitive lipase

Question 16

During a typical meal, what is glucagon and insulin secretion induced by?

Answer 16

• plasma aa (counteractive effects)
• insulin also induced by glucose, but glucagon is not

Question 17

What is more important, the insulin to glucagon ration or the absolute amount of each?

Answer 17

insulin to glucagon ratio

Question 18

How is the insulin to glucagon ratio affected if during absorption, postabsorption, and exercise?

Answer 18

absorptive: high
postabsorptive: low
exercise: low

Question 19

Although insulin is low during exercise, why is glucose transported into muscle greater than during rest?

Answer 19

bc increased glucose transporters in cell membrane of skeletal muscle fibers

Question 20

How is the insulin and glucagon ratio different in ruminants?

Answer 20

Relatively low and constant concentration of insulin and glucagon
- reflects the constant need for gluconeogenesis

Question 21

What is the trademark of diabetes?

Answer 21

High blood glucose
- reduced entry into muscle and adipose
- increased glucose production by the liver

Question 22

What is required for glucose uptake in most cells?

Answer 22

INSULIN
- exception of brain, RBC, hepatocytes and renal cortex
- cells can use fatty acids, ketones and aa for energy

Question 23

Why is glucose in urine a trademark of diabetes?

Answer 23

• renal threshold for reabsorption surpassed
• increases water loss in urine = symptom of excessive urination and thirst

Question 24

Type 1 diabetes

Answer 24

• beta cells fail to produce adequate insulin
• auto-immune
• patient must be given insulin
• common in dogs

Question 25

Type 2 diabetes

Answer 25

• cellular actions of insulin hampered (insulin resistance)
• cats

Question 26

What is insulin resistance (type 2 diabetes) induced by?

Answer 26

Inflammation
- makes cells less responsive to insulin
- initial response is to produce more insulin