NURS 5663 Exam 3 Review Key
Questions and Correct Answers
,Steps involved in the synthesis of thyroid hormones - CORRECT ANS:(1) iodide (I-) trapped by the thyroid
follicular cells;
(2) diffusion of iodide to the apex of the cells;
(3) transport of iodide into the colloid;
(4) oxidation of inorganic iodide to iodine and incorporation of iodine into tyrosine residues within
thyroglobulin molecules in the colloid;
(5) combination of two DIT molecules to form tetraiodothyronine (T4) or of MIT with DIT to form T3;
(6) uptake of thyroglobulin from the colloid into the follicular cell by endocytosis, fusion of the
thyroglobulin with a lysosome, and proteolysis and release of T4, T3, DIT, and MIT;
(7) release of T4 and T3 into the circulation; and
(8) deiodination of DIT and MIT to yield tyrosine. T3 is also formed from monodeiodination of T4 in the
thyroid and in peripheral tissues.
Insulin Definition - CORRECT ANS:the storage and anabolic hormone of the body
General characteristics of Insulin - CORRECT ANS:- small protein that contains 51 amino acids arranged
in 2 chains (A & B) linked by disulfide bridges.
- stored in beta cells of pancreas in form of hexameric crystals
1. Entire human pancreas stores up to 8mg (200 units) of insulin.
- Insulin is released from pancreatic beta cells at a low BASAL rate --> plus with stimulation releases at a
much higher rate
Insulin synthesis - CORRECT ANS:Insulin is synthesized as preproinsulin and processed to proinsulin.
Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release
on demand. Insulin synthesis is regulated at both the transcriptional and translational level.
insulin Stimulates release - CORRECT ANS:glucose, sugars (eg. Mannose), amino acids (esp.
glyconeogenic amino acids like leucine, arginine), hormones like glucagon-like polypeptide 1 (GLP-1),
glucose-dependent insulinotropic polypeptide (GIP), glucagon, cholecystokinin, high concentrations of
fatty acids, and B-adrenergic sympathetic activity
,Stimulatory drugs of insulin - CORRECT ANS:sulfonylureas, meglitinides, D-phenylalanine derivatives,
isoproterenol, and acetylcholine
Insulin Inhibitory hormones: - CORRECT ANS:insulin, islet amyloid polypeptide, somatostatin, and leptin;
alpha-adrenergic sympathetic activity; chronically elevated glucose; low concentrations of fatty acids
Insulin Inhibitory drugs: - CORRECT ANS:diazoxide, phenytoin, vinblastine, clonidine, verapamil, and
colchicine
One mechanism of stimulated insulin release - CORRECT ANS:1. in resting cell: normal (low) ATP levels→
K+ diffuses down its concentration gradient through ATP-gated K+ channels, maintaining the
intracellular potential @fully polarized, negative level→ insulin release is minimal
2. if glucose concentration rises → ATP production increases → K+ channels close --> depolarization
results → in muscle/nerve voltage-gated Ca2+ channels open in response to depolarization --> allows
more Ca2+ to enter cell --> increased intracellular Ca2+ results in increased insulin secretion → insulin
secretagugues close the ATP-dependent K+ channel→ depolarizes membrane→ increased insulin
release by same mechanism
Effects of insulin - CORRECT ANS:- Promotes the storage of fat as well as glucose (both sources of
energy) within specialized target cells & influences cell growth and the metabolic functions of a wide
range of tissues
-Promotes synthesis and storage of glycogen, triglycerides, and protein in its major target tissues: liver,
fat, and muscle. Release of insulin from pancreas is stimulated by increased blood glucose, incretins,
vagal nerve stimulation, and other factors.
Endocrine Effects of Insulin - CORRECT ANS:LIVER:
-Reversal of Catabolic features of insulin deficiency:
1. inhibits glycogenolysis
2. inhibits conversion of fatty acids & amino acids to keto acids
3. inhibits conversion of amino acids to glucose
, -Anabolic action:
1. promotes glucose storage as glycogen (induces glucokinase & glycogen synthase, inhibits
phosphorylase)
2. increases triglyceride synthesis & very-low-density lipoprotein formation
MUSCLE:
- Increased protein synthesis
1. increases amino acid transport
2. Increases ribosomal protein synthesis
- Increased glycogen synthesis
1. increases glucose transport
2. induces glycogen synthase & inhibits phosphorylase
ADIPOSE TISSUE:
- Increased triglyceride storage
1. Lipoprotein lipase is induced & activated by insulin to hydrolyze triglycerides from lipoproteins
2. Glucose transport into cell provides glycerol phosphate to permit esterification of fatty acids supplied
by lipoprotein transport
3. Intracellular lipase is inhibited by insulin
glucagon definition - CORRECT ANS:the hyperglycemic factor that mobilizes glycogen stores
Glucagon synthesis - CORRECT ANS:in the alpha cells of the pancreatic islets of Langerhans
Glucagon characteristics - CORRECT ANS:-Peptide (identical in ALL mammals) consisting of single chain of
29 amino acids
- Degraded in the liver and kidney as well as in plasma and at its tissue receptor
-half-life is between 3-6 months
Questions and Correct Answers
,Steps involved in the synthesis of thyroid hormones - CORRECT ANS:(1) iodide (I-) trapped by the thyroid
follicular cells;
(2) diffusion of iodide to the apex of the cells;
(3) transport of iodide into the colloid;
(4) oxidation of inorganic iodide to iodine and incorporation of iodine into tyrosine residues within
thyroglobulin molecules in the colloid;
(5) combination of two DIT molecules to form tetraiodothyronine (T4) or of MIT with DIT to form T3;
(6) uptake of thyroglobulin from the colloid into the follicular cell by endocytosis, fusion of the
thyroglobulin with a lysosome, and proteolysis and release of T4, T3, DIT, and MIT;
(7) release of T4 and T3 into the circulation; and
(8) deiodination of DIT and MIT to yield tyrosine. T3 is also formed from monodeiodination of T4 in the
thyroid and in peripheral tissues.
Insulin Definition - CORRECT ANS:the storage and anabolic hormone of the body
General characteristics of Insulin - CORRECT ANS:- small protein that contains 51 amino acids arranged
in 2 chains (A & B) linked by disulfide bridges.
- stored in beta cells of pancreas in form of hexameric crystals
1. Entire human pancreas stores up to 8mg (200 units) of insulin.
- Insulin is released from pancreatic beta cells at a low BASAL rate --> plus with stimulation releases at a
much higher rate
Insulin synthesis - CORRECT ANS:Insulin is synthesized as preproinsulin and processed to proinsulin.
Proinsulin is then converted to insulin and C-peptide and stored in secretary granules awaiting release
on demand. Insulin synthesis is regulated at both the transcriptional and translational level.
insulin Stimulates release - CORRECT ANS:glucose, sugars (eg. Mannose), amino acids (esp.
glyconeogenic amino acids like leucine, arginine), hormones like glucagon-like polypeptide 1 (GLP-1),
glucose-dependent insulinotropic polypeptide (GIP), glucagon, cholecystokinin, high concentrations of
fatty acids, and B-adrenergic sympathetic activity
,Stimulatory drugs of insulin - CORRECT ANS:sulfonylureas, meglitinides, D-phenylalanine derivatives,
isoproterenol, and acetylcholine
Insulin Inhibitory hormones: - CORRECT ANS:insulin, islet amyloid polypeptide, somatostatin, and leptin;
alpha-adrenergic sympathetic activity; chronically elevated glucose; low concentrations of fatty acids
Insulin Inhibitory drugs: - CORRECT ANS:diazoxide, phenytoin, vinblastine, clonidine, verapamil, and
colchicine
One mechanism of stimulated insulin release - CORRECT ANS:1. in resting cell: normal (low) ATP levels→
K+ diffuses down its concentration gradient through ATP-gated K+ channels, maintaining the
intracellular potential @fully polarized, negative level→ insulin release is minimal
2. if glucose concentration rises → ATP production increases → K+ channels close --> depolarization
results → in muscle/nerve voltage-gated Ca2+ channels open in response to depolarization --> allows
more Ca2+ to enter cell --> increased intracellular Ca2+ results in increased insulin secretion → insulin
secretagugues close the ATP-dependent K+ channel→ depolarizes membrane→ increased insulin
release by same mechanism
Effects of insulin - CORRECT ANS:- Promotes the storage of fat as well as glucose (both sources of
energy) within specialized target cells & influences cell growth and the metabolic functions of a wide
range of tissues
-Promotes synthesis and storage of glycogen, triglycerides, and protein in its major target tissues: liver,
fat, and muscle. Release of insulin from pancreas is stimulated by increased blood glucose, incretins,
vagal nerve stimulation, and other factors.
Endocrine Effects of Insulin - CORRECT ANS:LIVER:
-Reversal of Catabolic features of insulin deficiency:
1. inhibits glycogenolysis
2. inhibits conversion of fatty acids & amino acids to keto acids
3. inhibits conversion of amino acids to glucose
, -Anabolic action:
1. promotes glucose storage as glycogen (induces glucokinase & glycogen synthase, inhibits
phosphorylase)
2. increases triglyceride synthesis & very-low-density lipoprotein formation
MUSCLE:
- Increased protein synthesis
1. increases amino acid transport
2. Increases ribosomal protein synthesis
- Increased glycogen synthesis
1. increases glucose transport
2. induces glycogen synthase & inhibits phosphorylase
ADIPOSE TISSUE:
- Increased triglyceride storage
1. Lipoprotein lipase is induced & activated by insulin to hydrolyze triglycerides from lipoproteins
2. Glucose transport into cell provides glycerol phosphate to permit esterification of fatty acids supplied
by lipoprotein transport
3. Intracellular lipase is inhibited by insulin
glucagon definition - CORRECT ANS:the hyperglycemic factor that mobilizes glycogen stores
Glucagon synthesis - CORRECT ANS:in the alpha cells of the pancreatic islets of Langerhans
Glucagon characteristics - CORRECT ANS:-Peptide (identical in ALL mammals) consisting of single chain of
29 amino acids
- Degraded in the liver and kidney as well as in plasma and at its tissue receptor
-half-life is between 3-6 months
