39 Questions
What is the purpose of the C-peptide test?
All of the above
What is the primary function of the Golgi apparatus in the insulin synthesis process?
To package proinsulin into vesicles
Which of the following is NOT a factor that influences insulin release?
Genetic factors
What is the purpose of the disulfide bridges in the structure of active insulin?
To hold the alpha and beta peptide chains together
How do sulfonylureas (e.g., glipizide) work to decrease glucose levels?
By closing the potassium channels of the pancreatic beta cells
Which step in the insulin synthesis process occurs in the rough endoplasmic reticulum (rER)?
Synthesis of pre-proinsulin
What is the relationship between canine and porcine insulin?
Canine and porcine insulin have the same amino acid sequence
Which of the following is an example of a secretagogue that is important for omnivores?
Glucose
What is the primary function of GLUT-2 transporters on beta cells?
Help in the diffusion of glucose into beta cells
Which step triggers depolarization in a pancreatic beta cell during insulin secretion?
Closure of ATP-sensitive potassium channels
During the acute phase of insulin secretion, what triggers the quick spike of insulin release?
Storage vesicles releasing pre-synthesized insulin
Which protein is responsible for the activation of insulin gene expression in beta cells?
CREB (calcium responsive element binding protein)
What triggers the chronic phase of insulin secretion in beta cells?
Synthesis and secretion of insulin
In a pancreatic beta cell, what occurs when potassium channels close?
Depolarization takes place
Which event directly precedes the opening of voltage gated calcium channels in a beta cell?
Closure of potassium channels and depolarization
What is the immediate cellular response triggered by calcium entry through voltage-gated calcium channels in beta cells?
Insulin gene expression activation via CREB
What is the main reason for the delayed response time to glucose stimulation during the chronic phase of insulin releasing patterns?
Insulin has to be produced first before it can have an effect
What is the primary effect of insulin on insulin-sensitive tissues like muscle and adipose tissue?
All of the above
How does resistance exercise affect glucose uptake in muscle cells?
Resistance exercise stimulates the translocation of GLUT-4 transporters to the muscle cell membrane
What is the net effect of insulin on blood concentrations of glucose, fatty acids, and amino acids?
Insulin decreases the blood concentrations of these compounds
What is the catabolic effect of insulin?
Insulin promotes the conversion of glucose, amino acids, and fatty acids to their storage forms
How does insulin affect glycogen synthesis in muscle tissue?
Insulin stimulates the enzymes involved in glycogen synthesis, promoting glycogenesis
Which of the following statements about the Islets of Langerhans is true?
They consist of alpha, beta, delta, and f-cells.
What is the primary energy source used by muscles in the absence of insulin?
Fatty acids
How does insulin promote muscle growth?
By promoting amino acid usage, not storage
How does insulin affect fatty acid synthesis in the liver?
Insulin promotes fatty acid synthesis within the hepatocytes
How does insulin affect lipolysis in adipose tissue?
Insulin inhibits lipolysis
How does the liver uptake glucose in the presence of insulin?
Glucose enters the liver using the GLUT-2 transporter and does not require insulin
How does insulin affect fatty acid oxidation in muscle tissue?
Insulin decreases fatty acid oxidation
What is the primary function of insulin on adipose tissue?
Increase lipogenesis
What is the effect of insulin on gluconeogenesis in the liver?
Insulin inhibits gluconeogenesis
How does insulin affect glycogenolysis in the liver?
Insulin inhibits glycogenolysis
Which of the following statements about the endocrine pancreas is true?
More than 1 choice is correct
Which of the following statements about pancreatic hormones is false?
They circulate bound to carrier proteins in the blood.
What is the primary function of the beta cells in the Islets of Langerhans?
Secrete insulin in response to hyperglycemia.
Which cell type in the Islets of Langerhans is responsible for secreting glucagon?
Alpha cells
What is the primary function of the acini surrounding the Islets of Langerhans?
Secrete digestive enzymes (exocrine function).
Which statement about the pancreas is incorrect?
It contains only one lobe positioned behind the stomach.
What is the primary function of the f-cells in the Islets of Langerhans?
Secrete pancreatic peptide.
Study Notes
Pancreas: Structure and Function
- Located in the abdominal cavity, the pancreas has two lobes: one behind the stomach and one adjacent to the proximal duodenum
- Consists of exocrine and endocrine components
Exocrine Pancreas
- Composed of acinar cells that produce digestive enzymes and duct cells
- Digestive enzymes are secreted into the duodenum through the pancreatic duct
Endocrine Pancreas
- Composed of four types of cells (alpha, beta, delta, and f-cells) organized into islets (Islets of Langerhans)
- Involved in glucose metabolism and regulation of blood glucose levels
- Comprises 2-3% of the pancreas
Islets of Langerhans
- Consists of acini (exocrine function) and four cell types:
- Alpha cells: secrete glucagon
- Beta cells: secrete insulin in response to hyperglycemia
- Delta cells: secrete somatostatin
- F-cells: secrete pancreatic peptide
Pancreatic Hormones
- All pancreatic hormones are polypeptides
- Examples: somatostatin, pancreatic peptides, glucagon, insulin
- Circulate unbound in blood due to hydrophilicity and have a short half-life of ≤ 30 minutes
- Bind to cell surface receptors
Insulin Secretion
- Beta cells use GLUT-2 insulin-dependent transporters to facilitate glucose entry
- Glucose stimulates insulin secretion through a series of steps:
- Glucose enters the beta cell
- Glucose is converted to ATP
- High ATP concentration triggers depolarization
- Depolarization opens voltage-gated calcium channels
- Calcium influx triggers insulin gene expression and secretion
Insulin Release Pattern
- Insulin secretion follows biphasic kinetics:
- Acute phase: pre-synthesized insulin is released
- Chronic phase: insulin is synthesized and secreted
Insulin Action
- Increases glucose uptake in insulin-sensitive tissues (muscle and adipose tissue) by increasing GLUT-4 transporters
- Net effect: decreases blood glucose, fatty acid, and amino acid concentrations
- Promotes intracellular conversion of glucose, fatty acids, and amino acids to their storage forms
Insulin Action on Muscle
- Stimulates glycogen synthesis enzymes
- Promotes glycogenesis and glucose use as an energy source
- Inhibits fatty acid oxidation
Insulin Synthesis
- Proinsulin is synthesized in the rER
- Signal sequence is removed to form proinsulin
- Proinsulin is cleaved to form mature insulin in the golgi apparatus
Test your knowledge about the pancreas, a glandular organ located in the abdominal cavity with exocrine and endocrine functions. Explore topics such as acinar cells, digestive enzymes, and the different types of endocrine cells in the islets of Langerhans.
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