Pancreas and Insulin

Overview

• Structure and function of the pancreas
• Types and roles of pancreatic cells
• Importance of hormones like insulin

Pancreatic Cells

• Alpha Cells: Release glucagon (~20% of cells)
• Beta Cells: Release insulin
• Delta Cells: Release somatostatin
• PP Cells: Release pancreatic polypeptide

Insulin

• Isolated from pancreas by Banting and Best
• Comprised of two chains connected by disulfide bonds
• Synthesized as a longer protein, then cleaved to active form
• Secreted in response to high blood glucose levels
• Reduces blood glucose by promoting uptake and storage

Mechanism of Insulin Secretion

• Glucose enters beta cells via GLUT2 transporters
• Oxidation of glucose to ATP closes K+ channels, causing depolarization
• Ca2+ channels open, increasing intracellular Ca2+
• Insulin vesicles release insulin into blood

Insulin Function in Tissues

• Muscle: Increases glucose uptake and glycogen synthesis
• Liver: Promotes glycogen synthesis, inhibits glucose production
• Adipose Tissue: Enhances fat storage

Key Mechanisms and Effects

Muscle

• Increases glucose and amino acid uptake
• Increases protein synthesis and glycogen storage

Liver

• Promotes glycogen formation from glucose
• Converts excess glucose to fatty acids, transported as VLDL, stored as fat

Adipose Tissue

• Increases storage of triglycerides
• Decreases free fatty acid release

Insulin Deficiency

• Leads to increased blood glucose levels (diabetes)
• Promotes release of stored fats and proteins
• Can cause ketoacidosis (excess ketone bodies)

Factors Affecting Insulin Secretion

Stimulatory Factors

• High blood glucose and amino acids
• Gastrointestinal hormones (e.g., GLP-1, GIP)
• Parasympathetic stimulation

Inhibitory Factors

• Low blood glucose
• Somatostatin
• Sympathetic stimulation

Clinical Relevance

• Understanding mechanisms helps manage conditions like diabetes
• Monitoring insulin and glucose levels critical for health

Summary

• Pancreas crucial for metabolic regulation through hormones like insulin
• Insulin plays multiple roles in reducing blood glucose and storing energy
• Dysregulation leads to serious metabolic issues such as diabetes

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