Pancreas

• Pancreas

  • Small organ just below stomach w/ endocrine + exocrine functions
  • Most cells secrete pancreatic juice w/ digestive enzymes
  • Islets of Langerhans cells:
  • Produce + secrete two hormones
  • α (alpha) cells make + secrete glucagon (blood glucose up)
  • β (beta) cells make + secrete insulin (blood glucose down)
  • Exocrine function
  • Produces pancreatic fluid
  • Alkaline contain sodium hydrogen carbonate to neutralise acidic chyme from stomach for digestive system
  • Pancreatic fluid is rich in digestive enzymes secreted to duodenum; e.g. amylase, trypsinogen and lipase
  • Endocrine function
  • Alpha cells produce + secrete glucagon, raises blood glucose by stimulating glycogenolysis + lipolysis
  • Beta cells produce + secrete insulin, lowers blood glucose by stimulating glucose uptake + increasing metabolism
• Blood Glucose Regulation

  • Blood plasma glucose carefully controlled, normal conc is 90mg 100cm-3 (or 4-6 mmoldm-3)
  • If levels rise - hyperglycaemia
  • β-cells detect rise + secrete insulin
  • Bind to cell surface receptors on target cells
  • More glucose channels placed to cell membrane, plasma membrane permeability inc; more glucose uptake
  • Inc respiration rate + glucose used, also glucose converted to glycogen (glycogenesis) or lipid (lipogenesis)
  • Blood plasma + tissue fluid become very hypertonic + low WP
  • Body cells lose water by osmosis
  • Shrivel/crenate losing metabolic functions
  • If levels fall - hypoglycaemia
  • α-cells detect fall + secrete glucagon
  • Glycogen to glucose - glycogenolysis
  • More fatty acids in respiration + inc glucose production from AA/lipids - gluconeogenesis
  • Blood plasma + tissue fluid become very hypotonic + high WP
  • Body cells gain water by osmosis
  • Burst/cytolysis losing metabolic functions
• Insulin

  • Insulin facilitates glucose entry to muscle, adipose + several other tissues
  • Some tissues eg brain + liver don’t require insulin for efficient uptake
  • Stimulates liver to store glucose as glycogen, promotes fatty acid synthesis in liver + inhibits fat adipose tissue breakdown
  • Glycogenesis: Make glycogen (polymer); condensation reaction
  • Glycogenolysis: Hydrolysis glycogen to glucose
  • Gluconeogenesis: Make new glucose from non-carbohydrates
  • Supply glucose needs between meals
  • Made w/ glycerol, lactate (from muscles) + some amino acids