Pancreas and Adrenal Glands

Pancreas

  • Located posterior to the stomach.
  • Primarily an exocrine gland (digestive enzymes). The endocrine pancreas makes up only about 1% of its mass.
  • Releases digestive juices into the small intestine.

Adrenal Gland

  • Composed of two main sections: the cortex (outer layer) and the medulla (inner layer).

Objectives

  • Distinguish between the cortex and medulla of the adrenal gland.
  • Identify the stimuli, target tissues, and effects of mineralocorticoid hormones (released by the adrenal cortex).
  • Identify the stimuli, target tissues, and effects of glucocorticoid hormones (released by the adrenal cortex).
  • Understand the adrenal medulla's relationship to the sympathetic nervous system.
  • Identify the stimuli, target tissues, and effects of hormones released by the adrenal medulla.
  • Focus on the endocrine pancreas.
  • Identify the hormones secreted by the endocrine pancreas (glucagon and insulin) and the cells that secrete them.
  • Identify the stimuli, target tissues, and effects of glucagon and insulin.
  • Understand how insulin and glucagon work together to maintain blood glucose levels.
  • Discuss diabetes, including its types and symptoms.

Hormones Controlling Blood Sugar

  • Insulin: Decreases blood sugar levels.
  • Glucagon: Increases blood sugar levels.
  • Normally, only one of these hormones is active at a given time, depending on blood sugar levels and feeding status.

Endocrine Pancreas

  • Pancreatic islets (islets of Langerhans) are clusters of alpha and beta cells.
  • Alpha cells: Release glucagon.
  • Beta cells: Release insulin.
Glucagon
  • Stimulus: Decreased blood sugar levels.
  • Targets:
    • Muscle: Causes protein breakdown, converting amino acids into sugar.
    • Liver: Induces gluconeogenesis (making new glucose from non-sugar molecules) and glycogenolysis (breakdown of glycogen).
    • Adipocytes (fat cells): Causes lipolysis (breakdown of lipids into fatty acids).
  • Effects: Mobilizes energy, ensuring sugar molecules are available in the blood.
  • Responsible for mobilizing energy molecules to the blood when the supply is running low.
  • Protein breakdown into amino acids.
  • In the liver: Gluconeogenesis and glycogenolysis break down into glucose.
  • Adipocytes produce fatty acids.
  • All of those molecules can enter the Krebs cycle, which produces ATP in our mitochondria.
  • Glucose is the preferable way, but we can still do it.
Insulin
  • Stimulus: High glucose levels.
  • Targets: Most cells of the body.
  • Effects:
    • Causes glucose uptake and amino acid uptake in most cells.
    • Liver: Induces glycogenesis (building up glycogen).
    • Fat tissues: Promotes glycogenesis (using fatty acids to produce more fat tissue).
    • Causes satiety (feeling of fullness).
  • Action of Insulin:
    • Binds to receptors on cell membranes.
    • Triggers the production of vesicles containing GLUT4.
    • GLUT4 molecules insert into the plasma membrane, creating channels for glucose to enter the cell.
    • Glucose moves down the concentration gradient from the blood into the cells.
    • Specific transport is a symporter using gradient of sodium as well.
Example
  • After a meal: Glucose levels are high, leading to insulin production.
  • Insulin causes cells to take up glucose, decreasing blood sugar levels.
  • Fasting for four hours: Glucose levels are low, leading to glucagon production.
  • Glucagon causes the liver to release glucose into the blood, increasing blood sugar levels.

Diabetes Mellitus

  • Initially identified by the presence of glucose in the urine.
Normal Kidney Function
  • Blood is filtered in the kidneys.
  • Glucose enters kidney tubules but is reabsorbed back into the blood.
  • 100% of filtered glucose is reclaimed.
  • Urine contains no glucose.
Diabetes
  • Hyperglycemia (high blood sugar levels).
  • Kidneys filter blood, but glucose transporters are overwhelmed.
  • Excess glucose remains in the kidney tubules and is excreted in the urine (glucosuria).
Types of Diabetes
  • Type 1 diabetes:
    • Autoimmune destruction of beta cells in the pancreas.
    • Leads to a decline in insulin production.
    • Results in hyperglycemia, glucosuria, polyuria, and dehydration.
    • Treatment: Insulin injections.
  • Type 2 diabetes:
    • Beta cells become less sensitive to insulin.
    • Produce less insulin than normal.
    • Cells have fewer insulin receptors and GLUT4 channels.
    • Multifactorial causes: obesity, age above 40, genetic predisposition.
    • Cellular insensitivity to insulin due to chronic hyperglycemia.
    • Inflammation of the pancreas triggered by high sugar/saturated fat intake.
    • Immediate effects: insulin sensitivity to the cells that would cause hyperinsulinemia and hyperglycemia.
  • Resulting conditions could be very similar to what we saw in diabetes two.
  • In some cases those beta cells will completely lose the sensitivity.
  • We could actually develop diabetes type one from diabetes type two.
    • Treatment:
      • Change the diet to lose weight if obesity is something that is triggering.
      • Drugs to control blood sugar and improve insulin sensitivity.
      • Lifestyle changes.
  • Gestational diabetes: Develops during pregnancy.
Adrenal Gland
  • Located on top of each kidney.
  • Two main parts: medulla (inner), cortex (outer).
  • Both covered by Connective tissue capsule protecting the entire gland.
  • The cortex is divided into three regions: outer, middle, and inner.
  • Each region produces different hormones.
Adrenal Medulla
  • Controlled by the sympathetic nervous system.
  • Sympathetic stimulation causes the adrenal medulla to produce epinephrine and norepinephrine (catecholamines).
  • Effects: Fuel mobilization and stimulation of the body (fight or flight response).
  • Preganglionic sympathetic stimulation, preganglionic from the sympathetic central nervous system.
  • Releases neurotransmitters, which will then trigger the cells of the adrenal medulla to release epinephrine and norepinephrine.
  • Acts on the effects of fight or flight.
  • Heart rate, dilation of your people
  • Airways increase dilation for more breathing,etc.
Metabolic Effects of Epinephrine and Norepinephrine
  • Stimulate lipolysis (breakdown of triglycerides into fatty acids).
  • Stimulate glycogenolysis (breakdown of glycogen).
  • Promote gluconeogenesis (making glucose from non-carbohydrate sources).
Comparison with Glucagon
  • Both glucagon and epinephrine/norepinephrine promote fuel mobilization.
  • Glucagon release is triggered by hypoglycemia (low blood sugar).
  • Epinephrine/norepinephrine release is triggered by fight or flight situations requiring quick energy.
Question & Answer
  • Adrenal medulla secretions are triggered by both responds to sympathetic stimulation, not the parasympathetic.
  • The adrenal medulla is modified post synaptic sympathetic ganglion. This is correct.
  • The production of the adrenal medulla prolong the effects of the sympathetic response. Yes, that is also correct.
Adrenal Cortex
  • Outer part of the adrenal gland.
  • Divided into three regions, each releasing a different hormone.
  • Three hormones: aldosterone, cortisol, and androgens.
  • Aldosterone: Released by the outer cortex.
  • Cortisol: Released by the middle cortex.
  • Androgens: Released by the inner cortex.
Aldosterone
  • Regulates salt balance.
  • Stimulus: Low sodium concentration (low osmolarity).
  • Effects:
    • Kidney reabsorption of sodium and water.
    • Excretion of potassium and hydrogen ions.
    • Helps maintain pH balance.
Comparison with ADH
  • ADH (antidiuretic hormone) and aldosterone have similar actions but opposite stimuli.
  • Low sodium concentration: Aldosterone is released, causing sodium and water retention.
  • High osmolarity: ADH is released, causing water retention.
  • Both ADH and aldosterone can be found in the circulation at the same time if you were experience some type of dehydration.
Cortisol
  • Associated with stress.
  • Stress -> hypothalamus (corticotropic releasing hormone) -> anterior pituitary gland (adrenocorticotropic hormone) -> adrenal cortex (cortisol).
  • Stress defined: Any physical or mental state that upsets homeostasis or threatens well-being.
  • Examples of stress: Injury, illness, intense exercise, pain, grief, depression, anger.
Effects of Cortisol
  • Mobilization of fuel.
  • Suppression of the immune system.
  • Fuel Mobilization:
    • Lipolysis.
    • Glycogenolysis.
    • Gluconeogenesis.
Comparison with Glucagon and Epinephrine/Norepinephrine
  • Cortisol, glucagon, and epinephrine/norepinephrine all promote fuel mobilization.
  • Stimuli:
    • Hypoglycemia: Glucagon.
    • Fight or flight: Epinephrine/norepinephrine.
    • Stress: Cortisol.
Androgens
  • Sex hormones.
  • Released by the inner adrenal cortex.
  • Small contribution to sex hormone production compared to the gonads (ovaries and testes).
Roles of Sex Hormones

  • Control of menstrual cycle (females).

  • Sperm production (males).

  • Development of secondary sex characteristics (both males and females).

  • Salt. Aldosterone is related to salt

  • Sugar (Cortisol) because it causes that sugar mobilization.

  • Androgen sex is releases the sex hormones. They can become testosterone.

Adrenal Tumors
  • Can cause hypersecretion of hormones.
  • During embryonic development: A genetically female individual could develop male genitalia.
  • Later in life: Females could develop male secondary characteristics.
  • Supplement androgenes produced by ovaries or tests.