Adrenal Gland and Blood Glucose Control Notes

Adrenal Gland

  • Triangular gland superior to the kidneys, also known as the suprarenal gland.
  • Two main regions:
    • Adrenal Cortex (outer region)
      • Three zones:
        • Zona glomerulosa
          • Function:
          • Hormone:
        • Zona fasciculata
          • Function:
          • Hormone:
        • Zona reticularis
          • Function:
          • Hormone:
    • Adrenal Medulla (center)
      • Produces hormones used in the sympathetic nervous system (similar to neurotransmitters).
      • Main hormones: epinephrine (adrenaline) and norepinephrine.
      • Cortisol: manages chronic stress.

Renin-Angiotensin-Aldosterone System (RAAS)

  • Crucial system for chronic blood pressure management.

  • Kidney's Role:

    • Kidney contains sensors that detect changes in blood volume and pressure.
    • If there's a drop in volume or pressure, the kidney produces renin.

  • Liver's Role:

    • The liver produces angiotensinogen.
    • Renin converts angiotensinogen into angiotensin I.
    • Renin+Angiotensinogen→AngiotensinIRenin + Angiotensinogen \rightarrow Angiotensin I

  • Lungs' Role:

    • The lungs contain angiotensin-converting enzyme (ACE).
    • ACE converts angiotensin I into angiotensin II.
    • AngiotensinI+ACE→AngiotensinIIAngiotensin I + ACE \rightarrow Angiotensin II

  • Angiotensin II's Functions:

    • Stimulates the sympathetic nervous system causing vasoconstriction, which elevates blood pressure.
      • Analogy: constricting a water hose opening increases water pressure.
    • Stimulates the adrenal cortex (zona glomerulosa) to produce aldosterone.
      • Aldosterone reabsorbs sodium ions (Na+Na^+), leading to water reabsorption.
      • This increases blood volume which corrects the initial drop.
    • Stimulates the release of antidiuretic hormone (ADH) from the posterior pituitary gland.
      • ADH causes the kidneys to retain water, increasing blood volume.

  • RAAS Mechanism Summary:

    • Drop in blood volume/pressure triggers renin release.
    • Renin initiates a cascade, ultimately causing the body to retain volume and increase pressure.

  • Clinical Significance:

    • Hypertension Treatment:
      • ACE inhibitors inhibit angiotensin converting enzyme (ACE).
      • This reduces vasoconstriction, volume retention, and lowers blood pressure.
      • Knowing normal RAAS function helps understand how ACE inhibitors work to treat hypertension.

Blood Glucose Control by the Pancreas

  • Function of the Pancreas:

    • The pancreas produces hormones to regulate glucose levels.

  • Normal Blood Glucose:

    • Blood glucose levels fluctuate throughout the day within an upper and lower limit.
    • Levels outside of these limits indicate a problem.

  • Hyperglycemia:

    • Condition: High blood glucose levels (exceeding the upper limit).
    • Pancreas increases insulin production.

  • Insulin's Role:

    • Promotes the uptake of glucose from the bloodstream into cells.
    • Reduces glucose levels in the bloodstream.
    • Inside the cells, glucose is broken down to produce energy - ATP.
    • \Process:
      • Glycolysis: The first step of the breaking down of Glucose (6-carbon) into 2 molecules with 3 carbons each.
        • Glucose→2×(3−carbon molecules)Glucose \rightarrow 2 \times (3-carbon \ molecules)
      • Krebs cycle (citric acid cycle).
      • Electron transport chain.

  • Hypoglycemia:

    • Condition: Low blood glucose levels (falling below the lower limit).
    • Pancreas increases glucagon production.

  • Glucagon's Role:

    • Promotes the breakdown of stored glucose (glycogen) in the liver into glucose.
    • Increases glucose levels in the bloodstream, bringing it back to normal range.