Fluid and Electrolyte Balance in the Body

Acid-Base Balance and Fluid Electrolyte Balance

• Metabolic alkalosis is characterized by an increase in bicarbonate (HCO3) levels.
• Osmoreceptors in the hypothalamus are stimulated by a drop in plasma volume of 10%–15% or a rise in plasma osmolality by 1–2%.
• The three primary hormones that mediate fluid and electrolyte balance are Antidiuretic hormone (ADH), Aldosterone, and Natriuretic peptides (ANP and BNP).
• The body has two major fluid compartments: Intracellular fluid (ICF) and Extracellular fluid (ECF), which includes plasma and interstitial fluid.
• An acid is a substance that can donate a hydrogen ion (H+) to another substance, while a base is a substance that can accept a hydrogen ion (H+) from another substance.
• A buffer is a solution that can resist changes in pH upon the addition of an acid or a base.
• The three physiological buffers are the Carbonic acid-bicarbonate buffer system, Phosphate buffer system, and Protein buffer system.
• The Carbonic acid-bicarbonate buffer system is the most important ECF buffer system.

Respiratory and Metabolic Acid-Base Disturbances

• An increase in CO2 can lead to a lower pH (acidic), while a decrease in CO2 can lead to a higher pH (alkaline).
• Respiratory acidosis is caused by an increase in CO2, while respiratory alkalosis is caused by a decrease in CO2.
• An increase in HCO3 can lead to a higher pH (alkaline), while a decrease in HCO3 can lead to a lower pH (acidic).
• Metabolic alkalosis is caused by an increase in HCO3, while metabolic acidosis is caused by a decrease in HCO3.

Energy Pathways and Hormones

• Glucose is the primary fuel for the body's energy needs.
• Insulin is the hormone that controls the absorptive state, promoting the uptake and utilization of nutrients.
• Electron transport chain (ETC) combined with oxidative phosphorylation is the energy pathway responsible for producing the most ATP in cells.
• During the postabsorptive state (fasting state), glucose levels fall, and the dominant hormones are glucagon, cortisol, and epinephrine.
• Insulin stimulates glycogenesis.
• Gluconeogenesis is the metabolic process by which glucose is synthesized from non-carbohydrate sources, such as amino acids, glycerol, and lactate, primarily in the liver.

Fatty Acid Metabolism and Vitamins

• Fat-soluble vitamins include Vitamins A, D, E, and K, which are absorbed along with dietary fats and can be stored in the body's fatty tissues.
• Beta oxidation is the metabolic process by which fatty acid molecules are broken down in the mitochondria to generate acetyl-CoA, NADH, and FADH2, which enter the Krebs cycle and electron transport chain to produce ATP.
• The products of fatty acid beta oxidation are acetyl-CoA, NADH, and FADH2.
• Ketoacidosis is a dangerous condition characterized by high levels of ketones in the blood, which can be fatal for diabetics if left untreated.

Electrolyte Balance

• The major ECF cations and anions are Sodium (Na+), Potassium (K+), Calcium (Ca2+), and Magnesium (Mg2+) as cations, and Chloride (Cl-), Bicarbonate (HCO3-), and Phosphate (PO4-) as anions.
• Major ICF cation: Potassium (K+) and Major ICF anions: Proteins and Phosphate (PO4-)