lOMoARcPSD|70468202
Comprehensive Study Guide: Fluid,
Electrolytes, Acid-Base, and Nervous System
Disorders
This study guide synthesizes complex pathophysiological concepts regarding fluid and
electrolyte homeostasis, acid-base imbalances, neurological disorders, and renal/gastrointestinal
conditions. It is designed to facilitate deep review and mastery of the provided course materials.
--------------------------------------------------------------------------------
I. Fluid and Electrolyte Homeostasis
Fluid Compartments and Composition
The human body is approximately 60% water (70% in infants; 50% in females; 45% in elderly
women). Fluid is distributed into two primary compartments:
• Intracellular Fluid (ICF): Fluid contained within the cells (approx. 40% of body
weight).
• Extracellular Fluid (ECF): Fluid outside the cells (approx. 20% of body weight),
further divided into:
o Intravascular Fluid: Plasma within the capillaries/blood vessels.
o Interstitial Fluid: Fluid "stuck" between cells.
o Transcellular Fluid: Includes specialized fluids like cerebrospinal fluid (CSF).
Regulatory Mechanisms
The body employs several mechanisms to maintain fluid balance:
• Thirst Mechanism: Located in the hypothalamus; osmoreceptors identify changes in
fluid volume and concentration to promote intake.
• Antidiuretic Hormone (ADH): Controls fluid exit via urine by promoting water
reabsorption in kidney tubules.
• Aldosterone: Promotes reabsorption of water and sodium (Na+) while excreting
potassium (K+).
, lOMoARcPSD|70468202
• ANP/BNP: Released by cardiac muscle in response to increased pressure; these
hormones excrete water and sodium while retaining potassium.
Pressure Dynamics and Edema
Fluid movement is governed by two main pressures:
1. Hydrostatic Pressure: A "pushing" pressure that moves fluid out of the vessel.
2. Osmotic Pressure: A "pulling" pressure (often driven by proteins like albumin) that
draws fluid into the vessel.
Causes of Edema (SATA):
• Increased capillary hydrostatic pressure (pushes fluid out).
• Decreased capillary osmotic pressure (loss of "pulling" power due to low plasma
proteins).
• Increased capillary permeability (seen in inflammatory responses where histamine allows
leakage).
• Obstruction of lymphatic circulation (prevents fluid return to general circulation).
Fluid Volume Imbalances
Fluid Volume Excess
Feature Fluid Volume Deficit (Dehydration)
(Hypervolemia)
Kidney, liver, or heart failure; high
Causes Fluid loss, inadequate intake.
sodium intake; IV fluid overload.
Low BP, Tachycardia, Weak pulse, High BP, Bounding pulse, Jugular
Dry mucous membranes, Decreased Vein Distention (JVD), Weight
Manifestations
skin turgor, Confusion, Decreased gain, Edema, Dyspnea/Pulmonary
urine output. congestion.
Hemoconcentration (Increased lab Hemodilution (Decreased lab
Labs
values). values).
Comprehensive Study Guide: Fluid,
Electrolytes, Acid-Base, and Nervous System
Disorders
This study guide synthesizes complex pathophysiological concepts regarding fluid and
electrolyte homeostasis, acid-base imbalances, neurological disorders, and renal/gastrointestinal
conditions. It is designed to facilitate deep review and mastery of the provided course materials.
--------------------------------------------------------------------------------
I. Fluid and Electrolyte Homeostasis
Fluid Compartments and Composition
The human body is approximately 60% water (70% in infants; 50% in females; 45% in elderly
women). Fluid is distributed into two primary compartments:
• Intracellular Fluid (ICF): Fluid contained within the cells (approx. 40% of body
weight).
• Extracellular Fluid (ECF): Fluid outside the cells (approx. 20% of body weight),
further divided into:
o Intravascular Fluid: Plasma within the capillaries/blood vessels.
o Interstitial Fluid: Fluid "stuck" between cells.
o Transcellular Fluid: Includes specialized fluids like cerebrospinal fluid (CSF).
Regulatory Mechanisms
The body employs several mechanisms to maintain fluid balance:
• Thirst Mechanism: Located in the hypothalamus; osmoreceptors identify changes in
fluid volume and concentration to promote intake.
• Antidiuretic Hormone (ADH): Controls fluid exit via urine by promoting water
reabsorption in kidney tubules.
• Aldosterone: Promotes reabsorption of water and sodium (Na+) while excreting
potassium (K+).
, lOMoARcPSD|70468202
• ANP/BNP: Released by cardiac muscle in response to increased pressure; these
hormones excrete water and sodium while retaining potassium.
Pressure Dynamics and Edema
Fluid movement is governed by two main pressures:
1. Hydrostatic Pressure: A "pushing" pressure that moves fluid out of the vessel.
2. Osmotic Pressure: A "pulling" pressure (often driven by proteins like albumin) that
draws fluid into the vessel.
Causes of Edema (SATA):
• Increased capillary hydrostatic pressure (pushes fluid out).
• Decreased capillary osmotic pressure (loss of "pulling" power due to low plasma
proteins).
• Increased capillary permeability (seen in inflammatory responses where histamine allows
leakage).
• Obstruction of lymphatic circulation (prevents fluid return to general circulation).
Fluid Volume Imbalances
Fluid Volume Excess
Feature Fluid Volume Deficit (Dehydration)
(Hypervolemia)
Kidney, liver, or heart failure; high
Causes Fluid loss, inadequate intake.
sodium intake; IV fluid overload.
Low BP, Tachycardia, Weak pulse, High BP, Bounding pulse, Jugular
Dry mucous membranes, Decreased Vein Distention (JVD), Weight
Manifestations
skin turgor, Confusion, Decreased gain, Edema, Dyspnea/Pulmonary
urine output. congestion.
Hemoconcentration (Increased lab Hemodilution (Decreased lab
Labs
values). values).
