Alterations in Cell Function - Part 3

Recap of Parts 1 and 2

• Disruptions in cell function can reduce ATP production.
• Causes include:
  • Hypoxia
  • Nutritional problems: Less glucose or vitamins
  • Solute imbalances: Resting membrane potential abnormalities, acid-base balance

Fluid Shifts

• Importance of Water:
  • The body is 60% water; blood is 90% water.
  • Water moves between body compartments to maintain balance.
• Osmosis:
  • Movement of water across semi-permeable membranes.
  • Water moves from low concentration to high concentration areas.
  • Osmolality: Measure of concentration (water to solute ratio).

Understanding Osmolality

• Concentration and Osmolality:
  • High concentration = More solutes, less water.
  • Low concentration = Less solutes, more water.
• Juice Analogy:
  • Removing water increases concentration (analogous to dehydration).
• Measuring Osmolality:
  • Serum osmolality can be measured as a lab value.

Tonicity and Related Terms

• Tonicity: Related to salinity of a substance (e.g., 0.9% normal saline for isotonic).
• Osmotic Pressure:
  • Pressure caused by solutes.
  • Oncotic Pressure: Specific to proteins.
• Conditions:
  • Hyperosmolar: High concentration, high osmotic pressure.
  • Hypoosmolar: Low concentration, low osmotic pressure.

Clinical Scenarios and Treatment

• IV Fluids:
  • Isotonic: 0.9% saline.
  • Hypotonic: 0.45% saline.
  • Hypertonic: 3% saline.

Fluid Volume Deficit (Dehydration)

• Causes:
  • Inability to intake water (e.g., vomiting, diarrhea).
  • Diuretics or increased urination.
• Symptoms:
  • Dry mucous membranes, poor skin turgor, sunken eyes.
  • Low blood pressure, oliguria (low urine output), CNS changes.
• Compensation: Renin-angiotensin-aldosterone system (RAAS).

Renin-Angiotensin-Aldosterone System (RAAS)

• Triggered by:
  • High blood osmolality, low fluid volume, low blood pressure.
• Mechanism:
  • Renin → Angiotensin I → Angiotensin II.
  • Angiotensin II: Vasoconstriction, aldosterone release (sodium and water retention).

Fluid Volume Overload (Edema)

• Causes:
  • Excessive water intake, kidney dysfunction, hormonal imbalances (e.g., SIADH).
• Symptoms:
  • Edema, pulmonary edema (cough, shortness of breath), CNS effects.
• Compensation: Natriuretic peptide system (NPS) - Diuresis stimulation.

Summary

• Key Players:

  • Fluid Shifts: Sodium, chloride, proteins, water.
  • Acid-Base Imbalance: pH, CO2, bicarbonate.
  • Resting Membrane Potential: Calcium, potassium (hyper/hypo polarization).

• Commonality: All can lead to decreased cell function and ATP production.

Study Tip: Understand the concepts of osmosis, osmolality, and compensatory mechanisms to manage fluid shifts.