Master Nursing Study Guide: Homeostasis, Perfusion, Shock, Kidney, and Immune System

Master Nursing Study Guide

Homeostasis

  • Definition: Homeostasis refers to the body's ability to maintain a stable internal environment despite external changes.

  • Key Mechanisms of Homeostasis:

    • Buffers: Substances that help maintain pH levels by neutralizing acids or bases.

    • Lungs: Regulate carbon dioxide and oxygen levels in the blood.

    • Kidneys: Maintain fluid and electrolyte balance, as well as acid-base balance.

Mechanisms that Maintain Internal Balance

Key Mechanisms

  • Sweating: Helps in thermoregulation.

  • Shivering: Generates heat to maintain body temperature.

  • Vasodilation: Expands blood vessels to dissipate heat.

  • Vasoconstriction: Narrows blood vessels to retain heat.

Balance Types and Regulators

  • Temperature:

    • Main Regulator: Hypothalamus

  • pH:

    • Main Regulators: Kidneys and hormones

  • Electrolytes:

    • Regulated by kidneys and hormones

  • Fluid Volume:

    • Regulated by kidneys and heart. Key hormones include:

    • ADH (Antidiuretic Hormone): Promotes water reabsorption in kidneys.

    • Aldosterone: Increases sodium reabsorption and potassium excretion.

    • ANP (Atrial Natriuretic Peptide): Reduces blood volume by promoting sodium excretion.

    • Thirst Mechanism: Stimulated by dehydration.

  • Cardiac Output Control and CO2/HCO3 Balance:

    • Key Regulators: Aldosterone, PTH (Parathyroid Hormone), and Na/K pump.

Perfusion and Oxygen/Nutrient Delivery

  • Definition of Perfusion: Refers to the passage of blood through the blood vessels to deliver oxygen and nutrients to tissues.

  • Requirements for Adequate Perfusion:

    • Normal cardiac output

    • Appropriate vascular tone

    • Sufficient blood volume

  • Consequences of Impaired Perfusion:

    • Leads to hypoxia (lack of oxygen), ischemia (lack of blood flow), and organ dysfunction.

Compensatory Mechanisms During Hypovolemia

System

Mechanism

Effect

Neural (SNS)

↑ Heart Rate (HR), vasoconstriction

Maintains blood pressure (BP), directs blood to vital organs

Hormonal (RAAS)

Renin → Angiotensin II → Aldosterone

Increases blood volume and pressure

ADH

Water reabsorption in kidneys

Reduces urine output

Adrenal Medulla

Release of epinephrine/norepinephrine

Increases heart rate and vascular resistance

Renal

Capillary shift of fluid into vessels

Aids in maintaining perfusion

Early Signs and Symptoms of Imbalance

  • Increased Sodium and Water Retention:

    • Leads to increased blood volume.

  • Increased Heart Rate and Contractility:

    • A response to maintain adequate perfusion.

Type-Specific Early Signs

  • Temperature Imbalance:

    • Symptoms: Sweating, shivering, flushed or cool skin, confusion.

  • pH Imbalance:

    • Symptoms: Abnormal breathing patterns, tingling, dizziness.

  • Electrolyte Imbalance:

    • Symptoms: Weakness, muscle cramping, arrhythmias, numbness.

  • Fluid Volume Imbalance:

    • Symptoms: Thirst, weak pulse, edema, orthostatic hypotension.

  • Perfusion Issues:

    • Symptoms: Tachycardia, pallor, anxiety, delayed capillary refill.

Hypovolemia and Hypovolemic Shock

  • Definition of Hypovolemia: A condition resulting from fluid or blood loss.

  • Hypovolemic Shock: A severe progression that leads to decreased perfusion and organ failure.

Stages of Hypovolemic Shock

Stage

Description

Findings

Initial

Mild loss (less than 15%)

Thirst, anxiety, normal BP

Compensatory

15-30% loss

Tachycardia, cool skin, ↓ urine output

Progressive

30-40% loss

Hypotension, confusion, oliguria

Refractory

More than 40% loss

Severe hypotension, organ failure

Management of Hypovolemic Shock

  • Stop fluid loss.

  • Restore volume through:

    • IV crystalloids

    • Blood transfusion

  • Provide oxygen.

  • Monitor urine output and mental status.

Waste Elimination and Osmotic Control

  • Kidney Functions:

    • Fluid Balance: Regulates water reabsorption and excretion.

    • Electrolyte Balance: Adjusts levels of Na, K, Ca²⁺, Cl⁻, and PO₄³⁻.

    • Acid-Base Balance: Excretes H⁺ ions, reabsorbs HCO₃⁻.

    • Blood Pressure Regulation: Activates RAAS (Renin-Angiotensin-Aldosterone System).

    • Waste Removal: Excretes urea, creatinine, and toxins.

  • Outcome of Kidney Function:

    • Stable blood volume and pressure.

    • Supports nerve and muscle function.

    • Maintains blood pH within the range of 7.35 to 7.45.

    • Provides long-term blood pressure control.

    • Prevents buildup of metabolic wastes.

Key Immune Cells

Overview of Immune Cells

Cell Type

System

Main Function

Clinical Note

Neutrophils

Innate

Phagocytosis; first responders

Increase in bacterial infections

Macrophages

Innate to Adaptive

Phagocytosis; antigen presentation

Activate lymphocytes; increase in viral infections

Lymphocytes

Adaptive

B cells: produce antibodies; T cells: cell-mediated defense

Decrease in immunosuppressed conditions

NK Cells

Innate

Destroy virus-infected and tumor cells

Patrol for abnormalities

Summary of Immune Functions

  • Neutrophils: Provide fast defense against bacterial infections.

  • Macrophages: Involved in phagocytosis and activation of the immune response.

  • Lymphocytes: Provide targeted, long-term immunity through memory cells.

  • NK Cells: Survey the body for tumor and virus-infected cells, acting as part of the innate immune system.