Learn: Chapter 14 and 15 Study Guide | Quizlet

Hydrogen Ion Regulation

The body must tightly regulate the concentration of hydrogen ions (H⁺) because even small changes can disrupt cellular function.

Isohydric buffering

Means that all buffer systems in the body function together to maintain a constant pH.

Note: All buffer systems are in equilibrium, meaning a change in one system affects the others.

What is Carbonic anhydrase?

The enzyme that accelerates the conversion of CO₂ and water into carbonic acid.

What are the 2 major buffer systems

(Open buffer) Bicarbonate buffer system

(Closed buffer) Non-Bicarbonate Buffer system

bicarbonate buffer system

The bicarbonate buffer system is called an open system because one component (CO₂) can leave the body through the lungs.

CO₂ controlled by lungs. HCO₃⁻ controlled by kidneys

Non Bicarbonate Buffers

Closed buffer systems do not leave the body and remain within body fluids

Types of non bicarbonate buffers

Hemoglobin buffer system: Hemoglobin binds hydrogen ions.

Protein buffers: Proteins contain amino groups that can bind H⁺.

Phosphate buffers: Important mainly inside cells and in the kidneys. These systems help temporarily stabilize pH until the lungs or kidneys correct the imbalance.

What is a buffer solution?

A buffer solution is a mixture of a weak acid and its corresponding base. Buffers work by minimizing changes in pH when acids or bases are added.

Henderson-Hasselbalch Equation

Double validation. The Henderson-Hasselbalch equation describes the relationship between: pH, bicarbonate (HCO₃⁻), and carbon dioxide (PaCO₂).

𝑝𝐻 = 6.1 + log ( 𝐻𝐶𝑂3/ 0.03 × 𝑃𝑎𝐶𝑂2)

Acid Excretion (Kidneys)

The kidneys regulate acid-base balance by removing hydrogen ions and controlling bicarbonate levels3

3 Kidney Functions in Acid-Base Balance

1. Excretion of hydrogen ions (H⁺) in urine

2. Reabsorption of bicarbonate (HCO₃⁻) into the blood

3. Secretion of Bicarbonate into the Kidney (Tubules)

Nephron

The nephron is the functional unit of the kidney responsible for regulating: Acid-base balance, Electrolyte balance, and Fluid balance

Kidney Anatomy

• Renal artery → brings blood to the kidney

• Renal vein → carries filtered blood away

• Renal tubule → site where acid-base regulation occurs

• Kidney → organ responsible for filtration and acid excretion

Reabsorption of Bicarbonate (HCO₃⁻)

The kidneys reabsorb bicarbonate back into the blood to maintain normal pH. Most bicarbonate reabsorption occurs in the: Proximal tubule

Process of Reabsorption of Bicarbonate (HCO₃⁻)

1. CO₂ diffuses into tubular cells

2. Carbonic anhydrase forms carbonic acid

3. Carbonic acid splits into: 𝐻 + + 𝐻𝐶𝑂3

4. HCO₃⁻ returns to the blood. This helps maintain normal buffering capacity.

Secretion of Bicarbonate into the Kidney (Tubules)

When the body has too much base (alkalosis), the kidneys can: Secrete bicarbonate into urine and store or remove excess bicarbonate. This helps lower blood pH toward normal.

Excretion of Hydrogen Ions

The kidneys remove acid from the body by excreting H⁺ into the urine. This process helps eliminate non-volatile acids that cannot be removed by the lungs.

Anion Gap

The anion gap helps identify causes of metabolic acidosis. Formula: Anion Gap = 𝑁𝑎 + − (𝐶𝑙 − + 𝐶𝑂₂)

Normal anion gap range

9-14 𝑚𝐸𝑞/L

What does a normal gap mean? A high gap?

Normal gap - Bicarbonate loss or dilution

High gap - Metabolic acidosis from acid accumulation

Common Causes of High Anion Gap

MUDPILES:

• M - Methanol

• U - Uremia (kidney failure)

• D - Diabetic ketoacidosis

• P - Propylene glycol

• I - Infection / Iron / Isoniazid

• L - Lactic acidosis

• E - Ethylene glycol

• S - Salicylates

Respiratory Compensation (Lungs)

Controls CO₂ levels by altering ventilation.

Example: Metabolic acidosis → hyperventilation → ↓ CO₂

Renal Compensation (Kidneys)

Controls H⁺ excretion and HCO₃⁻ reabsorption.

Example: Respiratory acidosis → kidneys retain bicarbonate

Causes of Respiratory Acidosis

• Drug overdose (opioids, sedatives)

• Head injury

• Stroke

• COPD

Causes of Respiratory Alkalosis

• Pulmonary embolism

• Pneumonia (early stages)

• Anxiety / panic attacks

• Pain

• Fever

Causes of Metabolic Acidosis

• Diabetic ketoacidosis (DKA)

• Lactic acidosis

• Kidney failure (uremia)

• Methanol poisoning

• Severe diarrhea

Causes of Metabolic Alkalosis

• Vomiting

• Diuretic therapy (loop or thiazide)

• Hypokalemia

• Hypochloremia

The Medullary Center

The medulla oblongata in the brainstem contains the main centers that control breathing. These centers generate the basic rhythm of respiration.

Two neuron groups that regulate breathing

Dorsal and Ventral Groups

Where is the Dorsal Respiratory Group (DRG) and what are it's functions?

Location: medulla

Function: Controls inspiration, Generates the basic breathing rhythm, and Sends signals to the diaphragm through the phrenic nerve

Where is the Ventral Respiratory Group (DRG) and what are it's functions?

Location: medulla

Function: Controls both inspiration and expiration, Mainly active during forced breathing

Pons

The pons modifies and fine-tunes the breathing pattern

What are the two important centers that exist in the pons?

Pneumotaxic Center and Apneustic Center

Pneumotaxic Center

Location: upper pons

Function: Limits inspiration and helps regulate respiratory rate

If stimulation increases → shorter inspiration and faster breathing

Apneustic Center

Location: lower pons

Function: Promotes prolonged inspiration and stimulates inspiratory neurons.

Balance between pneumotaxic and apneustic centers produces a normal breathing rhythm.

Hering-Breuer reflex

If the lungs stretch too much: → Vagus nerve signals the brain → Inspiration stops

Head Paradoxical Reflex

The Head paradoxical reflex is a lung reflex that stimulates further inspiration when the lungs are inflated. Instead of stopping inspiration like the Hering-Breuer inflation reflex, it enhances or prolongs inspiration.

Vasovagal

Blood and vagus response when airways need to restrict due to a pollutant

Central Chemoreceptors

Central chemoreceptors are specialized receptors located in the medulla oblongata that regulate breathing by detecting changes in pH of the cerebrospinal fluid (CSF). Their primary stimulus is carbon dioxide (CO₂).

Peripheral Chemoreceptors

Peripheral chemoreceptors are sensory receptors that detect changes in arterial blood oxygen, carbon dioxide, and pH. They help regulate ventilation by sending signals to the respiratory centers in the medulla.

Hypoxic drive

Stimulation to breathe is low CO2