Chemical Balance

What is the normal blood pH?

7.35–7.45

What blood pH values are generally incompatible with life?

• Below 7.0

• Above 7.7

What is acidosis?

Blood pH below 7.35 due to excess hydrogen ions (H⁺).

What happens to potassium during acidosis?

• H⁺ moves into cells.

• K⁺ moves out of cells.

  • Results in hyperkalemia.

What are the effects of acidosis on nerve and muscle cells?

Cells become less responsive due to membrane hyperpolarization.

What are symptoms of severe acidosis?

• Confusion

• Disorientation

• CNS depression

• Coma

  • Death

What is alkalosis?

Blood pH above 7.45 due to decreased hydrogen ions.

What happens to potassium during alkalosis?

• H⁺ moves out of cells.

• K⁺ moves into cells.

  • Results in hypokalemia.

What happens to nerve and muscle cells during alkalosis?

They become overstimulated because membranes are depolarized.

What causes respiratory acidosis?

Hypoventilation

• Breathing is too slow for the amount of CO₂ being produced.

What happens to CO₂ during respiratory acidosis?

CO₂ accumulates in the blood.

What happens to pH during respiratory acidosis?

blood pH decreases below the normal range of 7.35 to 7.45 (becoming acidic)

What is a common cause of respiratory acidosis?

Emphysema

What would an ABG show in respiratory acidosis?

High PCO₂

What causes respiratory alkalosis?

Hyperventilation

What happens to CO₂ during respiratory alkalosis?

CO₂ is eliminated faster than it is produced.

What happens to blood pH during respiratory alkalosis?

Less CO₂ means fewer H⁺ ions are produced, so pH increases.

What causes metabolic acidosis?

Excess acid production or loss of base.

What are common causes of metabolic acidosis?

• Lactic acid buildup

• Ketone bodies (diabetes mellitus or alcoholism)

• Aspirin overdose

• Chronic diarrhea

  • Laxative abuse

Which acids commonly cause metabolic acidosis?

• Lactic acid

  • Ketone bodies

What causes metabolic alkalosis?

Too much base or loss of acid.

What are common causes of metabolic alkalosis?

• Excessive antacid use

  • Chronic vomiting (loss of stomach acid)

What is respiratory compensation?

The lungs adjust ventilation to correct a metabolic acid-base disorder.

How do the lungs compensate for metabolic acidosis?

Increase ventilation (hyperventilation)

How do the lungs compensate for metabolic alkalosis?

the body compensates through alveolar hypoventilation, slowing breathing to retain carbon dioxide (PaCO₂

What is renal compensation?

The kidneys adjust H⁺ secretion to correct a respiratory acid-base disorder.

How do the kidneys compensate for respiratory acidosis?

• Secrete more H⁺

• Retain more bicarbonate (HCO₃⁻)

This raises blood pH.

How do the kidneys compensate for respiratory alkalosis?

• Secrete less H⁺

• Excrete more bicarbonate (HCO₃⁻)

This lowers blood pH.

Is renal compensation fast or slow?

slow

Which compensation system is faster?

The respiratory system (minutes).

Which compensation system is stronger?

The renal system, because it can fully restore normal pH.

What is compensated acidosis or alkalosis?

The body has corrected the pH imbalance through either:

• Respiratory compensation

  • Renal compensation

What is uncompensated acidosis or alkalosis?

The body cannot correct the pH imbalance without medical intervention.

Why is acid-base balance important?

Because enzymes are very sensitive to pH. Even small changes in pH can:

• Shut down metabolic pathways

• Alter protein structure

  • Disrupt normal cellular function

What is the normal blood pH?

7.35–7.45

What constantly challenges acid-base balance?

Normal metabolism produces acids, including:

• Lactic acid

• Fatty acids

• Ketone bodies

  • Carbonic acid (from CO₂)

What is a buffer?

A mechanism that resists changes in pH.

What are the two major categories of buffers?

• Chemical buffers

  • Physiological buffers

What is a chemical buffer?

A substance that:

• Binds H⁺ when hydrogen ion concentration rises

• Releases H⁺ when hydrogen ion concentration falls

This helps maintain a stable pH.

How quickly do chemical buffers work?

In less than one second.

What determines how much acid or base a chemical buffer can neutralize?

• Buffer concentration

  • pH of the environment

What are the three major chemical buffer systems?

• Bicarbonate buffer system

• Phosphate buffer system

  • Protein buffer system

What is a physiological buffer?

A body system that controls the output of:

• Acids

• Bases

  • CO₂

Which physiological buffer works the fastest?

The respiratory system (within minutes).

Which physiological buffer is the most powerful?

The urinary (renal) system, because it removes the greatest quantity of acid or base.

How long does the urinary system take to buffer pH?

Several hours to days.

What makes up the bicarbonate buffer system?

• Carbonic acid (H₂CO₃)

  • Bicarbonate ion (HCO₃⁻)

Why is acid-base balance important?

Because enzymes are very sensitive to pH. Even small changes in pH can:

• Shut down metabolic pathways

• Alter protein structure

  • Disrupt normal cellular function

What is the bicarbonate buffer equation?

CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺

When does the bicarbonate buffer lower pH?

When the reaction moves to the right, releasing H⁺.

When does the bicarbonate buffer raise pH?

When the reaction moves to the left, binding H⁺.

Where does the bicarbonate buffer system work best?

• Lungs

  • Kidneys

How do the kidneys raise pH using the bicarbonate buffer?

• Excrete H⁺

  • Retain bicarbonate (HCO₃⁻)

How do the lungs raise pH?

They remove CO₂ through exhalation.

How do the kidneys lower pH?

They excrete bicarbonate (HCO₃⁻).

What makes up the phosphate buffer system?

• HPO₄²⁻

  • H₂PO₄⁻

What reaction occurs in the phosphate buffer system?

H₂PO₄⁻ ⇌ HPO₄²⁻ + H⁺

When does the phosphate buffer lower pH?

When it releases H⁺ (reaction moves right).

Where is the phosphate buffer system most important?

• Intracellular fluid (ICF)

  • Renal tubules

Which is the most abundant chemical buffer system?

The protein buffer system.

Approximately how much of the body's chemical buffering is performed by proteins?

About 75%.

Why are proteins good buffers?

Because amino acid side groups can either:

• Release H⁺

  • Bind H⁺

Which amino acid side group releases H⁺ when pH rises?

The carboxyl (-COOH) group.

Which amino acid side group binds H⁺ when pH falls?

The amino (-NH₂) group.

What are electrolytes?

Charged ions that:

• Participate in metabolism

• Determine membrane potential

• Affect osmolarity

  • Regulate water distribution

What are the four major cations?

• Sodium (Na⁺)

• Potassium (K⁺)

• Calcium (Ca²⁺)

  • Hydrogen (H⁺)

What are the three major anions?

• Chloride (Cl⁻)

• Bicarbonate (HCO₃⁻)

  • Phosphate (PO₄³⁻)

Which electrolyte is the major cation of the extracellular fluid (ECF)?

Sodium (Na⁺)

Which electrolyte is the major cation of the intracellular fluid (ICF)?

Potassium (K⁺)

What are the major functions of sodium?

• Resting membrane potential

• Depolarization of nerves and muscles

• Major cation of ECF

• Determines ECF osmolarity

• Helps regulate body water

• Provides energy for cotransport

  • Na⁺/K⁺ pump generates body heat

Which hormone is called the "salt-retaining hormone"?

Aldosterone

How does aldosterone affect sodium?

Increases Na⁺ reabsorption in:

• Ascending limb

• Distal convoluted tubule

  • Collecting duct

How does ADH affect sodium concentration?

ADH increases water reabsorption, which slows any further increase in blood sodium concentration.

How does ANP affect sodium?

ANP inhibits sodium reabsorption, increasing sodium excretion.

What is hypernatremia?

High blood sodium concentration.

What causes hypernatremia?

• Water loss faster than sodium

• Diarrhea

  • Not drinking enough water

What are the effects of hypernatremia?

• Water retention

• Hypertension

  • Edema

What is hyponatremia?

Low blood sodium concentration.

What causes hyponatremia?

drinking too much water, losing sodium through severe vomiting or diarrhea, or medical conditions like heart, kidney, or liver disease that trap fluid in the body

What are the major functions of potassium?

• Major cation of ICF

• Regulates intracellular osmolarity

• Resting membrane potential

• Action potentials

• Na⁺/K⁺ pump

  • Protein synthesis

Where is most potassium reabsorbed?

The proximal convoluted tubule (PCT)

Where is potassium secreted?

The distal convoluted tubule and collecting duct

Which hormone increases potassium secretion?

Aldosterone

Which electrolyte imbalance is considered the most dangerous?

Potassium imbalance

What is hyperkalemia?

High blood potassium concentration.

What causes hyperkalemia?

Rapid potassium release (example: crush injury).

What are the effects of hyperkalemia?

• Increased excitability initially

• Decreased excitability if prolonged

  • Cardiac arrest

What is hypokalemia?

Low blood potassium concentration.

What causes hypokalemia?

• Sweating

• Chronic vomiting

  • Diarrhea

What are the effects of hypokalemia?

• muscle cramps, extreme tiredness, dangerous heart rhythms, and muscle breakdown

What are the major functions of chloride?

• Major anion of ECF

• Needed to make hydrochloric acid (HCl)

• Chloride shift in RBCs

  • Helps regulate body pH

How is chloride homeostasis maintained?

systemic regulation by the kidneys and intestines

What causes hyperchloremia?

• Excess dietary chloride

  • Excess IV saline

What causes hypochloremia?

• Hyponatremia

• Hyperkalemia

  • Acidosis

What is the primary effect of chloride imbalances?

Disturbances in acid-base balance.

What are the major functions of calcium?

• Strengthens bones

• Muscle contraction

• Neurotransmitter release

  • Blood clotting

Which hormones regulate calcium homeostasis?

• Parathyroid hormone (PTH)

• Calcitriol (Vitamin D)

  • Calcitonin

Why do cells keep intracellular calcium levels very low?

To prevent calcium phosphate crystal formation.

What is hypercalcemia?

High blood calcium concentration.

What causes hypercalcemia?

• Alkalosis

• Hyperparathyroidism

  • Hypothyroidism